1.\" $KAME: inet6.4,v 1.21 2001/04/05 01:00:18 itojun Exp $ 2.\" 3.\" Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the project nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" $FreeBSD$ 31.\" 32.Dd September 2, 2009 33.Dt INET6 4 34.Os 35.Sh NAME 36.Nm inet6 37.Nd Internet protocol version 6 family 38.Sh SYNOPSIS 39.In sys/types.h 40.In netinet/in.h 41.Sh DESCRIPTION 42The 43.Nm 44family is an updated version of 45.Xr inet 4 46family. 47While 48.Xr inet 4 49implements Internet Protocol version 4, 50.Nm 51implements Internet Protocol version 6. 52.Pp 53.Nm 54is a collection of protocols layered atop the 55.Em Internet Protocol version 6 56.Pq Tn IPv6 57transport layer, and utilizing the IPv6 address format. 58The 59.Nm 60family provides protocol support for the 61.Dv SOCK_STREAM , SOCK_DGRAM , 62and 63.Dv SOCK_RAW 64socket types; the 65.Dv SOCK_RAW 66interface provides access to the 67.Tn IPv6 68protocol. 69.Sh ADDRESSING 70IPv6 addresses are 16 byte quantities, stored in network standard byteorder. 71The include file 72.In netinet/in.h 73defines this address 74as a discriminated union. 75.Pp 76Sockets bound to the 77.Nm 78family utilize the following addressing structure: 79.Bd -literal -offset indent 80struct sockaddr_in6 { 81 uint8_t sin6_len; 82 sa_family_t sin6_family; 83 in_port_t sin6_port; 84 uint32_t sin6_flowinfo; 85 struct in6_addr sin6_addr; 86 uint32_t sin6_scope_id; 87}; 88.Ed 89.Pp 90Sockets may be created with the local address 91.Dq Dv :: 92(which is equal to IPv6 address 93.Dv 0:0:0:0:0:0:0:0 ) 94to affect 95.Dq wildcard 96matching on incoming messages. 97.Pp 98The IPv6 specification defines scoped addresses, 99like link-local or site-local addresses. 100A scoped address is ambiguous to the kernel, 101if it is specified without a scope identifier. 102To manipulate scoped addresses properly from the userland, 103programs must use the advanced API defined in RFC2292. 104A compact description of the advanced API is available in 105.Xr ip6 4 . 106If a scoped address is specified without an explicit scope, 107the kernel may raise an error. 108Note that scoped addresses are not for daily use at this moment, 109both from a specification and an implementation point of view. 110.Pp 111The KAME implementation supports an extended numeric IPv6 address notation 112for link-local addresses, 113like 114.Dq Li fe80::1%de0 115to specify 116.Do 117.Li fe80::1 118on 119.Li de0 120interface 121.Dc . 122This notation is supported by 123.Xr getaddrinfo 3 124and 125.Xr getnameinfo 3 . 126Some of normal userland programs, such as 127.Xr telnet 1 128or 129.Xr ftp 1 , 130are able to use this notation. 131With special programs 132like 133.Xr ping6 8 , 134you can specify the outgoing interface by an extra command line option 135to disambiguate scoped addresses. 136.Pp 137Scoped addresses are handled specially in the kernel. 138In kernel structures like routing tables or interface structures, 139a scoped address will have its interface index embedded into the address. 140Therefore, 141the address in some kernel structures is not the same as that on the wire. 142The embedded index will become visible through a 143.Dv PF_ROUTE 144socket, kernel memory accesses via 145.Xr kvm 3 146and on some other occasions. 147HOWEVER, users should never use the embedded form. 148For details please consult 149.Pa IMPLEMENTATION 150supplied with KAME kit. 151.Sh PROTOCOLS 152The 153.Nm 154family is comprised of the 155.Tn IPv6 156network protocol, Internet Control 157Message Protocol version 6 158.Pq Tn ICMPv6 , 159Transmission Control Protocol 160.Pq Tn TCP , 161and User Datagram Protocol 162.Pq Tn UDP . 163.Tn TCP 164is used to support the 165.Dv SOCK_STREAM 166abstraction while 167.Tn UDP 168is used to support the 169.Dv SOCK_DGRAM 170abstraction. 