{ "content": [ { "type": "text", "text": "# IPV6 (man)\n\n## NAME\n\nipv6 - Linux IPv6 protocol implementation\n\n## DESCRIPTION\n\nLinux 2.2 optionally implements the Internet Protocol, version 6. This man page contains a\ndescription of the IPv6 basic API as implemented by the Linux kernel and glibc 2.1. The in‐\nterface is based on the BSD sockets interface; see socket(7).\n\n## Sections\n\n- **NAME**\n- **SYNOPSIS** (2 subsections)\n- **DESCRIPTION** (2 subsections)\n- **ERRORS**\n- **VERSIONS**\n- **NOTES**\n- **BUGS**\n- **SEE ALSO**\n- **COLOPHON**\n\nUse structuredContent.sections for detailed options, examples, and full documentation.\n" } ], "structuredContent": { "command": "IPV6", "section": "", "mode": "man", "summary": "ipv6 - Linux IPv6 protocol implementation", "synopsis": "", "tldr_summary": null, "tldr_examples": [], "tldr_source": null, "flags": [], "examples": [], "see_also": [ { "name": "cmsg", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/cmsg/3/json" }, { "name": "ip", "section": "7", "url": "https://www.chedong.com/phpMan.php/man/ip/7/json" } ], "section_outline": [ { "name": "NAME", "lines": 2, "subsections": [] }, { "name": "SYNOPSIS", "lines": 1, "subsections": [ { "name": "#include ", "lines": 1 }, { "name": "#include ", "lines": 4 } ] }, { "name": "DESCRIPTION", "lines": 22, "subsections": [ { "name": "Address format", "lines": 28 }, { "name": "Socket options", "lines": 84 } ] }, { "name": "ERRORS", "lines": 3, "subsections": [] }, { "name": "VERSIONS", "lines": 9, "subsections": [] }, { "name": "NOTES", "lines": 7, "subsections": [] }, { "name": "BUGS", "lines": 10, "subsections": [] }, { "name": "SEE ALSO", "lines": 4, "subsections": [] }, { "name": "COLOPHON", "lines": 7, "subsections": [] } ], "sections": { "NAME": { "content": "ipv6 - Linux IPv6 protocol implementation\n", "subsections": [] }, "SYNOPSIS": { "content": "", "subsections": [ { "name": "#include ", "content": "" }, { "name": "#include ", "content": "tcp6socket = socket(AFINET6, SOCKSTREAM, 0);\nraw6socket = socket(AFINET6, SOCKRAW, protocol);\nudp6socket = socket(AFINET6, SOCKDGRAM, protocol);\n" } ] }, "DESCRIPTION": { "content": "Linux 2.2 optionally implements the Internet Protocol, version 6. This man page contains a\ndescription of the IPv6 basic API as implemented by the Linux kernel and glibc 2.1. The in‐\nterface is based on the BSD sockets interface; see socket(7).\n\nThe IPv6 API aims to be mostly compatible with the IPv4 API (see ip(7)). Only differences\nare described in this man page.\n\nTo bind an AFINET6 socket to any process, the local address should be copied from the\nin6addrany variable which has in6addr type. In static initializations, IN6ADDRANYINIT\nmay also be used, which expands to a constant expression. Both of them are in network byte\norder.\n\nThe IPv6 loopback address (::1) is available in the global in6addrloopback variable. For\ninitializations, IN6ADDRLOOPBACKINIT should be used.\n\nIPv4 connections can be handled with the v6 API by using the v4-mapped-on-v6 address type;\nthus a program needs to support only this API type to support both protocols. This is han‐\ndled transparently by the address handling functions in the C library.\n\nIPv4 and IPv6 share the local port space. When you get an IPv4 connection or packet to an\nIPv6 socket, its source address will be mapped to v6 and it will be mapped to v6.\n", "subsections": [ { "name": "Address format", "content": "struct sockaddrin6 {\nsafamilyt sin6family; /* AFINET6 */\ninportt sin6port; /* port number */\nuint32t sin6flowinfo; /* IPv6 flow information */\nstruct in6addr sin6addr; /* IPv6 address */\nuint32t sin6scopeid; /* Scope ID (new in 2.4) */\n};\n\nstruct in6addr {\nunsigned char s6addr[16]; /* IPv6 address */\n};\n\nsin6family is always set to AFINET6; sin6port is the protocol port (see sinport in\nip(7)); sin6flowinfo is the IPv6 flow identifier; sin6addr is the 128-bit IPv6 address.