RFC3542 日本語訳
3542 Advanced Sockets Application Program Interface (API) for IPv6. W.Stevens, M. Thomas, E. Nordmark, T. Jinmei. May 2003. (Format: TXT=173028 bytes) (Obsoletes RFC2292) (Status: INFORMATIONAL)
プログラムでの自動翻訳です。
英語原文
Network Working Group W. Stevens
Request for Comments: 3542 M. Thomas
Obsoletes: 2292 Consultant
Category: Informational E. Nordmark
Sun
T. Jinmei
Toshiba
May 2003
Network Working Group W. Stevens Request for Comments: 3542 M. Thomas Obsoletes: 2292 Consultant Category: Informational E. Nordmark Sun T. Jinmei Toshiba May 2003
Advanced Sockets Application Program Interface (API) for IPv6
Advanced Sockets Application Program Interface (API) for IPv6
Status of this Memo
Status of this Memo
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
Copyright Notice
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
Abstract
This document provides sockets Application Program Interface (API) to support "advanced" IPv6 applications, as a supplement to a separate specification, RFC 3493. The expected applications include Ping, Traceroute, routing daemons and the like, which typically use raw sockets to access IPv6 or ICMPv6 header fields. This document proposes some portable interfaces for applications that use raw sockets under IPv6. There are other features of IPv6 that some applications will need to access: interface identification (specifying the outgoing interface and determining the incoming interface), IPv6 extension headers, and path Maximum Transmission Unit (MTU) information. This document provides API access to these features too. Additionally, some extended interfaces to libraries for the "r" commands are defined. The extension will provide better backward compatibility to existing implementations that are not IPv6-capable.
This document provides sockets Application Program Interface (API) to support "advanced" IPv6 applications, as a supplement to a separate specification, RFC 3493. The expected applications include Ping, Traceroute, routing daemons and the like, which typically use raw sockets to access IPv6 or ICMPv6 header fields. This document proposes some portable interfaces for applications that use raw sockets under IPv6. There are other features of IPv6 that some applications will need to access: interface identification (specifying the outgoing interface and determining the incoming interface), IPv6 extension headers, and path Maximum Transmission Unit (MTU) information. This document provides API access to these features too. Additionally, some extended interfaces to libraries for the "r" commands are defined. The extension will provide better backward compatibility to existing implementations that are not IPv6-capable.
Stevens, et al. Informational [Page 1] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 1] RFC 3542 Advanced Sockets API for IPv6 May 2003
Table of Contents
Table of Contents
1. Introduction .............................................. 3
2. Common Structures and Definitions ......................... 5
2.1 The ip6_hdr Structure ................................ 6
2.1.1 IPv6 Next Header Values ....................... 6
2.1.2 IPv6 Extension Headers ........................ 7
2.1.3 IPv6 Options .................................. 8
2.2 The icmp6_hdr Structure .............................. 10
2.2.1 ICMPv6 Type and Code Values ................... 10
2.2.2 ICMPv6 Neighbor Discovery Definitions ......... 11
2.2.3 Multicast Listener Discovery Definitions ...... 14
2.2.4 ICMPv6 Router Renumbering Definitions ......... 14
2.3 Address Testing Macros ............................... 16
2.4 Protocols File ....................................... 16
3. IPv6 Raw Sockets .......................................... 17
3.1 Checksums ............................................ 18
3.2 ICMPv6 Type Filtering ................................ 19
3.3 ICMPv6 Verification of Received Packets .............. 22
4. Access to IPv6 and Extension Headers ...................... 22
4.1 TCP Implications ..................................... 24
4.2 UDP and Raw Socket Implications ...................... 25
5. Extensions to Socket Ancillary Data ....................... 26
5.1 CMSG_NXTHDR .......................................... 26
5.2 CMSG_SPACE ........................................... 26
5.3 CMSG_LEN ............................................. 27
6. Packet Information ........................................ 27
6.1 Specifying/Receiving the Interface ................... 28
6.2 Specifying/Receiving Source/Destination Address ...... 29
6.3 Specifying/Receiving the Hop Limit ................... 29
6.4 Specifying the Next Hop Address ...................... 30
6.5 Specifying/Receiving the Traffic Class value ......... 31
6.6 Additional Errors with sendmsg() and setsockopt() .... 32
6.7 Summary of Outgoing Interface Selection .............. 32
7. Routing Header Option ..................................... 33
7.1 inet6_rth_space ...................................... 35
7.2 inet6_rth_init ....................................... 35
7.3 inet6_rth_add ........................................ 36
7.4 inet6_rth_reverse .................................... 36
7.5 inet6_rth_segments ................................... 36
7.6 inet6_rth_getaddr .................................... 36
8. Hop-By-Hop Options ........................................ 37
8.1 Receiving Hop-by-Hop Options ......................... 38
8.2 Sending Hop-by-Hop Options ........................... 38
9. Destination Options ....................................... 39
9.1 Receiving Destination Options ........................ 39
9.2 Sending Destination Options .......................... 39
10. Hop-by-Hop and Destination Options Processing ............. 40
1. Introduction .............................................. 3 2. Common Structures and Definitions ......................... 5 2.1 The ip6_hdr Structure ................................ 6 2.1.1 IPv6 Next Header Values ....................... 6 2.1.2 IPv6 Extension Headers ........................ 7 2.1.3 IPv6 Options .................................. 8 2.2 The icmp6_hdr Structure .............................. 10 2.2.1 ICMPv6 Type and Code Values ................... 10 2.2.2 ICMPv6 Neighbor Discovery Definitions ......... 11 2.2.3 Multicast Listener Discovery Definitions ...... 14 2.2.4 ICMPv6 Router Renumbering Definitions ......... 14 2.3 Address Testing Macros ............................... 16 2.4 Protocols File ....................................... 16 3. IPv6 Raw Sockets .......................................... 17 3.1 Checksums ............................................ 18 3.2 ICMPv6 Type Filtering ................................ 19 3.3 ICMPv6 Verification of Received Packets .............. 22 4. Access to IPv6 and Extension Headers ...................... 22 4.1 TCP Implications ..................................... 24 4.2 UDP and Raw Socket Implications ...................... 25 5. Extensions to Socket Ancillary Data ....................... 26 5.1 CMSG_NXTHDR .......................................... 26 5.2 CMSG_SPACE ........................................... 26 5.3 CMSG_LEN ............................................. 27 6. Packet Information ........................................ 27 6.1 Specifying/Receiving the Interface ................... 28 6.2 Specifying/Receiving Source/Destination Address ...... 29 6.3 Specifying/Receiving the Hop Limit ................... 29 6.4 Specifying the Next Hop Address ...................... 30 6.5 Specifying/Receiving the Traffic Class value ......... 31 6.6 Additional Errors with sendmsg() and setsockopt() .... 32 6.7 Summary of Outgoing Interface Selection .............. 32 7. Routing Header Option ..................................... 33 7.1 inet6_rth_space ...................................... 35 7.2 inet6_rth_init ....................................... 35 7.3 inet6_rth_add ........................................ 36 7.4 inet6_rth_reverse .................................... 36 7.5 inet6_rth_segments ................................... 36 7.6 inet6_rth_getaddr .................................... 36 8. Hop-By-Hop Options ........................................ 37 8.1 Receiving Hop-by-Hop Options ......................... 38 8.2 Sending Hop-by-Hop Options ........................... 38 9. Destination Options ....................................... 39 9.1 Receiving Destination Options ........................ 39 9.2 Sending Destination Options .......................... 39 10. Hop-by-Hop and Destination Options Processing ............. 40
Stevens, et al. Informational [Page 2] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 2] RFC 3542 Advanced Sockets API for IPv6 May 2003
10.1 inet6_opt_init ...................................... 41
10.2 inet6_opt_append .................................... 41
10.3 inet6_opt_finish .................................... 42
10.4 inet6_opt_set_val ................................... 42
10.5 inet6_opt_next ...................................... 42
10.6 inet6_opt_find ...................................... 43
10.7 inet6_opt_get_val ................................... 43
11. Additional Advanced API Functions ......................... 44
11.1 Sending with the Minimum MTU ........................ 44
11.2 Sending without Fragmentation ....................... 45
11.3 Path MTU Discovery and UDP .......................... 46
11.4 Determining the Current Path MTU .................... 47
12. Ordering of Ancillary Data and IPv6 Extension Headers ..... 48
13. IPv6-Specific Options with IPv4-Mapped IPv6 Addresses ..... 50
14. Extended interfaces for rresvport, rcmd and rexec ......... 51
14.1 rresvport_af ........................................ 51
14.2 rcmd_af ............................................. 51
14.3 rexec_af ............................................ 52
15. Summary of New Definitions ................................ 52
16. Security Considerations ................................... 56
17. Changes from RFC 2292 ..................................... 57
18. References ................................................ 59
19. Acknowledgments ........................................... 59
20. Appendix A: Ancillary Data Overview ....................... 60
20.1 The msghdr Structure ................................ 60
20.2 The cmsghdr Structure ............................... 61
20.3 Ancillary Data Object Macros ........................ 62
20.3.1 CMSG_FIRSTHDR ............................... 63
20.3.2 CMSG_NXTHDR ................................. 64
20.3.3 CMSG_DATA ................................... 65
20.3.4 CMSG_SPACE .................................. 65
20.3.5 CMSG_LEN .................................... 65
21. Appendix B: Examples Using the inet6_rth_XXX() Functions .. 65
21.1 Sending a Routing Header ............................ 65
21.2 Receiving Routing Headers ........................... 70
22. Appendix C: Examples Using the inet6_opt_XXX() Functions .. 72
22.1 Building Options .................................... 72
22.2 Parsing Received Options ............................ 74
23. Authors' Addresses ........................................ 76
24. Full Copyright Statement .................................. 77
10.1 inet6_opt_init ...................................... 41 10.2 inet6_opt_append .................................... 41 10.3 inet6_opt_finish .................................... 42 10.4 inet6_opt_set_val ................................... 42 10.5 inet6_opt_next ...................................... 42 10.6 inet6_opt_find ...................................... 43 10.7 inet6_opt_get_val ................................... 43 11. Additional Advanced API Functions ......................... 44 11.1 Sending with the Minimum MTU ........................ 44 11.2 Sending without Fragmentation ....................... 45 11.3 Path MTU Discovery and UDP .......................... 46 11.4 Determining the Current Path MTU .................... 47 12. Ordering of Ancillary Data and IPv6 Extension Headers ..... 48 13. IPv6-Specific Options with IPv4-Mapped IPv6 Addresses ..... 50 14. Extended interfaces for rresvport, rcmd and rexec ......... 51 14.1 rresvport_af ........................................ 51 14.2 rcmd_af ............................................. 51 14.3 rexec_af ............................................ 52 15. Summary of New Definitions ................................ 52 16. Security Considerations ................................... 56 17. Changes from RFC 2292 ..................................... 57 18. References ................................................ 59 19. Acknowledgments ........................................... 59 20. Appendix A: Ancillary Data Overview ....................... 60 20.1 The msghdr Structure ................................ 60 20.2 The cmsghdr Structure ............................... 61 20.3 Ancillary Data Object Macros ........................ 62 20.3.1 CMSG_FIRSTHDR ............................... 63 20.3.2 CMSG_NXTHDR ................................. 64 20.3.3 CMSG_DATA ................................... 65 20.3.4 CMSG_SPACE .................................. 65 20.3.5 CMSG_LEN .................................... 65 21. Appendix B: Examples Using the inet6_rth_XXX() Functions .. 65 21.1 Sending a Routing Header ............................ 65 21.2 Receiving Routing Headers ........................... 70 22. Appendix C: Examples Using the inet6_opt_XXX() Functions .. 72 22.1 Building Options .................................... 72 22.2 Parsing Received Options ............................ 74 23. Authors' Addresses ........................................ 76 24. Full Copyright Statement .................................. 77
1. Introduction
1. Introduction
A separate specification [RFC-3493] contains changes to the sockets API to support IP version 6. Those changes are for TCP and UDP-based applications. This document defines some of the "advanced" features of the sockets API that are required for applications to take advantage of additional features of IPv6.
A separate specification [RFC-3493] contains changes to the sockets API to support IP version 6. Those changes are for TCP and UDP-based applications. This document defines some of the "advanced" features of the sockets API that are required for applications to take advantage of additional features of IPv6.
Stevens, et al. Informational [Page 3] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 3] RFC 3542 Advanced Sockets API for IPv6 May 2003
Today, the portability of applications using IPv4 raw sockets is quite high, but this is mainly because most IPv4 implementations started from a common base (the Berkeley source code) or at least started with the Berkeley header files. This allows programs such as Ping and Traceroute, for example, to compile with minimal effort on many hosts that support the sockets API. With IPv6, however, there is no common source code base that implementors are starting from, and the possibility for divergence at this level between different implementations is high. To avoid a complete lack of portability amongst applications that use raw IPv6 sockets, some standardization is necessary.
Today, the portability of applications using IPv4 raw sockets is quite high, but this is mainly because most IPv4 implementations started from a common base (the Berkeley source code) or at least started with the Berkeley header files. This allows programs such as Ping and Traceroute, for example, to compile with minimal effort on many hosts that support the sockets API. With IPv6, however, there is no common source code base that implementors are starting from, and the possibility for divergence at this level between different implementations is high. To avoid a complete lack of portability amongst applications that use raw IPv6 sockets, some standardization is necessary.
There are also features from the basic IPv6 specification that are not addressed in [RFC-3493]: sending and receiving Routing headers, Hop-by-Hop options, and Destination options, specifying the outgoing interface, being told of the receiving interface, and control of path MTU information.
There are also features from the basic IPv6 specification that are not addressed in [RFC-3493]: sending and receiving Routing headers, Hop-by-Hop options, and Destination options, specifying the outgoing interface, being told of the receiving interface, and control of path MTU information.
This document updates and replaces RFC 2292. This revision is based on implementation experience of RFC 2292, as well as some additional extensions that have been found to be useful through the IPv6 deployment. Note, however, that further work on this document may still be needed. Once the API specification becomes mature and is deployed among implementations, it may be formally standardized by a more appropriate body, such as has been done with the Basic API [RFC-3493].
This document updates and replaces RFC 2292. This revision is based on implementation experience of RFC 2292, as well as some additional extensions that have been found to be useful through the IPv6 deployment. Note, however, that further work on this document may still be needed. Once the API specification becomes mature and is deployed among implementations, it may be formally standardized by a more appropriate body, such as has been done with the Basic API [RFC-3493].
This document can be divided into the following main sections.
This document can be divided into the following main sections.
1. Definitions of the basic constants and structures required for
applications to use raw IPv6 sockets. This includes structure
definitions for the IPv6 and ICMPv6 headers and all associated
constants (e.g., values for the Next Header field).
1. Definitions of the basic constants and structures required for applications to use raw IPv6 sockets. This includes structure definitions for the IPv6 and ICMPv6 headers and all associated constants (e.g., values for the Next Header field).
2. Some basic semantic definitions for IPv6 raw sockets. For
example, a raw ICMPv4 socket requires the application to calculate
and store the ICMPv4 header checksum. But with IPv6 this would
require the application to choose the source IPv6 address because
the source address is part of the pseudo header that ICMPv6 now
uses for its checksum computation. It should be defined that with
a raw ICMPv6 socket the kernel always calculates and stores the
ICMPv6 header checksum.
2. Some basic semantic definitions for IPv6 raw sockets. For example, a raw ICMPv4 socket requires the application to calculate and store the ICMPv4 header checksum. But with IPv6 this would require the application to choose the source IPv6 address because the source address is part of the pseudo header that ICMPv6 now uses for its checksum computation. It should be defined that with a raw ICMPv6 socket the kernel always calculates and stores the ICMPv6 header checksum.
3. Packet information: how applications can obtain the received
interface, destination address, and received hop limit, along with
specifying these values on a per-packet basis. There are a class
of applications that need this capability and the technique should
be portable.
3. Packet information: how applications can obtain the received interface, destination address, and received hop limit, along with specifying these values on a per-packet basis. There are a class of applications that need this capability and the technique should be portable.
Stevens, et al. Informational [Page 4] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 4] RFC 3542 Advanced Sockets API for IPv6 May 2003
4. Access to the optional Routing header, Hop-by-Hop options, and
Destination options extension headers.
4. Access to the optional Routing header, Hop-by-Hop options, and Destination options extension headers.
5. Additional features required for improved IPv6 application
portability.
5. Additional features required for improved IPv6 application portability.
The packet information along with access to the extension headers (Routing header, Hop-by-Hop options, and Destination options) are specified using the "ancillary data" fields that were added to the 4.3BSD Reno sockets API in 1990. The reason is that these ancillary data fields are part of the Posix standard [POSIX] and should therefore be adopted by most vendors.
The packet information along with access to the extension headers (Routing header, Hop-by-Hop options, and Destination options) are specified using the "ancillary data" fields that were added to the 4.3BSD Reno sockets API in 1990. The reason is that these ancillary data fields are part of the Posix standard [POSIX] and should therefore be adopted by most vendors.
This document does not address application access to either the authentication header or the encapsulating security payload header.
This document does not address application access to either the authentication header or the encapsulating security payload header.
Many examples in this document omit error checking in favor of brevity and clarity.
Many examples in this document omit error checking in favor of brevity and clarity.
We note that some of the functions and socket options defined in this document may have error returns that are not defined in this document. Some of these possible error returns will be recognized only as implementations proceed.
We note that some of the functions and socket options defined in this document may have error returns that are not defined in this document. Some of these possible error returns will be recognized only as implementations proceed.
Datatypes in this document follow the Posix format: intN_t means a signed integer of exactly N bits (e.g., int16_t) and uintN_t means an unsigned integer of exactly N bits (e.g., uint32_t).
Datatypes in this document follow the Posix format: intN_t means a signed integer of exactly N bits (e.g., int16_t) and uintN_t means an unsigned integer of exactly N bits (e.g., uint32_t).
Note that we use the (unofficial) terminology ICMPv4, IGMPv4, and ARPv4 to avoid any confusion with the newer ICMPv6 protocol.
Note that we use the (unofficial) terminology ICMPv4, IGMPv4, and ARPv4 to avoid any confusion with the newer ICMPv6 protocol.
2. Common Structures and Definitions
2. Common Structures and Definitions
Many advanced applications examine fields in the IPv6 header and set and examine fields in the various ICMPv6 headers. Common structure definitions for these protocol headers are required, along with common constant definitions for the structure members.
Many advanced applications examine fields in the IPv6 header and set and examine fields in the various ICMPv6 headers. Common structure definitions for these protocol headers are required, along with common constant definitions for the structure members.
This API assumes that the fields in the protocol headers are left in the network byte order, which is big-endian for the Internet protocols. If not, then either these constants or the fields being tested must be converted at run-time, using something like htons() or htonl().
This API assumes that the fields in the protocol headers are left in the network byte order, which is big-endian for the Internet protocols. If not, then either these constants or the fields being tested must be converted at run-time, using something like htons() or htonl().
Two new header files are defined: <netinet/ip6.h> and <netinet/icmp6.h>.
Two new header files are defined: <netinet/ip6.h> and <netinet/icmp6.h>.
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Stevens, et al. Informational [Page 5] RFC 3542 Advanced Sockets API for IPv6 May 2003
When an include file is specified, that include file is allowed to include other files that do the actual declaration or definition.
When an include file is specified, that include file is allowed to include other files that do the actual declaration or definition.
2.1. The ip6_hdr Structure
2.1. The ip6_hdr Structure
The following structure is defined as a result of including <netinet/ip6.h>. Note that this is a new header.
The following structure is defined as a result of including <netinet/ip6.h>. Note that this is a new header.
struct ip6_hdr {
union {
struct ip6_hdrctl {
uint32_t ip6_un1_flow; /* 4 bits version, 8 bits TC, 20 bits
flow-ID */
uint16_t ip6_un1_plen; /* payload length */
uint8_t ip6_un1_nxt; /* next header */
uint8_t ip6_un1_hlim; /* hop limit */
} ip6_un1;
uint8_t ip6_un2_vfc; /* 4 bits version, top 4 bits
tclass */
} ip6_ctlun;
struct in6_addr ip6_src; /* source address */
struct in6_addr ip6_dst; /* destination address */
};
struct ip6_hdr { union { struct ip6_hdrctl { uint32_t ip6_un1_flow; /* 4 bits version, 8 bits TC, 20 bits flow-ID */ uint16_t ip6_un1_plen; /* payload length */ uint8_t ip6_un1_nxt; /* next header */ uint8_t ip6_un1_hlim; /* hop limit */ } ip6_un1; uint8_t ip6_un2_vfc; /* 4 bits version, top 4 bits tclass */ } ip6_ctlun; struct in6_addr ip6_src; /* source address */ struct in6_addr ip6_dst; /* destination address */ };
#define ip6_vfc ip6_ctlun.ip6_un2_vfc
#define ip6_flow ip6_ctlun.ip6_un1.ip6_un1_flow
#define ip6_plen ip6_ctlun.ip6_un1.ip6_un1_plen
#define ip6_nxt ip6_ctlun.ip6_un1.ip6_un1_nxt
#define ip6_hlim ip6_ctlun.ip6_un1.ip6_un1_hlim
#define ip6_hops ip6_ctlun.ip6_un1.ip6_un1_hlim
#define ip6_vfc ip6_ctlun.ip6_un2_vfc #define ip6_flow ip6_ctlun.ip6_un1.ip6_un1_flow #define ip6_plen ip6_ctlun.ip6_un1.ip6_un1_plen #define ip6_nxt ip6_ctlun.ip6_un1.ip6_un1_nxt #define ip6_hlim ip6_ctlun.ip6_un1.ip6_un1_hlim #define ip6_hops ip6_ctlun.ip6_un1.ip6_un1_hlim
2.1.1. IPv6 Next Header Values
2.1.1. IPv6 Next Header Values
IPv6 defines many new values for the Next Header field. The following constants are defined as a result of including <netinet/in.h>.
IPv6 defines many new values for the Next Header field. The following constants are defined as a result of including <netinet/in.h>.
#define IPPROTO_HOPOPTS 0 /* IPv6 Hop-by-Hop options */
#define IPPROTO_IPV6 41 /* IPv6 header */
#define IPPROTO_ROUTING 43 /* IPv6 Routing header */
#define IPPROTO_FRAGMENT 44 /* IPv6 fragment header */
#define IPPROTO_ESP 50 /* encapsulating security payload */
#define IPPROTO_AH 51 /* authentication header */
#define IPPROTO_ICMPV6 58 /* ICMPv6 */
#define IPPROTO_NONE 59 /* IPv6 no next header */
#define IPPROTO_DSTOPTS 60 /* IPv6 Destination options */
#define IPPROTO_HOPOPTS 0 /* IPv6 Hop-by-Hop options */ #define IPPROTO_IPV6 41 /* IPv6 header */ #define IPPROTO_ROUTING 43 /* IPv6 Routing header */ #define IPPROTO_FRAGMENT 44 /* IPv6 fragment header */ #define IPPROTO_ESP 50 /* encapsulating security payload */ #define IPPROTO_AH 51 /* authentication header */ #define IPPROTO_ICMPV6 58 /* ICMPv6 */ #define IPPROTO_NONE 59 /* IPv6 no next header */ #define IPPROTO_DSTOPTS 60 /* IPv6 Destination options */
Stevens, et al. Informational [Page 6] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 6] RFC 3542 Advanced Sockets API for IPv6 May 2003
Berkeley-derived IPv4 implementations also define IPPROTO_IP to be 0. This should not be a problem since IPPROTO_IP is used only with IPv4 sockets and IPPROTO_HOPOPTS only with IPv6 sockets.
Berkeley-derived IPv4 implementations also define IPPROTO_IP to be 0. This should not be a problem since IPPROTO_IP is used only with IPv4 sockets and IPPROTO_HOPOPTS only with IPv6 sockets.
2.1.2. IPv6 Extension Headers
2.1.2. IPv6 Extension Headers
Six extension headers are defined for IPv6. We define structures for all except the Authentication header and Encapsulating Security Payload header, both of which are beyond the scope of this document. The following structures are defined as a result of including <netinet/ip6.h>.
Six extension headers are defined for IPv6. We define structures for all except the Authentication header and Encapsulating Security Payload header, both of which are beyond the scope of this document. The following structures are defined as a result of including <netinet/ip6.h>.
/* Hop-by-Hop options header */
struct ip6_hbh {
uint8_t ip6h_nxt; /* next header */
uint8_t ip6h_len; /* length in units of 8 octets */
/* followed by options */
};
/* Hop-by-Hop options header */ struct ip6_hbh { uint8_t ip6h_nxt; /* next header */ uint8_t ip6h_len; /* length in units of 8 octets */ /* followed by options */ };
/* Destination options header */
struct ip6_dest {
uint8_t ip6d_nxt; /* next header */
uint8_t ip6d_len; /* length in units of 8 octets */
/* followed by options */
};
/* Destination options header */ struct ip6_dest { uint8_t ip6d_nxt; /* next header */ uint8_t ip6d_len; /* length in units of 8 octets */ /* followed by options */ };
/* Routing header */
struct ip6_rthdr {
uint8_t ip6r_nxt; /* next header */
uint8_t ip6r_len; /* length in units of 8 octets */
uint8_t ip6r_type; /* routing type */
uint8_t ip6r_segleft; /* segments left */
/* followed by routing type specific data */
};
/* Routing header */ struct ip6_rthdr { uint8_t ip6r_nxt; /* next header */ uint8_t ip6r_len; /* length in units of 8 octets */ uint8_t ip6r_type; /* routing type */ uint8_t ip6r_segleft; /* segments left */ /* followed by routing type specific data */ };
/* Type 0 Routing header */
struct ip6_rthdr0 {
uint8_t ip6r0_nxt; /* next header */
uint8_t ip6r0_len; /* length in units of 8 octets */
uint8_t ip6r0_type; /* always zero */
uint8_t ip6r0_segleft; /* segments left */
uint32_t ip6r0_reserved; /* reserved field */
/* followed by up to 127 struct in6_addr */
};
/* Type 0 Routing header */ struct ip6_rthdr0 { uint8_t ip6r0_nxt; /* next header */ uint8_t ip6r0_len; /* length in units of 8 octets */ uint8_t ip6r0_type; /* always zero */ uint8_t ip6r0_segleft; /* segments left */ uint32_t ip6r0_reserved; /* reserved field */ /* followed by up to 127 struct in6_addr */ };
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Stevens, et al. Informational [Page 7] RFC 3542 Advanced Sockets API for IPv6 May 2003
/* Fragment header */
struct ip6_frag {
uint8_t ip6f_nxt; /* next header */
uint8_t ip6f_reserved; /* reserved field */
uint16_t ip6f_offlg; /* offset, reserved, and flag */
uint32_t ip6f_ident; /* identification */
};
/* Fragment header */ struct ip6_frag { uint8_t ip6f_nxt; /* next header */ uint8_t ip6f_reserved; /* reserved field */ uint16_t ip6f_offlg; /* offset, reserved, and flag */ uint32_t ip6f_ident; /* identification */ };
#if BYTE_ORDER == BIG_ENDIAN
#define IP6F_OFF_MASK 0xfff8 /* mask out offset from
ip6f_offlg */
#define IP6F_RESERVED_MASK 0x0006 /* reserved bits in
ip6f_offlg */
#define IP6F_MORE_FRAG 0x0001 /* more-fragments flag */
#else /* BYTE_ORDER == LITTLE_ENDIAN */
#define IP6F_OFF_MASK 0xf8ff /* mask out offset from
ip6f_offlg */
#define IP6F_RESERVED_MASK 0x0600 /* reserved bits in
ip6f_offlg */
#define IP6F_MORE_FRAG 0x0100 /* more-fragments flag */
#endif
#if BYTE_ORDER == BIG_ENDIAN #define IP6F_OFF_MASK 0xfff8 /* mask out offset from ip6f_offlg */ #define IP6F_RESERVED_MASK 0x0006 /* reserved bits in ip6f_offlg */ #define IP6F_MORE_FRAG 0x0001 /* more-fragments flag */ #else /* BYTE_ORDER == LITTLE_ENDIAN */ #define IP6F_OFF_MASK 0xf8ff /* mask out offset from ip6f_offlg */ #define IP6F_RESERVED_MASK 0x0600 /* reserved bits in ip6f_offlg */ #define IP6F_MORE_FRAG 0x0100 /* more-fragments flag */ #endif
2.1.3. IPv6 Options
2.1.3. IPv6 Options
Several options are defined for IPv6, and we define structures and macro definitions for some of them below. The following structures are defined as a result of including <netinet/ip6.h>.
Several options are defined for IPv6, and we define structures and macro definitions for some of them below. The following structures are defined as a result of including <netinet/ip6.h>.
/* IPv6 options */
struct ip6_opt {
uint8_t ip6o_type;
uint8_t ip6o_len;
};
/* IPv6 options */ struct ip6_opt { uint8_t ip6o_type; uint8_t ip6o_len; };
/*
* The high-order 3 bits of the option type define the behavior
* when processing an unknown option and whether or not the option
* content changes in flight.
*/
#define IP6OPT_TYPE(o) ((o) & 0xc0)
#define IP6OPT_TYPE_SKIP 0x00
#define IP6OPT_TYPE_DISCARD 0x40
#define IP6OPT_TYPE_FORCEICMP 0x80
#define IP6OPT_TYPE_ICMP 0xc0
#define IP6OPT_MUTABLE 0x20
/* * The high-order 3 bits of the option type define the behavior * when processing an unknown option and whether or not the option * content changes in flight. */ #define IP6OPT_TYPE(o) ((o) & 0xc0) #define IP6OPT_TYPE_SKIP 0x00 #define IP6OPT_TYPE_DISCARD 0x40 #define IP6OPT_TYPE_FORCEICMP 0x80 #define IP6OPT_TYPE_ICMP 0xc0 #define IP6OPT_MUTABLE 0x20
#define IP6OPT_PAD1 0x00 /* 00 0 00000 */
#define IP6OPT_PADN 0x01 /* 00 0 00001 */
#define IP6OPT_PAD1 0x00 /* 00 0 00000 */ #define IP6OPT_PADN 0x01 /* 00 0 00001 */
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#define IP6OPT_JUMBO 0xc2 /* 11 0 00010 */
#define IP6OPT_NSAP_ADDR 0xc3 /* 11 0 00011 */
#define IP6OPT_TUNNEL_LIMIT 0x04 /* 00 0 00100 */
#define IP6OPT_ROUTER_ALERT 0x05 /* 00 0 00101 */
#define IP6OPT_JUMBO 0xc2 /* 11 0 00010 */ #define IP6OPT_NSAP_ADDR 0xc3 /* 11 0 00011 */ #define IP6OPT_TUNNEL_LIMIT 0x04 /* 00 0 00100 */ #define IP6OPT_ROUTER_ALERT 0x05 /* 00 0 00101 */
/* Jumbo Payload Option */
struct ip6_opt_jumbo {
uint8_t ip6oj_type;
uint8_t ip6oj_len;
uint8_t ip6oj_jumbo_len[4];
};
#define IP6OPT_JUMBO_LEN 6
/* Jumbo Payload Option */ struct ip6_opt_jumbo { uint8_t ip6oj_type; uint8_t ip6oj_len; uint8_t ip6oj_jumbo_len[4]; }; #define IP6OPT_JUMBO_LEN 6
/* NSAP Address Option */
struct ip6_opt_nsap {
uint8_t ip6on_type;
uint8_t ip6on_len;
uint8_t ip6on_src_nsap_len;
uint8_t ip6on_dst_nsap_len;
/* followed by source NSAP */
/* followed by destination NSAP */
};
/* NSAP Address Option */ struct ip6_opt_nsap { uint8_t ip6on_type; uint8_t ip6on_len; uint8_t ip6on_src_nsap_len; uint8_t ip6on_dst_nsap_len; /* followed by source NSAP */ /* followed by destination NSAP */ };
/* Tunnel Limit Option */
struct ip6_opt_tunnel {
uint8_t ip6ot_type;
uint8_t ip6ot_len;
uint8_t ip6ot_encap_limit;
};
/* Tunnel Limit Option */ struct ip6_opt_tunnel { uint8_t ip6ot_type; uint8_t ip6ot_len; uint8_t ip6ot_encap_limit; };
/* Router Alert Option */
struct ip6_opt_router {
uint8_t ip6or_type;
uint8_t ip6or_len;
uint8_t ip6or_value[2];
};
/* Router Alert Option */ struct ip6_opt_router { uint8_t ip6or_type; uint8_t ip6or_len; uint8_t ip6or_value[2]; };
/* Router alert values (in network byte order) */
#ifdef _BIG_ENDIAN
#define IP6_ALERT_MLD 0x0000
#define IP6_ALERT_RSVP 0x0001
#define IP6_ALERT_AN 0x0002
#else
#define IP6_ALERT_MLD 0x0000
#define IP6_ALERT_RSVP 0x0100
#define IP6_ALERT_AN 0x0200
#endif
/* Router alert values (in network byte order) */ #ifdef _BIG_ENDIAN #define IP6_ALERT_MLD 0x0000 #define IP6_ALERT_RSVP 0x0001 #define IP6_ALERT_AN 0x0002 #else #define IP6_ALERT_MLD 0x0000 #define IP6_ALERT_RSVP 0x0100 #define IP6_ALERT_AN 0x0200 #endif
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2.2. The icmp6_hdr Structure
2.2. The icmp6_hdr Structure
The ICMPv6 header is needed by numerous IPv6 applications including Ping, Traceroute, router discovery daemons, and neighbor discovery daemons. The following structure is defined as a result of including <netinet/icmp6.h>. Note that this is a new header.
