.\" $OpenBSD: inet6.4,v 1.22 2001/06/24 19:42:23 itojun Exp $ .\" $KAME: inet6.4,v 1.19 2000/11/24 10:13:18 itojun Exp $ .\" .\" Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the project nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .Dd January 29, 1999 .Dt INET6 4 .Os .Sh NAME .Nm inet6 .Nd Internet protocol version 6 family .Sh SYNOPSIS .Fd #include .Fd #include .Sh DESCRIPTION The .Nm family is an updated version of .Xr inet 4 family. While .Xr inet 4 implements Internet Protocol version 4, .Nm implements Internet Protocol version 6. .Pp .Nm is a collection of protocols layered atop the .Em Internet Protocol version 6 .Pq Tn IPv6 transport layer, and utilizing the IPv6 address format. The .Nm family provides protocol support for the .Dv SOCK_STREAM , .Dv SOCK_DGRAM , and .Dv SOCK_RAW socket types; the .Dv SOCK_RAW interface provides access to the .Tn IPv6 protocol. .Sh ADDRESSING IPv6 addresses are 16 byte quantities, stored in network standard byteorder. The include file .Aq Pa netinet/in.h defines this address as a discriminated union. .Pp Sockets bound to the .Nm family utilize the following addressing structure: .Bd -literal -offset indent struct sockaddr_in6 { u_int8_t sin6_len; sa_family_t sin6_family; in_port_t sin6_port; u_int32_t sin6_flowinfo; struct in6_addr sin6_addr; u_int32_t sin6_scope_id; }; .Ed .Pp Sockets may be created with the local address .Dq Dv :: .Po which is equal to IPv6 address .Dv 0:0:0:0:0:0:0:0 .Pc to effect .Dq wildcard matching on incoming messages. .Pp IPv6 specification defines scoped address, like link-local or site-local address. A scoped address is ambiguous to the kernel, if it is specified without scope identifier. To manipulate scoped addresses properly from the userland, programs must use advanced API defined in RFC2292. Compact description on the advanced API is available in .Xr ip6 4 . If scoped addresses are specified without explicit scope, the kernel may raise error. Note that scoped addresses are not for daily use at this moment, both from specification and implementation point of view. .Pp KAME implementation supports extended numeric IPv6 address notation for link-local addresses, like .Dq Li fe80::1%de0 to specify .Do .Li fe80::1 on .Li de0 interface .Dc . The notation is supported by .Xr getaddrinfo 3 and .Xr getnameinfo 3 . Some of normal userland programs, such as .Xr telnet 1 or .Xr ftp 1 , are able to use the notation. With special programs like .Xr ping6 8 , you can specify outgoing interface by extra command line option to disambiguate scoped addresses. .Pp Scoped addresses are handled specially in the kernel. In the kernel structures like routing tables or interface structure, scoped addresses will have its interface index embedded into the address. Therefore, the address on some of the kernel structure is not the same as that on the wire. The embedded index will become visible on .Dv PF_ROUTE socket, kernel memory accesses via .Xr kvm 3 and some other occasions. HOWEVER, users should never use the embedded form. For details please consult .Pa http://www.kame.net/dev/cvsweb.cgi/kame/IMPLEMENTATION . Note that the above URL describes the situation with the latest KAME tree, not the .Ox tree. .Sh PROTOCOLS The .Nm family is comprised of the .Tn IPv6 network protocol, Internet Control Message Protocol version 6 .Pq Tn ICMPv6 , Transmission Control Protocol .Pq Tn TCP , and User Datagram Protocol .Pq Tn UDP . .Tn TCP is used to support the .Dv SOCK_STREAM abstraction while .Tn UDP is used to support the .Dv SOCK_DGRAM abstraction. Note that .Tn TCP and .Tn UDP are common to .Xr inet 4 and .Nm inet6 . A raw interface to .Tn IPv6 is available by creating an Internet socket of type .Dv SOCK_RAW . The .Tn ICMPv6 message protocol is accessible from a raw socket. .\" .Pp .