\nsin6scopeid is an ID depending on the scope of the address. It is new in Linux 2.4. Linux\nsupports it only for link-local addresses, in that case sin6scopeid contains the interface\nindex (see netdevice(7))\n\nIPv6 supports several address types: unicast to address a single host, multicast to address a\ngroup of hosts, anycast to address the nearest member of a group of hosts (not implemented in\nLinux), IPv4-on-IPv6 to address an IPv4 host, and other reserved address types.\n\nThe address notation for IPv6 is a group of 8 4-digit hexadecimal numbers, separated with a\n':'. \"::\" stands for a string of 0 bits. Special addresses are ::1 for loopback and\n::FFFF: for IPv4-mapped-on-IPv6.\n\nThe port space of IPv6 is shared with IPv4.\n" }, { "name": "Socket options", "content": "IPv6 supports some protocol-specific socket options that can be set with setsockopt(2) and\nread with getsockopt(2). The socket option level for IPv6 is IPPROTOIPV6. A boolean inte‐\nger flag is zero when it is false, otherwise true.\n\nIPV6ADDRFORM\nTurn an AFINET6 socket into a socket of a different address family. Only AFINET is\ncurrently supported for that. It is allowed only for IPv6 sockets that are connected\nand bound to a v4-mapped-on-v6 address. The argument is a pointer to an integer con‐\ntaining AFINET. This is useful to pass v4-mapped sockets as file descriptors to pro‐\ngrams that don't know how to deal with the IPv6 API.\n\nIPV6ADDMEMBERSHIP, IPV6DROPMEMBERSHIP\nControl membership in multicast groups. Argument is a pointer to a struct ipv6mreq.\n\nIPV6MTU\ngetsockopt(): Retrieve the current known path MTU of the current socket. Valid only\nwhen the socket has been connected. Returns an integer.\n\nsetsockopt(): Set the MTU to be used for the socket. The MTU is limited by the device\nMTU or the path MTU when path MTU discovery is enabled. Argument is a pointer to in‐\nteger.\n\nIPV6MTUDISCOVER\nControl path-MTU discovery on the socket. See IPMTUDISCOVER in ip(7) for details.\n\nIPV6MULTICASTHOPS\nSet the multicast hop limit for the socket. Argument is a pointer to an integer. -1\nin the value means use the route default, otherwise it should be between 0 and 255.\n\nIPV6MULTICASTIF\nSet the device for outgoing multicast packets on the socket. This is allowed only for\nSOCKDGRAM and SOCKRAW socket. The argument is a pointer to an interface index (see\nnetdevice(7)) in an integer.\n\nIPV6MULTICASTLOOP\nControl whether the socket sees multicast packets that it has send itself. Argument\nis a pointer to boolean.\n\nIPV6RECVPKTINFO (since Linux 2.6.14)\nSet delivery of the IPV6PKTINFO control message on incoming datagrams. Such control\nmessages contain a struct in6pktinfo, as per RFC 3542. Allowed only for SOCKDGRAM\nor SOCKRAW sockets. Argument is a pointer to a boolean value in an integer.\n\nIPV6RTHDR, IPV6AUTHHDR, IPV6DSTOPTS, IPV6HOPOPTS, IPV6FLOWINFO, IPV6HOPLIMIT\nSet delivery of control messages for incoming datagrams containing extension headers\nfrom the received packet. IPV6RTHDR delivers the routing header, IPV6AUTHHDR deliv‐\ners the authentication header, IPV6DSTOPTS delivers the destination options,\nIPV6HOPOPTS delivers the hop options, IPV6FLOWINFO delivers an integer containing\nthe flow ID, IPV6HOPLIMIT delivers an integer containing the hop count of the packet.\nThe control messages have the same type as the socket option. All these header op‐\ntions can also be set for outgoing packets by putting the appropriate control message\ninto the control buffer of sendmsg(2). Allowed only for SOCKDGRAM or SOCKRAW sock‐\nets. Argument is a pointer to a boolean value.