The ICMPv6 header is needed by numerous IPv6 applications including Ping, Traceroute, router discovery daemons, and neighbor discovery daemons. The following structure is defined as a result of including <netinet/icmp6.h>. Note that this is a new header.
struct icmp6_hdr {
uint8_t icmp6_type; /* type field */
uint8_t icmp6_code; /* code field */
uint16_t icmp6_cksum; /* checksum field */
union {
uint32_t icmp6_un_data32[1]; /* type-specific field */
uint16_t icmp6_un_data16[2]; /* type-specific field */
uint8_t icmp6_un_data8[4]; /* type-specific field */
} icmp6_dataun;
};
struct icmp6_hdr { uint8_t icmp6_type; /* type field */ uint8_t icmp6_code; /* code field */ uint16_t icmp6_cksum; /* checksum field */ union { uint32_t icmp6_un_data32[1]; /* type-specific field */ uint16_t icmp6_un_data16[2]; /* type-specific field */ uint8_t icmp6_un_data8[4]; /* type-specific field */ } icmp6_dataun; };
#define icmp6_data32 icmp6_dataun.icmp6_un_data32
#define icmp6_data16 icmp6_dataun.icmp6_un_data16
#define icmp6_data8 icmp6_dataun.icmp6_un_data8
#define icmp6_pptr icmp6_data32[0] /* parameter prob */
#define icmp6_mtu icmp6_data32[0] /* packet too big */
#define icmp6_id icmp6_data16[0] /* echo request/reply */
#define icmp6_seq icmp6_data16[1] /* echo request/reply */
#define icmp6_maxdelay icmp6_data16[0] /* mcast group
membership */
#define icmp6_data32 icmp6_dataun.icmp6_un_data32 #define icmp6_data16 icmp6_dataun.icmp6_un_data16 #define icmp6_data8 icmp6_dataun.icmp6_un_data8 #define icmp6_pptr icmp6_data32[0] /* parameter prob */ #define icmp6_mtu icmp6_data32[0] /* packet too big */ #define icmp6_id icmp6_data16[0] /* echo request/reply */ #define icmp6_seq icmp6_data16[1] /* echo request/reply */ #define icmp6_maxdelay icmp6_data16[0] /* mcast group membership */
2.2.1. ICMPv6 Type and Code Values
2.2.1. ICMPv6 Type and Code Values
In addition to a common structure for the ICMPv6 header, common definitions are required for the ICMPv6 type and code fields. The following constants are also defined as a result of including <netinet/icmp6.h>.
In addition to a common structure for the ICMPv6 header, common definitions are required for the ICMPv6 type and code fields. The following constants are also defined as a result of including <netinet/icmp6.h>.
#define ICMP6_DST_UNREACH 1
#define ICMP6_PACKET_TOO_BIG 2
#define ICMP6_TIME_EXCEEDED 3
#define ICMP6_PARAM_PROB 4
#define ICMP6_DST_UNREACH 1 #define ICMP6_PACKET_TOO_BIG 2 #define ICMP6_TIME_EXCEEDED 3 #define ICMP6_PARAM_PROB 4
#define ICMP6_INFOMSG_MASK 0x80 /* all informational
messages */
#define ICMP6_INFOMSG_MASK 0x80 /* all informational messages */
#define ICMP6_ECHO_REQUEST 128
#define ICMP6_ECHO_REPLY 129
#define ICMP6_ECHO_REQUEST 128 #define ICMP6_ECHO_REPLY 129
#define ICMP6_DST_UNREACH_NOROUTE 0 /* no route to
destination */
#define ICMP6_DST_UNREACH_NOROUTE 0 /* no route to destination */
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#define ICMP6_DST_UNREACH_ADMIN 1 /* communication with
destination */
/* admin. prohibited */
#define ICMP6_DST_UNREACH_BEYONDSCOPE 2 /* beyond scope of source
address */
#define ICMP6_DST_UNREACH_ADDR 3 /* address unreachable */
#define ICMP6_DST_UNREACH_NOPORT 4 /* bad port */
#define ICMP6_DST_UNREACH_ADMIN 1 /* communication with destination */ /* admin. prohibited */ #define ICMP6_DST_UNREACH_BEYONDSCOPE 2 /* beyond scope of source address */ #define ICMP6_DST_UNREACH_ADDR 3 /* address unreachable */ #define ICMP6_DST_UNREACH_NOPORT 4 /* bad port */
#define ICMP6_TIME_EXCEED_TRANSIT 0 /* Hop Limit == 0 in
transit */
#define ICMP6_TIME_EXCEED_REASSEMBLY 1 /* Reassembly time out */
#define ICMP6_TIME_EXCEED_TRANSIT 0 /* Hop Limit == 0 in transit */ #define ICMP6_TIME_EXCEED_REASSEMBLY 1 /* Reassembly time out */
#define ICMP6_PARAMPROB_HEADER 0 /* erroneous header
field */
#define ICMP6_PARAMPROB_NEXTHEADER 1 /* unrecognized
Next Header */
#define ICMP6_PARAMPROB_OPTION 2 /* unrecognized
IPv6 option */
#define ICMP6_PARAMPROB_HEADER 0 /* erroneous header field */ #define ICMP6_PARAMPROB_NEXTHEADER 1 /* unrecognized Next Header */ #define ICMP6_PARAMPROB_OPTION 2 /* unrecognized IPv6 option */
The five ICMP message types defined by IPv6 neighbor discovery (133- 137) are defined in the next section.
The five ICMP message types defined by IPv6 neighbor discovery (133- 137) are defined in the next section.
2.2.2. ICMPv6 Neighbor Discovery Definitions
2.2.2. ICMPv6 Neighbor Discovery Definitions
The following structures and definitions are defined as a result of including <netinet/icmp6.h>.
The following structures and definitions are defined as a result of including <netinet/icmp6.h>.
#define ND_ROUTER_SOLICIT 133
#define ND_ROUTER_ADVERT 134
#define ND_NEIGHBOR_SOLICIT 135
#define ND_NEIGHBOR_ADVERT 136
#define ND_REDIRECT 137
#define ND_ROUTER_SOLICIT 133 #define ND_ROUTER_ADVERT 134 #define ND_NEIGHBOR_SOLICIT 135 #define ND_NEIGHBOR_ADVERT 136 #define ND_REDIRECT 137
struct nd_router_solicit { /* router solicitation */
struct icmp6_hdr nd_rs_hdr;
/* could be followed by options */
};
struct nd_router_solicit { /* router solicitation */ struct icmp6_hdr nd_rs_hdr; /* could be followed by options */ };
#define nd_rs_type nd_rs_hdr.icmp6_type
#define nd_rs_code nd_rs_hdr.icmp6_code
#define nd_rs_cksum nd_rs_hdr.icmp6_cksum
#define nd_rs_reserved nd_rs_hdr.icmp6_data32[0]
#define nd_rs_type nd_rs_hdr.icmp6_type #define nd_rs_code nd_rs_hdr.icmp6_code #define nd_rs_cksum nd_rs_hdr.icmp6_cksum #define nd_rs_reserved nd_rs_hdr.icmp6_data32[0]
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struct nd_router_advert { /* router advertisement */
struct icmp6_hdr nd_ra_hdr;
uint32_t nd_ra_reachable; /* reachable time */
uint32_t nd_ra_retransmit; /* retransmit timer */
/* could be followed by options */
};
struct nd_router_advert { /* router advertisement */ struct icmp6_hdr nd_ra_hdr; uint32_t nd_ra_reachable; /* reachable time */ uint32_t nd_ra_retransmit; /* retransmit timer */ /* could be followed by options */ };
#define nd_ra_type nd_ra_hdr.icmp6_type
#define nd_ra_code nd_ra_hdr.icmp6_code
#define nd_ra_cksum nd_ra_hdr.icmp6_cksum
#define nd_ra_curhoplimit nd_ra_hdr.icmp6_data8[0]
#define nd_ra_flags_reserved nd_ra_hdr.icmp6_data8[1]
#define ND_RA_FLAG_MANAGED 0x80
#define ND_RA_FLAG_OTHER 0x40
#define nd_ra_router_lifetime nd_ra_hdr.icmp6_data16[1]
#define nd_ra_type nd_ra_hdr.icmp6_type #define nd_ra_code nd_ra_hdr.icmp6_code #define nd_ra_cksum nd_ra_hdr.icmp6_cksum #define nd_ra_curhoplimit nd_ra_hdr.icmp6_data8[0] #define nd_ra_flags_reserved nd_ra_hdr.icmp6_data8[1] #define ND_RA_FLAG_MANAGED 0x80 #define ND_RA_FLAG_OTHER 0x40 #define nd_ra_router_lifetime nd_ra_hdr.icmp6_data16[1]
struct nd_neighbor_solicit { /* neighbor solicitation */
struct icmp6_hdr nd_ns_hdr;
struct in6_addr nd_ns_target; /* target address */
/* could be followed by options */
};
struct nd_neighbor_solicit { /* neighbor solicitation */ struct icmp6_hdr nd_ns_hdr; struct in6_addr nd_ns_target; /* target address */ /* could be followed by options */ };
#define nd_ns_type nd_ns_hdr.icmp6_type
#define nd_ns_code nd_ns_hdr.icmp6_code
#define nd_ns_cksum nd_ns_hdr.icmp6_cksum
#define nd_ns_reserved nd_ns_hdr.icmp6_data32[0]
#define nd_ns_type nd_ns_hdr.icmp6_type #define nd_ns_code nd_ns_hdr.icmp6_code #define nd_ns_cksum nd_ns_hdr.icmp6_cksum #define nd_ns_reserved nd_ns_hdr.icmp6_data32[0]
struct nd_neighbor_advert { /* neighbor advertisement */
struct icmp6_hdr nd_na_hdr;
struct in6_addr nd_na_target; /* target address */
/* could be followed by options */
};
struct nd_neighbor_advert { /* neighbor advertisement */ struct icmp6_hdr nd_na_hdr; struct in6_addr nd_na_target; /* target address */ /* could be followed by options */ };
#define nd_na_type nd_na_hdr.icmp6_type
#define nd_na_code nd_na_hdr.icmp6_code
#define nd_na_cksum nd_na_hdr.icmp6_cksum
#define nd_na_flags_reserved nd_na_hdr.icmp6_data32[0]
#if BYTE_ORDER == BIG_ENDIAN
#define ND_NA_FLAG_ROUTER 0x80000000
#define ND_NA_FLAG_SOLICITED 0x40000000
#define ND_NA_FLAG_OVERRIDE 0x20000000
#else /* BYTE_ORDER == LITTLE_ENDIAN */
#define ND_NA_FLAG_ROUTER 0x00000080
#define ND_NA_FLAG_SOLICITED 0x00000040
#define ND_NA_FLAG_OVERRIDE 0x00000020
#endif
#define nd_na_type nd_na_hdr.icmp6_type #define nd_na_code nd_na_hdr.icmp6_code #define nd_na_cksum nd_na_hdr.icmp6_cksum #define nd_na_flags_reserved nd_na_hdr.icmp6_data32[0] #if BYTE_ORDER == BIG_ENDIAN #define ND_NA_FLAG_ROUTER 0x80000000 #define ND_NA_FLAG_SOLICITED 0x40000000 #define ND_NA_FLAG_OVERRIDE 0x20000000 #else /* BYTE_ORDER == LITTLE_ENDIAN */ #define ND_NA_FLAG_ROUTER 0x00000080 #define ND_NA_FLAG_SOLICITED 0x00000040 #define ND_NA_FLAG_OVERRIDE 0x00000020 #endif
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struct nd_redirect { /* redirect */
struct icmp6_hdr nd_rd_hdr;
struct in6_addr nd_rd_target; /* target address */
struct in6_addr nd_rd_dst; /* destination address */
/* could be followed by options */
};
struct nd_redirect { /* redirect */ struct icmp6_hdr nd_rd_hdr; struct in6_addr nd_rd_target; /* target address */ struct in6_addr nd_rd_dst; /* destination address */ /* could be followed by options */ };
#define nd_rd_type nd_rd_hdr.icmp6_type
#define nd_rd_code nd_rd_hdr.icmp6_code
#define nd_rd_cksum nd_rd_hdr.icmp6_cksum
#define nd_rd_reserved nd_rd_hdr.icmp6_data32[0]
#define nd_rd_type nd_rd_hdr.icmp6_type #define nd_rd_code nd_rd_hdr.icmp6_code #define nd_rd_cksum nd_rd_hdr.icmp6_cksum #define nd_rd_reserved nd_rd_hdr.icmp6_data32[0]
struct nd_opt_hdr { /* Neighbor discovery option header */
uint8_t nd_opt_type;
uint8_t nd_opt_len; /* in units of 8 octets */
/* followed by option specific data */
};
struct nd_opt_hdr { /* Neighbor discovery option header */ uint8_t nd_opt_type; uint8_t nd_opt_len; /* in units of 8 octets */ /* followed by option specific data */ };
#define ND_OPT_SOURCE_LINKADDR 1
#define ND_OPT_TARGET_LINKADDR 2
#define ND_OPT_PREFIX_INFORMATION 3
#define ND_OPT_REDIRECTED_HEADER 4
#define ND_OPT_MTU 5
#define ND_OPT_SOURCE_LINKADDR 1 #define ND_OPT_TARGET_LINKADDR 2 #define ND_OPT_PREFIX_INFORMATION 3 #define ND_OPT_REDIRECTED_HEADER 4 #define ND_OPT_MTU 5
struct nd_opt_prefix_info { /* prefix information */
uint8_t nd_opt_pi_type;
uint8_t nd_opt_pi_len;
uint8_t nd_opt_pi_prefix_len;
uint8_t nd_opt_pi_flags_reserved;
uint32_t nd_opt_pi_valid_time;
uint32_t nd_opt_pi_preferred_time;
uint32_t nd_opt_pi_reserved2;
struct in6_addr nd_opt_pi_prefix;
};
struct nd_opt_prefix_info { /* prefix information */ uint8_t nd_opt_pi_type; uint8_t nd_opt_pi_len; uint8_t nd_opt_pi_prefix_len; uint8_t nd_opt_pi_flags_reserved; uint32_t nd_opt_pi_valid_time; uint32_t nd_opt_pi_preferred_time; uint32_t nd_opt_pi_reserved2; struct in6_addr nd_opt_pi_prefix; };
#define ND_OPT_PI_FLAG_ONLINK 0x80
#define ND_OPT_PI_FLAG_AUTO 0x40
#define ND_OPT_PI_FLAG_ONLINK 0x80 #define ND_OPT_PI_FLAG_AUTO 0x40
struct nd_opt_rd_hdr { /* redirected header */
uint8_t nd_opt_rh_type;
uint8_t nd_opt_rh_len;
uint16_t nd_opt_rh_reserved1;
uint32_t nd_opt_rh_reserved2;
/* followed by IP header and data */
};
struct nd_opt_rd_hdr { /* redirected header */ uint8_t nd_opt_rh_type; uint8_t nd_opt_rh_len; uint16_t nd_opt_rh_reserved1; uint32_t nd_opt_rh_reserved2; /* followed by IP header and data */ };
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struct nd_opt_mtu { /* MTU option */
uint8_t nd_opt_mtu_type;
uint8_t nd_opt_mtu_len;
uint16_t nd_opt_mtu_reserved;
uint32_t nd_opt_mtu_mtu;
};
struct nd_opt_mtu { /* MTU option */ uint8_t nd_opt_mtu_type; uint8_t nd_opt_mtu_len; uint16_t nd_opt_mtu_reserved; uint32_t nd_opt_mtu_mtu; };
We note that the nd_na_flags_reserved flags have the same byte ordering problems as we showed with ip6f_offlg.
We note that the nd_na_flags_reserved flags have the same byte ordering problems as we showed with ip6f_offlg.
2.2.3. Multicast Listener Discovery Definitions
2.2.3. Multicast Listener Discovery Definitions
The following structures and definitions are defined as a result of including <netinet/icmp6.h>.
The following structures and definitions are defined as a result of including <netinet/icmp6.h>.
#define MLD_LISTENER_QUERY 130
#define MLD_LISTENER_REPORT 131
#define MLD_LISTENER_REDUCTION 132
#define MLD_LISTENER_QUERY 130 #define MLD_LISTENER_REPORT 131 #define MLD_LISTENER_REDUCTION 132
struct mld_hdr {
struct icmp6_hdr mld_icmp6_hdr;
struct in6_addr mld_addr; /* multicast address */
};
#define mld_type mld_icmp6_hdr.icmp6_type
#define mld_code mld_icmp6_hdr.icmp6_code
#define mld_cksum mld_icmp6_hdr.icmp6_cksum
#define mld_maxdelay mld_icmp6_hdr.icmp6_data16[0]
#define mld_reserved mld_icmp6_hdr.icmp6_data16[1]
struct mld_hdr { struct icmp6_hdr mld_icmp6_hdr; struct in6_addr mld_addr; /* multicast address */ }; #define mld_type mld_icmp6_hdr.icmp6_type #define mld_code mld_icmp6_hdr.icmp6_code #define mld_cksum mld_icmp6_hdr.icmp6_cksum #define mld_maxdelay mld_icmp6_hdr.icmp6_data16[0] #define mld_reserved mld_icmp6_hdr.icmp6_data16[1]
2.2.4. ICMPv6 Router Renumbering Definitions
2.2.4. ICMPv6 Router Renumbering Definitions
The following structures and definitions are defined as a result of including <netinet/icmp6.h>.
The following structures and definitions are defined as a result of including <netinet/icmp6.h>.
#define ICMP6_ROUTER_RENUMBERING 138 /* router renumbering */
#define ICMP6_ROUTER_RENUMBERING 138 /* router renumbering */
struct icmp6_router_renum { /* router renumbering header */
struct icmp6_hdr rr_hdr;
uint8_t rr_segnum;
uint8_t rr_flags;
uint16_t rr_maxdelay;
uint32_t rr_reserved;
};
#define rr_type rr_hdr.icmp6_type
#define rr_code rr_hdr.icmp6_code
#define rr_cksum rr_hdr.icmp6_cksum
#define rr_seqnum rr_hdr.icmp6_data32[0]
struct icmp6_router_renum { /* router renumbering header */ struct icmp6_hdr rr_hdr; uint8_t rr_segnum; uint8_t rr_flags; uint16_t rr_maxdelay; uint32_t rr_reserved; }; #define rr_type rr_hdr.icmp6_type #define rr_code rr_hdr.icmp6_code #define rr_cksum rr_hdr.icmp6_cksum #define rr_seqnum rr_hdr.icmp6_data32[0]
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/* Router renumbering flags */
#define ICMP6_RR_FLAGS_TEST 0x80
#define ICMP6_RR_FLAGS_REQRESULT 0x40
#define ICMP6_RR_FLAGS_FORCEAPPLY 0x20
#define ICMP6_RR_FLAGS_SPECSITE 0x10
#define ICMP6_RR_FLAGS_PREVDONE 0x08
/* Router renumbering flags */ #define ICMP6_RR_FLAGS_TEST 0x80 #define ICMP6_RR_FLAGS_REQRESULT 0x40 #define ICMP6_RR_FLAGS_FORCEAPPLY 0x20 #define ICMP6_RR_FLAGS_SPECSITE 0x10 #define ICMP6_RR_FLAGS_PREVDONE 0x08
struct rr_pco_match { /* match prefix part */
uint8_t rpm_code;
uint8_t rpm_len;
uint8_t rpm_ordinal;
uint8_t rpm_matchlen;
uint8_t rpm_minlen;
uint8_t rpm_maxlen;
uint16_t rpm_reserved;
struct in6_addr rpm_prefix;
};
struct rr_pco_match { /* match prefix part */ uint8_t rpm_code; uint8_t rpm_len; uint8_t rpm_ordinal; uint8_t rpm_matchlen; uint8_t rpm_minlen; uint8_t rpm_maxlen; uint16_t rpm_reserved; struct in6_addr rpm_prefix; };
/* PCO code values */
#define RPM_PCO_ADD 1
#define RPM_PCO_CHANGE 2
#define RPM_PCO_SETGLOBAL 3
/* PCO code values */ #define RPM_PCO_ADD 1 #define RPM_PCO_CHANGE 2 #define RPM_PCO_SETGLOBAL 3
struct rr_pco_use { /* use prefix part */
uint8_t rpu_uselen;
uint8_t rpu_keeplen;
uint8_t rpu_ramask;
uint8_t rpu_raflags;
uint32_t rpu_vltime;
uint32_t rpu_pltime;
uint32_t rpu_flags;
struct in6_addr rpu_prefix;
};
#define ICMP6_RR_PCOUSE_RAFLAGS_ONLINK 0x20
#define ICMP6_RR_PCOUSE_RAFLAGS_AUTO 0x10
struct rr_pco_use { /* use prefix part */ uint8_t rpu_uselen; uint8_t rpu_keeplen; uint8_t rpu_ramask; uint8_t rpu_raflags; uint32_t rpu_vltime; uint32_t rpu_pltime; uint32_t rpu_flags; struct in6_addr rpu_prefix; }; #define ICMP6_RR_PCOUSE_RAFLAGS_ONLINK 0x20 #define ICMP6_RR_PCOUSE_RAFLAGS_AUTO 0x10
#if BYTE_ORDER == BIG_ENDIAN
#define ICMP6_RR_PCOUSE_FLAGS_DECRVLTIME 0x80000000
#define ICMP6_RR_PCOUSE_FLAGS_DECRPLTIME 0x40000000
#elif BYTE_ORDER == LITTLE_ENDIAN
#define ICMP6_RR_PCOUSE_FLAGS_DECRVLTIME 0x80
#define ICMP6_RR_PCOUSE_FLAGS_DECRPLTIME 0x40
#endif
#if BYTE_ORDER == BIG_ENDIAN #define ICMP6_RR_PCOUSE_FLAGS_DECRVLTIME 0x80000000 #define ICMP6_RR_PCOUSE_FLAGS_DECRPLTIME 0x40000000 #elif BYTE_ORDER == LITTLE_ENDIAN #define ICMP6_RR_PCOUSE_FLAGS_DECRVLTIME 0x80 #define ICMP6_RR_PCOUSE_FLAGS_DECRPLTIME 0x40 #endif
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Stevens, et al. Informational [Page 15] RFC 3542 Advanced Sockets API for IPv6 May 2003
struct rr_result { /* router renumbering result message */
uint16_t rrr_flags;
uint8_t rrr_ordinal;
uint8_t rrr_matchedlen;
uint32_t rrr_ifid;
struct in6_addr rrr_prefix;
};
struct rr_result { /* router renumbering result message */ uint16_t rrr_flags; uint8_t rrr_ordinal; uint8_t rrr_matchedlen; uint32_t rrr_ifid; struct in6_addr rrr_prefix; };
#if BYTE_ORDER == BIG_ENDIAN
#define ICMP6_RR_RESULT_FLAGS_OOB 0x0002
#define ICMP6_RR_RESULT_FLAGS_FORBIDDEN 0x0001
#elif BYTE_ORDER == LITTLE_ENDIAN
#define ICMP6_RR_RESULT_FLAGS_OOB 0x0200
#define ICMP6_RR_RESULT_FLAGS_FORBIDDEN 0x0100
#endif
#if BYTE_ORDER == BIG_ENDIAN #define ICMP6_RR_RESULT_FLAGS_OOB 0x0002 #define ICMP6_RR_RESULT_FLAGS_FORBIDDEN 0x0001 #elif BYTE_ORDER == LITTLE_ENDIAN #define ICMP6_RR_RESULT_FLAGS_OOB 0x0200 #define ICMP6_RR_RESULT_FLAGS_FORBIDDEN 0x0100 #endif
2.3. Address Testing Macros
2.3. Address Testing Macros
The basic API ([RFC-3493]) defines some macros for testing an IPv6 address for certain properties. This API extends those definitions with additional address testing macros, defined as a result of including <netinet/in.h>.
The basic API ([RFC-3493]) defines some macros for testing an IPv6 address for certain properties. This API extends those definitions with additional address testing macros, defined as a result of including <netinet/in.h>.
int IN6_ARE_ADDR_EQUAL(const struct in6_addr *,
const struct in6_addr *);
int IN6_ARE_ADDR_EQUAL(const struct in6_addr *, const struct in6_addr *);
This macro returns non-zero if the addresses are equal; otherwise it returns zero.
This macro returns non-zero if the addresses are equal; otherwise it returns zero.
2.4. Protocols File
2.4. Protocols File
Many hosts provide the file /etc/protocols that contains the names of the various IP protocols and their protocol number (e.g., the value of the protocol field in the IPv4 header for that protocol, such as 1 for ICMP). Some programs then call the function getprotobyname() to obtain the protocol value that is then specified as the third argument to the socket() function. For example, the Ping program contains code of the form
Many hosts provide the file /etc/protocols that contains the names of the various IP protocols and their protocol number (e.g., the value of the protocol field in the IPv4 header for that protocol, such as 1 for ICMP). Some programs then call the function getprotobyname() to obtain the protocol value that is then specified as the third argument to the socket() function. For example, the Ping program contains code of the form
struct protoent *proto;
struct protoent *proto;
proto = getprotobyname("icmp");
proto = getprotobyname("icmp");
s = socket(AF_INET, SOCK_RAW, proto->p_proto);
s = socket(AF_INET, SOCK_RAW, proto->p_proto);
Common names are required for the new IPv6 protocols in this file, to provide portability of applications that call the getprotoXXX() functions.
Common names are required for the new IPv6 protocols in this file, to provide portability of applications that call the getprotoXXX() functions.
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We define the following protocol names with the values shown. These are taken under http://www.iana.org/numbers.html.
We define the following protocol names with the values shown. These are taken under http://www.iana.org/numbers.html.
hopopt 0 # hop-by-hop options for ipv6
ipv6 41 # ipv6
ipv6-route 43 # routing header for ipv6
ipv6-frag 44 # fragment header for ipv6
esp 50 # encapsulating security payload for ipv6
ah 51 # authentication header for ipv6
ipv6-icmp 58 # icmp for ipv6
ipv6-nonxt 59 # no next header for ipv6
ipv6-opts 60 # destination options for ipv6
hopopt 0 # hop-by-hop options for ipv6 ipv6 41 # ipv6 ipv6-route 43 # routing header for ipv6 ipv6-frag 44 # fragment header for ipv6 esp 50 # encapsulating security payload for ipv6 ah 51 # authentication header for ipv6 ipv6-icmp 58 # icmp for ipv6 ipv6-nonxt 59 # no next header for ipv6 ipv6-opts 60 # destination options for ipv6
3. IPv6 Raw Sockets
3. IPv6 Raw Sockets
Raw sockets bypass the transport layer (TCP or UDP). With IPv4, raw sockets are used to access ICMPv4, IGMPv4, and to read and write IPv4 datagrams containing a protocol field that the kernel does not process. An example of the latter is a routing daemon for OSPF, since it uses IPv4 protocol field 89. With IPv6 raw sockets will be used for ICMPv6 and to read and write IPv6 datagrams containing a Next Header field that the kernel does not process. Examples of the latter are a routing daemon for OSPF for IPv6 and RSVP (protocol field 46).
Raw sockets bypass the transport layer (TCP or UDP). With IPv4, raw sockets are used to access ICMPv4, IGMPv4, and to read and write IPv4 datagrams containing a protocol field that the kernel does not process. An example of the latter is a routing daemon for OSPF, since it uses IPv4 protocol field 89. With IPv6 raw sockets will be used for ICMPv6 and to read and write IPv6 datagrams containing a Next Header field that the kernel does not process. Examples of the latter are a routing daemon for OSPF for IPv6 and RSVP (protocol field 46).
All data sent via raw sockets must be in network byte order and all data received via raw sockets will be in network byte order. This differs from the IPv4 raw sockets, which did not specify a byte ordering and used the host's byte order for certain IP header fields.
All data sent via raw sockets must be in network byte order and all data received via raw sockets will be in network byte order. This differs from the IPv4 raw sockets, which did not specify a byte ordering and used the host's byte order for certain IP header fields.
Another difference from IPv4 raw sockets is that complete packets (that is, IPv6 packets with extension headers) cannot be sent or received using the IPv6 raw sockets API. Instead, ancillary data objects are used to transfer the extension headers and hoplimit information, as described in Section 6. Should an application need access to the complete IPv6 packet, some other technique, such as the datalink interfaces BPF or DLPI, must be used.
Another difference from IPv4 raw sockets is that complete packets (that is, IPv6 packets with extension headers) cannot be sent or received using the IPv6 raw sockets API. Instead, ancillary data objects are used to transfer the extension headers and hoplimit information, as described in Section 6. Should an application need access to the complete IPv6 packet, some other technique, such as the datalink interfaces BPF or DLPI, must be used.
All fields except the flow label in the IPv6 header that an application might want to change (i.e., everything other than the version number) can be modified using ancillary data and/or socket options by the application for output. All fields except the flow label in a received IPv6 header (other than the version number and Next Header fields) and all extension headers that an application might want to know are also made available to the application as ancillary data on input. Hence there is no need for a socket option
All fields except the flow label in the IPv6 header that an application might want to change (i.e., everything other than the version number) can be modified using ancillary data and/or socket options by the application for output. All fields except the flow label in a received IPv6 header (other than the version number and Next Header fields) and all extension headers that an application might want to know are also made available to the application as ancillary data on input. Hence there is no need for a socket option
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similar to the IPv4 IP_HDRINCL socket option and on receipt the application will only receive the payload i.e., the data after the IPv6 header and all the extension headers.
similar to the IPv4 IP_HDRINCL socket option and on receipt the application will only receive the payload i.e., the data after the IPv6 header and all the extension headers.
This API does not define access to the flow label field, because today there is no standard usage of the field.
This API does not define access to the flow label field, because today there is no standard usage of the field.
When writing to a raw socket the kernel will automatically fragment the packet if its size exceeds the path MTU, inserting the required fragment headers. On input the kernel reassembles received fragments, so the reader of a raw socket never sees any fragment headers.
When writing to a raw socket the kernel will automatically fragment the packet if its size exceeds the path MTU, inserting the required fragment headers. On input the kernel reassembles received fragments, so the reader of a raw socket never sees any fragment headers.
When we say "an ICMPv6 raw socket" we mean a socket created by calling the socket function with the three arguments AF_INET6, SOCK_RAW, and IPPROTO_ICMPV6.
When we say "an ICMPv6 raw socket" we mean a socket created by calling the socket function with the three arguments AF_INET6, SOCK_RAW, and IPPROTO_ICMPV6.
Most IPv4 implementations give special treatment to a raw socket created with a third argument to socket() of IPPROTO_RAW, whose value is normally 255, to have it mean that the application will send down complete packets including the IPv4 header. (Note: This feature was added to IPv4 in 1988 by Van Jacobson to support traceroute, allowing a complete IP header to be passed by the application, before the IP_HDRINCL socket option was added.) We note that IPPROTO_RAW has no special meaning to an IPv6 raw socket (and the IANA currently reserves the value of 255 when used as a next-header field).
Most IPv4 implementations give special treatment to a raw socket created with a third argument to socket() of IPPROTO_RAW, whose value is normally 255, to have it mean that the application will send down complete packets including the IPv4 header. (Note: This feature was added to IPv4 in 1988 by Van Jacobson to support traceroute, allowing a complete IP header to be passed by the application, before the IP_HDRINCL socket option was added.) We note that IPPROTO_RAW has no special meaning to an IPv6 raw socket (and the IANA currently reserves the value of 255 when used as a next-header field).
3.1. Checksums
3.1. Checksums
The kernel will calculate and insert the ICMPv6 checksum for ICMPv6 raw sockets, since this checksum is mandatory.
The kernel will calculate and insert the ICMPv6 checksum for ICMPv6 raw sockets, since this checksum is mandatory.
For other raw IPv6 sockets (that is, for raw IPv6 sockets created with a third argument other than IPPROTO_ICMPV6), the application must set the new IPV6_CHECKSUM socket option to have the kernel (1) compute and store a checksum for output, and (2) verify the received checksum on input, discarding the packet if the checksum is in error. This option prevents applications from having to perform source address selection on the packets they send. The checksum will incorporate the IPv6 pseudo-header, defined in Section 8.1 of [RFC- 2460]. This new socket option also specifies an integer offset into the user data of where the checksum is located.
For other raw IPv6 sockets (that is, for raw IPv6 sockets created with a third argument other than IPPROTO_ICMPV6), the application must set the new IPV6_CHECKSUM socket option to have the kernel (1) compute and store a checksum for output, and (2) verify the received checksum on input, discarding the packet if the checksum is in error. This option prevents applications from having to perform source address selection on the packets they send. The checksum will incorporate the IPv6 pseudo-header, defined in Section 8.1 of [RFC- 2460]. This new socket option also specifies an integer offset into the user data of where the checksum is located.
int offset = 2;
setsockopt(fd, IPPROTO_IPV6, IPV6_CHECKSUM, &offset,
sizeof(offset));
int offset = 2; setsockopt(fd, IPPROTO_IPV6, IPV6_CHECKSUM, &offset, sizeof(offset));
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Stevens, et al. Informational [Page 18] RFC 3542 Advanced Sockets API for IPv6 May 2003
By default, this socket option is disabled. Setting the offset to -1 also disables the option. By disabled we mean (1) the kernel will not calculate and store a checksum for outgoing packets, and (2) the kernel will not verify a checksum for received packets.
By default, this socket option is disabled. Setting the offset to -1 also disables the option. By disabled we mean (1) the kernel will not calculate and store a checksum for outgoing packets, and (2) the kernel will not verify a checksum for received packets.
This option assumes the use of the 16-bit one's complement of the one's complement sum as the checksum algorithm and that the checksum field is aligned on a 16-bit boundary. Thus, specifying a positive odd value as offset is invalid, and setsockopt() will fail for such offset values.
This option assumes the use of the 16-bit one's complement of the one's complement sum as the checksum algorithm and that the checksum field is aligned on a 16-bit boundary. Thus, specifying a positive odd value as offset is invalid, and setsockopt() will fail for such offset values.