171Note that 172.Tn TCP 173and 174.Tn UDP 175are common to 176.Xr inet 4 177and 178.Nm . 179A raw interface to 180.Tn IPv6 181is available 182by creating an Internet socket of type 183.Dv SOCK_RAW . 184The 185.Tn ICMPv6 186message protocol is accessible from a raw socket. 187.Ss MIB Variables 188A number of variables are implemented in the net.inet6 branch of the 189.Xr sysctl 3 190MIB. 191In addition to the variables supported by the transport protocols 192(for which the respective manual pages may be consulted), 193the following general variables are defined: 194.Bl -tag -width IPV6CTL_MAXFRAGPACKETS 195.It Dv IPV6CTL_FORWARDING 196.Pq ip6.forwarding 197Boolean: enable/disable forwarding of 198.Tn IPv6 199packets. 200Also, identify if the node is acting as a router. 201Defaults to off. 202.It Dv IPV6CTL_SENDREDIRECTS 203.Pq ip6.redirect 204Boolean: enable/disable sending of 205.Tn ICMPv6 206redirects in response to unforwardable 207.Tn IPv6 208packets. 209This option is ignored unless the node is routing 210.Tn IPv6 211packets, 212and should normally be enabled on all systems. 213Defaults to on. 214.It Dv IPV6CTL_DEFHLIM 215.Pq ip6.hlim 216Integer: default hop limit value to use for outgoing 217.Tn IPv6 218packets. 219This value applies to all the transport protocols on top of 220.Tn IPv6 . 221There are APIs to override the value. 222.It Dv IPV6CTL_MAXFRAGPACKETS 223.Pq ip6.maxfragpackets 224Integer: default maximum number of fragmented packets the node will accept. 2250 means that the node will not accept any fragmented packets. 226-1 means that the node will accept as many fragmented packets as it receives. 227The flag is provided basically for avoiding possible DoS attacks. 228.It Dv IPV6CTL_ACCEPT_RTADV 229.Pq ip6.accept_rtadv 230Boolean: the default value of a per-interface flag to 231enable/disable receiving of 232.Tn ICMPv6 233router advertisement packets, 234and autoconfiguration of address prefixes and default routers. 235The node must be a host 236(not a router) 237for the option to be meaningful. 238Defaults to off. 239.It Dv IPV6CTL_AUTO_LINKLOCAL 240.Pq ip6.auto_linklocal 241Boolean: the default value of a per-interface flag to 242enable/disable performing automatic link-local address configuration. 243Defaults to on. 244.It Dv IPV6CTL_LOG_INTERVAL 245.Pq ip6.log_interval 246Integer: default interval between 247.Tn IPv6 248packet forwarding engine log output 249(in seconds). 250.It Dv IPV6CTL_HDRNESTLIMIT 251.Pq ip6.hdrnestlimit 252Integer: default number of the maximum 253.Tn IPv6 254extension headers 255permitted on incoming 256.Tn IPv6 257packets. 258If set to 0, the node will accept as many extension headers as possible. 259.It Dv IPV6CTL_DAD_COUNT 260.Pq ip6.dad_count 261Integer: default number of 262.Tn IPv6 263DAD 264.Pq duplicated address detection 265probe packets. 266The packets will be generated when 267.Tn IPv6 268interface addresses are configured. 269.It Dv IPV6CTL_AUTO_FLOWLABEL 270.Pq ip6.auto_flowlabel 271Boolean: enable/disable automatic filling of 272.Tn IPv6 273flowlabel field, for outstanding connected transport protocol packets. 274The field might be used by intermediate routers to identify packet flows. 275Defaults to on. 276.It Dv IPV6CTL_DEFMCASTHLIM 277.Pq ip6.defmcasthlim 278Integer: default hop limit value for an 279.Tn IPv6 280multicast packet sourced by the node. 281This value applies to all the transport protocols on top of 282.Tn IPv6 . 283There are APIs to override the value as documented in 284.Xr ip6 4 . 285.It Dv IPV6CTL_GIF_HLIM 286.Pq ip6.gifhlim 287Integer: default maximum hop limit value for an 288.Tn IPv6 289packet generated by 290.Xr gif 4 291tunnel interface. 292.It Dv IPV6CTL_KAME_VERSION 293.Pq ip6.kame_version 294String: identifies the version of KAME 295.Tn IPv6 296stack implemented in the kernel. 