\n\nIPV6RECVERR\nControl receiving of asynchronous error options. See IPRECVERR in ip(7) for details.\nArgument is a pointer to boolean.\n\nIPV6ROUTERALERT\nPass forwarded packets containing a router alert hop-by-hop option to this socket.\nAllowed only for SOCKRAW sockets. The tapped packets are not forwarded by the ker‐\nnel, it is the user's responsibility to send them out again. Argument is a pointer to\nan integer. A positive integer indicates a router alert option value to intercept.\nPackets carrying a router alert option with a value field containing this integer will\nbe delivered to the socket. A negative integer disables delivery of packets with\nrouter alert options to this socket.\n\nIPV6UNICASTHOPS\nSet the unicast hop limit for the socket. Argument is a pointer to an integer. -1 in\nthe value means use the route default, otherwise it should be between 0 and 255.\n\nIPV6V6ONLY (since Linux 2.4.21 and 2.6)\nIf this flag is set to true (nonzero), then the socket is restricted to sending and\nreceiving IPv6 packets only. In this case, an IPv4 and an IPv6 application can bind\nto a single port at the same time.\n\nIf this flag is set to false (zero), then the socket can be used to send and receive\npackets to and from an IPv6 address or an IPv4-mapped IPv6 address.\n\nThe argument is a pointer to a boolean value in an integer.\n\nThe default value for this flag is defined by the contents of the file\n/proc/sys/net/ipv6/bindv6only. The default value for that file is 0 (false).\n" } ] }, "ERRORS": { "content": "ENODEV The user tried to bind(2) to a link-local IPv6 address, but the sin6scopeid in the\nsupplied sockaddrin6 structure is not a valid interface index.\n", "subsections": [] }, "VERSIONS": { "content": "Linux 2.4 will break binary compatibility for the sockaddrin6 for 64-bit hosts by changing\nthe alignment of in6addr and adding an additional sin6scopeid field. The kernel inter‐\nfaces stay compatible, but a program including sockaddrin6 or in6addr into other structures\nmay not be. This is not a problem for 32-bit hosts like i386.\n\nThe sin6flowinfo field is new in Linux 2.4. It is transparently passed/read by the kernel\nwhen the passed address length contains it. Some programs that pass a longer address buffer\nand then check the outgoing address length may break.\n", "subsections": [] }, "NOTES": { "content": "The sockaddrin6 structure is bigger than the generic sockaddr. Programs that assume that\nall address types can be stored safely in a struct sockaddr need to be changed to use struct\nsockaddrstorage for that instead.\n\nSOLIP, SOLIPV6, SOLICMPV6, and other SOL* socket options are nonportable variants of IP‐‐\nPROTO*. See also ip(7).\n", "subsections": [] }, "BUGS": { "content": "The IPv6 extended API as in RFC 2292 is currently only partly implemented; although the 2.2\nkernel has near complete support for receiving options, the macros for generating IPv6 op‐\ntions are missing in glibc 2.1.\n\nIPSec support for EH and AH headers is missing.\n\nFlow label management is not complete and not documented here.\n\nThis man page is not complete.\n", "subsections": [] }, "SEE ALSO": { "content": "cmsg(3), ip(7)\n\nRFC 2553: IPv6 BASIC API; Linux tries to be compliant to this. RFC 2460: IPv6 specification.\n", "subsections": [] }, "COLOPHON": { "content": "This page is part of release 5.10 of the Linux man-pages project. A description of the\nproject, information about reporting bugs, and the latest version of this page, can be found\nat https://www.kernel.org/doc/man-pages/.\n\n\n\nLinux 2020-12-21 IPV6(7)", "subsections": [] } } } }