An attempt to set IPV6_CHECKSUM for an ICMPv6 socket will fail. Also, an attempt to set or get IPV6_CHECKSUM for a non-raw IPv6 socket will fail.
An attempt to set IPV6_CHECKSUM for an ICMPv6 socket will fail. Also, an attempt to set or get IPV6_CHECKSUM for a non-raw IPv6 socket will fail.
(Note: Since the checksum is always calculated by the kernel for an ICMPv6 socket, applications are not able to generate ICMPv6 packets with incorrect checksums (presumably for testing purposes) using this API.)
(Note: Since the checksum is always calculated by the kernel for an ICMPv6 socket, applications are not able to generate ICMPv6 packets with incorrect checksums (presumably for testing purposes) using this API.)
3.2. ICMPv6 Type Filtering
3.2. ICMPv6 Type Filtering
ICMPv4 raw sockets receive most ICMPv4 messages received by the kernel. (We say "most" and not "all" because Berkeley-derived kernels never pass echo requests, timestamp requests, or address mask requests to a raw socket. Instead these three messages are processed entirely by the kernel.) But ICMPv6 is a superset of ICMPv4, also including the functionality of IGMPv4 and ARPv4. This means that an ICMPv6 raw socket can potentially receive many more messages than would be received with an ICMPv4 raw socket: ICMP messages similar to ICMPv4, along with neighbor solicitations, neighbor advertisements, and the three multicast listener discovery messages.
ICMPv4 raw sockets receive most ICMPv4 messages received by the kernel. (We say "most" and not "all" because Berkeley-derived kernels never pass echo requests, timestamp requests, or address mask requests to a raw socket. Instead these three messages are processed entirely by the kernel.) But ICMPv6 is a superset of ICMPv4, also including the functionality of IGMPv4 and ARPv4. This means that an ICMPv6 raw socket can potentially receive many more messages than would be received with an ICMPv4 raw socket: ICMP messages similar to ICMPv4, along with neighbor solicitations, neighbor advertisements, and the three multicast listener discovery messages.
Most applications using an ICMPv6 raw socket care about only a small subset of the ICMPv6 message types. To transfer extraneous ICMPv6 messages from the kernel to user can incur a significant overhead. Therefore this API includes a method of filtering ICMPv6 messages by the ICMPv6 type field.
Most applications using an ICMPv6 raw socket care about only a small subset of the ICMPv6 message types. To transfer extraneous ICMPv6 messages from the kernel to user can incur a significant overhead. Therefore this API includes a method of filtering ICMPv6 messages by the ICMPv6 type field.
Each ICMPv6 raw socket has an associated filter whose datatype is defined as
Each ICMPv6 raw socket has an associated filter whose datatype is defined as
struct icmp6_filter;
struct icmp6_filter;
This structure, along with the macros and constants defined later in this section, are defined as a result of including the <netinet/icmp6.h>.
This structure, along with the macros and constants defined later in this section, are defined as a result of including the <netinet/icmp6.h>.
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Stevens, et al. Informational [Page 19] RFC 3542 Advanced Sockets API for IPv6 May 2003
The current filter is fetched and stored using getsockopt() and setsockopt() with a level of IPPROTO_ICMPV6 and an option name of ICMP6_FILTER.
The current filter is fetched and stored using getsockopt() and setsockopt() with a level of IPPROTO_ICMPV6 and an option name of ICMP6_FILTER.
Six macros operate on an icmp6_filter structure:
Six macros operate on an icmp6_filter structure:
void ICMP6_FILTER_SETPASSALL (struct icmp6_filter *);
void ICMP6_FILTER_SETBLOCKALL(struct icmp6_filter *);
void ICMP6_FILTER_SETPASSALL (struct icmp6_filter *); void ICMP6_FILTER_SETBLOCKALL(struct icmp6_filter *);
void ICMP6_FILTER_SETPASS ( int, struct icmp6_filter *);
void ICMP6_FILTER_SETBLOCK( int, struct icmp6_filter *);
void ICMP6_FILTER_SETPASS ( int, struct icmp6_filter *); void ICMP6_FILTER_SETBLOCK( int, struct icmp6_filter *);
int ICMP6_FILTER_WILLPASS (int,
const struct icmp6_filter *);
int ICMP6_FILTER_WILLBLOCK(int,
const struct icmp6_filter *);
int ICMP6_FILTER_WILLPASS (int, const struct icmp6_filter *); int ICMP6_FILTER_WILLBLOCK(int, const struct icmp6_filter *);
The first argument to the last four macros (an integer) is an ICMPv6 message type, between 0 and 255. The pointer argument to all six macros is a pointer to a filter that is modified by the first four macros and is examined by the last two macros.
The first argument to the last four macros (an integer) is an ICMPv6 message type, between 0 and 255. The pointer argument to all six macros is a pointer to a filter that is modified by the first four macros and is examined by the last two macros.
The first two macros, SETPASSALL and SETBLOCKALL, let us specify that all ICMPv6 messages are passed to the application or that all ICMPv6 messages are blocked from being passed to the application.
The first two macros, SETPASSALL and SETBLOCKALL, let us specify that all ICMPv6 messages are passed to the application or that all ICMPv6 messages are blocked from being passed to the application.
The next two macros, SETPASS and SETBLOCK, let us specify that messages of a given ICMPv6 type should be passed to the application or not passed to the application (blocked).
The next two macros, SETPASS and SETBLOCK, let us specify that messages of a given ICMPv6 type should be passed to the application or not passed to the application (blocked).
The final two macros, WILLPASS and WILLBLOCK, return true or false depending whether the specified message type is passed to the application or blocked from being passed to the application by the filter pointed to by the second argument.
The final two macros, WILLPASS and WILLBLOCK, return true or false depending whether the specified message type is passed to the application or blocked from being passed to the application by the filter pointed to by the second argument.
When an ICMPv6 raw socket is created, it will by default pass all ICMPv6 message types to the application.
When an ICMPv6 raw socket is created, it will by default pass all ICMPv6 message types to the application.
As an example, a program that wants to receive only router advertisements could execute the following:
As an example, a program that wants to receive only router advertisements could execute the following:
struct icmp6_filter myfilt;
struct icmp6_filter myfilt;
fd = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
fd = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
ICMP6_FILTER_SETBLOCKALL(&myfilt);
ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &myfilt);
setsockopt(fd, IPPROTO_ICMPV6, ICMP6_FILTER, &myfilt,
ICMP6_FILTER_SETBLOCKALL(&myfilt); ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &myfilt); setsockopt(fd, IPPROTO_ICMPV6, ICMP6_FILTER, &myfilt,
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sizeof(myfilt));
sizeof(myfilt));
The filter structure is declared and then initialized to block all messages types. The filter structure is then changed to allow router advertisement messages to be passed to the application and the filter is installed using setsockopt().
The filter structure is declared and then initialized to block all messages types. The filter structure is then changed to allow router advertisement messages to be passed to the application and the filter is installed using setsockopt().
In order to clear an installed filter the application can issue a setsockopt for ICMP6_FILTER with a zero length. When no such filter has been installed, getsockopt() will return the kernel default filter.
In order to clear an installed filter the application can issue a setsockopt for ICMP6_FILTER with a zero length. When no such filter has been installed, getsockopt() will return the kernel default filter.
The icmp6_filter structure is similar to the fd_set datatype used with the select() function in the sockets API. The icmp6_filter structure is an opaque datatype and the application should not care how it is implemented. All the application does with this datatype is allocate a variable of this type, pass a pointer to a variable of this type to getsockopt() and setsockopt(), and operate on a variable of this type using the six macros that we just defined.
The icmp6_filter structure is similar to the fd_set datatype used with the select() function in the sockets API. The icmp6_filter structure is an opaque datatype and the application should not care how it is implemented. All the application does with this datatype is allocate a variable of this type, pass a pointer to a variable of this type to getsockopt() and setsockopt(), and operate on a variable of this type using the six macros that we just defined.
Nevertheless, it is worth showing a simple implementation of this datatype and the six macros.
Nevertheless, it is worth showing a simple implementation of this datatype and the six macros.
struct icmp6_filter {
uint32_t icmp6_filt[8]; /* 8*32 = 256 bits */
};
struct icmp6_filter { uint32_t icmp6_filt[8]; /* 8*32 = 256 bits */ };
#define ICMP6_FILTER_WILLPASS(type, filterp) \
((((filterp)->icmp6_filt[(type) >> 5]) & \
(1 << ((type) & 31))) != 0)
#define ICMP6_FILTER_WILLBLOCK(type, filterp) \
((((filterp)->icmp6_filt[(type) >> 5]) & \
(1 << ((type) & 31))) == 0)
#define ICMP6_FILTER_SETPASS(type, filterp) \
((((filterp)->icmp6_filt[(type) >> 5]) |= \
(1 << ((type) & 31))))
#define ICMP6_FILTER_SETBLOCK(type, filterp) \
((((filterp)->icmp6_filt[(type) >> 5]) &= \
~(1 << ((type) & 31))))
#define ICMP6_FILTER_SETPASSALL(filterp) \
memset((filterp), 0xFF, sizeof(struct icmp6_filter))
#define ICMP6_FILTER_SETBLOCKALL(filterp) \
memset((filterp), 0, sizeof(struct icmp6_filter))
#define ICMP6_FILTER_WILLPASS(type, filterp) \ ((((filterp)->icmp6_filt[(type) >> 5]) & \ (1 << ((type) & 31))) != 0) #define ICMP6_FILTER_WILLBLOCK(type, filterp) \ ((((filterp)->icmp6_filt[(type) >> 5]) & \ (1 << ((type) & 31))) == 0) #define ICMP6_FILTER_SETPASS(type, filterp) \ ((((filterp)->icmp6_filt[(type) >> 5]) |= \ (1 << ((type) & 31)))) #define ICMP6_FILTER_SETBLOCK(type, filterp) \ ((((filterp)->icmp6_filt[(type) >> 5]) &= \ ~(1 << ((type) & 31)))) #define ICMP6_FILTER_SETPASSALL(filterp) \ memset((filterp), 0xFF, sizeof(struct icmp6_filter)) #define ICMP6_FILTER_SETBLOCKALL(filterp) \ memset((filterp), 0, sizeof(struct icmp6_filter))
(Note: These sample definitions have two limitations that an implementation may want to change. The first four macros evaluate their first argument two times. The second two macros require the inclusion of the <string.h> header for the memset() function.)
(Note: These sample definitions have two limitations that an implementation may want to change. The first four macros evaluate their first argument two times. The second two macros require the inclusion of the <string.h> header for the memset() function.)
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3.3. ICMPv6 Verification of Received Packets
3.3. ICMPv6 Verification of Received Packets
The protocol stack will verify the ICMPv6 checksum and discard any packets with invalid checksums.
The protocol stack will verify the ICMPv6 checksum and discard any packets with invalid checksums.
An implementation might perform additional validity checks on the ICMPv6 message content and discard malformed packets. However, a portable application must not assume that such validity checks have been performed.
An implementation might perform additional validity checks on the ICMPv6 message content and discard malformed packets. However, a portable application must not assume that such validity checks have been performed.
The protocol stack should not automatically discard packets if the ICMP type is unknown to the stack. For extensibility reasons received ICMP packets with any type (informational or error) must be passed to the applications (subject to ICMP6_FILTER filtering on the type value and the checksum verification).
The protocol stack should not automatically discard packets if the ICMP type is unknown to the stack. For extensibility reasons received ICMP packets with any type (informational or error) must be passed to the applications (subject to ICMP6_FILTER filtering on the type value and the checksum verification).
4. Access to IPv6 and Extension Headers
4. Access to IPv6 and Extension Headers
Applications need to be able to control IPv6 header and extension header content when sending as well as being able to receive the content of these headers. This is done by defining socket option types which can be used both with setsockopt and with ancillary data. Ancillary data is discussed in Appendix A. The following optional information can be exchanged between the application and the kernel:
Applications need to be able to control IPv6 header and extension header content when sending as well as being able to receive the content of these headers. This is done by defining socket option types which can be used both with setsockopt and with ancillary data. Ancillary data is discussed in Appendix A. The following optional information can be exchanged between the application and the kernel:
1. The send/receive interface and source/destination address, 2. The hop limit, 3. Next hop address, 4. The traffic class, 5. Routing header, 6. Hop-by-Hop options header, and 7. Destination options header.
1. The send/receive interface and source/destination address, 2. The hop limit, 3. Next hop address, 4. The traffic class, 5. Routing header, 6. Hop-by-Hop options header, and 7. Destination options header.
First, to receive any of this optional information (other than the next hop address, which can only be set) on a UDP or raw socket, the application must call setsockopt() to turn on the corresponding flag:
First, to receive any of this optional information (other than the next hop address, which can only be set) on a UDP or raw socket, the application must call setsockopt() to turn on the corresponding flag:
int on = 1;
int on = 1;
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &on, sizeof(on));
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &on, sizeof(on));
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVRTHDR, &on, sizeof(on));
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVHOPOPTS, &on, sizeof(on));
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVDSTOPTS, &on, sizeof(on));
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVTCLASS, &on, sizeof(on));
setsockopt、(fd、IPV6_RECVPKTINFOの、そして、オンなIPPROTO_IPV6、sizeof(on))。 setsockopt、(fd、IPV6_RECVHOPLIMITの、そして、オンなIPPROTO_IPV6、sizeof(on))。 setsockopt、(fd、IPV6_RECVRTHDRの、そして、オンなIPPROTO_IPV6、sizeof(on))。 setsockopt、(fd、IPV6_RECVHOPOPTSの、そして、オンなIPPROTO_IPV6、sizeof(on))。 setsockopt、(fd、IPV6_RECVDSTOPTSの、そして、オンなIPPROTO_IPV6、sizeof(on))。 setsockopt、(fd、IPV6_RECVTCLASSの、そして、オンなIPPROTO_IPV6、sizeof(on))。
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When any of these options are enabled, the corresponding data is returned as control information by recvmsg(), as one or more ancillary data objects.
これらのオプションのどれかが可能にされるとき、対応するデータは制御情報としてrecvmsg()によって返されます、1個以上の補助データオブジェクトとして。
This document does not define how to receive the optional information on a TCP socket. See Section 4.1 for more details.
このドキュメントはTCPソケットに関する任意情報を受け取る方法を定義しません。 その他の詳細に関してセクション4.1を見てください。
Two different mechanisms exist for sending this optional information:
2つの異なったメカニズムがこの任意情報を送るために存在しています:
1. Using setsockopt to specify the option content for a socket.
These are known "sticky" options since they affect all transmitted
packets on the socket until either a new setsockopt is done or the
options are overridden using ancillary data.
1. ソケットのためのオプション内容を指定するのにsetsockoptを使用します。 新しいsetsockoptが完了しているか、またはオプションが補助データを使用することでくつがえされるまでソケットの上のすべての伝えられたパケットに影響するので、これらは知られている「ねばねばする」オプションです。
2. Using ancillary data to specify the option content for a single
datagram. This only applies to datagram and raw sockets; not to
TCP sockets.
2. 単一のデータグラムのためのオプション内容を指定するのに補助データを使用します。 これはデータグラムと生のソケットに適用されるだけです。 どんなTCPソケットにもそうしません。
The three socket option parameters and the three cmsghdr fields that describe the options/ancillary data objects are summarized as:
オプション/補助データオブジェクトについて説明する3つのソケットオプションパラメタと3つのcmsghdr分野が以下としてまとめられます。
opt level/ optname/ optval/
cmsg_level cmsg_type cmsg_data[]
------------ ------------ ------------------------
IPPROTO_IPV6 IPV6_PKTINFO in6_pktinfo structure
IPPROTO_IPV6 IPV6_HOPLIMIT int
IPPROTO_IPV6 IPV6_NEXTHOP socket address structure
IPPROTO_IPV6 IPV6_RTHDR ip6_rthdr structure
IPPROTO_IPV6 IPV6_HOPOPTS ip6_hbh structure
IPPROTO_IPV6 IPV6_DSTOPTS ip6_dest structure
IPPROTO_IPV6 IPV6_RTHDRDSTOPTS ip6_dest structure
IPPROTO_IPV6 IPV6_TCLASS int
レベル/optname/optval/cmsg_レベルcmsg_タイプcmsg_データ[]を選んでください。------------ ------------ ------------------------ IPPROTO_IPV6 IPV6_PKTINFO in6_pktinfo構造IPPROTO_IPV6 IPV6_HOPLIMIT int IPPROTO_IPV6 IPV6_NEXTHOPソケットアドレス構造IPPROTO_IPV6 IPV6_RTHDR ip6_rthdr構造IPPROTO_IPV6 IPV6_HOPOPTS ip6_hbh構造IPPROTO_IPV6 IPV6_DSTOPTS ip6_dest構造IPPROTO_IPV6 IPV6_RTHDRDSTOPTS ip6_dest構造IPPROTO_IPV6 IPV6_TCLASS int
(Note: IPV6_HOPLIMIT can be used as ancillary data items only)
(補助データ項目だけとして注意: IPV6_HOPLIMITを使用できます)
All these options are described in detail in Section 6, 7, 8 and 9. All the constants beginning with IPV6_ are defined as a result of including <netinet/in.h>.
これらのすべてのオプションがセクション6、7、8、および9で詳細に説明されます。 <netinet/in.h>を含んでいることの結果、IPV6_で始まるすべての定数が定義されます。
Note: We intentionally use the same constant for the cmsg_level member as is used as the second argument to getsockopt() and setsockopt() (what is called the "level"), and the same constant for the cmsg_type member as is used as the third argument to getsockopt() and setsockopt() (what is called the "option name").
以下に注意してください。 私たちは3番目の議論としてgetsockopt()とsetsockopt()(いわゆる「オプション名」)に慣れているcmsg_タイプメンバーに故意に同じ2番目の議論としてgetsockopt()とsetsockopt()(いわゆる「レベル」)に慣れているcmsg_レベルメンバーにとって一定で、同じ定数を使用します。
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Issuing getsockopt() for the above options will return the sticky option value i.e., the value set with setsockopt(). If no sticky option value has been set getsockopt() will return the following values:
上のオプションのためにgetsockopt()を発行すると、すなわち、setsockopt()がある選択値群はねばねばするオプション価値に返るでしょう。 どんなねばねばするオプション価値も設定されていないと、getsockopt()は以下の値を返すでしょう:
- For the IPV6_PKTINFO option, it will return an in6_pktinfo
structure with ipi6_addr being in6addr_any and ipi6_ifindex being
zero.
- IPV6_PKTINFOオプションのために、それは、in6addrであるipi6_addrでのin6_pktinfo構造に_いずれも返して、ipi6_ifindexに存在ゼロを返すでしょう。
- For the IPV6_TCLASS option, it will return the kernel default
value.
- IPV6_TCLASSオプションのために、それはカーネルデフォルト値を返すでしょう。
- For other options, it will indicate the lack of the option value
with optlen being zero.
- 別の選択肢のために、それはゼロであるoptlenでオプション価値の不足を示すでしょう。
The application does not explicitly need to access the data structures for the Routing header, Hop-by-Hop options header, and Destination options header, since the API to these features is through a set of inet6_rth_XXX() and inet6_opt_XXX() functions that we define in Section 7 and Section 10. Those functions simplify the interface to these features instead of requiring the application to know the intimate details of the extension header formats.
_アプリケーションはルート設定ヘッダー、ホップによるHopオプションヘッダー、およびDestinationオプションヘッダーのために明らかにデータ構造にアクセスする必要はなくて、inet6の1セットを通してこれらの特徴へのAPIがあるので、rth_XXX()とinet6_は_私たちがセクション7とセクション10で定義するXXX()機能を選びます。 それらの機能はアプリケーションを必要とすることの代わりに拡大ヘッダー形式の詳細な詳細を知るこれらの特徴にインタフェースを簡素化します。
When specifying extension headers, this API assumes the header ordering and the number of occurrences of each header as described in [RFC-2460]. More details about the ordering issue will be discussed in Section 12.
拡張ヘッダーを指定するとき、このAPIは、[RFC-2460]で説明されるようにヘッダーがそれぞれのヘッダーの注文と反復回数であると仮定します。 セクション12で注文問題に関するその他の詳細について議論するでしょう。
4.1. TCP Implications
4.1. TCP含意
It is not possible to use ancillary data to transmit the above options for TCP since there is not a one-to-one mapping between send operations and the TCP segments being transmitted. Instead an application can use setsockopt to specify them as sticky options. When the application uses setsockopt to specify the above options it is expected that TCP will start using the new information when sending segments. However, TCP may or may not use the new information when retransmitting segments that were originally sent when the old sticky options were in effect.
使用には、TCPのための1〜1つのマッピングがなくて以来の上のオプションを伝える補助データで操作とTCPセグメントを伝えるのは、可能ではありません。 代わりに、アプリケーションは、ねばねばするオプションとしてそれらを指定するのにsetsockoptを使用できます。 アプリケーションが上のオプションを指定するのにsetsockoptを使用すると、TCPが、セグメントを送るとき、新情報を使用するのを出発すると予想されます。 しかしながら、古いねばねばするオプションが元々有効であったときに送られたセグメントを再送するとき、TCPは新情報を使用するかもしれません。
It is unclear how a TCP application can use received information (such as extension headers) due to the lack of mapping between received TCP segments and receive operations. In particular, the received information could not be used for access control purposes like on UDP and raw sockets.
TCPアプリケーションがどうしたら容認されたTCPセグメントの間のマッピングの不足のため、受信された情報(拡張ヘッダーなどの)を使用して、操作を受けることができるかは、不明瞭です。 特に、UDPと生のソケットなどのようなアクセス管理目的に受信された情報を使用できませんでした。
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This specification therefore does not define how to get the received information on TCP sockets. The result of the IPV6_RECVxxx options on a TCP socket is undefined as well.
したがって、この仕様はTCPソケットの受信された情報を得る方法を定義しません。 また、TCPソケットにおけるIPV6_RECVxxxオプションの結果は未定義です。
4.2. UDP and Raw Socket Implications
4.2. UDPと生のソケット含意
The receive behavior for UDP and raw sockets is quite straightforward. After the application has enabled an IPV6_RECVxxx socket option it will receive ancillary data items for every recvmsg() call containing the requested information. However, if the information is not present in the packet the ancillary data item will not be included. For example, if the application enables IPV6_RECVRTHDR and a received datagram does not contain a Routing header there will not be an IPV6_RTHDR ancillary data item. Note that due to buffering in the socket implementation there might be some packets queued when an IPV6_RECVxxx option is enabled and they might not have the ancillary data information.
UDPのために振舞いを受けてください。そうすれば、生のソケットはかなり簡単です。 アプリケーションがIPV6_RECVxxxソケットオプションを可能にした後に、それは求められた情報を含むあらゆるrecvmsg()呼び出しのために補助データ項目を受けるでしょう。 しかしながら、情報がパケットに存在していないと、補助データ項目は含まれないでしょう。 例えば、アプリケーションがIPV6_RECVRTHDRを有効にして、容認されたデータグラムがルート設定ヘッダーを含んでいないと、IPV6_RTHDR補助データの品目がないでしょう。 あるかもしれないソケット実装でIPV6_RECVxxxオプションが可能にされて、それらに補助データ情報がないかもしれないなら列に並ばせられたいくつかのパケットをバッファリングするためそれに注意してください。
For sending the application has the choice between using sticky options and ancillary data. The application can also use both having the sticky options specify the "default" and using ancillary data to override the default options.
送付のために、アプリケーションには、ねばねばするオプションと補助データを使用するとき、選択があります。 また、アプリケーションは、ねばねばするオプションに「デフォルト」を指定させて、省略時のオプションをくつがえすのに補助データを使用することで両方を使用できます。
When an ancillary data item is specified in a call to sendmsg(), the item will override an existing sticky option of the same name (if previously specified). For example, if the application has set IPV6_RTHDR using a sticky option and later passes IPV6_RTHDR as ancillary data this will override the IPV6_RTHDR sticky option and the routing header of the outgoing packet will be from the ancillary data item, not from the sticky option. Note, however, that other sticky options than IPV6_RTHDR will not be affected by the IPV6_RTHDR ancillary data item; the overriding mechanism only works for the same type of sticky options and ancillary data items.
補助データ項目が呼び出しでsendmsg()に指定されるとき、項目は同じ名前の既存のねばねばするオプションをくつがえすでしょう(以前に指定されるなら)。 例えば、アプリケーションがねばねばするオプションを使用することでセットIPV6_RTHDRを持って、後でこれが優越する補助データとしてIPV6_RTHDRを渡すと、IPV6_RTHDRのねばねばするオプションと出発しているパケットのルーティングヘッダーはねばねばするオプションからあるのではなく、補助データ項目から来ているでしょう。 しかしながら、IPV6_RTHDR以外のねばねばするオプションがIPV6_RTHDR補助データの品目で影響を受けないことに注意してください。 最優先のメカニズムは同じタイプのねばねばするオプションと補助データ項目のために動作するだけです。
(Note: the overriding rule is different from the one in RFC 2292. In RFC 2292, an ancillary data item overrode all sticky options previously defined. This was reasonable, because sticky options could only be specified as a set by a single socket option. However, in this API, each option is separated so that it can be specified as a single sticky option. Additionally, there are much more ancillary data items and sticky options than in RFC 2292, including ancillary- only one. Thus, it should be natural for application programmers to separate the overriding rule as well.)
( 最優先の規則がRFC2292でRFC2292のものと異なっている、補助データ項目は以前に定義されたすべてのねばねばするオプションをくつがえしました。注意: これは妥当でした; ねばねばするオプションがそうすることができるだけであったので、セットとしてただ一つのソケットオプションで指定されてください。しかしながら、このAPIでは、それぞれのオプションは、ただ一つのねばねばするオプションとしてそれを指定できるように切り離されます。さらに、ずっと多くの補助データ項目とRFC2292年よりねばねばするオプションがあります、その結果、1だけに付属を含んで、アプリケーション・プログラマーがまた、最優先の規則を切り離すのは、当然であるべきです; )
An application can also temporarily disable a particular sticky option by specifying a corresponding ancillary data item that could disable the sticky option when being used as an argument for a socket option. For example, if the application has set IPV6_HOPOPTS as a
また、アプリケーションは、ソケットオプションに議論として使用されるとねばねばするオプションを無効にするかもしれない対応する補助データ項目を指定することによって、一時特定のねばねばするオプションを無効にすることができます。 例えば、アプリケーションはaとしてIPV6_HOPOPTSを設定しました。
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sticky option and later passes IPV6_HOPOPTS with a zero length as an ancillary data item, the packet will not have a Hop-by-Hop options header.
補助データ項目としてのゼロ・レングスがあるねばねばするオプションと、より遅いパスIPV6_HOPOPTS、パケットには、ホップによるHopオプションヘッダーがないでしょう。
5. Extensions to Socket Ancillary Data
5. ソケット補助データへの拡大
This specification uses ancillary data as defined in Posix with some compatible extensions, which are described in the following subsections. Section 20 will provide a detailed overview of ancillary data and related structures and macros, including the extensions.
この仕様は以下の小区分で説明されるいくつかのコンパチブル拡大を伴うPosixで定義されるように補助データを使用します。 セクション20は拡大を含む補助データ、関連組織、およびマクロの詳細な概要を提供するでしょう。
5.1. CMSG_NXTHDR
5.1. CMSG_NXTHDR
struct cmsghdr *CMSG_NXTHDR(const struct msghdr *mhdr,
const struct cmsghdr *cmsg);
struct cmsghdr*CMSG_NXTHDR(const struct msghdr*mhdr、const struct cmsghdr*cmsg)。
CMSG_NXTHDR() returns a pointer to the cmsghdr structure describing the next ancillary data object. Mhdr is a pointer to a msghdr structure and cmsg is a pointer to a cmsghdr structure. If there is not another ancillary data object, the return value is NULL.
CMSG_NXTHDR()は次の補助データオブジェクトについて説明するcmsghdr構造に指針を返します。 Mhdrはmsghdr構造への指針です、そして、cmsgはcmsghdr構造への指針です。 別の補助データオブジェクトがなければ、リターン値はNULLです。
The following behavior of this macro is new to this API: if the value of the cmsg pointer is NULL, a pointer to the cmsghdr structure describing the first ancillary data object is returned. That is, CMSG_NXTHDR(mhdr, NULL) is equivalent to CMSG_FIRSTHDR(mhdr). If there are no ancillary data objects, the return value is NULL.
このマクロの以下の振舞いはこのAPIに新しいです: cmsg指針の値がNULLであるなら、最初の補助データオブジェクトについて説明するcmsghdr構造への指針を返します。 すなわち、CMSG_NXTHDR(mhdr、NULL)はCMSG_FIRSTHDR(mhdr)に同等です。 補助データオブジェクトが全くなければ、リターン値はNULLです。
5.2. CMSG_SPACE
5.2. CMSG_スペース
socklen_t CMSG_SPACE(socklen_t length);
socklen_t CMSG_SPACE(socklen_tの長さ)。
This macro is new with this API. Given the length of an ancillary data object, CMSG_SPACE() returns an upper bound on the space required by the object and its cmsghdr structure, including any padding needed to satisfy alignment requirements. This macro can be used, for example, when allocating space dynamically for the ancillary data. This macro should not be used to initialize the cmsg_len member of a cmsghdr structure; instead use the CMSG_LEN() macro.
このマクロはこのAPIで新しいです。 補助データオブジェクトの長さを考えて、CMSG_SPACE()は目的とそのcmsghdr構造によって必要とされたスペースで上限を返します、整列要求を満たすのに必要であるどんな詰め物も含んでいて。 補助データのためにダイナミックにスペースを割り当てるとき、例えば、このマクロを使用できます。 cmsghdr構造のcmsg_len部材を初期化するのにこのマクロを使用するべきではありません。 代わりにCMSG_LEN()マクロを使用してください。
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5.3. CMSG_LEN
5.3. CMSG_レン
socklen_t CMSG_LEN(socklen_t length);
socklen_t CMSG_LEN(socklen_tの長さ)。
This macro is new with this API. Given the length of an ancillary data object, CMSG_LEN() returns the value to store in the cmsg_len member of the cmsghdr structure, taking into account any padding needed to satisfy alignment requirements.
このマクロはこのAPIで新しいです。 補助データオブジェクトの長さを考えて、CMSG_LEN()はcmsghdr構造のcmsg_len部材に保存する値を返します、整列要求を満たすのに必要であるどんな詰め物も考慮に入れて。
Note the difference between CMSG_SPACE() and CMSG_LEN(), shown also in the figure in Section 20.2: the former accounts for any required padding at the end of the ancillary data object and the latter is the actual length to store in the cmsg_len member of the ancillary data object.
また、セクション20.2の図に示されて、CMSG_SPACE()とCMSG_LEN()の違いに注意してください: 前者は補助データオブジェクトの端のどんな必要な詰め物も説明します、そして、後者は補助データオブジェクトのcmsg_lenメンバーに保存する実際の長さです。
6. Packet Information
6. パケット情報
There are five pieces of information that an application can specify for an outgoing packet using ancillary data:
アプリケーションが補助データを使用することで出発しているパケットに指定できるという情報の5つの断片があります:
1. the source IPv6 address,
2. the outgoing interface index,
3. the outgoing hop limit,
4. the next hop address, and
5. the outgoing traffic class value.
1. ソースIPv6アドレス、2 外向的なインタフェースインデックス、3 外向的なホップ限界、4 次のホップアドレス、および5 外向的なトラフィック階級値。
Four similar pieces of information can be returned for a received packet as ancillary data:
容認されたパケットのために補助データとして4つの同様の情報を返すことができます:
1. the destination IPv6 address,
2. the arriving interface index,
3. the arriving hop limit, and
4. the arriving traffic class value.
1. 送付先IPv6アドレス、2 到着しているインタフェースインデックス、3 到着しているホップ限界、および4 到着しているトラフィック階級値。
The first two pieces of information are contained in an in6_pktinfo structure that is set with setsockopt() or sent as ancillary data with sendmsg() and received as ancillary data with recvmsg(). This structure is defined as a result of including <netinet/in.h>.
情報の最初の2つの断片をsetsockopt()で設定されるin6_pktinfo構造に含んでいるか、補助データとしてsendmsg()で送って、または補助データとしてrecvmsg()で受け取ります。 <netinet/in.h>を含んでいることの結果、この構造は定義されます。
struct in6_pktinfo {
struct in6_addr ipi6_addr; /* src/dst IPv6 address */
unsigned int ipi6_ifindex; /* send/recv interface index */
};
struct in6_addr ipi6_addr; /*src/dst IPv6アドレス*/未署名のint ipi6_ifindex; /*が/recvインタフェースインデックス*/を送るstruct in6_pktinfo。
In the socket option and cmsghdr level will be IPPROTO_IPV6, the type will be IPV6_PKTINFO, and the first byte of the option value and cmsg_data[] will be the first byte of the in6_pktinfo structure. An application can clear any sticky IPV6_PKTINFO option by doing a
ソケットでは、オプションとcmsghdrレベルはIPPROTO_IPV6でしょう、そして、タイプはIPV6_PKTINFOでしょう、そして、オプション価値とcmsg_データ[]の最初のバイトはin6_pktinfo構造の最初のバイトになるでしょう。 アプリケーションは、aをすることによって、どんなねばねばするIPV6_PKTINFOオプションもクリアすることができます。
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"regular" setsockopt with ipi6_addr being in6addr_any and ipi6_ifindex being zero.
