mirror of https://github.com/mkerrisk/man-pages
300 lines
8.5 KiB
Groff
300 lines
8.5 KiB
Groff
.\" This man page is Copyright (C) 2000 Andi Kleen <ak@muc.de>.
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.\" Permission is granted to distribute possibly modified copies
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.\" of this page provided the header is included verbatim,
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.\" and in case of nontrivial modification author and date
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.\" of the modification is added to the header.
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.\" $Id: ipv6.7,v 1.3 2000/12/20 18:10:31 ak Exp $
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.TH IPV6 7 1999-06-29 "Linux" "Linux Programmer's Manual"
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.SH NAME
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ipv6, PF_INET6 \- Linux IPv6 protocol implementation
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.SH SYNOPSIS
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.B #include <sys/socket.h>
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.br
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.B #include <netinet/in.h>
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.sp
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.IB tcp6_socket " = socket(PF_INET6, SOCK_STREAM, 0);"
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.br
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.IB raw6_socket " = socket(PF_INET6, SOCK_RAW, " protocol ");"
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.br
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.IB udp6_socket " = socket(PF_INET6, SOCK_DGRAM, " protocol ");"
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.SH DESCRIPTION
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Linux 2.2 optionally implements the Internet Protocol, version 6.
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This man page contains a description of the IPv6 basic API as
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implemented by the Linux kernel and glibc 2.1.
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The interface
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is based on the BSD sockets interface; see
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.BR socket (7).
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.PP
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The IPv6 API aims to be mostly compatible with the
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.BR ip (7)
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v4 API.
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Only differences are described in this man page.
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.PP
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To bind an
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.I AF_INET6
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socket to any process the local address should be copied from the
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.B in6addr_any
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variable which has
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.I in6_addr
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type.
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In static initializations
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.B IN6ADDR_ANY_INIT
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may also be used, which expands to a constant expression.
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Both of them are in network order.
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.PP
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The IPv6 loopback address (::1) is available in the global
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.B in6addr_loopback
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variable.
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For initializations
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.B IN6ADDR_LOOPBACK_INIT
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should be used.
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.PP
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IPv4 connections can be handled with the v6 API by using the
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v4-mapped-on-v6 address type;
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thus a program only needs only to support this API type to
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support both protocols.
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This is handled transparently by the address
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handling functions in libc.
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.PP
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IPv4 and IPv6 share the local port space.
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When you get an IPv4 connection
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or packet to a IPv6 socket its source address will be mapped
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to v6 and it'll be mapped to v6.
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.SH "ADDRESS FORMAT"
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.sp
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.RS
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.nf
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struct sockaddr_in6 {
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u_int16_t sin6_family; /* AF_INET6 */
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u_int16_t sin6_port; /* port number */
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u_int32_t sin6_flowinfo; /* IPv6 flow information */
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struct in6_addr sin6_addr; /* IPv6 address */
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u_int32_t sin6_scope_id; /* Scope ID (new in 2.4) */
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};
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struct in6_addr {
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unsigned char s6_addr[16]; /* IPv6 address */
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};
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.fi
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.RE
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.sp
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.B sin6_family
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is always set to
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.BR AF_INET6 ;
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.B sin6_port
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is the protocol port (see
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.B sin_port
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in
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.BR ip (7));
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.B sin6_flowinfo
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is the IPv6 flow identifier;
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.B sin6_addr
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is the 128bit IPv6 address.
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.B sin6_scope_id
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is an ID of depending of on the scope of the address.
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It is new in Linux 2.4.
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Linux only supports it for link scope addresses, in that case
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.I sin6_scope_id
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contains the interface index (see
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.BR netdevice (7))
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.PP
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IPv6 supports several address types: unicast to address a single
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host, multicast to address a group of hosts,
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anycast to address the nearest member of a group of hosts
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(not implemented in Linux), IPv4-on-IPv6 to
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address a IPv4 host, and other reserved address types.
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.PP
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The address notation for IPv6 is a group of 16 2 digit hexadecimal
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numbers, separated with a ':'. '::' stands for a string of 0 bits.
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Special addresses are ::1 for loopback and ::FFFF:<IPv4 address>
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for IPv4-mapped-on-IPv6.
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.PP
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The port space of IPv6 is shared with IPv4.
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.SH "SOCKET OPTIONS"
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IPv6 supports some protocol specific socket options that can be set with
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.BR setsockopt (2)
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and read with
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.BR getsockopt (2).
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The socket option level for IPv6 is
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.BR IPPROTO_IPV6 .
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A boolean integer flag is zero when it is false, otherwise true.
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.TP
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.B IPV6_ADDRFORM
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Turn an
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.I AF_INET6
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socket into a socket of a different address family.
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Only
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.I AF_INET
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is currently supported for that.
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It is only allowed for IPv6 sockets
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that are connected and bound to a v4-mapped-on-v6 address.
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The argument is a pointer to a integer containing
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.BR AF_INET .
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This is useful to pass v4-mapped sockets as file descriptors to
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programs that don't know how to deal with the IPv6 API.
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.TP
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.B IPV6_ADD_MEMBERSHIP, IPV6_DROP_MEMBERSHIP
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Control membership in multicast groups.
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Argument is a pointer to a
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.I struct ipv6_mreq
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structure.