297.It Dv IPV6CTL_USE_DEPRECATED 298.Pq ip6.use_deprecated 299Boolean: enable/disable use of deprecated address, 300specified in RFC2462 5.5.4. 301Defaults to on. 302.It Dv IPV6CTL_RR_PRUNE 303.Pq ip6.rr_prune 304Integer: default interval between 305.Tn IPv6 306router renumbering prefix babysitting, in seconds. 307.It Dv IPV6CTL_V6ONLY 308.Pq ip6.v6only 309Boolean: enable/disable the prohibited use of 310.Tn IPv4 311mapped address on 312.Dv AF_INET6 313sockets. 314Defaults to on. 315.El 316.Ss Interaction between IPv4/v6 sockets 317By default, 318.Fx 319does not route IPv4 traffic to 320.Dv AF_INET6 321sockets. 322The default behavior intentionally violates RFC2553 for security reasons. 323Listen to two sockets if you want to accept both IPv4 and IPv6 traffic. 324IPv4 traffic may be routed with certain 325per-socket/per-node configuration, however, it is not recommended to do so. 326Consult 327.Xr ip6 4 328for details. 329.Pp 330The behavior of 331.Dv AF_INET6 332TCP/UDP socket is documented in RFC2553. 333Basically, it says this: 334.Bl -bullet -compact 335.It 336A specific bind on an 337.Dv AF_INET6 338socket 339.Xr ( bind 2 340with an address specified) 341should accept IPv6 traffic to that address only. 342.It 343If you perform a wildcard bind 344on an 345.Dv AF_INET6 346socket 347.Xr ( bind 2 348to IPv6 address 349.Li :: ) , 350and there is no wildcard bind 351.Dv AF_INET 352socket on that TCP/UDP port, IPv6 traffic as well as IPv4 traffic 353should be routed to that 354.Dv AF_INET6 355socket. 356IPv4 traffic should be seen as if it came from an IPv6 address like 357.Li ::ffff:10.1.1.1 . 358This is called an IPv4 mapped address. 359.It 360If there are both a wildcard bind 361.Dv AF_INET 362socket and a wildcard bind 363.Dv AF_INET6 364socket on one TCP/UDP port, they should behave separately. 365IPv4 traffic should be routed to the 366.Dv AF_INET 367socket and IPv6 should be routed to the 368.Dv AF_INET6 369socket. 370.El 371.Pp 372However, RFC2553 does not define the ordering constraint between calls to 373.Xr bind 2 , 374nor how IPv4 TCP/UDP port numbers and IPv6 TCP/UDP port numbers 375relate to each other 376(should they be integrated or separated). 377Implemented behavior is very different from kernel to kernel. 378Therefore, it is unwise to rely too much upon the behavior of 379.Dv AF_INET6 380wildcard bind sockets. 381It is recommended to listen to two sockets, one for 382.Dv AF_INET 383and another for 384.Dv AF_INET6 , 385when you would like to accept both IPv4 and IPv6 traffic. 386.Pp 387It should also be noted that 388malicious parties can take advantage of the complexity presented above, 389and are able to bypass access control, 390if the target node routes IPv4 traffic to 391.Dv AF_INET6 392socket. 393Users are advised to take care handling connections 394from IPv4 mapped address to 395.Dv AF_INET6 396sockets. 397.Sh SEE ALSO 398.Xr ioctl 2 , 399.Xr socket 2 , 400.Xr sysctl 3 , 401.Xr icmp6 4 , 402.Xr intro 4 , 403.Xr ip6 4 , 404.Xr tcp 4 , 405.Xr udp 4 406.Sh STANDARDS 407.Rs 408.%A Tatsuya Jinmei 409.%A Atsushi Onoe 410.%T "An Extension of Format for IPv6 Scoped Addresses" 411.%R internet draft 412.%D June 2000 413.%N draft-ietf-ipngwg-scopedaddr-format-02.txt 414.%O work in progress material 415.Re 416.Sh HISTORY 417The 418.Nm 419protocol interfaces are defined in RFC2553 and RFC2292. 420The implementation described herein appeared in the WIDE/KAME project. 421.Sh BUGS 422The IPv6 support is subject to change as the Internet protocols develop. 423Users should not depend on details of the current implementation, 424but rather the services exported. 425.Pp 426Users are suggested to implement 427.Dq version independent 428code as much as possible, as you will need to support both 429.Xr inet 4 430and 431.Nm . 432