いずれとipi6_ifindex存在が合っているゼロin6addr_であるipi6_addrでの「通常」のsetsockopt。
This information is returned as ancillary data by recvmsg() only if the application has enabled the IPV6_RECVPKTINFO socket option:
アプリケーションがIPV6_RECVPKTINFOソケットオプションを可能にした場合にだけ、この情報は補助データとしてrecvmsg()によって返されます:
int on = 1;
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &on, sizeof(on));
=1のint。 setsockopt、(fd、IPV6_RECVPKTINFOの、そして、オンなIPPROTO_IPV6、sizeof(on))。
(Note: The hop limit is not contained in the in6_pktinfo structure for the following reason. Some UDP servers want to respond to client requests by sending their reply out the same interface on which the request was received and with the source IPv6 address of the reply equal to the destination IPv6 address of the request. To do this the application can enable just the IPV6_RECVPKTINFO socket option and then use the received control information from recvmsg() as the outgoing control information for sendmsg(). The application need not examine or modify the in6_pktinfo structure at all. But if the hop limit were contained in this structure, the application would have to parse the received control information and change the hop limit member, since the received hop limit is not the desired value for an outgoing packet.)
(以下に注意してください。 ホップ限界は以下の理由によるin6_pktinfo構造に含まれていません。 いくつかのUDPサーバが要求がどれであったかに関して受け取って、同じように彼らの回答を出すのによる要求が連結するクライアントと要求の送付先IPv6アドレスと等しい回答のソースIPv6アドレスで応じたがっています。 アプリケーションは、これをするのに、まさしくIPV6_RECVPKTINFOソケットオプションを可能にして、次に、recvmsgからの受信された制御情報を使用できます。()、sendmsgのための送信する制御情報(). アプリケーションは、全くin6_pktinfo構造を調べる必要はありませんし、また変更する必要はありません。 しかし、ホップ限界がこの構造に含まれているなら、アプリケーションは、受信された制御情報を分析して、ホップ限界メンバーを変えなければならないでしょうに、容認されたホップ限界が出発しているパケットのための目標値でないので。)
6.1. Specifying/Receiving the Interface
6.1. インタフェースを指定するか、または受けます。
Interfaces on an IPv6 node are identified by a small positive integer, as described in Section 4 of [RFC-3493]. That document also describes a function to map an interface name to its interface index, a function to map an interface index to its interface name, and a function to return all the interface names and indexes. Notice from this document that no interface is ever assigned an index of 0.
IPv6ノードの上のインタフェースは[RFC-3493]のセクション4で説明されるようにわずかな正の整数によって特定されます。 また、そのドキュメントは、インタフェースインデックス(インタフェースインデックスをインタフェース名に写像して、すべてのインタフェースが命名するリターンとインデックスに機能を写像する機能)にインタフェース名を写像するために機能について説明します。 このドキュメントから、0のインデックスが今までにどんなインタフェースにも割り当てられないのに注意してください。
When specifying the outgoing interface, if the ipi6_ifindex value is 0, the kernel will choose the outgoing interface.
ipi6_ifindex値が0であるなら外向的なインタフェースを指定するとき、カーネルは外向的なインタフェースを選ぶでしょう。
The ordering among various options that can specify the outgoing interface, including IPV6_PKTINFO, is defined in Section 6.7.
IPV6_PKTINFOを含む外向的なインタフェースを指定できる様々なオプションの中の注文はセクション6.7で定義されます。
When the IPV6_RECVPKTINFO socket option is enabled, the received interface index is always returned as the ipi6_ifindex member of the in6_pktinfo structure.
IPV6_RECVPKTINFOソケットオプションが可能にされるとき、受け取られていているインタフェースインデックスはin6_pktinfo構造のipi6_ifindex部材としていつも返されます。
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6.2. Specifying/Receiving Source/Destination Address
6.2. 指定/受信ソース/送付先アドレス
The source IPv6 address can be specified by calling bind() before each output operation, but supplying the source address together with the data requires less overhead (i.e., fewer system calls) and requires less state to be stored and protected in a multithreaded application.
そして、すなわち、それぞれが操作を出力する前にひもを()と呼ぶことによってソースIPv6アドレスを指定できますが、データと共にソースアドレスを供給するのが、より少ないオーバーヘッドを必要とする、(より少ないシステムコール)、 より少ない状態がマルチスレッド化されたアプリケーションに保存されて、保護されるのが必要です。
When specifying the source IPv6 address as ancillary data, if the ipi6_addr member of the in6_pktinfo structure is the unspecified address (IN6ADDR_ANY_INIT or in6addr_any), then (a) if an address is currently bound to the socket, it is used as the source address, or (b) if no address is currently bound to the socket, the kernel will choose the source address. If the ipi6_addr member is not the unspecified address, but the socket has already bound a source address, then the ipi6_addr value overrides the already-bound source address for this output operation only.
in6_pktinfo構造のipi6_addr部材が不特定のアドレスであるなら補助データとしてソースIPv6アドレスを指定する、(IN6ADDR、_INITかin6addrの_いずれのも_、いずれも)、そして、(a) アドレスが現在ソケットに縛られるなら、(b) ソースアドレスかそれともどんなアドレスも現在ソケット(意志がソースアドレスを選ぶカーネル)に制限されていないかどうかとしてそれは使用されます。 ipi6_addrメンバーが不特定のアドレスではありませんが、ソケットが既にソースアドレスを縛ったなら、ipi6_addr値はこの出力操作だけのための既に行きのソースアドレスをくつがえします。
The kernel must verify that the requested source address is indeed a unicast address assigned to the node. When the address is a scoped one, there may be ambiguity about its scope zone. This is particularly the case for link-local addresses. In such a case, the kernel must first determine the appropriate scope zone based on the zone of the destination address or the outgoing interface (if known), then qualify the address. This also means that it is not feasible to specify the source address for a non-binding socket by the IPV6_PKTINFO sticky option, unless the outgoing interface is also specified. The application should simply use bind() for such purposes.
カーネルは、本当に、要求されたソースアドレスがノードに割り当てられたユニキャストアドレスであることを確かめなければなりません。 アドレスが見られたものであるときに、範囲ゾーンに関してあいまいさがあるかもしれません。 これは特にリンクローカルのアドレスのためのそうです。 このような場合には、カーネルは、最初に、送付先アドレスのゾーンに基づく適切な範囲ゾーンか外向的なインタフェース(知られているなら)を決定して、次に、アドレスに資格を与えなければなりません。 また、これは、IPV6_PKTINFOのねばねばするオプションで拘束力がないソケットのためのソースアドレスを指定するのが可能でないことを意味します、また、外向的なインタフェースが指定されない場合。 アプリケーションはそのような目的に単にひも()を使用するべきです。
IPV6_PKTINFO can also be used as a sticky option for specifying the socket's default source address. However, the ipi6_addr member must be the unspecified address for TCP sockets, because it is not possible to dynamically change the source address of a TCP connection. When the IPV6_PKTINFO option is specified for a TCP socket with a non-unspecified address, the call will fail. This restriction should be applied even before the socket binds a specific address.
また、ソケットのデフォルトソースアドレスを指定するのにねばねばするオプションとしてIPV6_PKTINFOを使用できます。 しかしながら、ipi6_addrメンバーはTCPソケットのための不特定のアドレスでなければなりません、ダイナミックにTCP接続のソースアドレスを変えるのが可能でないので。 IPV6_PKTINFOオプションが非不特定のアドレスでTCPソケットに指定されるとき、呼び出しは失敗するでしょう。 ソケットが特定のアドレスを縛る前にさえこの制限は適用されるべきです。
When the in6_pktinfo structure is returned as ancillary data by recvmsg(), the ipi6_addr member contains the destination IPv6 address from the received packet.
in6_pktinfo構造が補助データとしてrecvmsg()によって返されるとき、ipi6_addrメンバーは容認されたパケットからの送付先IPv6アドレスを含みます。
6.3. Specifying/Receiving the Hop Limit
6.3. ホップ限界を指定するか、または受けます。
The outgoing hop limit is normally specified with either the IPV6_UNICAST_HOPS socket option or the IPV6_MULTICAST_HOPS socket option, both of which are described in [RFC-3493]. Specifying the
通常、外向的なホップ限界はIPV6_UNICAST_ホップスのソケットオプションかIPV6_MULTICAST_ホップスのソケットオプションのどちらかで指定されます。その両方が[RFC-3493]で説明されます。 指定
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hop limit as ancillary data lets the application override either the kernel's default or a previously specified value, for either a unicast destination or a multicast destination, for a single output operation. Returning the received hop limit is useful for IPv6 applications that need to verify that the received hop limit is 255 (e.g., that the packet has not been forwarded).
アプリケーションが補助データでカーネルのデフォルトか以前に指定された値のどちらかをくつがえすとき、ユニキャストの目的地かマルチキャストの目的地のどちらか、ただ一つの出力操作のために限界を飛び越してください。 容認されたホップ限界を返すのが容認されたホップ限界が255であることを確かめる必要があるIPv6アプリケーションの役に立つ、(例えば、パケットは進められていません)
The received hop limit is returned as ancillary data by recvmsg() only if the application has enabled the IPV6_RECVHOPLIMIT socket option:
アプリケーションがIPV6_RECVHOPLIMITソケットオプションを可能にした場合にだけ、容認されたホップ限界は補助データとしてrecvmsg()によって返されます:
int on = 1;
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &on, sizeof(on));
=1のint。 setsockopt、(fd、IPV6_RECVHOPLIMITの、そして、オンなIPPROTO_IPV6、sizeof(on))。
In the cmsghdr structure containing this ancillary data, the cmsg_level member will be IPPROTO_IPV6, the cmsg_type member will be IPV6_HOPLIMIT, and the first byte of cmsg_data[] will be the first byte of the integer hop limit.
この補助データを含むcmsghdr構造では、cmsg_レベルメンバーはIPPROTO_IPV6でしょう、そして、cmsg_タイプメンバーはIPV6_HOPLIMITでしょう、そして、cmsg_データ[]の最初のバイトは整数ホップ限界の最初のバイトになるでしょう。
Nothing special need be done to specify the outgoing hop limit: just specify the control information as ancillary data for sendmsg(). As specified in [RFC-3493], the interpretation of the integer hop limit value is
外向的なホップ限界を指定するために何も特別なことをする必要はありません: sendmsg()のための補助データとしてただ制御情報を指定してください。 [RFC-3493]で指定されるように、整数ホップ制限値の解釈は指定されます。
x < -1: return an error of EINVAL
x == -1: use kernel default
0 <= x <= 255: use x
x >= 256: return an error of EINVAL
x<-1: EINVAL x=-1の誤りを返してください: カーネルデフォルト0<=x<=255を使用してください: x x>=256を使用してください: EINVALの誤りを返してください。
This API defines IPV6_HOPLIMIT as an ancillary-only option, that is, the option name cannot be used as a socket option. This is because [RFC-3493] has more fine-grained socket options; IPV6_UNICAST_HOPS and IPV6_MULTICAST_HOPS.
このAPIはIPV6_HOPLIMITを付属だけオプションと定義します、すなわち、ソケットオプションとしてオプション名を使用できません。 これは[RFC-3493]にはきめ細かにより粒状のソケットオプションがあるからです。 IPV6_ユニキャスト_は跳びます、そして、IPV6_マルチキャスト_は跳びます。
6.4. Specifying the Next Hop Address
6.4. 次のホップアドレスを指定します。
The IPV6_NEXTHOP ancillary data object specifies the next hop for the datagram as a socket address structure. In the cmsghdr structure containing this ancillary data, the cmsg_level member will be IPPROTO_IPV6, the cmsg_type member will be IPV6_NEXTHOP, and the first byte of cmsg_data[] will be the first byte of the socket address structure.
IPV6_NEXTHOP補助データオブジェクトはソケットアドレス構造として次のホップをデータグラムに指定します。 この補助データを含むcmsghdr構造では、cmsg_レベルメンバーはIPPROTO_IPV6でしょう、そして、cmsg_タイプメンバーはIPV6_NEXTHOPでしょう、そして、cmsg_データ[]の最初のバイトはソケットアドレス構造の最初のバイトになるでしょう。
This is a privileged option. (Note: It is implementation defined and beyond the scope of this document to define what "privileged" means. Unix systems use this term to mean the process must have an effective user ID of 0.)
これは特権があるオプションです。 (以下に注意してください。 それは「特権があること」が意味することを定義するために定義されて、このドキュメントの範囲を超えてそうする実装です。 unixシステムは、プロセスには0の実効ユーザーIDがなければならないことを意味するのに今期を使用します。)
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This API only defines the case where the socket address contains an IPv6 address (i.e., the sa_family member is AF_INET6). And, in this case, the node identified by that address must be a neighbor of the sending host. If that address equals the destination IPv6 address of the datagram, then this is equivalent to the existing SO_DONTROUTE socket option.
このAPIはソケットアドレスがIPv6アドレスを含む(すなわち、sa_親族はAF_INET6です)ケースを定義するだけです。 そして、この場合、そのアドレスによって特定されたノードは送付ホストの隣接物であるに違いありません。 そのアドレスがデータグラムの送付先IPv6アドレスと等しいなら、これは既存のSO_DONTROUTEソケットオプションに同等です。
This option does not have any meaning for multicast destinations. In such a case, the specified next hop will be ignored.
このオプションには、マルチキャストの目的地への少しの意味もありません。 そのような場合、次のホップがそうする指定では、無視されてください。
When the outgoing interface is specified by IPV6_PKTINFO as well, the next hop specified by this option must be reachable via the specified interface.
外向的なインタフェースがまた、IPV6_PKTINFOによって指定されるとき、このオプションで指定された次のホップは指定されたインタフェースを通して届いているに違いありません。
In order to clear a sticky IPV6_NEXTHOP option the application must issue a setsockopt for IPV6_NEXTHOP with a zero length.
ねばねばするIPV6_NEXTHOPオプションをクリアして、アプリケーションはIPV6_NEXTHOPのためにゼロ・レングスでsetsockoptを発行しなければなりません。
6.5. Specifying/Receiving the Traffic Class value
6.5. Traffic Class値を指定するか、または受けます。
The outgoing traffic class is normally set to 0. Specifying the traffic class as ancillary data lets the application override either the kernel's default or a previously specified value, for either a unicast destination or a multicast destination, for a single output operation. Returning the received traffic class is useful for programs such as a diffserv debugging tool and for user level ECN (explicit congestion notification) implementation.
通常、出発しているトラフィックのクラスは0に設定されます。 アプリケーションは補助データとしてトラフィックのクラスを指定するのにカーネルのデフォルトか以前に指定された値のどちらかをくつがえします、ユニキャストの目的地かマルチキャストの目的地のどちらかに、ただ一つの出力操作のために。 容認されたトラフィックのクラスを返すのはdiffservデバッグ用ツールなどのプログラムとユーザレベル電子証券取引ネットワーク(明白な混雑通知)実装の役に立ちます。
The received traffic class is returned as ancillary data by recvmsg() only if the application has enabled the IPV6_RECVTCLASS socket option:
アプリケーションがIPV6_RECVTCLASSソケットオプションを可能にした場合にだけ、容認されたトラフィックのクラスは補助データとしてrecvmsg()によって返されます:
int on = 1;
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVTCLASS, &on, sizeof(on));
=1のint。 setsockopt、(fd、IPV6_RECVTCLASSの、そして、オンなIPPROTO_IPV6、sizeof(on))。
In the cmsghdr structure containing this ancillary data, the cmsg_level member will be IPPROTO_IPV6, the cmsg_type member will be IPV6_TCLASS, and the first byte of cmsg_data[] will be the first byte of the integer traffic class.
この補助データを含むcmsghdr構造では、cmsg_レベルメンバーはIPPROTO_IPV6でしょう、そして、cmsg_タイプメンバーはIPV6_TCLASSでしょう、そして、cmsg_データ[]の最初のバイトは整数トラフィックのクラスの最初のバイトになるでしょう。
To specify the outgoing traffic class value, just specify the control information as ancillary data for sendmsg() or using setsockopt(). Just like the hop limit value, the interpretation of the integer traffic class value is
外向的なトラフィック階級値を指定するには、sendmsg()かsetsockopt()を使用するための補助データとしてただ制御情報を指定してください。 まさしくホップ制限値のように、整数トラフィック階級値の解釈はそうです。
x < -1: return an error of EINVAL
x == -1: use kernel default
0 <= x <= 255: use x
x >= 256: return an error of EINVAL
x<-1: EINVAL x=-1の誤りを返してください: カーネルデフォルト0<=x<=255を使用してください: x x>=256を使用してください: EINVALの誤りを返してください。
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In order to clear a sticky IPV6_TCLASS option the application can specify -1 as the value.
ねばねばするIPV6_TCLASSオプションをクリアするために、アプリケーションは値として-1を指定できます。
There are cases where the kernel needs to control the traffic class value and conflicts with the user-specified value on the outgoing traffic. An example is an implementation of ECN in the kernel, setting 2 bits of the traffic class value. In such cases, the kernel should override the user-specified value. On the incoming traffic, the kernel may mask some of the bits in the traffic class field.
ケースがカーネルが外向的なトラフィックのユーザ規定値とのトラフィック階級値と闘争を制御する必要があるところにあります。 トラフィック階級値の2ビットを設定して、例はカーネルにおける電子証券取引ネットワークの実装です。 そのような場合、カーネルはユーザ規定値をくつがえすべきです。 入って来るトラフィックでは、カーネルはトラフィック類体で数ビットにマスクをかけるかもしれません。
6.6. Additional Errors with sendmsg() and setsockopt()
6.6. sendmsg()とsetsockoptと追加Errors()
With the IPV6_PKTINFO socket option there are no additional errors possible with the call to recvmsg(). But when specifying the outgoing interface or the source address, additional errors are possible from sendmsg() or setsockopt(). Note that some implementations might only be able to return this type of errors for setsockopt(). The following are examples, but some of these may not be provided by some implementations, and some implementations may define additional errors:
IPV6_PKTINFOソケットオプションと共に、呼び出しでrecvmsg()に可能などんな追加誤りもありません。 しかし、外向的なインタフェースかソースアドレスを指定するとき、追加誤りはsendmsg()かsetsockopt()から可能です。 いくつかの実装がsetsockopt()のためにこのタイプの誤りを返すことができるだけであるかもしれないことに注意してください。 これらの或るものはいくつかの実装によって提供されないかもしれません、そして、↓これは例ですが、いくつかの実装が追加誤りを定義するかもしれません:
ENXIO The interface specified by ipi6_ifindex does not exist.
インタフェースがipi6_ifindexで指定したENXIOは存在していません。
ENETDOWN The interface specified by ipi6_ifindex is not enabled
for IPv6 use.
インタフェースがipi6_ifindexで指定したENETDOWNはIPv6使用のために有効にされません。
EADDRNOTAVAIL ipi6_ifindex specifies an interface but the address
ipi6_addr is not available for use on that interface.
EADDRNOTAVAIL ipi6_ifindexはインタフェースを指定しますが、そのインタフェースのにおける使用について、アドレスipi6_addrがありません。
EHOSTUNREACH No route to the destination exists over the interface
specified by ipi6_ifindex.
目的地へのEHOSTUNREACHいいえルートはipi6_ifindexによって指定されたインタフェースの上に存在しています。
6.7. Summary of Outgoing Interface Selection
6.7. 外向的なインタフェース選択の概要
This document and [RFC-3493] specify various methods that affect the selection of the packet's outgoing interface. This subsection summarizes the ordering among those in order to ensure deterministic behavior.
このドキュメントと[RFC-3493]はパケットの外向的なインタフェースの選択に影響する様々なメソッドを指定します。 この小区分は、決定論的な振舞いを確実にするためにそれらの中に注文をまとめます。
For a given outgoing packet on a given socket, the outgoing interface is determined in the following order:
与えられたソケットの上の与えられた出発しているパケットに関しては、外向的なインタフェースは以下のオーダーで断固としています:
1. if an interface is specified in an IPV6_PKTINFO ancillary data
item, the interface is used.
1. インタフェースがIPV6_PKTINFO補助データの品目で指定されるなら、インタフェースは使用されています。
2. otherwise, if an interface is specified in an IPV6_PKTINFO sticky
option, the interface is used.
2. さもなければ、インタフェースがIPV6_PKTINFOのねばねばするオプションで指定されるなら、インタフェースは使用されています。
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3. otherwise, if the destination address is a multicast address and
the IPV6_MULTICAST_IF socket option is specified for the socket,
the interface is used.
3. さもなければ、_ソケットオプションがソケットに指定されるなら、送付先アドレスがマルチキャストアドレスとIPV6_MULTICASTであるなら、インタフェースは使用されています。
4. otherwise, if an IPV6_NEXTHOP ancillary data item is specified,
the interface to the next hop is used.
4. さもなければ、IPV6_NEXTHOP補助データの品目が指定されるなら、次のホップへのインタフェースは使用されています。
5. otherwise, if an IPV6_NEXTHOP sticky option is specified, the
interface to the next hop is used.
5. さもなければ、IPV6_NEXTHOPのねばねばするオプションが指定されるなら、次のホップへのインタフェースは使用されています。
6. otherwise, the outgoing interface should be determined in an
implementation dependent manner.
6. さもなければ、外向的なインタフェースは実装に依存する方法で決定するべきです。
The ordering above particularly means if the application specifies an interface by the IPV6_MULTICAST_IF socket option (described in [RFC- 3493]) as well as specifying a different interface by the IPV6_PKTINFO sticky option, the latter will override the former for every multicast packet on the corresponding socket. The reason for the ordering comes from expectation that the source address is specified as well and that the pair of the address and the outgoing interface should be preferred.
The ordering above particularly means if the application specifies an interface by the IPV6_MULTICAST_IF socket option (described in [RFC- 3493]) as well as specifying a different interface by the IPV6_PKTINFO sticky option, the latter will override the former for every multicast packet on the corresponding socket. The reason for the ordering comes from expectation that the source address is specified as well and that the pair of the address and the outgoing interface should be preferred.
In any case, the kernel must also verify that the source and destination addresses do not break their scope zones with regard to the outgoing interface.
In any case, the kernel must also verify that the source and destination addresses do not break their scope zones with regard to the outgoing interface.
7. Routing Header Option
7. Routing Header Option
Source routing in IPv6 is accomplished by specifying a Routing header as an extension header. There can be different types of Routing headers, but IPv6 currently defines only the Type 0 Routing header [RFC-2460]. This type supports up to 127 intermediate nodes (limited by the length field in the extension header). With this maximum number of intermediate nodes, a source, and a destination, there are 128 hops.
Source routing in IPv6 is accomplished by specifying a Routing header as an extension header. There can be different types of Routing headers, but IPv6 currently defines only the Type 0 Routing header [RFC-2460]. This type supports up to 127 intermediate nodes (limited by the length field in the extension header). With this maximum number of intermediate nodes, a source, and a destination, there are 128 hops.
Source routing with the IPv4 sockets API (the IP_OPTIONS socket option) requires the application to build the source route in the format that appears as the IPv4 header option, requiring intimate knowledge of the IPv4 options format. This IPv6 API, however, defines six functions that the application calls to build and examine a Routing header, and the ability to use sticky options or ancillary data to communicate this information between the application and the kernel using the IPV6_RTHDR option.
Source routing with the IPv4 sockets API (the IP_OPTIONS socket option) requires the application to build the source route in the format that appears as the IPv4 header option, requiring intimate knowledge of the IPv4 options format. This IPv6 API, however, defines six functions that the application calls to build and examine a Routing header, and the ability to use sticky options or ancillary data to communicate this information between the application and the kernel using the IPV6_RTHDR option.
Stevens, et al. Informational [Page 33] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 33] RFC 3542 Advanced Sockets API for IPv6 May 2003
Three functions build a Routing header:
Three functions build a Routing header:
inet6_rth_space() - return #bytes required for Routing header
inet6_rth_init() - initialize buffer data for Routing header
inet6_rth_add() - add one IPv6 address to the Routing header
inet6_rth_space() - return #bytes required for Routing header inet6_rth_init() - initialize buffer data for Routing header inet6_rth_add() - add one IPv6 address to the Routing header
Three functions deal with a returned Routing header:
Three functions deal with a returned Routing header:
inet6_rth_reverse() - reverse a Routing header
inet6_rth_segments() - return #segments in a Routing header
inet6_rth_getaddr() - fetch one address from a Routing header
inet6_rth_reverse() - reverse a Routing header inet6_rth_segments() - return #segments in a Routing header inet6_rth_getaddr() - fetch one address from a Routing header
The function prototypes for these functions are defined as a result of including <netinet/in.h>.
The function prototypes for these functions are defined as a result of including <netinet/in.h>.
To receive a Routing header the application must enable the IPV6_RECVRTHDR socket option:
To receive a Routing header the application must enable the IPV6_RECVRTHDR socket option:
int on = 1;
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVRTHDR, &on, sizeof(on));
int on = 1; setsockopt(fd, IPPROTO_IPV6, IPV6_RECVRTHDR, &on, sizeof(on));
Each received Routing header is returned as one ancillary data object described by a cmsghdr structure with cmsg_type set to IPV6_RTHDR. When multiple Routing headers are received, multiple ancillary data objects (with cmsg_type set to IPV6_RTHDR) will be returned to the application.
Each received Routing header is returned as one ancillary data object described by a cmsghdr structure with cmsg_type set to IPV6_RTHDR. When multiple Routing headers are received, multiple ancillary data objects (with cmsg_type set to IPV6_RTHDR) will be returned to the application.
To send a Routing header the application specifies it either as ancillary data in a call to sendmsg() or using setsockopt(). For the sending side, this API assumes the number of occurrences of the Routing header as described in [RFC-2460]. That is, applications can only specify at most one outgoing Routing header.
To send a Routing header the application specifies it either as ancillary data in a call to sendmsg() or using setsockopt(). For the sending side, this API assumes the number of occurrences of the Routing header as described in [RFC-2460]. That is, applications can only specify at most one outgoing Routing header.
The application can remove any sticky Routing header by calling setsockopt() for IPV6_RTHDR with a zero option length.
The application can remove any sticky Routing header by calling setsockopt() for IPV6_RTHDR with a zero option length.
When using ancillary data a Routing header is passed between the application and the kernel as follows: The cmsg_level member has a value of IPPROTO_IPV6 and the cmsg_type member has a value of IPV6_RTHDR. The contents of the cmsg_data[] member is implementation dependent and should not be accessed directly by the application, but should be accessed using the six functions that we are about to describe.
When using ancillary data a Routing header is passed between the application and the kernel as follows: The cmsg_level member has a value of IPPROTO_IPV6 and the cmsg_type member has a value of IPV6_RTHDR. The contents of the cmsg_data[] member is implementation dependent and should not be accessed directly by the application, but should be accessed using the six functions that we are about to describe.
The following constant is defined as a result of including the <netinet/in.h>:
The following constant is defined as a result of including the <netinet/in.h>:
#define IPV6_RTHDR_TYPE_0 0 /* IPv6 Routing header type 0 */
#define IPV6_RTHDR_TYPE_0 0 /* IPv6 Routing header type 0 */
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Stevens, et al. Informational [Page 34] RFC 3542 Advanced Sockets API for IPv6 May 2003
When a Routing header is specified, the destination address specified for connect(), sendto(), or sendmsg() is the final destination address of the datagram. The Routing header then contains the addresses of all the intermediate nodes.
When a Routing header is specified, the destination address specified for connect(), sendto(), or sendmsg() is the final destination address of the datagram. The Routing header then contains the addresses of all the intermediate nodes.
7.1. inet6_rth_space
7.1. inet6_rth_space
socklen_t inet6_rth_space(int type, int segments);
socklen_t inet6_rth_space(int type, int segments);
This function returns the number of bytes required to hold a Routing header of the specified type containing the specified number of segments (addresses). For an IPv6 Type 0 Routing header, the number of segments must be between 0 and 127, inclusive. The return value is just the space for the Routing header. When the application uses ancillary data it must pass the returned length to CMSG_SPACE() to determine how much memory is needed for the ancillary data object (including the cmsghdr structure).
This function returns the number of bytes required to hold a Routing header of the specified type containing the specified number of segments (addresses). For an IPv6 Type 0 Routing header, the number of segments must be between 0 and 127, inclusive. The return value is just the space for the Routing header. When the application uses ancillary data it must pass the returned length to CMSG_SPACE() to determine how much memory is needed for the ancillary data object (including the cmsghdr structure).
If the return value is 0, then either the type of the Routing header is not supported by this implementation or the number of segments is invalid for this type of Routing header.
If the return value is 0, then either the type of the Routing header is not supported by this implementation or the number of segments is invalid for this type of Routing header.
(Note: This function returns the size but does not allocate the space required for the ancillary data. This allows an application to allocate a larger buffer, if other ancillary data objects are desired, since all the ancillary data objects must be specified to sendmsg() as a single msg_control buffer.)
(Note: This function returns the size but does not allocate the space required for the ancillary data. This allows an application to allocate a larger buffer, if other ancillary data objects are desired, since all the ancillary data objects must be specified to sendmsg() as a single msg_control buffer.)
7.2. inet6_rth_init
7.2. inet6_rth_init
void *inet6_rth_init(void *bp, socklen_t bp_len, int type,
int segments);
void *inet6_rth_init(void *bp, socklen_t bp_len, int type, int segments);
This function initializes the buffer pointed to by bp to contain a Routing header of the specified type and sets ip6r_len based on the segments parameter. bp_len is only used to verify that the buffer is large enough. The ip6r_segleft field is set to zero; inet6_rth_add() will increment it.
This function initializes the buffer pointed to by bp to contain a Routing header of the specified type and sets ip6r_len based on the segments parameter. bp_len is only used to verify that the buffer is large enough. The ip6r_segleft field is set to zero; inet6_rth_add() will increment it.
When the application uses ancillary data the application must initialize any cmsghdr fields.
When the application uses ancillary data the application must initialize any cmsghdr fields.
The caller must allocate the buffer and its size can be determined by calling inet6_rth_space().
The caller must allocate the buffer and its size can be determined by calling inet6_rth_space().
Upon success the return value is the pointer to the buffer (bp), and this is then used as the first argument to the inet6_rth_add() function. Upon an error the return value is NULL.
Upon success the return value is the pointer to the buffer (bp), and this is then used as the first argument to the inet6_rth_add() function. Upon an error the return value is NULL.
Stevens, et al. Informational [Page 35] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 35] RFC 3542 Advanced Sockets API for IPv6 May 2003
7.3. inet6_rth_add
7.3. inet6_rth_add
int inet6_rth_add(void *bp, const struct in6_addr *addr);
int inet6_rth_add(void *bp, const struct in6_addr *addr);
This function adds the IPv6 address pointed to by addr to the end of the Routing header being constructed.
This function adds the IPv6 address pointed to by addr to the end of the Routing header being constructed.
If successful, the segleft member of the Routing Header is updated to account for the new address in the Routing header and the return value of the function is 0. Upon an error the return value of the function is -1.
If successful, the segleft member of the Routing Header is updated to account for the new address in the Routing header and the return value of the function is 0. Upon an error the return value of the function is -1.
7.4. inet6_rth_reverse
7.4. inet6_rth_reverse
int inet6_rth_reverse(const void *in, void *out);
int inet6_rth_reverse(const void *in, void *out);
This function takes a Routing header extension header (pointed to by the first argument) and writes a new Routing header that sends datagrams along the reverse of that route. The function reverses the order of the addresses and sets the segleft member in the new Routing header to the number of segments. Both arguments are allowed to point to the same buffer (that is, the reversal can occur in place).
This function takes a Routing header extension header (pointed to by the first argument) and writes a new Routing header that sends datagrams along the reverse of that route. The function reverses the order of the addresses and sets the segleft member in the new Routing header to the number of segments. Both arguments are allowed to point to the same buffer (that is, the reversal can occur in place).
The return value of the function is 0 on success, or -1 upon an error.
The return value of the function is 0 on success, or -1 upon an error.
7.5. inet6_rth_segments
7.5. inet6_rth_segments
int inet6_rth_segments(const void *bp);
int inet6_rth_segments(const void *bp);
This function returns the number of segments (addresses) contained in the Routing header described by bp. On success the return value is zero or greater. The return value of the function is -1 upon an error.
This function returns the number of segments (addresses) contained in the Routing header described by bp. On success the return value is zero or greater. The return value of the function is -1 upon an error.
7.6. inet6_rth_getaddr
7.6. inet6_rth_getaddr
struct in6_addr *inet6_rth_getaddr(const void *bp, int index);
struct in6_addr *inet6_rth_getaddr(const void *bp, int index);
This function returns a pointer to the IPv6 address specified by index (which must have a value between 0 and one less than the value returned by inet6_rth_segments()) in the Routing header described by bp. An application should first call inet6_rth_segments() to obtain the number of segments in the Routing header.
This function returns a pointer to the IPv6 address specified by index (which must have a value between 0 and one less than the value returned by inet6_rth_segments()) in the Routing header described by bp. An application should first call inet6_rth_segments() to obtain the number of segments in the Routing header.
Upon an error the return value of the function is NULL.
Upon an error the return value of the function is NULL.
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Stevens, et al. Informational [Page 36] RFC 3542 Advanced Sockets API for IPv6 May 2003
8. Hop-By-Hop Options
8. Hop-By-Hop Options
A variable number of Hop-by-Hop options can appear in a single Hop- by-Hop options header. Each option in the header is TLV-encoded with a type, length, and value. This IPv6 API defines seven functions that the application calls to build and examine a Hop-by_Hop options header, and the ability to use sticky options or ancillary data to communicate this information between the application and the kernel. This uses the IPV6_HOPOPTS for a Hop-by-Hop options header.
A variable number of Hop-by-Hop options can appear in a single Hop- by-Hop options header. Each option in the header is TLV-encoded with a type, length, and value. This IPv6 API defines seven functions that the application calls to build and examine a Hop-by_Hop options header, and the ability to use sticky options or ancillary data to communicate this information between the application and the kernel. This uses the IPV6_HOPOPTS for a Hop-by-Hop options header.
Today several Hop-by-Hop options are defined for IPv6. Two pad options, Pad1 and PadN, are for alignment purposes and are automatically inserted by the inet6_opt_XXX() routines and ignored by the inet6_opt_XXX() routines on the receive side. This section of the API is therefore defined for other (and future) Hop-by-Hop options that an application may need to specify and receive.