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.\" FIXME IPV6_CHECKSUM is not documented, and probably should be
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.\" FIXME IPV6_JOIN_ANYCAST is not documented, and probably should be
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.\" FIXME IPV6_LEAVE_ANYCAST is not documented, and probably should be
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.\" FIXME IPV6_V6ONLY is not documented, and probably should be
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.\" FIXME IPV6_RECVPKTINFO is not documented, and probably should be
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.\" FIXME IPV6_2292PKTINFO is not documented, and probably should be
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.\" FIXME there are probably many other IPV6_* socket options that
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.\" should be documented
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.TP
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.B IPV6_MTU
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Set the MTU to be used for the socket.
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The MTU is limited by the device
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MTU or the path mtu when path mtu discovery is enabled.
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Argument is a pointer to integer.
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.TP
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.B IPV6_MTU_DISCOVER
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Control path mtu discovery on the socket.
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See
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.I IP_MTU_DISCOVER
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in
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.BR ip (7)
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for details.
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.TP
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.B IPV6_MULTICAST_HOPS
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Set the multicast hop limit for the socket.
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Argument is a pointer to an
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integer.
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\-1 in the value means use the route default, otherwise it should be
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between 0 and 255.
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.TP
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.B IPV6_MULTICAST_IF
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Set the device for outgoing multicast packets on the socket.
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This is only allowed
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for
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.I SOCK_DGRAM
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and
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.I SOCK_RAW
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socket.
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The argument is an pointer to an interface index (see
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.BR netdevice (7))
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in an integer.
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.TP
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.B IPV6_MULTICAST_LOOP
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Control whether the socket sees multicast packets that it has send itself.
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Argument is a pointer to boolean.
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.TP
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.B IPV6_PKTINFO
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Set delivery of the
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.B IPV6_PKTINFO
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control message on incoming datagrams.
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Only allowed for
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.B SOCK_DGRAM
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or
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.B SOCK_RAW
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sockets.
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Argument is a pointer to a boolean value in an integer.
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.TP
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.nh
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.B IPV6_RTHDR, IPV6_AUTHHDR, IPV6_DSTOPS, IPV6_HOPOPTS, IPV6_FLOWINFO, IPV6_HOPLIMIT
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.hy
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Set delivery of control messages for incoming datagrams containing
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extension headers from the received packet.
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.I IPV6_RTHDR
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delivers the routing header,
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.I IPV6_AUTHHDR
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delivers the authentication header,
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.I IPV6_DSTOPTS
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delivers the destination options,
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.I IPV6_HOPOPTS
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delivers the hop options,
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.I IPV6_FLOWINFO
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delivers an integer containing the flow ID,
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.I IPV6_HOPLIMIT
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delivers an integer containing the hop count of the packet.
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The control messages have the same type as the socket option.
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All these header options can also be set for outgoing packets
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by putting the appropriate control message into the control buffer of
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.BR sendmsg (2).
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Only allowed for
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.B SOCK_DGRAM
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or
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.B SOCK_RAW
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sockets.
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Argument is a pointer to a boolean value.
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.TP
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.B IPV6_RECVERR
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Control receiving of asynchronous error options.
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See
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.I IP_RECVERR
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in
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.BR ip (7)
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for details.
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Argument is a pointer to boolean.
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.TP
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.B IPV6_ROUTER_ALERT
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Pass all forwarded packets containing an router alert option to
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this socket.
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Only allowed for datagram sockets and for root.
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Argument is a pointer to boolean.
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.TP
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.B IPV6_UNICAST_HOPS
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Set the unicast hop limit for the socket.
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Argument is an pointer to an integer.
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\-1 in the value means use the route default,
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otherwise it should be between 0 and 255.
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.\" FLOWLABEL_MGR, FLOWINFO_SEND
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.SH VERSIONS
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The older
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.I libinet6
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libc5 based IPv6 API implementation for Linux is not described here
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and may vary in details.
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.PP
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Linux 2.4 will break binary compatibility for the sockaddr_in6 for 64bit
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hosts by changing the alignment of
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.I in6_addr
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and adding an additional
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.I sin6_scope_id
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field.
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The kernel interfaces stay compatible, but a program including
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sockaddr_in6 or in6_addr into other structures may not be.
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This is not
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a problem for 32bit hosts like i386.
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.PP
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The
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.B sin6_flowinfo
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field is new in Linux 2.4.
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It is transparently passed/read by the kernel
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when the passed address length contains it.
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Some programs that pass a longer address buffer and then
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check the outgoing address length may break.
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.SH "PORTING NOTES"
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The
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.I sockaddr_in6
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structure is bigger than the generic
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.BR sockaddr .
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Programs that assume that all address types can be stored safely in a
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.I struct sockaddr
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need to be changed to use
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.I struct sockaddr_storage
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for that instead.
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.SH BUGS
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The IPv6 extended API as in RFC\ 2292 is currently only partly
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implemented;
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although the 2.2 kernel has near complete support for receiving options,
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the macros for generating IPv6 options are missing in glibc 2.1.
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.PP
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IPSec support for EH and AH headers is missing.
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.PP
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Flow label management is not complete and not documented here.
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.PP
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This man page is not complete.
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.SH "SEE ALSO"
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.BR cmsg (3),
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.BR ip (7)
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.PP
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RFC\ 2553: IPv6 BASIC API.
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Linux tries to be compliant to this.
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.PP
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RFC\ 2460: IPv6 specification.
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