Today several Hop-by-Hop options are defined for IPv6. Two pad options, Pad1 and PadN, are for alignment purposes and are automatically inserted by the inet6_opt_XXX() routines and ignored by the inet6_opt_XXX() routines on the receive side. This section of the API is therefore defined for other (and future) Hop-by-Hop options that an application may need to specify and receive.
Four functions build an options header:
Four functions build an options header:
inet6_opt_init() - initialize buffer data for options header
inet6_opt_append() - add one TLV option to the options header
inet6_opt_finish() - finish adding TLV options to the options
header
inet6_opt_set_val() - add one component of the option content to
the option
inet6_opt_init() - initialize buffer data for options header inet6_opt_append() - add one TLV option to the options header inet6_opt_finish() - finish adding TLV options to the options header inet6_opt_set_val() - add one component of the option content to the option
Three functions deal with a returned options header:
Three functions deal with a returned options header:
inet6_opt_next() - extract the next option from the options
header
inet6_opt_find() - extract an option of a specified type from
the header
inet6_opt_get_val() - retrieve one component of the option
content
inet6_opt_next() - extract the next option from the options header inet6_opt_find() - extract an option of a specified type from the header inet6_opt_get_val() - retrieve one component of the option content
Individual Hop-by-Hop options (and Destination options, which are described in Section 9 and are very similar to the Hop-by-Hop options) may have specific alignment requirements. For example, the 4-byte Jumbo Payload length should appear on a 4-byte boundary, and IPv6 addresses are normally aligned on an 8-byte boundary. These requirements and the terminology used with these options are discussed in Section 4.2 and Appendix B of [RFC-2460]. The alignment of first byte of each option is specified by two values, called x and y, written as "xn + y". This states that the option must appear at an integer multiple of x bytes from the beginning of the options header (x can have the values 1, 2, 4, or 8), plus y bytes (y can have a value between 0 and 7, inclusive). The Pad1 and PadN options are inserted as needed to maintain the required alignment. The
Individual Hop-by-Hop options (and Destination options, which are described in Section 9 and are very similar to the Hop-by-Hop options) may have specific alignment requirements. For example, the 4-byte Jumbo Payload length should appear on a 4-byte boundary, and IPv6 addresses are normally aligned on an 8-byte boundary. These requirements and the terminology used with these options are discussed in Section 4.2 and Appendix B of [RFC-2460]. The alignment of first byte of each option is specified by two values, called x and y, written as "xn + y". This states that the option must appear at an integer multiple of x bytes from the beginning of the options header (x can have the values 1, 2, 4, or 8), plus y bytes (y can have a value between 0 and 7, inclusive). The Pad1 and PadN options are inserted as needed to maintain the required alignment. The
Stevens, et al. Informational [Page 37] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 37] RFC 3542 Advanced Sockets API for IPv6 May 2003
functions below need to know the alignment of the end of the option (which is always in the form "xn," where x can have the values 1, 2, 4, or 8) and the total size of the data portion of the option. These are passed as the "align" and "len" arguments to inet6_opt_append().
functions below need to know the alignment of the end of the option (which is always in the form "xn," where x can have the values 1, 2, 4, or 8) and the total size of the data portion of the option. These are passed as the "align" and "len" arguments to inet6_opt_append().
Multiple Hop-by-Hop options must be specified by the application by placing them in a single extension header.
Multiple Hop-by-Hop options must be specified by the application by placing them in a single extension header.
Finally, we note that use of some Hop-by-Hop options or some Destination options, might require special privilege. That is, normal applications (without special privilege) might be forbidden from setting certain options in outgoing packets, and might never see certain options in received packets.
Finally, we note that use of some Hop-by-Hop options or some Destination options, might require special privilege. That is, normal applications (without special privilege) might be forbidden from setting certain options in outgoing packets, and might never see certain options in received packets.
8.1. Receiving Hop-by-Hop Options
8.1. Receiving Hop-by-Hop Options
To receive a Hop-by-Hop options header the application must enable the IPV6_RECVHOPOPTS socket option:
To receive a Hop-by-Hop options header the application must enable the IPV6_RECVHOPOPTS socket option:
int on = 1;
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVHOPOPTS, &on, sizeof(on));
int on = 1; setsockopt(fd, IPPROTO_IPV6, IPV6_RECVHOPOPTS, &on, sizeof(on));
When using ancillary data a Hop-by-hop options header is passed between the application and the kernel as follows: The cmsg_level member will be IPPROTO_IPV6 and the cmsg_type member will be IPV6_HOPOPTS. These options are then processed by calling the inet6_opt_next(), inet6_opt_find(), and inet6_opt_get_val() functions, described in Section 10.
When using ancillary data a Hop-by-hop options header is passed between the application and the kernel as follows: The cmsg_level member will be IPPROTO_IPV6 and the cmsg_type member will be IPV6_HOPOPTS. These options are then processed by calling the inet6_opt_next(), inet6_opt_find(), and inet6_opt_get_val() functions, described in Section 10.
8.2. Sending Hop-by-Hop Options
8.2. Sending Hop-by-Hop Options
To send a Hop-by-Hop options header, the application specifies the header either as ancillary data in a call to sendmsg() or using setsockopt().
To send a Hop-by-Hop options header, the application specifies the header either as ancillary data in a call to sendmsg() or using setsockopt().
The application can remove any sticky Hop-by-Hop options header by calling setsockopt() for IPV6_HOPOPTS with a zero option length.
The application can remove any sticky Hop-by-Hop options header by calling setsockopt() for IPV6_HOPOPTS with a zero option length.
All the Hop-by-Hop options must be specified by a single ancillary data object. The cmsg_level member is set to IPPROTO_IPV6 and the cmsg_type member is set to IPV6_HOPOPTS. The option is normally constructed using the inet6_opt_init(), inet6_opt_append(), inet6_opt_finish(), and inet6_opt_set_val() functions, described in Section 10.
All the Hop-by-Hop options must be specified by a single ancillary data object. The cmsg_level member is set to IPPROTO_IPV6 and the cmsg_type member is set to IPV6_HOPOPTS. The option is normally constructed using the inet6_opt_init(), inet6_opt_append(), inet6_opt_finish(), and inet6_opt_set_val() functions, described in Section 10.
Additional errors may be possible from sendmsg() and setsockopt() if the specified option is in error.
Additional errors may be possible from sendmsg() and setsockopt() if the specified option is in error.
Stevens, et al. Informational [Page 38] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 38] RFC 3542 Advanced Sockets API for IPv6 May 2003
9. Destination Options
9. Destination Options
A variable number of Destination options can appear in one or more Destination options headers. As defined in [RFC-2460], a Destination options header appearing before a Routing header is processed by the first destination plus any subsequent destinations specified in the Routing header, while a Destination options header that is not followed by a Routing header is processed only by the final destination. As with the Hop-by-Hop options, each option in a Destination options header is TLV-encoded with a type, length, and value.
A variable number of Destination options can appear in one or more Destination options headers. As defined in [RFC-2460], a Destination options header appearing before a Routing header is processed by the first destination plus any subsequent destinations specified in the Routing header, while a Destination options header that is not followed by a Routing header is processed only by the final destination. As with the Hop-by-Hop options, each option in a Destination options header is TLV-encoded with a type, length, and value.
9.1. Receiving Destination Options
9.1. Receiving Destination Options
To receive Destination options header the application must enable the IPV6_RECVDSTOPTS socket option:
To receive Destination options header the application must enable the IPV6_RECVDSTOPTS socket option:
int on = 1;
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVDSTOPTS, &on, sizeof(on));
int on = 1; setsockopt(fd, IPPROTO_IPV6, IPV6_RECVDSTOPTS, &on, sizeof(on));
Each Destination options header is returned as one ancillary data object described by a cmsghdr structure with cmsg_level set to IPPROTO_IPV6 and cmsg_type set to IPV6_DSTOPTS.
Each Destination options header is returned as one ancillary data object described by a cmsghdr structure with cmsg_level set to IPPROTO_IPV6 and cmsg_type set to IPV6_DSTOPTS.
These options are then processed by calling the inet6_opt_next(), inet6_opt_find(), and inet6_opt_get_value() functions.
These options are then processed by calling the inet6_opt_next(), inet6_opt_find(), and inet6_opt_get_value() functions.
9.2. Sending Destination Options
9.2. Sending Destination Options
To send a Destination options header, the application specifies it either as ancillary data in a call to sendmsg() or using setsockopt().
To send a Destination options header, the application specifies it either as ancillary data in a call to sendmsg() or using setsockopt().
The application can remove any sticky Destination options header by calling setsockopt() for IPV6_RTHDRDSTOPTS/IPV6_DSTOPTS with a zero option length.
The application can remove any sticky Destination options header by calling setsockopt() for IPV6_RTHDRDSTOPTS/IPV6_DSTOPTS with a zero option length.
This API assumes the ordering about extension headers as described in [RFC-2460]. Thus, one set of Destination options can only appear before a Routing header, and one set can only appear after a Routing header (or in a packet with no Routing header). Each set can consist of one or more options but each set is a single extension header.
This API assumes the ordering about extension headers as described in [RFC-2460]. Thus, one set of Destination options can only appear before a Routing header, and one set can only appear after a Routing header (or in a packet with no Routing header). Each set can consist of one or more options but each set is a single extension header.
Today all destination options that an application may want to specify can be put after (or without) a Routing header. Thus, applications should usually need IPV6_DSTOPTS only and should avoid using IPV6_RTHDRDSTOPTS whenever possible.
Today all destination options that an application may want to specify can be put after (or without) a Routing header. Thus, applications should usually need IPV6_DSTOPTS only and should avoid using IPV6_RTHDRDSTOPTS whenever possible.
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Stevens, et al. Informational [Page 39] RFC 3542 Advanced Sockets API for IPv6 May 2003
When using ancillary data a Destination options header is passed between the application and the kernel as follows: The set preceding a Routing header are specified with the cmsg_level member set to IPPROTO_IPV6 and the cmsg_type member set to IPV6_RTHDRDSTOPTS. Any setsockopt or ancillary data for IPV6_RTHDRDSTOPTS is silently ignored when sending packets unless a Routing header is also specified. Note that the "Routing header" here means the one specified by this API. Even when the kernel inserts a routing header in its internal routine (e.g., in a mobile IPv6 stack), the Destination options header specified by IPV6_RTHDRDSTOPTS will still be ignored unless the application explicitly specifies its own Routing header.
When using ancillary data a Destination options header is passed between the application and the kernel as follows: The set preceding a Routing header are specified with the cmsg_level member set to IPPROTO_IPV6 and the cmsg_type member set to IPV6_RTHDRDSTOPTS. Any setsockopt or ancillary data for IPV6_RTHDRDSTOPTS is silently ignored when sending packets unless a Routing header is also specified. Note that the "Routing header" here means the one specified by this API. Even when the kernel inserts a routing header in its internal routine (e.g., in a mobile IPv6 stack), the Destination options header specified by IPV6_RTHDRDSTOPTS will still be ignored unless the application explicitly specifies its own Routing header.
The set of Destination options after a Routing header, which are also used when no Routing header is present, are specified with the cmsg_level member is set to IPPROTO_IPV6 and the cmsg_type member is set to IPV6_DSTOPTS.
The set of Destination options after a Routing header, which are also used when no Routing header is present, are specified with the cmsg_level member is set to IPPROTO_IPV6 and the cmsg_type member is set to IPV6_DSTOPTS.
The Destination options are normally constructed using the inet6_opt_init(), inet6_opt_append(), inet6_opt_finish(), and inet6_opt_set_val() functions, described in Section 10.
The Destination options are normally constructed using the inet6_opt_init(), inet6_opt_append(), inet6_opt_finish(), and inet6_opt_set_val() functions, described in Section 10.
Additional errors may be possible from sendmsg() and setsockopt() if the specified option is in error.
Additional errors may be possible from sendmsg() and setsockopt() if the specified option is in error.
10. Hop-by-Hop and Destination Options Processing
10. Hop-by-Hop and Destination Options Processing
Building and parsing the Hop-by-Hop and Destination options is complicated for the reasons given earlier. We therefore define a set of functions to help the application. These functions assume the formatting rules specified in Appendix B in [RFC-2460] i.e., that the largest field is placed last in the option.
Building and parsing the Hop-by-Hop and Destination options is complicated for the reasons given earlier. We therefore define a set of functions to help the application. These functions assume the formatting rules specified in Appendix B in [RFC-2460] i.e., that the largest field is placed last in the option.
The function prototypes for these functions are defined as a result of including <netinet/in.h>.
The function prototypes for these functions are defined as a result of including <netinet/in.h>.
The first 3 functions (init, append, and finish) are used both to calculate the needed buffer size for the options, and to actually encode the options once the application has allocated a buffer for the header. In order to only calculate the size the application must pass a NULL extbuf and a zero extlen to those functions.
The first 3 functions (init, append, and finish) are used both to calculate the needed buffer size for the options, and to actually encode the options once the application has allocated a buffer for the header. In order to only calculate the size the application must pass a NULL extbuf and a zero extlen to those functions.
Stevens, et al. Informational [Page 40] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 40] RFC 3542 Advanced Sockets API for IPv6 May 2003
10.1. inet6_opt_init
10.1. inet6_opt_init
int inet6_opt_init(void *extbuf, socklen_t extlen);
int inet6_opt_init(void *extbuf, socklen_t extlen);
This function returns the number of bytes needed for the empty extension header i.e., without any options. If extbuf is not NULL it also initializes the extension header to have the correct length field. In that case if the extlen value is not a positive (i.e., non-zero) multiple of 8 the function fails and returns -1.
This function returns the number of bytes needed for the empty extension header i.e., without any options. If extbuf is not NULL it also initializes the extension header to have the correct length field. In that case if the extlen value is not a positive (i.e., non-zero) multiple of 8 the function fails and returns -1.
(Note: since the return value on success is based on a "constant" parameter, i.e., the empty extension header, an implementation may return a constant value. However, this specification does not require the value be constant, and leaves it as implementation dependent. The application should not assume a particular constant value as a successful return value of this function.)
(Note: since the return value on success is based on a "constant" parameter, i.e., the empty extension header, an implementation may return a constant value. However, this specification does not require the value be constant, and leaves it as implementation dependent. The application should not assume a particular constant value as a successful return value of this function.)
10.2. inet6_opt_append
10.2. inet6_opt_append
int inet6_opt_append(void *extbuf, socklen_t extlen, int offset,
uint8_t type, socklen_t len, uint_t align,
void **databufp);
int inet6_opt_append(void *extbuf, socklen_t extlen, int offset, uint8_t type, socklen_t len, uint_t align, void **databufp);
Offset should be the length returned by inet6_opt_init() or a previous inet6_opt_append(). This function returns the updated total length taking into account adding an option with length 'len' and alignment 'align'. If extbuf is not NULL then, in addition to returning the length, the function inserts any needed pad option, initializes the option (setting the type and length fields) and returns a pointer to the location for the option content in databufp. If the option does not fit in the extension header buffer the function returns -1.
Offset should be the length returned by inet6_opt_init() or a previous inet6_opt_append(). This function returns the updated total length taking into account adding an option with length 'len' and alignment 'align'. If extbuf is not NULL then, in addition to returning the length, the function inserts any needed pad option, initializes the option (setting the type and length fields) and returns a pointer to the location for the option content in databufp. If the option does not fit in the extension header buffer the function returns -1.
Type is the 8-bit option type. Len is the length of the option data (i.e., excluding the option type and option length fields).
Type is the 8-bit option type. Len is the length of the option data (i.e., excluding the option type and option length fields).
Once inet6_opt_append() has been called the application can use the databuf directly, or use inet6_opt_set_val() to specify the content of the option.
Once inet6_opt_append() has been called the application can use the databuf directly, or use inet6_opt_set_val() to specify the content of the option.
The option type must have a value from 2 to 255, inclusive. (0 and 1 are reserved for the Pad1 and PadN options, respectively.)
The option type must have a value from 2 to 255, inclusive. (0 and 1 are reserved for the Pad1 and PadN options, respectively.)
The option data length must have a value between 0 and 255, inclusive, and is the length of the option data that follows.
The option data length must have a value between 0 and 255, inclusive, and is the length of the option data that follows.
The align parameter must have a value of 1, 2, 4, or 8. The align value can not exceed the value of len.
The align parameter must have a value of 1, 2, 4, or 8. The align value can not exceed the value of len.
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Stevens, et al. Informational [Page 41] RFC 3542 Advanced Sockets API for IPv6 May 2003
10.3. inet6_opt_finish
10.3. inet6_opt_finish
int inet6_opt_finish(void *extbuf, socklen_t extlen, int offset);
int inet6_opt_finish(void *extbuf, socklen_t extlen, int offset);
Offset should be the length returned by inet6_opt_init() or inet6_opt_append(). This function returns the updated total length taking into account the final padding of the extension header to make it a multiple of 8 bytes. If extbuf is not NULL the function also initializes the option by inserting a Pad1 or PadN option of the proper length.
Offset should be the length returned by inet6_opt_init() or inet6_opt_append(). This function returns the updated total length taking into account the final padding of the extension header to make it a multiple of 8 bytes. If extbuf is not NULL the function also initializes the option by inserting a Pad1 or PadN option of the proper length.
If the necessary pad does not fit in the extension header buffer the function returns -1.
If the necessary pad does not fit in the extension header buffer the function returns -1.
10.4. inet6_opt_set_val
10.4. inet6_opt_set_val
int inet6_opt_set_val(void *databuf, int offset, void *val,
socklen_t vallen);
int inet6_opt_set_val(void *databuf, int offset, void *val, socklen_t vallen);
Databuf should be a pointer returned by inet6_opt_append(). This function inserts data items of various sizes in the data portion of the option. Val should point to the data to be inserted. Offset specifies where in the data portion of the option the value should be inserted; the first byte after the option type and length is accessed by specifying an offset of zero.
Databuf should be a pointer returned by inet6_opt_append(). This function inserts data items of various sizes in the data portion of the option. Val should point to the data to be inserted. Offset specifies where in the data portion of the option the value should be inserted; the first byte after the option type and length is accessed by specifying an offset of zero.
The caller should ensure that each field is aligned on its natural boundaries as described in Appendix B of [RFC-2460], but the function must not rely on the caller's behavior. Even when the alignment requirement is not satisfied, inet6_opt_set_val should just copy the data as required.
The caller should ensure that each field is aligned on its natural boundaries as described in Appendix B of [RFC-2460], but the function must not rely on the caller's behavior. Even when the alignment requirement is not satisfied, inet6_opt_set_val should just copy the data as required.
The function returns the offset for the next field (i.e., offset + vallen) which can be used when composing option content with multiple fields.
The function returns the offset for the next field (i.e., offset + vallen) which can be used when composing option content with multiple fields.
10.5. inet6_opt_next
10.5. inet6_opt_next
int inet6_opt_next(void *extbuf, socklen_t extlen, int offset,
uint8_t *typep, socklen_t *lenp,
void **databufp);
int inet6_opt_next(void *extbuf, socklen_t extlen, int offset, uint8_t *typep, socklen_t *lenp, void **databufp);
This function parses received option extension headers returning the next option. Extbuf and extlen specifies the extension header. Offset should either be zero (for the first option) or the length returned by a previous call to inet6_opt_next() or inet6_opt_find(). It specifies the position where to continue scanning the extension buffer. The next option is returned by updating typep, lenp, and
This function parses received option extension headers returning the next option. Extbuf and extlen specifies the extension header. Offset should either be zero (for the first option) or the length returned by a previous call to inet6_opt_next() or inet6_opt_find(). It specifies the position where to continue scanning the extension buffer. The next option is returned by updating typep, lenp, and
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databufp. Typep stores the option type, lenp stores the length of the option data (i.e., excluding the option type and option length fields), and databufp points the data field of the option. This function returns the updated "previous" length computed by advancing past the option that was returned. This returned "previous" length can then be passed to subsequent calls to inet6_opt_next(). This function does not return any PAD1 or PADN options. When there are no more options or if the option extension header is malformed the return value is -1.
databufp. Typep stores the option type, lenp stores the length of the option data (i.e., excluding the option type and option length fields), and databufp points the data field of the option. This function returns the updated "previous" length computed by advancing past the option that was returned. This returned "previous" length can then be passed to subsequent calls to inet6_opt_next(). This function does not return any PAD1 or PADN options. When there are no more options or if the option extension header is malformed the return value is -1.
10.6. inet6_opt_find
10.6. inet6_opt_find
int inet6_opt_find(void *extbuf, socklen_t extlen, int offset,
uint8_t type, socklen_t *lenp,
void **databufp);
int inet6_opt_find(void *extbuf, socklen_t extlen, int offset, uint8_t type, socklen_t *lenp, void **databufp);
This function is similar to the previously described inet6_opt_next() function, except this function lets the caller specify the option type to be searched for, instead of always returning the next option in the extension header.
This function is similar to the previously described inet6_opt_next() function, except this function lets the caller specify the option type to be searched for, instead of always returning the next option in the extension header.
If an option of the specified type is located, the function returns the updated "previous" total length computed by advancing past the option that was returned and past any options that didn't match the type. This returned "previous" length can then be passed to subsequent calls to inet6_opt_find() for finding the next occurrence of the same option type.
If an option of the specified type is located, the function returns the updated "previous" total length computed by advancing past the option that was returned and past any options that didn't match the type. This returned "previous" length can then be passed to subsequent calls to inet6_opt_find() for finding the next occurrence of the same option type.
If an option of the specified type is not located, the return value is -1. If the option extension header is malformed, the return value is -1.
If an option of the specified type is not located, the return value is -1. If the option extension header is malformed, the return value is -1.
10.7. inet6_opt_get_val
10.7. inet6_opt_get_val
int inet6_opt_get_val(void *databuf, int offset, void *val,
socklen_t vallen);
int inet6_opt_get_val(void *databuf, int offset, void *val, socklen_t vallen);
Databuf should be a pointer returned by inet6_opt_next() or inet6_opt_find(). This function extracts data items of various sizes in the data portion of the option. Val should point to the destination for the extracted data. Offset specifies from where in the data portion of the option the value should be extracted; the first byte after the option type and length is accessed by specifying an offset of zero.
Databuf should be a pointer returned by inet6_opt_next() or inet6_opt_find(). This function extracts data items of various sizes in the data portion of the option. Val should point to the destination for the extracted data. Offset specifies from where in the data portion of the option the value should be extracted; the first byte after the option type and length is accessed by specifying an offset of zero.
It is expected that each field is aligned on its natural boundaries as described in Appendix B of [RFC-2460], but the function must not rely on the alignment.
It is expected that each field is aligned on its natural boundaries as described in Appendix B of [RFC-2460], but the function must not rely on the alignment.
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The function returns the offset for the next field (i.e., offset + vallen) which can be used when extracting option content with multiple fields.
The function returns the offset for the next field (i.e., offset + vallen) which can be used when extracting option content with multiple fields.
11. Additional Advanced API Functions
11. Additional Advanced API Functions
11.1. Sending with the Minimum MTU
11.1. Sending with the Minimum MTU
Unicast applications should usually let the kernel perform path MTU discovery [RFC-1981], as long as the kernel supports it, and should not care about the path MTU. Some applications, however, might not want to incur the overhead of path MTU discovery, especially if the applications only send a single datagram to a destination. A potential example is a DNS server.
Unicast applications should usually let the kernel perform path MTU discovery [RFC-1981], as long as the kernel supports it, and should not care about the path MTU. Some applications, however, might not want to incur the overhead of path MTU discovery, especially if the applications only send a single datagram to a destination. A potential example is a DNS server.
[RFC-1981] describes how path MTU discovery works for multicast destinations. From practice in using IPv4 multicast, however, many careless applications that send large multicast packets on the wire have caused implosion of ICMPv4 error messages. The situation can be worse when there is a filtering node that blocks the ICMPv4 messages. Though the filtering issue applies to unicast as well, the impact is much larger in the multicast cases.
[RFC-1981] describes how path MTU discovery works for multicast destinations. From practice in using IPv4 multicast, however, many careless applications that send large multicast packets on the wire have caused implosion of ICMPv4 error messages. The situation can be worse when there is a filtering node that blocks the ICMPv4 messages. Though the filtering issue applies to unicast as well, the impact is much larger in the multicast cases.
Thus, applications sending multicast traffic should explicitly enable path MTU discovery only when they understand that the benefit of possibly larger MTU usage outweighs the possible impact of MTU discovery for active sources across the delivery tree(s). This default behavior is based on the today's practice with IPv4 multicast and path MTU discovery. The behavior may change in the future once it is found that path MTU discovery effectively works with actual multicast applications and network configurations.
Thus, applications sending multicast traffic should explicitly enable path MTU discovery only when they understand that the benefit of possibly larger MTU usage outweighs the possible impact of MTU discovery for active sources across the delivery tree(s). This default behavior is based on the today's practice with IPv4 multicast and path MTU discovery. The behavior may change in the future once it is found that path MTU discovery effectively works with actual multicast applications and network configurations.
This specification defines a mechanism to avoid path MTU discovery by sending at the minimum IPv6 MTU [RFC-2460]. If the packet is larger than the minimum MTU and this feature has been enabled the IP layer will fragment to the minimum MTU. To control the policy about path MTU discovery, applications can use the IPV6_USE_MIN_MTU socket option.
This specification defines a mechanism to avoid path MTU discovery by sending at the minimum IPv6 MTU [RFC-2460]. If the packet is larger than the minimum MTU and this feature has been enabled the IP layer will fragment to the minimum MTU. To control the policy about path MTU discovery, applications can use the IPV6_USE_MIN_MTU socket option.
As described above, the default policy should depend on whether the destination is unicast or multicast. For unicast destinations path MTU discovery should be performed by default. For multicast destinations path MTU discovery should be disabled by default. This option thus takes the following three types of integer arguments:
As described above, the default policy should depend on whether the destination is unicast or multicast. For unicast destinations path MTU discovery should be performed by default. For multicast destinations path MTU discovery should be disabled by default. This option thus takes the following three types of integer arguments:
-1: perform path MTU discovery for unicast destinations but do not
perform it for multicast destinations. Packets to multicast
destinations are therefore sent with the minimum MTU.
-1: perform path MTU discovery for unicast destinations but do not perform it for multicast destinations. Packets to multicast destinations are therefore sent with the minimum MTU.
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Stevens, et al. Informational [Page 44] RFC 3542 Advanced Sockets API for IPv6 May 2003
0: always perform path MTU discovery.
0: always perform path MTU discovery.
1: always disable path MTU discovery and send packets at the minimum
MTU.
1: always disable path MTU discovery and send packets at the minimum MTU.
The default value of this option is -1. Values other than -1, 0, and 1 are invalid, and an error EINVAL will be returned for those values.
The default value of this option is -1. Values other than -1, 0, and 1 are invalid, and an error EINVAL will be returned for those values.
As an example, if a unicast application intentionally wants to disable path MTU discovery, it will add the following lines:
As an example, if a unicast application intentionally wants to disable path MTU discovery, it will add the following lines:
int on = 1;
setsockopt(fd, IPPROTO_IPV6, IPV6_USE_MIN_MTU, &on, sizeof(on));
int on = 1; setsockopt(fd, IPPROTO_IPV6, IPV6_USE_MIN_MTU, &on, sizeof(on));
Note that this API intentionally excludes the case where the application wants to perform path MTU discovery for multicast but to disable it for unicast. This is because such usage is not feasible considering a scale of performance issues around whether to do path MTU discovery or not. When path MTU discovery makes sense to a destination but not to a different destination, regardless of whether the destination is unicast or multicast, applications either need to toggle the option between sending such packets on the same socket, or use different sockets for the two classes of destinations.
Note that this API intentionally excludes the case where the application wants to perform path MTU discovery for multicast but to disable it for unicast. This is because such usage is not feasible considering a scale of performance issues around whether to do path MTU discovery or not. When path MTU discovery makes sense to a destination but not to a different destination, regardless of whether the destination is unicast or multicast, applications either need to toggle the option between sending such packets on the same socket, or use different sockets for the two classes of destinations.
This option can also be sent as ancillary data. In the cmsghdr structure containing this ancillary data, the cmsg_level member will be IPPROTO_IPV6, the cmsg_type member will be IPV6_USE_MIN_MTU, and the first byte of cmsg_data[] will be the first byte of the integer.
This option can also be sent as ancillary data. In the cmsghdr structure containing this ancillary data, the cmsg_level member will be IPPROTO_IPV6, the cmsg_type member will be IPV6_USE_MIN_MTU, and the first byte of cmsg_data[] will be the first byte of the integer.
11.2. Sending without Fragmentation
11.2. Sending without Fragmentation
In order to provide for easy porting of existing UDP and raw socket applications IPv6 implementations will, when originating packets, automatically insert a fragment header in the packet if the packet is too big for the path MTU.
In order to provide for easy porting of existing UDP and raw socket applications IPv6 implementations will, when originating packets, automatically insert a fragment header in the packet if the packet is too big for the path MTU.
Some applications might not want this behavior. An example is traceroute which might want to discover the actual path MTU.
Some applications might not want this behavior. An example is traceroute which might want to discover the actual path MTU.
This specification defines a mechanism to turn off the automatic inserting of a fragment header for UDP and raw sockets. This can be enabled using the IPV6_DONTFRAG socket option.
This specification defines a mechanism to turn off the automatic inserting of a fragment header for UDP and raw sockets. This can be enabled using the IPV6_DONTFRAG socket option.
int on = 1;
setsockopt(fd, IPPROTO_IPV6, IPV6_DONTFRAG, &on, sizeof(on));
int on = 1; setsockopt(fd, IPPROTO_IPV6, IPV6_DONTFRAG, &on, sizeof(on));
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Stevens, et al. Informational [Page 45] RFC 3542 Advanced Sockets API for IPv6 May 2003
By default, this socket option is disabled. Setting the value to 0 also disables the option i.e., reverts to the default behavior of automatic inserting. This option can also be sent as ancillary data. In the cmsghdr structure containing this ancillary data, the cmsg_level member will be IPPROTO_IPV6, the cmsg_type member will be IPV6_DONTFRAG, and the first byte of cmsg_data[] will be the first byte of the integer. This API only specifies the use of this option for UDP and raw sockets, and does not define the usage for TCP sockets.
By default, this socket option is disabled. Setting the value to 0 also disables the option i.e., reverts to the default behavior of automatic inserting. This option can also be sent as ancillary data. In the cmsghdr structure containing this ancillary data, the cmsg_level member will be IPPROTO_IPV6, the cmsg_type member will be IPV6_DONTFRAG, and the first byte of cmsg_data[] will be the first byte of the integer. This API only specifies the use of this option for UDP and raw sockets, and does not define the usage for TCP sockets.
When the data size is larger than the MTU of the outgoing interface, the packet will be discarded. Applications can know the result by enabling the IPV6_RECVPATHMTU option described below and receiving the corresponding ancillary data items. An additional error EMSGSIZE may also be returned in some implementations. Note, however, that some other implementations might not be able to return this additional error when sending a message.
When the data size is larger than the MTU of the outgoing interface, the packet will be discarded. Applications can know the result by enabling the IPV6_RECVPATHMTU option described below and receiving the corresponding ancillary data items. An additional error EMSGSIZE may also be returned in some implementations. Note, however, that some other implementations might not be able to return this additional error when sending a message.
11.3. Path MTU Discovery and UDP
11.3. Path MTU Discovery and UDP
UDP and raw socket applications need to be able to determine the "maximum send transport-message size" (Section 5.1 of [RFC-1981]) to a given destination so that those applications can participate in path MTU discovery. This lets those applications send smaller datagrams to the destination, avoiding fragmentation.
UDP and raw socket applications need to be able to determine the "maximum send transport-message size" (Section 5.1 of [RFC-1981]) to a given destination so that those applications can participate in path MTU discovery. This lets those applications send smaller datagrams to the destination, avoiding fragmentation.
This is accomplished using a new ancillary data item (IPV6_PATHMTU) which is delivered to recvmsg() without any actual data. The application can enable the receipt of IPV6_PATHMTU ancillary data items by setting the IPV6_RECVPATHMTU socket option.
This is accomplished using a new ancillary data item (IPV6_PATHMTU) which is delivered to recvmsg() without any actual data. The application can enable the receipt of IPV6_PATHMTU ancillary data items by setting the IPV6_RECVPATHMTU socket option.
int on = 1;
setsockopt(fd, IPPROTO_IPV6, IPV6_RECVPATHMTU, &on, sizeof(on));
int on = 1; setsockopt(fd, IPPROTO_IPV6, IPV6_RECVPATHMTU, &on, sizeof(on));
By default, this socket option is disabled. Setting the value to 0 also disables the option. This API only specifies the use of this option for UDP and raw sockets, and does not define the usage for TCP sockets.
By default, this socket option is disabled. Setting the value to 0 also disables the option. This API only specifies the use of this option for UDP and raw sockets, and does not define the usage for TCP sockets.
When the application is sending packets too big for the path MTU recvmsg() will return zero (indicating no data) but there will be a cmsghdr with cmsg_type set to IPV6_PATHMTU, and cmsg_len will indicate that cmsg_data is sizeof(struct ip6_mtuinfo) bytes long. This can happen when the sending node receives a corresponding ICMPv6 packet too big error, or when the packet is sent from a socket with the IPV6_DONTFRAG option being on and the packet size is larger than the MTU of the outgoing interface. This indication is considered as an ancillary data item for a separate (empty) message. Thus, when
When the application is sending packets too big for the path MTU recvmsg() will return zero (indicating no data) but there will be a cmsghdr with cmsg_type set to IPV6_PATHMTU, and cmsg_len will indicate that cmsg_data is sizeof(struct ip6_mtuinfo) bytes long. This can happen when the sending node receives a corresponding ICMPv6 packet too big error, or when the packet is sent from a socket with the IPV6_DONTFRAG option being on and the packet size is larger than the MTU of the outgoing interface. This indication is considered as an ancillary data item for a separate (empty) message. Thus, when
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there are buffered messages (i.e., messages that the application has not received yet) on the socket the application will first receive the buffered messages and then receive the indication.
there are buffered messages (i.e., messages that the application has not received yet) on the socket the application will first receive the buffered messages and then receive the indication.
The first byte of cmsg_data[] will point to a struct ip6_mtuinfo carrying the path MTU to use together with the IPv6 destination address.
The first byte of cmsg_data[] will point to a struct ip6_mtuinfo carrying the path MTU to use together with the IPv6 destination address.
struct ip6_mtuinfo {
struct sockaddr_in6 ip6m_addr; /* dst address including
zone ID */
uint32_t ip6m_mtu; /* path MTU in host byte order */
};
struct ip6_mtuinfo { struct sockaddr_in6 ip6m_addr; /* dst address including zone ID */ uint32_t ip6m_mtu; /* path MTU in host byte order */ };
This cmsghdr will be passed to every socket that sets the IPV6_RECVPATHMTU socket option, even if the socket is non-connected. Note that this also means an application that sets the option may receive an IPV6_MTU ancillary data item for each ICMP too big error the node receives, including such ICMP errors caused by other applications on the node. Thus, an application that wants to perform the path MTU discovery by itself needs to keep history of destinations that it has actually sent to and to compare the address returned in the ip6_mtuinfo structure to the history. An implementation may choose not to delivery data to a connected socket that has a foreign address that is different than the address specified in the ip6m_addr structure.
This cmsghdr will be passed to every socket that sets the IPV6_RECVPATHMTU socket option, even if the socket is non-connected. Note that this also means an application that sets the option may receive an IPV6_MTU ancillary data item for each ICMP too big error the node receives, including such ICMP errors caused by other applications on the node. Thus, an application that wants to perform the path MTU discovery by itself needs to keep history of destinations that it has actually sent to and to compare the address returned in the ip6_mtuinfo structure to the history. An implementation may choose not to delivery data to a connected socket that has a foreign address that is different than the address specified in the ip6m_addr structure.
When an application sends a packet with a routing header, the final destination stored in the ip6m_addr member does not necessarily contain complete information of the entire path.
When an application sends a packet with a routing header, the final destination stored in the ip6m_addr member does not necessarily contain complete information of the entire path.
11.4. Determining the Current Path MTU
11.4. Determining the Current Path MTU
Some applications might need to determine the current path MTU e.g., applications using IPV6_RECVPATHMTU might want to pick a good starting value.
Some applications might need to determine the current path MTU e.g., applications using IPV6_RECVPATHMTU might want to pick a good starting value.
This specification defines a get-only socket option to retrieve the current path MTU value for the destination of a given connected socket. If the IP layer does not have a cached path MTU value it will return the interface MTU for the interface that will be used when sending to the destination address.
This specification defines a get-only socket option to retrieve the current path MTU value for the destination of a given connected socket. If the IP layer does not have a cached path MTU value it will return the interface MTU for the interface that will be used when sending to the destination address.
This information is retrieved using the IPV6_PATHMTU socket option. This option takes a pointer to the ip6_mtuinfo structure as the fourth argument, and the size of the structure should be passed as a value-result parameter in the fifth argument.
This information is retrieved using the IPV6_PATHMTU socket option. This option takes a pointer to the ip6_mtuinfo structure as the fourth argument, and the size of the structure should be passed as a value-result parameter in the fifth argument.
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struct ip6_mtuinfo mtuinfo;
socklen_t infolen = sizeof(mtuinfo);
struct ip6_mtuinfo mtuinfo; socklen_t infolen = sizeof(mtuinfo);
getsockopt(fd, IPPROTO_IPV6, IPV6_PATHMTU, &mtuinfo, &infolen);
getsockopt(fd, IPPROTO_IPV6, IPV6_PATHMTU, &mtuinfo, &infolen);
When the call succeeds, the path MTU value is stored in the ip6m_mtu member of the ip6_mtuinfo structure. Since the socket is connected, the ip6m_addr member is meaningless and should not be referred to by the application.
When the call succeeds, the path MTU value is stored in the ip6m_mtu member of the ip6_mtuinfo structure. Since the socket is connected, the ip6m_addr member is meaningless and should not be referred to by the application.
This option can only be used for a connected socket, because a non- connected socket does not have the information of the destination and there is no way to pass the destination via getsockopt(). When getsockopt() for this option is issued on a non-connected socket, the call will fail. Despite this limitation, this option is still useful from a practical point of view, because applications that care about the path MTU tend to send a lot of packets to a single destination and to connect the socket to the destination for performance reasons. If the application needs to get the MTU value in a more generic way, it should use a more generic interface, such as routing sockets [TCPIPILLUST].
This option can only be used for a connected socket, because a non- connected socket does not have the information of the destination and there is no way to pass the destination via getsockopt(). When getsockopt() for this option is issued on a non-connected socket, the call will fail. Despite this limitation, this option is still useful from a practical point of view, because applications that care about the path MTU tend to send a lot of packets to a single destination and to connect the socket to the destination for performance reasons. If the application needs to get the MTU value in a more generic way, it should use a more generic interface, such as routing sockets [TCPIPILLUST].
12. Ordering of Ancillary Data and IPv6 Extension Headers
12. Ordering of Ancillary Data and IPv6 Extension Headers
Three IPv6 extension headers can be specified by the application and returned to the application using ancillary data with sendmsg() and recvmsg(): the Routing header, Hop-by-Hop options header, and Destination options header. When multiple ancillary data objects are transferred via recvmsg() and these objects represent any of these three extension headers, their placement in the control buffer is directly tied to their location in the corresponding IPv6 datagram. For example, when the application has enabled the IPV6_RECVRTHDR and IPV6_RECVDSTOPTS options and later receives an IPv6 packet with extension headers in the following order:
Three IPv6 extension headers can be specified by the application and returned to the application using ancillary data with sendmsg() and recvmsg(): the Routing header, Hop-by-Hop options header, and Destination options header. When multiple ancillary data objects are transferred via recvmsg() and these objects represent any of these three extension headers, their placement in the control buffer is directly tied to their location in the corresponding IPv6 datagram. For example, when the application has enabled the IPV6_RECVRTHDR and IPV6_RECVDSTOPTS options and later receives an IPv6 packet with extension headers in the following order:
The IPv6 header
A Hop-by-Hop options header
A Destination options header (1)
A Routing header
An Authentication header
A Destination options header (2)
A UDP header and UDP data
The IPv6 header A Hop-by-Hop options header A Destination options header (1) A Routing header An Authentication header A Destination options header (2) A UDP header and UDP data
Stevens, et al. Informational [Page 48] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 48] RFC 3542 Advanced Sockets API for IPv6 May 2003
then the application will receive three ancillary data objects in the following order:
then the application will receive three ancillary data objects in the following order:
an object with cmsg_type set to IPV6_DSTOPTS, which represents
the destination options header (1)
an object with cmsg_type set to IPV6_RTHDR, which represents the
Routing header
an object with cmsg_type set to IPV6_DSTOPTS, which represents the
destination options header (2)
an object with cmsg_type set to IPV6_DSTOPTS, which represents the destination options header (1) an object with cmsg_type set to IPV6_RTHDR, which represents the Routing header an object with cmsg_type set to IPV6_DSTOPTS, which represents the destination options header (2)
This example follows the header ordering described in [RFC-2460], but the receiving side of this specification does not assume the ordering. Applications may receive any numbers of objects in any order according to the ordering of the received IPv6 datagram.
This example follows the header ordering described in [RFC-2460], but the receiving side of this specification does not assume the ordering. Applications may receive any numbers of objects in any order according to the ordering of the received IPv6 datagram.
For the sending side, however, this API imposes some ordering constraints according to [RFC-2460]. Applications using this API cannot make a packet with extension headers that do not follow the ordering. Note, however, that this does not mean applications must always follow the restriction. This is just a limitation in this API in order to give application programmers a guideline to construct headers in a practical manner. Should an application need to make an outgoing packet in an arbitrary order about the extension headers, some other technique, such as the datalink interfaces BPF or DLPI, must be used.
For the sending side, however, this API imposes some ordering constraints according to [RFC-2460]. Applications using this API cannot make a packet with extension headers that do not follow the ordering. Note, however, that this does not mean applications must always follow the restriction. This is just a limitation in this API in order to give application programmers a guideline to construct headers in a practical manner. Should an application need to make an outgoing packet in an arbitrary order about the extension headers, some other technique, such as the datalink interfaces BPF or DLPI, must be used.
The followings are more details about the constraints:
The followings are more details about the constraints:
- Each IPV6_xxx ancillary data object for a particular type of
extension header can be specified at most once in a single control
buffer.
- Each IPV6_xxx ancillary data object for a particular type of extension header can be specified at most once in a single control buffer.
- IPV6_xxx ancillary data objects can appear in any order in a
control buffer, because there is no ambiguity of the ordering.
- IPV6_xxx ancillary data objects can appear in any order in a control buffer, because there is no ambiguity of the ordering.
- Each set of IPV6_xxx ancillary data objects and sticky options
will be put in the outgoing packet along with the header ordering
described in [RFC-2460].
- Each set of IPV6_xxx ancillary data objects and sticky options will be put in the outgoing packet along with the header ordering described in [RFC-2460].
- An ancillary data object or a sticky option of IPV6_RTHDRDSTOPTS
will affect the outgoing packet only when a Routing header is
specified as an ancillary data object or a sticky option.
Otherwise, the specified value for IPV6_RTHDRDSTOPTS will be
ignored.
- An ancillary data object or a sticky option of IPV6_RTHDRDSTOPTS will affect the outgoing packet only when a Routing header is specified as an ancillary data object or a sticky option. Otherwise, the specified value for IPV6_RTHDRDSTOPTS will be ignored.
Stevens, et al. Informational [Page 49] RFC 3542 Advanced Sockets API for IPv6 May 2003
Stevens, et al. Informational [Page 49] RFC 3542 Advanced Sockets API for IPv6 May 2003
For example, when an application sends a UDP datagram with a control data buffer containing ancillary data objects in the following order:
For example, when an application sends a UDP datagram with a control data buffer containing ancillary data objects in the following order:
an object with cmsg_type set to IPV6_DSTOPTS
an object with cmsg_type set to IPV6_RTHDRDSTOPTS
an object with cmsg_type set to IPV6_HOPOPTS
an object with cmsg_type set to IPV6_DSTOPTS an object with cmsg_type set to IPV6_RTHDRDSTOPTS an object with cmsg_type set to IPV6_HOPOPTS
and the sending socket does not have any sticky options, then the outgoing packet would be constructed as follows:
and the sending socket does not have any sticky options, then the outgoing packet would be constructed as follows:
The IPv6 header
A Hop-by-Hop options header
A Destination options header
A UDP header and UDP data
The IPv6 header A Hop-by-Hop options header A Destination options header A UDP header and UDP data
where the destination options header corresponds to the ancillary data object with the type IPV6_DSTOPTS.
where the destination options header corresponds to the ancillary data object with the type IPV6_DSTOPTS.
Note that the constraints above do not necessarily mean that the outgoing packet sent on the wire always follows the header ordering specified in this API document. The kernel may insert additional headers that break the ordering as a result. For example, if the kernel supports Mobile IPv6, an additional destination options header may be inserted before an authentication header, even without a routing header.
Note that the constraints above do not necessarily mean that the outgoing packet sent on the wire always follows the header ordering specified in this API document. The kernel may insert additional headers that break the ordering as a result. For example, if the kernel supports Mobile IPv6, an additional destination options header may be inserted before an authentication header, even without a routing header.
This API does not provide access to any other extension headers than the supported three types of headers. In particular, no information is provided about the IP security headers on an incoming packet, nor can be specified for an outgoing packet. This API is for applications that do not care about the existence of IP security headers.
This API does not provide access to any other extension headers than the supported three types of headers. In particular, no information is provided about the IP security headers on an incoming packet, nor can be specified for an outgoing packet. This API is for applications that do not care about the existence of IP security headers.
13. IPv6-Specific Options with IPv4-Mapped IPv6 Addresses
13. IPv6-Specific Options with IPv4-Mapped IPv6 Addresses
The various socket options and ancillary data specifications defined in this document apply only to true IPv6 sockets. It is possible to create an IPv6 socket that actually sends and receives IPv4 packets, using IPv4-mapped IPv6 addresses, but the mapping of the options defined in this document to an IPv4 datagram is beyond the scope of this document.
The various socket options and ancillary data specifications defined in this document apply only to true IPv6 sockets. It is possible to create an IPv6 socket that actually sends and receives IPv4 packets, using IPv4-mapped IPv6 addresses, but the mapping of the options defined in this document to an IPv4 datagram is beyond the scope of this document.
In general, attempting to specify an IPv6-only option, such as the Hop-by-Hop options, Destination options, or Routing header on an IPv6 socket that is using IPv4-mapped IPv6 addresses, will probably result in an error. Some implementations, however, may provide access to
In general, attempting to specify an IPv6-only option, such as the Hop-by-Hop options, Destination options, or Routing header on an IPv6 socket that is using IPv4-mapped IPv6 addresses, will probably result in an error. Some implementations, however, may provide access to
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Stevens, et al. Informational [Page 50] RFC 3542 Advanced Sockets API for IPv6 May 2003
the packet information (source/destination address, send/receive interface, and hop limit) on an IPv6 socket that is using IPv4-mapped IPv6 addresses.
the packet information (source/destination address, send/receive interface, and hop limit) on an IPv6 socket that is using IPv4-mapped IPv6 addresses.
14. Extended interfaces for rresvport, rcmd and rexec
14. Extended interfaces for rresvport, rcmd and rexec
Library functions that support the "r" commands hide the creation of a socket and the name resolution procedure from an application. When the libraries return an AF_INET6 socket to an application that do not support the address family, the application may encounter an unexpected result when, e.g., calling getpeername() for the socket. In order to support AF_INET6 sockets for the "r" commands while keeping backward compatibility, this section defines some extensions to the libraries.
Library functions that support the "r" commands hide the creation of a socket and the name resolution procedure from an application. When the libraries return an AF_INET6 socket to an application that do not support the address family, the application may encounter an unexpected result when, e.g., calling getpeername() for the socket. In order to support AF_INET6 sockets for the "r" commands while keeping backward compatibility, this section defines some extensions to the libraries.
14.1. rresvport_af
14.1. rresvport_af
The rresvport() function is used by the rcmd() function, and this function is in turn called by many of the "r" commands such as rlogin. While new applications are not being written to use the rcmd() function, legacy applications such as rlogin will continue to use it and these will be ported to IPv6.
The rresvport() function is used by the rcmd() function, and this function is in turn called by many of the "r" commands such as rlogin. While new applications are not being written to use the rcmd() function, legacy applications such as rlogin will continue to use it and these will be ported to IPv6.
rresvport() creates an IPv4/TCP socket and binds a "reserved port" to the socket. Instead of defining an IPv6 version of this function we define a new function that takes an address family as its argument.
rresvport() creates an IPv4/TCP socket and binds a "reserved port" to the socket. Instead of defining an IPv6 version of this function we define a new function that takes an address family as its argument.
#include <unistd.h>
#include <unistd.h>
int rresvport_af(int *port, int family);
int rresvport_af(int *port, int family);
This function behaves the same as the existing rresvport() function, but instead of creating an AF_INET TCP socket, it can also create an AF_INET6 TCP socket. The family argument is either AF_INET or AF_INET6, and a new error return is EAFNOSUPPORT if the address family is not supported.
This function behaves the same as the existing rresvport() function, but instead of creating an AF_INET TCP socket, it can also create an AF_INET6 TCP socket. The family argument is either AF_INET or AF_INET6, and a new error return is EAFNOSUPPORT if the address family is not supported.
(Note: There is little consensus on which header defines the rresvport() and rcmd() function prototypes. 4.4BSD defines it in <unistd.h>, others in <netdb.h>, and others don't define the function prototypes at all.)
(Note: There is little consensus on which header defines the rresvport() and rcmd() function prototypes. 4.4BSD defines it in <unistd.h>, others in <netdb.h>, and others don't define the function prototypes at all.)
14.2. rcmd_af
14.2. rcmd_af
The existing rcmd() function can not transparently use AF_INET6 sockets since an application would not be prepared to handle AF_INET6 addresses returned by e.g., getpeername() on the file descriptor created by rcmd(). Thus a new function is needed.
The existing rcmd() function can not transparently use AF_INET6 sockets since an application would not be prepared to handle AF_INET6 addresses returned by e.g., getpeername() on the file descriptor created by rcmd(). Thus a new function is needed.
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Stevens, et al. Informational [Page 51] RFC 3542 Advanced Sockets API for IPv6 May 2003
int rcmd_af(char **ahost, unsigned short rport,
const char *locuser, const char *remuser,
const char *cmd, int *fd2p, int af)
int rcmd_af(char **ahost, unsigned short rport, const char *locuser, const char *remuser, const char *cmd, int *fd2p, int af)
This function behaves the same as the existing rcmd() function, but instead of creating an AF_INET TCP socket, it can also create an AF_INET6 TCP socket. The family argument is AF_INET, AF_INET6, or AF_UNSPEC. When either AF_INET or AF_INET6 is specified, this function will create a socket of the specified address family. When AF_UNSPEC is specified, it will try all possible address families until a connection can be established, and will return the associated socket of the connection. A new error EAFNOSUPPORT will be returned if the address family is not supported.
This function behaves the same as the existing rcmd() function, but instead of creating an AF_INET TCP socket, it can also create an AF_INET6 TCP socket. The family argument is AF_INET, AF_INET6, or AF_UNSPEC. When either AF_INET or AF_INET6 is specified, this function will create a socket of the specified address family. When AF_UNSPEC is specified, it will try all possible address families until a connection can be established, and will return the associated socket of the connection. A new error EAFNOSUPPORT will be returned if the address family is not supported.
14.3. rexec_af
14.3. rexec_af
The existing rexec() function can not transparently use AF_INET6 sockets since an application would not be prepared to handle AF_INET6 addresses returned by e.g., getpeername() on the file descriptor created by rexec(). Thus a new function is needed.
The existing rexec() function can not transparently use AF_INET6 sockets since an application would not be prepared to handle AF_INET6 addresses returned by e.g., getpeername() on the file descriptor created by rexec(). Thus a new function is needed.
int rexec_af(char **ahost, unsigned short rport, const char *name,
const char *pass, const char *cmd, int *fd2p, int af)
int rexec_af(char **ahost, unsigned short rport, const char *name, const char *pass, const char *cmd, int *fd2p, int af)
This function behaves the same as the existing rexec() function, but instead of creating an AF_INET TCP socket, it can also create an AF_INET6 TCP socket. The family argument is AF_INET, AF_INET6, or AF_UNSPEC. When either AF_INET or AF_INET6 is specified, this function will create a socket of the specified address family. When AF_UNSPEC is specified, it will try all possible address families until a connection can be established, and will return the associated socket of the connection. A new error EAFNOSUPPORT will be returned if the address family is not supported.
This function behaves the same as the existing rexec() function, but instead of creating an AF_INET TCP socket, it can also create an AF_INET6 TCP socket. The family argument is AF_INET, AF_INET6, or AF_UNSPEC. When either AF_INET or AF_INET6 is specified, this function will create a socket of the specified address family. When AF_UNSPEC is specified, it will try all possible address families until a connection can be established, and will return the associated socket of the connection. A new error EAFNOSUPPORT will be returned if the address family is not supported.
15. Summary of New Definitions
15. Summary of New Definitions
The following list summarizes the constants and structure, definitions discussed in this memo, sorted by header.
The following list summarizes the constants and structure, definitions discussed in this memo, sorted by header.
<netinet/icmp6.h> ICMP6_DST_UNREACH
<netinet/icmp6.h> ICMP6_DST_UNREACH_ADDR
<netinet/icmp6.h> ICMP6_DST_UNREACH_ADMIN
<netinet/icmp6.h> ICMP6_DST_UNREACH_BEYONDSCOPE
<netinet/icmp6.h> ICMP6_DST_UNREACH_NOPORT
<netinet/icmp6.h> ICMP6_DST_UNREACH_NOROUTE
<netinet/icmp6.h> ICMP6_ECHO_REPLY
<netinet/icmp6.h> ICMP6_ECHO_REQUEST
<netinet/icmp6.h> ICMP6_INFOMSG_MASK
<netinet/icmp6.h> ICMP6_DST_UNREACH <netinet/icmp6.h> ICMP6_DST_UNREACH_ADDR <netinet/icmp6.h> ICMP6_DST_UNREACH_ADMIN <netinet/icmp6.h> ICMP6_DST_UNREACH_BEYONDSCOPE <netinet/icmp6.h> ICMP6_DST_UNREACH_NOPORT <netinet/icmp6.h> ICMP6_DST_UNREACH_NOROUTE <netinet/icmp6.h> ICMP6_ECHO_REPLY <netinet/icmp6.h> ICMP6_ECHO_REQUEST <netinet/icmp6.h> ICMP6_INFOMSG_MASK
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Stevens, et al. Informational [Page 52] RFC 3542 Advanced Sockets API for IPv6 May 2003
<netinet/icmp6.h> ICMP6_PACKET_TOO_BIG
<netinet/icmp6.h> ICMP6_PARAMPROB_HEADER
<netinet/icmp6.h> ICMP6_PARAMPROB_NEXTHEADER
<netinet/icmp6.h> ICMP6_PARAMPROB_OPTION
<netinet/icmp6.h> ICMP6_PARAM_PROB
<netinet/icmp6.h> ICMP6_ROUTER_RENUMBERING
<netinet/icmp6.h> ICMP6_RR_FLAGS_FORCEAPPLY
<netinet/icmp6.h> ICMP6_RR_FLAGS_PREVDONE
<netinet/icmp6.h> ICMP6_RR_FLAGS_REQRESULT
<netinet/icmp6.h> ICMP6_RR_FLAGS_SPECSITE
<netinet/icmp6.h> ICMP6_RR_FLAGS_TEST
<netinet/icmp6.h> ICMP6_RR_PCOUSE_FLAGS_DECRPLTIME
<netinet/icmp6.h> ICMP6_RR_PCOUSE_FLAGS_DECRVLTIME
<netinet/icmp6.h> ICMP6_RR_PCOUSE_RAFLAGS_AUTO
<netinet/icmp6.h> ICMP6_RR_PCOUSE_RAFLAGS_ONLINK
<netinet/icmp6.h> ICMP6_RR_RESULT_FLAGS_FORBIDDEN
<netinet/icmp6.h> ICMP6_RR_RESULT_FLAGS_OOB
<netinet/icmp6.h> ICMP6_TIME_EXCEEDED
<netinet/icmp6.h> ICMP6_TIME_EXCEED_REASSEMBLY
<netinet/icmp6.h> ICMP6_TIME_EXCEED_TRANSIT
<netinet/icmp6.h> MLD_LISTENER_QUERY
<netinet/icmp6.h> MLD_LISTENER_REDUCTION
<netinet/icmp6.h> MLD_LISTENER_REPORT
<netinet/icmp6.h> ND_NA_FLAG_OVERRIDE
<netinet/icmp6.h> ND_NA_FLAG_ROUTER
<netinet/icmp6.h> ND_NA_FLAG_SOLICITED
<netinet/icmp6.h> ND_NEIGHBOR_ADVERT
<netinet/icmp6.h> ND_NEIGHBOR_SOLICIT
<netinet/icmp6.h> ND_OPT_MTU
<netinet/icmp6.h> ND_OPT_PI_FLAG_AUTO
<netinet/icmp6.h> ND_OPT_PI_FLAG_ONLINK
<netinet/icmp6.h> ND_OPT_PREFIX_INFORMATION
<netinet/icmp6.h> ND_OPT_REDIRECTED_HEADER
<netinet/icmp6.h> ND_OPT_SOURCE_LINKADDR
<netinet/icmp6.h> ND_OPT_TARGET_LINKADDR
<netinet/icmp6.h> ND_RA_FLAG_MANAGED
<netinet/icmp6.h> ND_RA_FLAG_OTHER
<netinet/icmp6.h> ND_REDIRECT
<netinet/icmp6.h> ND_ROUTER_ADVERT
<netinet/icmp6.h> ND_ROUTER_SOLICIT
<netinet/icmp6.h> ICMP6_PACKET_TOO_BIG <netinet/icmp6.h> ICMP6_PARAMPROB_HEADER <netinet/icmp6.h> ICMP6_PARAMPROB_NEXTHEADER <netinet/icmp6.h> ICMP6_PARAMPROB_OPTION <netinet/icmp6.h> ICMP6_PARAM_PROB <netinet/icmp6.h> ICMP6_ROUTER_RENUMBERING <netinet/icmp6.h> ICMP6_RR_FLAGS_FORCEAPPLY <netinet/icmp6.h> ICMP6_RR_FLAGS_PREVDONE <netinet/icmp6.h> ICMP6_RR_FLAGS_REQRESULT <netinet/icmp6.h> ICMP6_RR_FLAGS_SPECSITE <netinet/icmp6.h> ICMP6_RR_FLAGS_TEST <netinet/icmp6.h> ICMP6_RR_PCOUSE_FLAGS_DECRPLTIME <netinet/icmp6.h> ICMP6_RR_PCOUSE_FLAGS_DECRVLTIME <netinet/icmp6.h> ICMP6_RR_PCOUSE_RAFLAGS_AUTO <netinet/icmp6.h> ICMP6_RR_PCOUSE_RAFLAGS_ONLINK <netinet/icmp6.h> ICMP6_RR_RESULT_FLAGS_FORBIDDEN <netinet/icmp6.h> ICMP6_RR_RESULT_FLAGS_OOB <netinet/icmp6.h> ICMP6_TIME_EXCEEDED <netinet/icmp6.h> ICMP6_TIME_EXCEED_REASSEMBLY <netinet/icmp6.h> ICMP6_TIME_EXCEED_TRANSIT <netinet/icmp6.h> MLD_LISTENER_QUERY <netinet/icmp6.h> MLD_LISTENER_REDUCTION <netinet/icmp6.h> MLD_LISTENER_REPORT <netinet/icmp6.h> ND_NA_FLAG_OVERRIDE <netinet/icmp6.h> ND_NA_FLAG_ROUTER <netinet/icmp6.h> ND_NA_FLAG_SOLICITED <netinet/icmp6.h> ND_NEIGHBOR_ADVERT <netinet/icmp6.h> ND_NEIGHBOR_SOLICIT <netinet/icmp6.h> ND_OPT_MTU <netinet/icmp6.h> ND_OPT_PI_FLAG_AUTO <netinet/icmp6.h> ND_OPT_PI_FLAG_ONLINK <netinet/icmp6.h> ND_OPT_PREFIX_INFORMATION <netinet/icmp6.h> ND_OPT_REDIRECTED_HEADER <netinet/icmp6.h> ND_OPT_SOURCE_LINKADDR <netinet/icmp6.h> ND_OPT_TARGET_LINKADDR <netinet/icmp6.h> ND_RA_FLAG_MANAGED <netinet/icmp6.h> ND_RA_FLAG_OTHER <netinet/icmp6.h> ND_REDIRECT <netinet/icmp6.h> ND_ROUTER_ADVERT <netinet/icmp6.h> ND_ROUTER_SOLICIT
<netinet/icmp6.h> struct icmp6_filter{};
<netinet/icmp6.h> struct icmp6_hdr{};
<netinet/icmp6.h> struct icmp6_router_renum{};
<netinet/icmp6.h> struct mld_hdr{};
<netinet/icmp6.h> struct nd_neighbor_advert{};
<netinet/icmp6.h> struct nd_neighbor_solicit{};
<netinet/icmp6.h> struct nd_opt_hdr{};
<netinet/icmp6.h> struct icmp6_filter{}; <netinet/icmp6.h> struct icmp6_hdr{}; <netinet/icmp6.h> struct icmp6_router_renum{}; <netinet/icmp6.h> struct mld_hdr{}; <netinet/icmp6.h> struct nd_neighbor_advert{}; <netinet/icmp6.h> struct nd_neighbor_solicit{}; <netinet/icmp6.h> struct nd_opt_hdr{};
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Stevens, et al. Informational [Page 53] RFC 3542 Advanced Sockets API for IPv6 May 2003
<netinet/icmp6.h> struct nd_opt_mtu{};
<netinet/icmp6.h> struct nd_opt_prefix_info{};
<netinet/icmp6.h> struct nd_opt_rd_hdr{};
<netinet/icmp6.h> struct nd_redirect{};
<netinet/icmp6.h> struct nd_router_advert{};
<netinet/icmp6.h> struct nd_router_solicit{};
<netinet/icmp6.h> struct rr_pco_match{};
<netinet/icmp6.h> struct rr_pco_use{};
<netinet/icmp6.h> struct rr_result{};
<netinet/icmp6.h> struct nd_opt_mtu{}; <netinet/icmp6.h> struct nd_opt_prefix_info{}; <netinet/icmp6.h> struct nd_opt_rd_hdr{}; <netinet/icmp6.h> struct nd_redirect{}; <netinet/icmp6.h> struct nd_router_advert{}; <netinet/icmp6.h> struct nd_router_solicit{}; <netinet/icmp6.h> struct rr_pco_match{}; <netinet/icmp6.h> struct rr_pco_use{}; <netinet/icmp6.h> struct rr_result{};
<netinet/in.h> IPPROTO_AH
<netinet/in.h> IPPROTO_DSTOPTS
<netinet/in.h> IPPROTO_ESP
<netinet/in.h> IPPROTO_FRAGMENT
<netinet/in.h> IPPROTO_HOPOPTS
<netinet/in.h> IPPROTO_ICMPV6
<netinet/in.h> IPPROTO_IPV6
<netinet/in.h> IPPROTO_NONE
<netinet/in.h> IPPROTO_ROUTING
<netinet/in.h> IPV6_CHECKSUM
<netinet/in.h> IPV6_DONTFRAG
<netinet/in.h> IPV6_DSTOPTS
<netinet/in.h> IPV6_HOPLIMIT
<netinet/in.h> IPV6_HOPOPTS
<netinet/in.h> IPPROTO_AH <netinet/in.h> IPPROTO_DSTOPTS <netinet/in.h> IPPROTO_ESP <netinet/in.h> IPPROTO_FRAGMENT <netinet/in.h> IPPROTO_HOPOPTS <netinet/in.h> IPPROTO_ICMPV6 <netinet/in.h> IPPROTO_IPV6 <netinet/in.h> IPPROTO_NONE <netinet/in.h> IPPROTO_ROUTING <netinet/in.h> IPV6_CHECKSUM <netinet/in.h> IPV6_DONTFRAG <netinet/in.h> IPV6_DSTOPTS <netinet/in.h> IPV6_HOPLIMIT <netinet/in.h> IPV6_HOPOPTS
<netinet/in.h> IPV6_NEXTHOP
<netinet/in.h> IPV6_PATHMTU
<netinet/in.h> IPV6_PKTINFO
<netinet/in.h> IPV6_RECVDSTOPTS
<netinet/in.h> IPV6_RECVHOPLIMIT
<netinet/in.h> IPV6_RECVHOPOPTS
<netinet/in.h> IPV6_RECVPKTINFO
<netinet/in.h> IPV6_RECVRTHDR
<netinet/in.h> IPV6_RECVTCLASS
<netinet/in.h> IPV6_RTHDR
<netinet/in.h> IPV6_RTHDRDSTOPTS
<netinet/in.h> IPV6_RTHDR_TYPE_0
<netinet/in.h> IPV6_RECVPATHMTU
<netinet/in.h> IPV6_TCLASS
<netinet/in.h> IPV6_USE_MIN_MTU
<netinet/in.h> struct in6_pktinfo{};
<netinet/in.h> struct ip6_mtuinfo{};
<netinet/in.h> IPV6_NEXTHOP <netinet/in.h> IPV6_PATHMTU <netinet/in.h> IPV6_PKTINFO <netinet/in.h> IPV6_RECVDSTOPTS <netinet/in.h> IPV6_RECVHOPLIMIT <netinet/in.h> IPV6_RECVHOPOPTS <netinet/in.h> IPV6_RECVPKTINFO <netinet/in.h> IPV6_RECVRTHDR <netinet/in.h> IPV6_RECVTCLASS <netinet/in.h> IPV6_RTHDR <netinet/in.h> IPV6_RTHDRDSTOPTS <netinet/in.h> IPV6_RTHDR_TYPE_0 <netinet/in.h> IPV6_RECVPATHMTU <netinet/in.h> IPV6_TCLASS <netinet/in.h> IPV6_USE_MIN_MTU <netinet/in.h> struct in6_pktinfo{}; <netinet/in.h> struct ip6_mtuinfo{};
<netinet/ip6.h> IP6F_MORE_FRAG
<netinet/ip6.h> IP6F_OFF_MASK
<netinet/ip6.h> IP6F_RESERVED_MASK
<netinet/ip6.h> IP6OPT_JUMBO
<netinet/ip6.h> IP6OPT_JUMBO_LEN
<netinet/ip6.h> IP6F_MORE_FRAG <netinet/ip6.h> IP6F_OFF_MASK <netinet/ip6.h> IP6F_RESERVED_MASK <netinet/ip6.h> IP6OPT_JUMBO <netinet/ip6.h> IP6OPT_JUMBO_LEN
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<netinet/ip6.h> IP6OPT_MUTABLE
<netinet/ip6.h> IP6OPT_NSAP_ADDR
<netinet/ip6.h> IP6OPT_PAD1
<netinet/ip6.h> IP6OPT_PADN
<netinet/ip6.h> IP6OPT_ROUTER_ALERT
<netinet/ip6.h> IP6OPT_TUNNEL_LIMIT
<netinet/ip6.h> IP6OPT_TYPE_DISCARD
<netinet/ip6.h> IP6OPT_TYPE_FORCEICMP
<netinet/ip6.h> IP6OPT_TYPE_ICMP
<netinet/ip6.h> IP6OPT_TYPE_SKIP
<netinet/ip6.h> IP6_ALERT_AN
<netinet/ip6.h> IP6_ALERT_MLD
<netinet/ip6.h> IP6_ALERT_RSVP
<netinet/ip6.h> struct ip6_dest{};
<netinet/ip6.h> struct ip6_frag{};
<netinet/ip6.h> struct ip6_hbh{};
<netinet/ip6.h> struct ip6_hdr{};
<netinet/ip6.h> struct ip6_opt{};
<netinet/ip6.h> struct ip6_opt_jumbo{};
<netinet/ip6.h> struct ip6_opt_nsap{};
<netinet/ip6.h> struct ip6_opt_router{};
<netinet/ip6.h> struct ip6_opt_tunnel{};
<netinet/ip6.h> struct ip6_rthdr{};
<netinet/ip6.h> struct ip6_rthdr0{};
<netinet/ip6.h> IP6OPT_MUTABLE <netinet/ip6.h> IP6OPT_NSAP_ADDR <netinet/ip6.h> IP6OPT_PAD1 <netinet/ip6.h> IP6OPT_PADN <netinet/ip6.h> IP6OPT_ROUTER_ALERT <netinet/ip6.h> IP6OPT_TUNNEL_LIMIT <netinet/ip6.h> IP6OPT_TYPE_DISCARD <netinet/ip6.h> IP6OPT_TYPE_FORCEICMP <netinet/ip6.h> IP6OPT_TYPE_ICMP <netinet/ip6.h> IP6OPT_TYPE_SKIP <netinet/ip6.h> IP6_ALERT_AN <netinet/ip6.h> IP6_ALERT_MLD <netinet/ip6.h> IP6_ALERT_RSVP <netinet/ip6.h> struct ip6_dest{}; <netinet/ip6.h> struct ip6_frag{}; <netinet/ip6.h> struct ip6_hbh{}; <netinet/ip6.h> struct ip6_hdr{}; <netinet/ip6.h> struct ip6_opt{}; <netinet/ip6.h> struct ip6_opt_jumbo{}; <netinet/ip6.h> struct ip6_opt_nsap{}; <netinet/ip6.h> struct ip6_opt_router{}; <netinet/ip6.h> struct ip6_opt_tunnel{}; <netinet/ip6.h> struct ip6_rthdr{}; <netinet/ip6.h> struct ip6_rthdr0{};
The following list summarizes the function and macro prototypes discussed in this memo, sorted by header.
The following list summarizes the function and macro prototypes discussed in this memo, sorted by header.
<netinet/icmp6.h> void ICMP6_FILTER_SETBLOCK(int, struct
icmp6_filter *);
<netinet/icmp6.h> void
ICMP6_FILTER_SETBLOCKALL(struct icmp6_filter *);
<netinet/icmp6.h> void
ICMP6_FILTER_SETPASS(int,
struct icmp6_filter *);
<netinet/icmp6.h> void
ICMP6_FILTER_SETPASSALL(struct icmp6_filter *);
<netinet/icmp6.h> int ICMP6_FILTER_WILLBLOCK(int,
const struct icmp6_filter *);
<netinet/icmp6.h> int ICMP6_FILTER_WILLPASS(int,
const struct icmp6_filter *);
<netinet/icmp6.h> void ICMP6_FILTER_SETBLOCK(int, struct icmp6_filter *); <netinet/icmp6.h> void ICMP6_FILTER_SETBLOCKALL(struct icmp6_filter *); <netinet/icmp6.h> void ICMP6_FILTER_SETPASS(int, struct icmp6_filter *); <netinet/icmp6.h> void ICMP6_FILTER_SETPASSALL(struct icmp6_filter *); <netinet/icmp6.h> int ICMP6_FILTER_WILLBLOCK(int, const struct icmp6_filter *); <netinet/icmp6.h> int ICMP6_FILTER_WILLPASS(int, const struct icmp6_filter *);
<netinet/in.h> int IN6_ARE_ADDR_EQUAL(const struct in6_addr *,
const struct in6_addr *);
<netinet/in.h> int IN6_ARE_ADDR_EQUAL(const struct in6_addr *, const struct in6_addr *);
<netinet/in.h> int inet6_opt_append(void *, socklen_t, int,
uint8_t, socklen_t, uint_t,
void **);
<netinet/in.h> int inet6_opt_append(void *, socklen_t, int, uint8_t, socklen_t, uint_t, void **);
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<netinet/in.h> int inet6_opt_get_val(void *, int, void *,
socklen_t);
<netinet/in.h> int inet6_opt_find(void *, socklen_t,
int, uint8_t ,
socklen_t *, void **);
<netinet/in.h> int inet6_opt_finish(void *, socklen_t, int);
<netinet/in.h> int inet6_opt_init(void *, socklen_t);
<netinet/in.h> int inet6_opt_next(void *, socklen_t,
int, uint8_t *,
socklen_t *, void **);
<netinet/in.h> int inet6_opt_set_val(void *, int,
void *, socklen_t);
<netinet/in.h> int inet6_opt_get_val(void *, int, void *, socklen_t); <netinet/in.h> int inet6_opt_find(void *, socklen_t, int, uint8_t , socklen_t *, void **); <netinet/in.h> int inet6_opt_finish(void *, socklen_t, int); <netinet/in.h> int inet6_opt_init(void *, socklen_t); <netinet/in.h> int inet6_opt_next(void *, socklen_t, int, uint8_t *, socklen_t *, void **); <netinet/in.h> int inet6_opt_set_val(void *, int, void *, socklen_t);
<netinet/in.h> int inet6_rth_add(void *,
const struct in6_addr *);
<netinet/in.h> struct in6_addr inet6_rth_getaddr(const void *,
int);
<netinet/in.h> void *inet6_rth_init(void *, socklen_t,
int, int);
<netinet/in.h> int inet6_rth_reverse(const void *, void *);
<netinet/in.h> int inet6_rth_segments(const void *);
<netinet/in.h> soccklen_t inet6_rth_space(int, int);
<netinet/in.h> int inet6_rth_add(void *, const struct in6_addr *); <netinet/in.h> struct in6_addr inet6_rth_getaddr(const void *, int); <netinet/in.h> void *inet6_rth_init(void *, socklen_t, int, int); <netinet/in.h> int inet6_rth_reverse(const void *, void *); <netinet/in.h> int inet6_rth_segments(const void *); <netinet/in.h> soccklen_t inet6_rth_space(int, int);
<netinet/ip6.h> int IP6OPT_TYPE(uint8_t);
<netinet/ip6.h> int IP6OPT_TYPE(uint8_t);
<sys/socket.h> socklen_t CMSG_LEN(socklen_t);
<sys/socket.h> socklen_t CMSG_SPACE(socklen_t);
<sys/socket.h> socklen_t CMSG_LEN(socklen_t); <sys/socket.h> socklen_t CMSG_SPACE(socklen_t);
<unistd.h> int rresvport_af(int *, int);
<unistd.h> int rcmd_af(char **, unsigned short,
const char *, const char *,
const char *, int *, int);
<unistd.h> int rexec_af(char **, unsigned short,
const char *, const char *,
const char *, int *, int);
<unistd.h> int rresvport_af(int *, int); <unistd.h> int rcmd_af(char **, unsigned short, const char *, const char *, const char *, int *, int); <unistd.h> int rexec_af(char **, unsigned short, const char *, const char *, const char *, int *, int);
16. Security Considerations
16. Security Considerations
The setting of certain Hop-by-Hop options and Destination options may be restricted to privileged processes. Similarly some Hop-by-Hop options and Destination options may not be returned to non-privileged applications.
The setting of certain Hop-by-Hop options and Destination options may be restricted to privileged processes. Similarly some Hop-by-Hop options and Destination options may not be returned to non-privileged applications.
The ability to specify an arbitrary source address using IPV6_PKTINFO must be prevented; at least for non-privileged processes.
The ability to specify an arbitrary source address using IPV6_PKTINFO must be prevented; at least for non-privileged processes.
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17. Changes from RFC 2292
17. Changes from RFC 2292
Significant changes that affect the compatibility to RFC 2292:
Significant changes that affect the compatibility to RFC 2292:
- Removed the IPV6_PKTOPTIONS socket option by allowing sticky
options to be set with individual setsockopt() calls.
- Removed the IPV6_PKTOPTIONS socket option by allowing sticky options to be set with individual setsockopt() calls.
- Removed the ability to be able to specify Hop-by-Hop and
Destination options using multiple ancillary data items. The
application, using the inet6_opt_xxx() routines (see below), is
responsible for formatting the whole extension header.
- Removed the ability to be able to specify Hop-by-Hop and Destination options using multiple ancillary data items. The application, using the inet6_opt_xxx() routines (see below), is responsible for formatting the whole extension header.
- Removed the support for the loose/strict Routing header since that
has been removed from the IPv6 specification.
- Removed the support for the loose/strict Routing header since that has been removed from the IPv6 specification.
- Loosened the constraints for jumbo payload option that this option
was always hidden from applications.
- Loosened the constraints for jumbo payload option that this option was always hidden from applications.
- Disabled the use of the IPV6_HOPLIMIT sticky option.
- Disabled the use of the IPV6_HOPLIMIT sticky option.
- Removed ip6r0_addr field from the ip6_rthdr structure.
- Removed ip6r0_addr field from the ip6_rthdr structure.
- Intentionally unspecified how to get received packet's information
on TCP sockets.
- Intentionally unspecified how to get received packet's information on TCP sockets.
New features:
New features:
- Added IPV6_RTHDRDSTOPTS to specify a Destination Options header
before the Routing header.
- Added IPV6_RTHDRDSTOPTS to specify a Destination Options header before the Routing header.
- Added separate IPV6_RECVxxx options to enable the receipt of the
corresponding ancillary data items.
- Added separate IPV6_RECVxxx options to enable the receipt of the corresponding ancillary data items.
- Added inet6_rth_xxx() and inet6_opt_xxx() functions to deal with
routing or IPv6 options headers.
- Added inet6_rth_xxx() and inet6_opt_xxx() functions to deal with routing or IPv6 options headers.
- Added extensions of libraries for the "r" commands.
- Added extensions of libraries for the "r" commands.
- Introduced additional IPv6 option definitions such as IP6OPT_PAD1.
- Introduced additional IPv6 option definitions such as IP6OPT_PAD1.
- Added MLD and router renumbering definitions.
- Added MLD and router renumbering definitions.
- Added MTU-related socket options and ancillary data items.
- Added MTU-related socket options and ancillary data items.
- Added options and ancillary data items to manipulate the traffic
class field.
- Added options and ancillary data items to manipulate the traffic class field.
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- Changed the name of ICMPv6 unreachable code 2 to be "beyond scope
of source address." ICMP6_DST_UNREACH_NOTNEIGHBOR was removed
with this change.
- Changed the name of ICMPv6 unreachable code 2 to be "beyond scope of source address." ICMP6_DST_UNREACH_NOTNEIGHBOR was removed with this change.
Clarifications:
Clarifications:
- Added clarifications on extension headers ordering; for the
sending side, assume the recommended ordering described in RFC
2460. For the receiving side, do not assume any ordering and pass
all headers to the application in the received order.
- Added clarifications on extension headers ordering; for the sending side, assume the recommended ordering described in RFC 2460. For the receiving side, do not assume any ordering and pass all headers to the application in the received order.
- Added a summary about the interface selection rule.
- Added a summary about the interface selection rule.
- Clarified the ordering between IPV6_MULTICAST_IF and the
IPV6_PKTINFO sticky option for multicast packets.
- Clarified the ordering between IPV6_MULTICAST_IF and the IPV6_PKTINFO sticky option for multicast packets.
- Clarified how sticky options and the ICMPv6 filter are turned off
and that getsockopt() of a sticky option returns what was set with
setsockopt().
- Clarified how sticky options and the ICMPv6 filter are turned off and that getsockopt() of a sticky option returns what was set with setsockopt().
- Clarified that IPV6_NEXTHOP should be ignored for a multicast
destination, that it should not contradict with the specified
outgoing interface, and that the next hop should be a sockaddr_in6
structure.
- Clarified that IPV6_NEXTHOP should be ignored for a multicast destination, that it should not contradict with the specified outgoing interface, and that the next hop should be a sockaddr_in6 structure.
- Clarified corner cases of IPV6_CHECKSUM.
- Clarified corner cases of IPV6_CHECKSUM.
- Aligned with the POSIX standard.
- Aligned with the POSIX standard.
Editorial changes:
Editorial changes:
- Replaced MUST with must (since this is an informational document).
- Replaced MUST with must (since this is an informational document).
- Revised abstract to be more clear and concise, particularly
concentrating on differences from RFC 2292.
- Revised abstract to be more clear and concise, particularly concentrating on differences from RFC 2292.
- Made the URL of assigned numbers less specific so that it would be
more robust for future changes.
- Made the URL of assigned numbers less specific so that it would be more robust for future changes.
- Updated the reference to the basic API.
- Updated the reference to the basic API.
- Added a reference to the latest POSIX standard.
- Added a reference to the latest POSIX standard.
- Moved general specifications of ancillary data and CMSG macros to
the appendix.
- Moved general specifications of ancillary data and CMSG macros to the appendix.
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18. References
18. References
[RFC-1981] McCann, J., Deering, S. and J. Mogul, "Path MTU
Discovery for IP version 6", RFC 1981, August 1996.
[RFC-1981] McCann, J., Deering, S. and J. Mogul, "Path MTU Discovery for IP version 6", RFC 1981, August 1996.
[RFC-2460] Deering, S. and R. Hinden, "Internet Protocol, Version
6 (IPv6) Specification", RFC 2460, December 1998.
[RFC-2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998.
[RFC-3493] Gilligan, R., Thomson, S., Bound, J., McCann, J. and
W. Stevens, "Basic Socket Interface Extensions for
IPv6", RFC 3493, March 2003.
[RFC-3493] Gilligan, R., Thomson, S., Bound, J., McCann, J. and W. Stevens, "Basic Socket Interface Extensions for IPv6", RFC 3493, March 2003.
[POSIX] IEEE Std. 1003.1-2001 Standard for Information
Technology -- Portable Operating System Interface
(POSIX). Open group Technical Standard: Base
Specifications, Issue 6, December 2001. ISO/IEC
9945:2002. http://www.opengroup.org/austin
[POSIX] IEEE Std. 1003.1-2001 Standard for Information Technology -- Portable Operating System Interface (POSIX). Open group Technical Standard: Base Specifications, Issue 6, December 2001. ISO/IEC 9945:2002. http://www.opengroup.org/austin
[TCPIPILLUST] Wright, G., Stevens, W., "TCP/IP Illustrated, Volume 2:
The Implementation", Addison Wesley, 1994.
[TCPIPILLUST] Wright, G., Stevens, W., "TCP/IP Illustrated, Volume 2: The Implementation", Addison Wesley, 1994.
19. Acknowledgments
19. Acknowledgments
Matt Thomas and Jim Bound have been working on the technical details in this document for over a year. Keith Sklower is the original implementor of ancillary data in the BSD networking code. Craig Metz provided lots of feedback, suggestions, and comments based on his implementing many of these features as the document was being written. Mark Andrews first proposed the idea of the IPV6_USE_MIN_MTU option. Jun-ichiro Hagino contributed text for the traffic class API from a document of his own.
Matt Thomas and Jim Bound have been working on the technical details in this document for over a year. Keith Sklower is the original implementor of ancillary data in the BSD networking code. Craig Metz provided lots of feedback, suggestions, and comments based on his implementing many of these features as the document was being written. Mark Andrews first proposed the idea of the IPV6_USE_MIN_MTU option. Jun-ichiro Hagino contributed text for the traffic class API from a document of his own.
The following provided comments on earlier drafts: Pascal Anelli, Hamid Asayesh, Ran Atkinson, Karl Auerbach, Hamid Asayesh, Don Coolidge, Matt Crawford, Sam T. Denton, Richard Draves, Francis Dupont, Toerless Eckert, Lilian Fernandes, Bob Gilligan, Gerri Harter, Tim Hartrick, Bob Halley, Masaki Hirabaru, Michael Hunter, Yoshinobu Inoue, Mukesh Kacker, A. N. Kuznetsov, Sam Manthorpe, Pedro Marques, Jack McCann, der Mouse, John Moy, Lori Napoli, Thomas Narten, Atsushi Onoe, Steve Parker, Charles Perkins, Ken Powell, Tom Pusateri, Pedro Roque, Sameer Shah, Peter Sjodin, Stephen P. Spackman, Jinmei Tatuya, Karen Tracey, Sowmini Varadhan, Quaizar Vohra, Carl Williams, Steve Wise, Eric Wong, Farrell Woods, Kazu Yamamoto, Vladislav Yasevich, and Yoshifuji Hideaki.
The following provided comments on earlier drafts: Pascal Anelli, Hamid Asayesh, Ran Atkinson, Karl Auerbach, Hamid Asayesh, Don Coolidge, Matt Crawford, Sam T. Denton, Richard Draves, Francis Dupont, Toerless Eckert, Lilian Fernandes, Bob Gilligan, Gerri Harter, Tim Hartrick, Bob Halley, Masaki Hirabaru, Michael Hunter, Yoshinobu Inoue, Mukesh Kacker, A. N. Kuznetsov, Sam Manthorpe, Pedro Marques, Jack McCann, der Mouse, John Moy, Lori Napoli, Thomas Narten, Atsushi Onoe, Steve Parker, Charles Perkins, Ken Powell, Tom Pusateri, Pedro Roque, Sameer Shah, Peter Sjodin, Stephen P. Spackman, Jinmei Tatuya, Karen Tracey, Sowmini Varadhan, Quaizar Vohra, Carl Williams, Steve Wise, Eric Wong, Farrell Woods, Kazu Yamamoto, Vladislav Yasevich, and Yoshifuji Hideaki.
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20. Appendix A: Ancillary Data Overview
20. Appendix A: Ancillary Data Overview
4.2BSD allowed file descriptors to be transferred between separate processes across a UNIX domain socket using the sendmsg() and recvmsg() functions. Two members of the msghdr structure, msg_accrights and msg_accrightslen, were used to send and receive the descriptors. When the OSI protocols were added to 4.3BSD Reno in 1990 the names of these two fields in the msghdr structure were changed to msg_control and msg_controllen, because they were used by the OSI protocols for "control information", although the comments in the source code call this "ancillary data".
4.2BSD allowed file descriptors to be transferred between separate processes across a UNIX domain socket using the sendmsg() and recvmsg() functions. Two members of the msghdr structure, msg_accrights and msg_accrightslen, were used to send and receive the descriptors. When the OSI protocols were added to 4.3BSD Reno in 1990 the names of these two fields in the msghdr structure were changed to msg_control and msg_controllen, because they were used by the OSI protocols for "control information", although the comments in the source code call this "ancillary data".
Other than the OSI protocols, the use of ancillary data has been rare. In 4.4BSD, for example, the only use of ancillary data with IPv4 is to return the destination address of a received UDP datagram if the IP_RECVDSTADDR socket option is set. With Unix domain sockets ancillary data is still used to send and receive descriptors.
Other than the OSI protocols, the use of ancillary data has been rare. In 4.4BSD, for example, the only use of ancillary data with IPv4 is to return the destination address of a received UDP datagram if the IP_RECVDSTADDR socket option is set. With Unix domain sockets ancillary data is still used to send and receive descriptors.
Nevertheless the ancillary data fields of the msghdr structure provide a clean way to pass information in addition to the data that is being read or written. The inclusion of the msg_control and msg_controllen members of the msghdr structure along with the cmsghdr structure that is pointed to by the msg_control member is required by the Posix sockets API standard.
Nevertheless the ancillary data fields of the msghdr structure provide a clean way to pass information in addition to the data that is being read or written. The inclusion of the msg_control and msg_controllen members of the msghdr structure along with the cmsghdr structure that is pointed to by the msg_control member is required by the Posix sockets API standard.
20.1. The msghdr Structure
20.1. The msghdr Structure
The msghdr structure is used by the recvmsg() and sendmsg() functions. Its Posix definition is:
The msghdr structure is used by the recvmsg() and sendmsg() functions. Its Posix definition is:
struct msghdr {
void *msg_name; /* ptr to socket address
structure */
socklen_t msg_namelen; /* size of socket address
structure */
struct iovec *msg_iov; /* scatter/gather array */
int msg_iovlen; /* # elements in msg_iov */
void *msg_control; /* ancillary data */
socklen_t msg_controllen; /* ancillary data buffer length */
int msg_flags; /* flags on received message */
};
struct msghdr { void *msg_name; /* ptr to socket address structure */ socklen_t msg_namelen; /* size of socket address structure */ struct iovec *msg_iov; /* scatter/gather array */ int msg_iovlen; /* # elements in msg_iov */ void *msg_control; /* ancillary data */ socklen_t msg_controllen; /* ancillary data buffer length */ int msg_flags; /* flags on received message */ };
The structure is declared as a result of including <sys/socket.h>.
The structure is declared as a result of including <sys/socket.h>.
(Note: Before Posix the two "void *" pointers were typically "char *", and the two socklen_t members were typically integers. Earlier drafts of Posix had the two socklen_t members as size_t, but it then changed these to socklen_t to simplify binary portability for 64-bit
(Note: Before Posix the two "void *" pointers were typically "char *", and the two socklen_t members were typically integers. Earlier drafts of Posix had the two socklen_t members as size_t, but it then changed these to socklen_t to simplify binary portability for 64-bit
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implementations and to align Posix with X/Open's Networking Services, Issue 5. The change in msg_control to a "void *" pointer affects any code that increments this pointer.)
implementations and to align Posix with X/Open's Networking Services, Issue 5. The change in msg_control to a "void *" pointer affects any code that increments this pointer.)
Most Berkeley-derived implementations limit the amount of ancillary data in a call to sendmsg() to no more than 108 bytes (an mbuf). This API requires a minimum of 10240 bytes of ancillary data, but it is recommended that the amount be limited only by the buffer space reserved by the socket (which can be modified by the SO_SNDBUF socket option). (Note: This magic number 10240 was picked as a value that should always be large enough. 108 bytes is clearly too small as the maximum size of a Routing header is 2048 bytes.)
Most Berkeley-derived implementations limit the amount of ancillary data in a call to sendmsg() to no more than 108 bytes (an mbuf). This API requires a minimum of 10240 bytes of ancillary data, but it is recommended that the amount be limited only by the buffer space reserved by the socket (which can be modified by the SO_SNDBUF socket option). (Note: This magic number 10240 was picked as a value that should always be large enough. 108 bytes is clearly too small as the maximum size of a Routing header is 2048 bytes.)
20.2. The cmsghdr Structure
20.2. The cmsghdr Structure
The cmsghdr structure describes ancillary data objects transferred by recvmsg() and sendmsg(). Its Posix definition is:
The cmsghdr structure describes ancillary data objects transferred by recvmsg() and sendmsg(). Its Posix definition is:
struct cmsghdr {
socklen_t cmsg_len; /* #bytes, including this header */
int cmsg_level; /* originating protocol */
int cmsg_type; /* protocol-specific type */
/* followed by unsigned char cmsg_data[]; */
};
struct cmsghdr { socklen_t cmsg_len; /* #bytes, including this header */ int cmsg_level; /* originating protocol */ int cmsg_type; /* protocol-specific type */ /* followed by unsigned char cmsg_data[]; */ };
This structure is declared as a result of including <sys/socket.h>.
This structure is declared as a result of including <sys/socket.h>.
(Note: Before Posix the cmsg_len member was an integer, and not a socklen_t. See the Note in the previous section for why socklen_t is used here.)
(Note: Before Posix the cmsg_len member was an integer, and not a socklen_t. See the Note in the previous section for why socklen_t is used here.)
As shown in this definition, normally there is no member with the name cmsg_data[]. Instead, the data portion is accessed using the CMSG_xxx() macros, as described in Section 20.3. Nevertheless, it is common to refer to the cmsg_data[] member.
As shown in this definition, normally there is no member with the name cmsg_data[]. Instead, the data portion is accessed using the CMSG_xxx() macros, as described in Section 20.3. Nevertheless, it is common to refer to the cmsg_data[] member.
When ancillary data is sent or received, any number of ancillary data objects can be specified by the msg_control and msg_controllen members of the msghdr structure, because each object is preceded by a cmsghdr structure defining the object's length (the cmsg_len member). Historically Berkeley-derived implementations have passed only one object at a time, but this API allows multiple objects to be passed in a single call to sendmsg() or recvmsg(). The following example shows two ancillary data objects in a control buffer.
When ancillary data is sent or received, any number of ancillary data objects can be specified by the msg_control and msg_controllen members of the msghdr structure, because each object is preceded by a cmsghdr structure defining the object's length (the cmsg_len member). Historically Berkeley-derived implementations have passed only one object at a time, but this API allows multiple objects to be passed in a single call to sendmsg() or recvmsg(). The following example shows two ancillary data objects in a control buffer.
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|<--------------------------- msg_controllen ------------------------->| | OR | |<--------------------------- msg_controllen ---------------------->| | | |<----- ancillary data object ----->|<---- ancillary data object ----->| |<------ min CMSG_SPACE() --------->|<----- min CMSG_SPACE() --------->| | | | |<---------- cmsg_len ---------->| |<-------- cmsg_len ----------->| | |<--------- CMSG_LEN() --------->| |<------- CMSG_LEN() ---------->| | | | | | | +-----+-----+-----+--+-----------+--+-----+-----+-----+--+----------+--+ |cmsg_|cmsg_|cmsg_|XX| cmsg_ |XX|cmsg_|cmsg_|cmsg_|XX| cmsg_ |XX| |len |level|type |XX| data[] |XX|len |level|type |XX| data[] |XX| +-----+-----+-----+--+-----------+--+-----+-----+-----+--+----------+--+ ^ | msg_control points here
|<--------------------------- msg_controllen ------------------------->| | OR | |<--------------------------- msg_controllen ---------------------->| | | |<----- ancillary data object ----->|<---- ancillary data object ----->| |<------ min CMSG_SPACE() --------->|<----- min CMSG_SPACE() --------->| | | | |<---------- cmsg_len ---------->| |<-------- cmsg_len ----------->| | |<--------- CMSG_LEN() --------->| |<------- CMSG_LEN() ---------->| | | | | | | +-----+-----+-----+--+-----------+--+-----+-----+-----+--+----------+--+ |cmsg_|cmsg_|cmsg_|XX| cmsg_ |XX|cmsg_|cmsg_|cmsg_|XX| cmsg_ |XX| |len |level|type |XX| data[] |XX|len |level|type |XX| data[] |XX| +-----+-----+-----+--+-----------+--+-----+-----+-----+--+----------+--+ ^ | msg_control points here
The fields shown as "XX" are possible padding, between the cmsghdr structure and the data, and between the data and the next cmsghdr structure, if required by the implementation. While sending an application may or may not include padding at the end of last ancillary data in msg_controllen and implementations must accept both as valid. On receiving a portable application must provide space for padding at the end of the last ancillary data as implementations may copy out the padding at the end of the control message buffer and include it in the received msg_controllen. When recvmsg() is called if msg_controllen is too small for all the ancillary data items including any trailing padding after the last item an implementation may set MSG_CTRUNC.
The fields shown as "XX" are possible padding, between the cmsghdr structure and the data, and between the data and the next cmsghdr structure, if required by the implementation. While sending an application may or may not include padding at the end of last ancillary data in msg_controllen and implementations must accept both as valid. On receiving a portable application must provide space for padding at the end of the last ancillary data as implementations may copy out the padding at the end of the control message buffer and include it in the received msg_controllen. When recvmsg() is called if msg_controllen is too small for all the ancillary data items including any trailing padding after the last item an implementation may set MSG_CTRUNC.
20.3. Ancillary Data Object Macros
20.3. Ancillary Data Object Macros
To aid in the manipulation of ancillary data objects, three macros from 4.4BSD are defined by Posix: CMSG_DATA(), CMSG_NXTHDR(), and CMSG_FIRSTHDR(). Before describing these macros, we show the following example of how they might be used with a call to recvmsg().
To aid in the manipulation of ancillary data objects, three macros from 4.4BSD are defined by Posix: CMSG_DATA(), CMSG_NXTHDR(), and CMSG_FIRSTHDR(). Before describing these macros, we show the following example of how they might be used with a call to recvmsg().
struct msghdr msg;
struct cmsghdr *cmsgptr;
struct msghdr msg; struct cmsghdr *cmsgptr;
/* fill in msg */
/* fill in msg */
/* call recvmsg() */
/* call recvmsg() */
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for (cmsgptr = CMSG_FIRSTHDR(&msg); cmsgptr != NULL;
cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)) {
if (cmsgptr->cmsg_len == 0) {
/* Error handling */
break;
}
if (cmsgptr->cmsg_level == ... &&
cmsgptr->cmsg_type == ... ) {
u_char *ptr;
for (cmsgptr = CMSG_FIRSTHDR(&msg); cmsgptr != NULL; cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)) { if (cmsgptr->cmsg_len == 0) { /* Error handling */ break; } if (cmsgptr->cmsg_level == ... && cmsgptr->cmsg_type == ... ) { u_char *ptr;
ptr = CMSG_DATA(cmsgptr);
/* process data pointed to by ptr */
}
}
ptr = CMSG_DATA(cmsgptr); /* process data pointed to by ptr */ } }
We now describe the three Posix macros, followed by two more that are new with this API: CMSG_SPACE() and CMSG_LEN(). All these macros are defined as a result of including <sys/socket.h>.
We now describe the three Posix macros, followed by two more that are new with this API: CMSG_SPACE() and CMSG_LEN(). All these macros are defined as a result of including <sys/socket.h>.
20.3.1. CMSG_FIRSTHDR
20.3.1. CMSG_FIRSTHDR
struct cmsghdr *CMSG_FIRSTHDR(const struct msghdr *mhdr);
struct cmsghdr *CMSG_FIRSTHDR(const struct msghdr *mhdr);
CMSG_FIRSTHDR() returns a pointer to the first cmsghdr structure in the msghdr structure pointed to by mhdr. The macro returns NULL if there is no ancillary data pointed to by the msghdr structure (that is, if either msg_control is NULL or if msg_controllen is less than the size of a cmsghdr structure).
CMSG_FIRSTHDR() returns a pointer to the first cmsghdr structure in the msghdr structure pointed to by mhdr. The macro returns NULL if there is no ancillary data pointed to by the msghdr structure (that is, if either msg_control is NULL or if msg_controllen is less than the size of a cmsghdr structure).
One possible implementation could be
One possible implementation could be
#define CMSG_FIRSTHDR(mhdr) \
( (mhdr)->msg_controllen >= sizeof(struct cmsghdr) ? \
(struct cmsghdr *)(mhdr)->msg_control : \
(struct cmsghdr *)NULL )
#define CMSG_FIRSTHDR(mhdr) \ ( (mhdr)->msg_controllen >= sizeof(struct cmsghdr) ? \ (struct cmsghdr *)(mhdr)->msg_control : \ (struct cmsghdr *)NULL )
(Note: Most existing implementations do not test the value of msg_controllen, and just return the value of msg_control. The value of msg_controllen must be tested, because if the application asks recvmsg() to return ancillary data, by setting msg_control to point to the application's buffer and setting msg_controllen to the length of this buffer, the kernel indicates that no ancillary data is available by setting msg_controllen to 0 on return. It is also easier to put this test into this macro, than making the application perform the test.)
(Note: Most existing implementations do not test the value of msg_controllen, and just return the value of msg_control. The value of msg_controllen must be tested, because if the application asks recvmsg() to return ancillary data, by setting msg_control to point to the application's buffer and setting msg_controllen to the length of this buffer, the kernel indicates that no ancillary data is available by setting msg_controllen to 0 on return. It is also easier to put this test into this macro, than making the application perform the test.)
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Stevens, et al. Informational [Page 63] RFC 3542 Advanced Sockets API for IPv6 May 2003
20.3.2. CMSG_NXTHDR
20.3.2. CMSG_NXTHDR
As described in Section 5.1, CMSG_NXTHDR has been extended to handle a NULL 2nd argument to mean "get the first header". This provides an alternative way of coding the processing loop shown earlier:
As described in Section 5.1, CMSG_NXTHDR has been extended to handle a NULL 2nd argument to mean "get the first header". This provides an alternative way of coding the processing loop shown earlier:
struct msghdr msg;
struct cmsghdr *cmsgptr = NULL;
struct msghdr msg; struct cmsghdr *cmsgptr = NULL;
/* fill in msg */
/* fill in msg */
/* call recvmsg() */
/* call recvmsg() */
while ((cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)) != NULL) {
if (cmsgptr->cmsg_len == 0) {
/* Error handling */
break;
}
if (cmsgptr->cmsg_level == ... &&
cmsgptr->cmsg_type == ... ) {
u_char *ptr;
while ((cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)) != NULL) { if (cmsgptr->cmsg_len == 0) { /* Error handling */ break; } if (cmsgptr->cmsg_level == ... && cmsgptr->cmsg_type == ... ) { u_char *ptr;
ptr = CMSG_DATA(cmsgptr);
/* process data pointed to by ptr */
}
}
ptr = CMSG_DATA(cmsgptr); /* process data pointed to by ptr */ } }
One possible implementation could be:
One possible implementation could be:
#define CMSG_NXTHDR(mhdr, cmsg) \
(((cmsg) == NULL) ? CMSG_FIRSTHDR(mhdr) : \
(((u_char *)(cmsg) + ALIGN_H((cmsg)->cmsg_len) \
+ ALIGN_D(sizeof(struct cmsghdr)) > \
(u_char *)((mhdr)->msg_control) + (mhdr)->msg_controllen) ? \
(struct cmsghdr *)NULL : \
(struct cmsghdr *)((u_char *)(cmsg) + \
ALIGN_H((cmsg)->cmsg_len))))
#define CMSG_NXTHDR(mhdr, cmsg) \ (((cmsg) == NULL) ? CMSG_FIRSTHDR(mhdr) : \ (((u_char *)(cmsg) + ALIGN_H((cmsg)->cmsg_len) \ + ALIGN_D(sizeof(struct cmsghdr)) > \ (u_char *)((mhdr)->msg_control) + (mhdr)->msg_controllen) ? \ (struct cmsghdr *)NULL : \ (struct cmsghdr *)((u_char *)(cmsg) + \ ALIGN_H((cmsg)->cmsg_len))))
The macros ALIGN_H() and ALIGN_D(), which are implementation dependent, round their arguments up to the next even multiple of whatever alignment is required for the start of the cmsghdr structure and the data, respectively. (This is probably a multiple of 4 or 8 bytes.) They are often the same macro in implementations platforms where alignment requirement for header and data is chosen to be identical.
マクロのALIGN_H()とALIGN()がそれぞれcmsghdr構造とデータの始まりに必要です。(ALIGN()は整列がことなら何でもであるかに関する次の同等の倍数までの彼らの議論の周りで実現に依存しています)。 (これはたぶん4バイトか8バイトの倍数です。) それらはヘッダーのための整列要求とデータが同じになるように選ばれている実現プラットホームのしばしば同じマクロです。
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20.3.3. CMSG_DATA
20.3.3. CMSG_データ
unsigned char *CMSG_DATA(const struct cmsghdr *cmsg);
無記名の炭*のCMSG_DATA(const struct cmsghdr*cmsg)。
CMSG_DATA() returns a pointer to the data (what is called the cmsg_data[] member, even though such a member is not defined in the structure) following a cmsghdr structure.
CMSG_DATA()がポインタをデータに返す、(そのようなメンバーは構造) 次のa cmsghdr構造で定義されませんが、何がcmsg_データ[]メンバーと呼ばれますか?
One possible implementation could be:
1つの可能な実現は以下の通りであるかもしれません。
#define CMSG_DATA(cmsg) ( (u_char *)(cmsg) + \
ALIGN_D(sizeof(struct cmsghdr)) )
#CMSG_DATA(cmsg)を定義してください。((u_炭*)(cmsg)+\ALIGN(sizeof(struct cmsghdr)))
20.3.4. CMSG_SPACE
20.3.4. CMSG_スペース
CMSG_SPACE is new with this API (see Section 5.2). It is used to determine how much space needs to be allocated for an ancillary data item.
CMSG_SPACEはこのAPIで新しいです(セクション5.2を見てください)。 それは、どのくらいのスペースが、補助データ項目のために割り当てられる必要であるかを決定するのに使用されます。
One possible implementation could be:
1つの可能な実現は以下の通りであるかもしれません。
#define CMSG_SPACE(length) ( ALIGN_D(sizeof(struct cmsghdr)) + \
ALIGN_H(length) )
#CMSG_SPACE(長さ)を定義してください。(ALIGN(sizeof(struct cmsghdr))+\ALIGN_H(長さ))
20.3.5. CMSG_LEN
20.3.5. CMSG_レン
CMSG_LEN is new with this API (see Section 5.3). It returns the value to store in the cmsg_len member of the cmsghdr structure, taking into account any padding needed to satisfy alignment requirements.
CMSG_LENはこのAPIで新しいです(セクション5.3を見てください)。 それはcmsghdr構造のcmsg_len部材に格納する値を返します、整列要求を満たすのに必要であるどんな詰め物も考慮に入れて。
One possible implementation could be:
1つの可能な実現は以下の通りであるかもしれません。
#define CMSG_LEN(length) ( ALIGN_D(sizeof(struct cmsghdr)) + \
length )
#CMSG_LEN(長さ)を定義してください。(ALIGN(sizeof(struct cmsghdr))+\長さ)
21. Appendix B: Examples Using the inet6_rth_XXX() Functions
21. 付録B: inet6_rth_XXX()機能を使用する例
Here we show an example for both sending Routing headers and processing and reversing a received Routing header.
ここに、私たちはルート設定ヘッダーと処理を送って、容認されたルート設定ヘッダーを逆にするための例を示しています。
21.1. Sending a Routing Header
21.1. ルート設定ヘッダーを送ります。
As an example of these Routing header functions defined in this document, we go through the function calls for the example on p. 17 of [RFC-2460]. The source is S, the destination is D, and the three intermediate nodes are I1, I2, and I3.
本書では定義されたこれらのルート設定ヘッダー機能に関する例として、私たちはpに関する例のためのファンクションコールに直面しています。 17[RFC-2460。] 3つの中間的ノードが、ソースはSであり、目的地はDであり、I1と、I2と、I3です。
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S -----> I1 -----> I2 -----> I3 -----> D
S----->I1----->I2----->I3----->D
src: * S S S S S
dst: D I1 I2 I3 D D
A[1]: I1 I2 I1 I1 I1 I1
A[2]: I2 I3 I3 I2 I2 I2
A[3]: I3 D D D I3 I3
#seg: 3 3 2 1 0 3
src: * S S S S S dst: D I1 I2 I3D D A[1]: I1 I2 I1 I1 I1 I1 A[2]: I2 I3 I3 I2 I2 I2 A[3]: I3D D D I3 I3#seg: 3 3 2 1 0 3
src and dst are the source and destination IPv6 addresses in the IPv6 header. A[1], A[2], and A[3] are the three addresses in the Routing header. #seg is the Segments Left field in the Routing header.
srcとdstはIPv6がIPv6ヘッダーで演説するソースと目的地です。 A[1]、A[2]、およびA[3]はルート設定ヘッダーの3つのアドレスです。 #segはルート設定ヘッダーのSegments Left分野です。
The six values in the column beneath node S are the values in the Routing header specified by the sending application using sendmsg() of setsockopt(). The function calls by the sender would look like:
ノードSの下のコラムの6つの値がsetsockopt()のsendmsg()を使用しながら送付アプリケーションで指定されたルート設定ヘッダーの値です。 送付者によるファンクションコールに似ているでしょう:
void *extptr;
socklen_t extlen;
struct msghdr msg;
struct cmsghdr *cmsgptr;
int cmsglen;
struct sockaddr_in6 I1, I2, I3, D;
*extptrを欠如させてください。 socklen_t extlen。 struct msghdr msg。 struct cmsghdr*cmsgptr。 int cmsglen。 struct sockaddr_in6 I1、I2、I3、D。
extlen = inet6_rth_space(IPV6_RTHDR_TYPE_0, 3);
cmsglen = CMSG_SPACE(extlen);
cmsgptr = malloc(cmsglen);
cmsgptr->cmsg_len = CMSG_LEN(extlen);
cmsgptr->cmsg_level = IPPROTO_IPV6;
cmsgptr->cmsg_type = IPV6_RTHDR;
extlenはinet6_rth_スペース(IPV6_RTHDR_TYPE_0、3)と等しいです。 cmsglenはCMSG_SPACEと等しいです(extlenします)。 cmsgptrはmallocと等しいです(cmsglenします)。 cmsgptr>のcmsg_lenはCMSG_LENと等しいです(extlenします)。 cmsgptr>cmsg_平らな=IPPROTO_IPV6。 cmsg_がIPV6_RTHDRと等しいのをタイプするcmsgptr->。
extptr = CMSG_DATA(cmsgptr);
extptr = inet6_rth_init(extptr, extlen, IPV6_RTHDR_TYPE_0, 3);
extptrはCMSG_DATAと等しいです(cmsgptr)。 extptrはinet6_rth_イニット(extptr、extlen、IPV6_RTHDR_TYPE_0、3)と等しいです。
inet6_rth_add(extptr, &I1.sin6_addr);
inet6_rth_add(extptr, &I2.sin6_addr);
inet6_rth_add(extptr, &I3.sin6_addr);
inet6_rth_は(extptr、およびI1.sin6_addr)を加えます。 inet6_rth_は(extptr、およびI2.sin6_addr)を加えます。 inet6_rth_は(extptr、およびI3.sin6_addr)を加えます。
msg.msg_control = cmsgptr;
msg.msg_controllen = cmsglen;
msg.msg_コントロールはcmsgptrと等しいです。 msg.msg_controllenはcmsglenと等しいです。
/* finish filling in msg{}, msg_name = D */
/* call sendmsg() */
中にmsgをいっぱいにする/*終わり、msg_名前=D*//*呼び出しsendmsg()*/
We also assume that the source address for the socket is not specified (i.e., the asterisk in the figure).
また、私たちは、ソケットのためのソースアドレスが指定されない(すなわち、図のアスタリスク)と思います。
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The four columns of six values that are then shown between the five nodes are the values of the fields in the packet while the packet is in transit between the two nodes. Notice that before the packet is sent by the source node S, the source address is chosen (replacing the asterisk), I1 becomes the destination address of the datagram, the two addresses A[2] and A[3] are "shifted up", and D is moved to A[3].
パケットはトランジット2つのノードの間で中ですが、次に5つのノードの間に示される4つのコラムの6つの値がパケットの分野の値です。 ソースノードSでパケットを送る前にソースアドレスを選んで(アスタリスクを置き換えて)、I1がアドレスのA[2]とA[3]が「移行する」データグラム、2つのものの送付先アドレスになって、DをA[3]に動かすのに注意してください。
The columns of values that are shown beneath the destination node are the values returned by recvmsg(), assuming the application has enabled both the IPV6_RECVPKTINFO and IPV6_RECVRTHDR socket options. The source address is S (contained in the sockaddr_in6 structure pointed to by the msg_name member), the destination address is D (returned as an ancillary data object in an in6_pktinfo structure), and the ancillary data object specifying the Routing header will contain three addresses (I1, I2, and I3). The number of segments in the Routing header is known from the Hdr Ext Len field in the Routing header (a value of 6, indicating 3 addresses).
目的地ノードの下に示される値に関するコラムはrecvmsg()によって返された値です、アプリケーションがIPV6_RECVPKTINFOとIPV6_RECVRTHDRソケットオプションの両方を可能にしたと仮定して。 ソースアドレスはS(メンバーというmsg_名前によって示されたsockaddr_in6構造では、含まれている)です、そして、送付先アドレスはD(補助データ物として、in6_pktinfo構造では、戻る)です、そして、ルート設定ヘッダーを指定する補助データ物は3つのアドレス(I1、I2、およびI3)を含むでしょう。 ルート設定ヘッダーのセグメントの数はルート設定ヘッダー(3つのアドレスを示す6の値)のHdr Extレン分野から知られています。
The return value from inet6_rth_segments() will be 3 and inet6_rth_getaddr(0) will return I1, inet6_rth_getaddr(1) will return I2, and inet6_rth_getaddr(2) will return I3,
inet6_rth_セグメント()からのリターン値は、3とinet6_になるでしょう、そして、rth_getaddr(0)がI1を返すinet6_rth_getaddr(1)はI2を返すでしょう、そして、inet6_rth_getaddr(2)はI3を返すでしょう。
If the receiving application then calls inet6_rth_reverse(), the order of the three addresses will become I3, I2, and I1.
次に、受信アプリケーションが呼ぶと、inet6_rth_逆()、3つのアドレスの注文はI3、I2、およびI1になるでしょう。
We can also show what an implementation might store in the ancillary data object as the Routing header is being built by the sending process. If we assume a 32-bit architecture where sizeof(struct cmsghdr) equals 12, with a desired alignment of 4-byte boundaries, then the call to inet6_rth_space(3) returns 68: 12 bytes for the cmsghdr structure and 56 bytes for the Routing header (8 + 3*16).
また、ルート設定ヘッダーが送付工程で造られているとき、私たちは実現が補助データ物に格納するかもしれないものを示すことができます。 私たちがsizeof(struct cmsghdr)が12と等しい32ビットの構造を仮定するなら、4バイトの境界の必要な整列で、inet6_rth_スペース(3)への呼び出しは68を返します: cmsghdr構造への12バイトとルート設定ヘッダーのための56バイト(8+3*16)。
The call to inet6_rth_init() initializes the ancillary data object to contain a Type 0 Routing header:
inet6_rth_イニット()への呼び出しはType0ルート設定ヘッダーを含むように補助データ物を初期化します:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_len = 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_level = IPPROTO_IPV6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_type = IPV6_RTHDR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len=6 | Routing Type=0| Seg Left=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_len=20| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_レベルはIPPROTO_IPV6と等しいです。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_タイプはIPV6_RTHDRと等しいです。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 次のヘッダー| Hdr Extレン=6| ルート設定タイプ=0| Segは=を0に残しました。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 予約されます。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The first call to inet6_rth_add() adds I1 to the list.
inet6_rth_への準備ラッパは、()がI1をリストに追加すると言い足します。
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_len = 36 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_level = IPPROTO_IPV6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_type = IPV6_RTHDR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len=6 | Routing Type=0| Seg Left=1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[1] = I1 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_len=36| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_レベルはIPPROTO_IPV6と等しいです。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_タイプはIPV6_RTHDRと等しいです。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 次のヘッダー| Hdr Extレン=6| ルート設定タイプ=0| Segは=を1に残しました。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 予約されます。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + アドレス[1]=I1+| | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
cmsg_len is incremented by 16, and the Segments Left field is incremented by 1.
cmsg_lenは16増加されます、そして、Segments Left分野は1つ増加されます。
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The next call to inet6_rth_add() adds I2 to the list.
inet6_rth_への次の呼び出しは、()がI2をリストに追加すると言い足します。
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_len = 52 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_level = IPPROTO_IPV6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_type = IPV6_RTHDR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len=6 | Routing Type=0| Seg Left=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[1] = I1 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[2] = I2 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_len=52| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_レベルはIPPROTO_IPV6と等しいです。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_タイプはIPV6_RTHDRと等しいです。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 次のヘッダー| Hdr Extレン=6| ルート設定タイプ=0| Segは=を2に残しました。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 予約されます。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + アドレス[1]=I1+| | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + アドレス[2]=I2+| | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
cmsg_len is incremented by 16, and the Segments Left field is incremented by 1.
cmsg_lenは16増加されます、そして、Segments Left分野は1つ増加されます。
Stevens, et al. Informational [Page 69] RFC 3542 Advanced Sockets API for IPv6 May 2003
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The last call to inet6_rth_add() adds I3 to the list.
inet6_rth_への最後の呼び出しは、()がI3をリストに追加すると言い足します。
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_len = 68 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_level = IPPROTO_IPV6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cmsg_type = IPV6_RTHDR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len=6 | Routing Type=0| Seg Left=3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[1] = I1 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[2] = I2 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[3] = I3 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_len=68| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_レベルはIPPROTO_IPV6と等しいです。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | cmsg_タイプはIPV6_RTHDRと等しいです。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 次のヘッダー| Hdr Extレン=6| ルート設定タイプ=0| Segは=を3に残しました。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 予約されます。| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + アドレス[1]=I1+| | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + アドレス[2]=I2+| | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + アドレス[3]=I3+| | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
cmsg_len is incremented by 16, and the Segments Left field is incremented by 1.
cmsg_lenは16増加されます、そして、Segments Left分野は1つ増加されます。
21.2. Receiving Routing Headers
21.2. ルート設定ヘッダーを受けます。
This example assumes that the application has enabled IPV6_RECVRTHDR socket option. The application prints and reverses a source route and uses that to echo the received data.
この例は、アプリケーションがIPV6_RECVRTHDRソケットオプションを可能にしたと仮定します。 アプリケーションは、印刷して、送信元経路を逆にして、受信データを反映するのにそれを使用します。
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struct sockaddr_in6 addr;
struct msghdr msg;
struct iovec iov;
struct cmsghdr *cmsgptr;
socklen_t cmsgspace;
void *extptr;
int extlen;
struct sockaddr_in6 addr。 struct msghdr msg。 struct iovec iov。 struct cmsghdr*cmsgptr。 socklen_t cmsgspace。 *extptrを欠如させてください。 int extlen。
int segments;
int i;
char databuf[8192];
intセグメント。 int i。 databuf[8192]を炭にしてください。
segments = 100; /* Enough */
extlen = inet6_rth_space(IPV6_RTHDR_TYPE_0, segments);
cmsgspace = CMSG_SPACE(extlen);
cmsgptr = malloc(cmsgspace);
if (cmsgptr == NULL) {
perror("malloc");
exit(1);
}
extptr = CMSG_DATA(cmsgptr);
セグメント=100。 十分な/**/extlenがinet6_rth_スペース(IPV6_RTHDR_TYPE_0、セグメント)と等しいです。 cmsgspaceはCMSG_SPACEと等しいです(extlenします)。 cmsgptrはmalloc(cmsgspace)と等しいです。 (cmsgptr=NULL)perror("malloc")(出口(1))extptrがCMSG_DATAと等しいなら(cmsgptr)。
msg.msg_control = cmsgptr;
msg.msg_controllen = cmsgspace;
msg.msg_name = (struct sockaddr *)&addr;
msg.msg_namelen = sizeof (addr);
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
iov.iov_base = databuf;
iov.iov_len = sizeof (databuf);
msg.msg_flags = 0;
if (recvmsg(s, &msg, 0) == -1) {
perror("recvmsg");
return;
}
if (msg.msg_controllen != 0 &&
cmsgptr->cmsg_level == IPPROTO_IPV6 &&
cmsgptr->cmsg_type == IPV6_RTHDR) {
struct in6_addr *in6;
char asciiname[INET6_ADDRSTRLEN];
struct ip6_rthdr *rthdr;
msg.msg_コントロールはcmsgptrと等しいです。 msg.msg_controllenはcmsgspaceと等しいです。 msg.msg_名前は(struct sockaddr*)とaddrと等しいです。 msg.msg_namelenはsizeof(addr)と等しいです。 msg.msg_iov=とiov。 msg.msg_iovlen=1。 iov.iov_ベースはdatabufと等しいです。 iov.iov_lenはsizeof(databuf)と等しいです。 msg.msg_は=0に旗を揚げさせます。 (recvmsg(s、およびmsg、0)=-1)perror("recvmsg")(リターン)である、(msg.msg_controllen!=0、cmsgptr>cmsg_平らな=IPPROTO_IPV6、cmsgptr>のcmsg_タイプ=IPV6_RTHDR)、struct in6_addr*in6; asciiname[INET6_ADDRSTRLEN]を炭にしてください; struct ip6_rthdr*rthdr
rthdr = (struct ip6_rthdr *)extptr;
segments = inet6_rth_segments(extptr);
printf("route (%d segments, %d left): ",
segments, rthdr->ip6r_segleft);
for (i = 0; i < segments; i++) {
in6 = inet6_rth_getaddr(extptr, i);
rthdr=(struct ip6_rthdr*)extptr。 セグメントはinet6_rth_セグメント(extptr)と等しいです。 printf、(「(残された%dセグメント、%d)を発送してください」、セグメント、rthdr>のip6r_segleft)、。 (i=0; i<セグメント; i++)、in6はinet6_rth_getaddr(extptr、i)と等しいです。
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if (in6 == NULL)
printf("<NULL> ");
else
printf("%s ", inet_ntop(AF_INET6,
(void *)in6->s6_addr,
asciiname, INET6_ADDRSTRLEN));
}
if (inet6_rth_reverse(extptr, extptr) == -1) {
printf("reverse failed");
return;
}
}
iov.iov_base = databuf;
iov.iov_len = strlen(databuf);
if (sendmsg(s, &msg, 0) == -1)
perror("sendmsg");
if (cmsgptr != NULL)
free(cmsgptr);
(in6=ヌル)printf(「<のヌル>」)であるなら。 ほかのprintf(「%s」、inet_ntop(AF_INET6、(空間*)in6->s6_addr、asciiname、INET6_ADDRSTRLEN))。 (inet6_rth_逆(extptr、extptr)=-1)である、printf(「逆は失敗しました」)。 戻ってください。 } iov.iov_ベース=databuf。 iov.iov_lenはstrlen(databuf)と等しいです。 (sendmsg(s、およびmsg、0)=-1)perror("sendmsg")であるなら。 (cmsgptr!=NULL)が(cmsgptr)を解放するなら。
Note: The above example is a simple illustration. It skips some error checks, including those involving the MSG_TRUNC and MSG_CTRUNC flags. It also leaves some type mismatches in favor of brevity.
以下に注意してください。 上記の例は簡単なイラストです。 それはエムエスジー_TRUNCとエムエスジー_CTRUNC旗にかかわるものを含むいくつかのエラーチェックをサボります。 また、いくつかのタイプミスマッチが簡潔さを支持して残っています。
22. Appendix C: Examples Using the inet6_opt_XXX() Functions
22. 付録C: inet6_を使用する例が_XXX()機能を選びます。
This shows how Hop-by-Hop and Destination options can be both built as well as parsed using the inet6_opt_XXX() functions. These examples assume that there are defined values for OPT_X and OPT_Y.
これはホップによるHopとinet6_を使用することで分析されるようにともにまた、オプションを組み込むことができるDestinationがどう_XXX()機能を選ぶかを示しています。 これらの例は、OPT_XとOPT_Yのための値が定義されると仮定します。
Note: The example is a simple illustration. It skips some error checks and leaves some type mismatches in favor of brevity.
以下に注意してください。 例は簡単なイラストです。 いくつかのエラーチェックをサボって、いくつかのタイプミスマッチが簡潔さを支持して残っています。
22.1. Building Options
22.1. ビルオプション
We now provide an example that builds two Hop-by-Hop options using the example in Appendix B of [RFC-2460].
私たちは、現在、[RFC-2460]のAppendix Bで例を使用することで2つのホップによるHopオプションをそれが築き上げる例に提供します。
void *extbuf;
socklen_t extlen;
int currentlen;
void *databuf;
int offset;
uint8_t value1;
uint16_t value2;
uint32_t value4;
uint64_t value8;
*extbufを欠如させてください。 socklen_t extlen。 int currentlen。 *databufを欠如させてください。 intは相殺されました。 uint8_t value1。 uint16_t value2。 uint32_t value4。 uint64_t value8。
/* Estimate the length */
/*は、長さが*/であると見積もっています。
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currentlen = inet6_opt_init(NULL, 0);
if (currentlen == -1)
return (-1);
currentlen = inet6_opt_append(NULL, 0, currentlen, OPT_X,
12, 8, NULL);
if (currentlen == -1)
return (-1);
currentlen = inet6_opt_append(NULL, 0, currentlen, OPT_Y,
7, 4, NULL);
if (currentlen == -1)
return (-1);
currentlen = inet6_opt_finish(NULL, 0, currentlen);
if (currentlen == -1)
return (-1);
extlen = currentlen;
inet6currentlen=_は_イニット(NULL、0)を選びます。 (currentlen=-1)が(-1)を返すなら。 inet6currentlen=_は選ばれます。_(NULL、0、currentlen、OPT_X、12、8、NULL)を追加してください。 (currentlen=-1)が(-1)を返すなら。 inet6currentlen=_は選ばれます。_(NULL、0、currentlen、OPT_Y、7、4、NULL)を追加してください。 (currentlen=-1)が(-1)を返すなら。 inet6currentlen=_は_終わりを選びます(NULL(0)はcurrentlenします)。 (currentlen=-1)が(-1)を返すなら。 extlenはcurrentlenと等しいです。
extbuf = malloc(extlen);
if (extbuf == NULL) {
perror("malloc");
return (-1);
}
currentlen = inet6_opt_init(extbuf, extlen);
if (currentlen == -1)
return (-1);
extbufはmallocと等しいです(extlenします)。 _(extbuf=NULL)perror("malloc")(リターン(-1))currentlenがinet6と等しいなら、_イニット(extbuf、extlen)を選んでください。 (currentlen=-1)が(-1)を返すなら。
currentlen = inet6_opt_append(extbuf, extlen, currentlen,
OPT_X, 12, 8, &databuf);
if (currentlen == -1)
return (-1);
/* Insert value 0x12345678 for 4-octet field */
offset = 0;
value4 = 0x12345678;
offset = inet6_opt_set_val(databuf, offset,
&value4, sizeof (value4));
/* Insert value 0x0102030405060708 for 8-octet field */
value8 = 0x0102030405060708;
offset = inet6_opt_set_val(databuf, offset,
&value8, sizeof (value8));
inet6currentlen=_は選ばれます。_(extbuf、extlen、currentlen、OPT_X、12、8、およびdatabuf)を追加してください。 (currentlen=-1)が(-1)を返すなら。 4八重奏の分野*/オフセット=0のための/*差し込み値0x12345678。 value4=0x12345678。 オフセット=inet6_は_セット_val(databuf、オフセット、およびvalue4、sizeof(value4))を選びます。 8八重奏の分野*/value8=0x0102030405060708のための/*差し込み値0x0102030405060708。 オフセット=inet6_は_セット_val(databuf、オフセット、およびvalue8、sizeof(value8))を選びます。
currentlen = inet6_opt_append(extbuf, extlen, currentlen,
OPT_Y, 7, 4, &databuf);
if (currentlen == -1)
return (-1);
/* Insert value 0x01 for 1-octet field */
offset = 0;
value1 = 0x01;
offset = inet6_opt_set_val(databuf, offset,
&value1, sizeof (value1));
inet6currentlen=_は選ばれます。_(extbuf、extlen、currentlen、OPT_Y、7、4、およびdatabuf)を追加してください。 (currentlen=-1)が(-1)を返すなら。 1八重奏の分野*/オフセット=0のための/*差し込み値0x01。 value1=0x01。 オフセット=inet6_は_セット_val(databuf、オフセット、およびvalue1、sizeof(value1))を選びます。
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/* Insert value 0x1331 for 2-octet field */
value2 = 0x1331;
offset = inet6_opt_set_val(databuf, offset,
&value2, sizeof (value2));
/* Insert value 0x01020304 for 4-octet field */
value4 = 0x01020304;
offset = inet6_opt_set_val(databuf, offset,
&value4, sizeof (value4));
2八重奏の分野*/value2=0x1331のための/*差し込み値0x1331。 オフセット=inet6_は_セット_val(databuf、オフセット、およびvalue2、sizeof(value2))を選びます。 4八重奏の分野*/value4=0x01020304のための/*差し込み値0x01020304。 オフセット=inet6_は_セット_val(databuf、オフセット、およびvalue4、sizeof(value4))を選びます。
currentlen = inet6_opt_finish(extbuf, extlen, currentlen);
if (currentlen == -1)
return (-1);
/* extbuf and extlen are now completely formatted */
inet6currentlen=_は_終わり(extlenであって、currentlenなextbuf)を選びます。 (currentlen=-1)が(-1)を返すなら。 /*extbufとextlenは現在完全にフォーマットされた*/です。
22.2. Parsing Received Options
22.2. 構文解析はオプションを受け取りました。
This example parses and prints the content of the two options in the previous example.
この例は、前の例における2つのオプションの内容を分析して、印刷します。
int
print_opt(void *extbuf, socklen_t extlen)
{
struct ip6_dest *ext;
int currentlen;
uint8_t type;
socklen_t len;
void *databuf;
int offset;
uint8_t value1;
uint16_t value2;
uint32_t value4;
uint64_t value8;
int print_opt(void *extbuf, socklen_t extlen) { struct ip6_dest *ext; int currentlen; uint8_t type; socklen_t len; void *databuf; int offset; uint8_t value1; uint16_t value2; uint32_t value4; uint64_t value8;
ext = (struct ip6_dest *)extbuf;
printf("nxt %u, len %u (bytes %d)\n", ext->ip6d_nxt,
ext->ip6d_len, (ext->ip6d_len + 1) * 8);
ext=(struct ip6_dest*)extbuf。 printf(ext>のip6d_は、「nxt%u、len%u(バイト%d)\n」とnxtして、lenであって、(ext>ip6d_len+1)のext>のip6d_は*8です)。
currentlen = 0;
while (1) {
currentlen = inet6_opt_next(extbuf, extlen,
currentlen, &type,
&len, &databuf);
if (currentlen == -1)
break;
printf("Received opt %u len %u\n",
type, len);
switch (type) {
case OPT_X:
currentlen=0。 (1)である、(currentlen=-1)がprintf(「受け取って、%u lenな%uの\nを選んでください」、タイプ、len)にスイッチ(タイプ)を壊すならinet6currentlen=_が_次に(extbuf、extlen、currentlen、タイプ、len、およびdatabuf)選ばれる、OPT_Xをケースに入れてください:
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offset = 0;
offset =
inet6_opt_get_val(databuf, offset,
&value4,
sizeof (value4));
printf("X 4-byte field %x\n", value4);
offset =
inet6_opt_get_val(databuf, offset,
&value8,
sizeof (value8));
printf("X 8-byte field %llx\n", value8);
break;
case OPT_Y:
offset = 0;
offset =
inet6_opt_get_val(databuf, offset,
&value1,
sizeof (value1));
printf("Y 1-byte field %x\n", value1);
offset =
inet6_opt_get_val(databuf, offset,
&value2,
sizeof (value2));
printf("Y 2-byte field %x\n", value2);
offset =
inet6_opt_get_val(databuf, offset,
&value4,
sizeof (value4));
printf("Y 4-byte field %x\n", value4);
break;
default:
printf("Unknown option %u\n", type);
break;
}
}
return (0);
}
=0を相殺してください。 オフセット=inet6_は選ばれます。__val(相殺されたdatabufとvalue4、sizeof(value4))を手に入れてください。 printf、(「X4バイトの分野%x、\n」、value4)、。 オフセット=inet6_は選ばれます。__val(相殺されたdatabufとvalue8、sizeof(value8))を手に入れてください。 printf(「X8バイトの分野%は\nをllxする」value8)。 壊れてください。 OPT_Yをケースに入れてください: =0を相殺してください。 オフセット=inet6_は選ばれます。__val(相殺されたdatabufとvalue1、sizeof(value1))を手に入れてください。 printf、(「Y1バイトの分野%x、\n」、value1)、。 オフセット=inet6_は選ばれます。__val(相殺されたdatabufとvalue2、sizeof(value2))を手に入れてください。 printf、(「Y2バイトの分野%x、\n」、value2)、。 オフセット=inet6_は選ばれます。__val(相殺されたdatabufとvalue4、sizeof(value4))を手に入れてください。 printf、(「Y4バイトの分野%x、\n」、value4)、。 壊れてください。 デフォルト: printf(「未知のオプション%uの\n」、タイプ)。 壊れてください。 } リターン(0)。 }
Stevens, et al. Informational [Page 75] RFC 3542 Advanced Sockets API for IPv6 May 2003
スティーブンス、他 3542年の情報[75ページ]のRFC IPv6 May 2003に、高度なソケットAPI
23. Authors' Addresses
23. 作者のアドレス
W. Richard Stevens (deceased)
W.リチャード・スティーブンス(死ぬ)です。
Matt Thomas 3am Software Foundry 8053 Park Villa Circle Cupertino, CA 95014
円のカルパチーノ、マットトーマス午前3時のソフトウェア鋳造場8053公園Villaカリフォルニア 95014
EMail: matt@3am-software.com
メール: matt@3am-software.com
Erik Nordmark Sun Microsystems Laboratories, Europe 180, avenue de l'Europe 38334 SAINT ISMIER Cedex, France
エリックNordmarkサン・マイクロシステムズ研究所、ヨーロッパ180、de l'Europe38334セイントISMIER Cedex、大通りフランス
Phone: +33 (0)4 74 18 88 03 Fax: +33 (0)4 76 18 88 88 EMail: Erik.Nordmark@sun.com
以下に電話をしてください。 +33 (0)4 74 18 88 03、Fax: +33(0) 4 76 18 88 88はメールされます: Erik.Nordmark@sun.com
Tatuya JINMEI Corporate Research & Development Center, Toshiba Corporation 1 Komukai Toshiba-cho, Kawasaki-shi Kanagawa 212-8582, Japan
Tatuya JINMEIの法人の研究開発センター、東芝1Komukai東芝町、神奈川212-8582、川崎市日本
EMail: jinmei@isl.rdc.toshiba.co.jp
メール: jinmei@isl.rdc.toshiba.co.jp
Stevens, et al. Informational [Page 76] RFC 3542 Advanced Sockets API for IPv6 May 2003
スティーブンス、他 3542年の情報[76ページ]のRFC IPv6 May 2003に、高度なソケットAPI
24. Full Copyright Statement
24. 完全な著作権宣言文
Copyright (C) The Internet Society (2003). All Rights Reserved.
Copyright(C)インターネット協会(2003)。 All rights reserved。
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
それに関するこのドキュメントと翻訳は、コピーして、それが批評するか、またはそうでなければわかる他のもの、および派生している作品に提供するか、または準備されているかもしれなくて、コピーされて、発行されて、全体か一部広げられた実現を助けるかもしれません、どんな種類の制限なしでも、上の版権情報とこのパラグラフがそのようなすべてのコピーと派生している作品の上に含まれていれば。 しかしながら、このドキュメント自体は何らかの方法で変更されないかもしれません、インターネット協会か他のインターネット組織の版権情報か参照を取り除くのなどように、それを英語以外の言語に翻訳するのが著作権のための手順がインターネットStandardsの過程で定義したどのケースに従わなければならないか、必要に応じてさもなければ、インターネット標準を開発する目的に必要であるのを除いて。
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
上に承諾された限られた許容は、永久であり、インターネット協会、後継者または案配によって取り消されないでしょう。
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
このドキュメントとそして、「そのままで」という基礎とインターネットの振興発展を目的とする組織に、インターネット・エンジニアリング・タスク・フォースが速達の、または、暗示しているすべての保証を放棄するかどうかというここにことであり、他を含んでいて、含まれて、情報の使用がここに侵害しないどんな保証も少しもまっすぐになるという情報か市場性か特定目的への適合性のどんな黙示的な保証。
Acknowledgement
承認
Funding for the RFC Editor function is currently provided by the Internet Society.
RFC Editor機能のための基金は現在、インターネット協会によって提供されます。
Stevens, et al. Informational [Page 77]
スティーブンス、他 情報[77ページ]
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