\" The 128-bit IPv6 address contains both network and host parts. .\" However, direct examination of addresses is discouraged. .\" For those programs which absolutely need to break addresses .\" into their component parts, the following .\" .Xr ioctl 2 .\" commands are provided for a datagram socket in the .\" .Nm .\" domain; they have the same form as the .\" .Dv SIOCIFADDR .\" command (see .\" .Xr intro 4 ) . .\" .Pp .\" .Bl -tag -width SIOCSIFNETMASK .\" .It Dv SIOCSIFNETMASK .\" Set interface network mask. .\" The network mask defines the network part of the address; .\" if it contains more of the address than the address type would indicate, .\" then subnets are in use. .\" .It Dv SIOCGIFNETMASK .\" Get interface network mask. .\" .El .\" .Sh ROUTING .\" The current implementation of Internet protocols includes some routing-table .\" adaptations to provide enhanced caching of certain end-to-end .\" information necessary for Transaction TCP and Path MTU Discovery. The .\" following changes are the most significant: .\" .Bl -enum .\" .It .\" All IP routes, except those with the .\" .Dv RTF_CLONING .\" flag and those to multicast destinations, have the .\" .Dv RTF_PRCLONING .\" flag forcibly enabled (they are thus said to be .\" .Dq "protocol cloning" ). .\" .It .\" When the last reference to an IP route is dropped, the route is .\" examined to determine if it was created by cloning such a route. If .\" this is the case, the .\" .Dv RTF_PROTO3 .\" flag is turned on, and the expiration timer is initialized to go off .\" in net.inet.ip.rtexpire seconds. If such a route is re-referenced, .\" the flag and expiration timer are reset. .\" .It .\" A kernel timeout runs once every ten minutes, or sooner if there are .\" soon-to-expire routes in the kernel routing table, and deletes the .\" expired routes. .\" .El .\" .Pp .\" A dynamic process is in place to modify the value of .\" net.inet.ip.rtexpire if the number of cached routes grows too large. .\" If after an expiration run there are still more than .\" net.inet.ip.rtmaxcache unreferenced routes remaining, the rtexpire .\" value is multiplied by 3/4, and any routes which have longer .\" expiration times have those times adjusted. This process is damped .\" somewhat by specification of a minimum rtexpire value .\" (net.inet.ip.rtminexpire), and by restricting the reduction to once in .\" a ten-minute period. .\" .Pp .\" If some external process deletes the original route from which a .\" protocol-cloned route was generated, the ``child route'' is deleted. .\" (This is actually a generic mechanism in the routing code support for .\" protocol-requested cloning.) .\" .Pp .\" No attempt is made to manage routes which were not created by protocol .\" cloning; these are assumed to be static, under the management of an .\" external routing process, or under the management of a link layer .\" (e.g., .\" .Tn ARP .\" for Ethernets). .\" .Pp .\" Only certain types of network activity will result in the cloning of a .\" route using this mechanism. Specifically, those protocols (such as .\" .Tn TCP .\" and .\" .Tn UDP ) .\" which themselves cache a long-lasting reference to route for a destination .\" will trigger the mechanism; whereas raw .\" .Tn IP .\" packets, whether locally-generated or forwarded, will not. .Ss Interaction between IPv4/v6 sockets The behavior of .Dv AF_INET6 TCP/UDP socket is documented in RFC2553. Basically, it says as follows: .Bl -bullet -compact .It Specific bind on .Dv AF_INET6 socket .Po .Xr bind 2 with address specified .Pc should accept IPv6 traffic to that address only. .It If you perform wildcard bind on .Dv AF_INET6 socket .Po .Xr bind 2 to IPv6 address .Li :: .Pc , and there is no wildcard bind .Dv AF_INET socket on that TCP/UDP port, IPv6 traffic as well as IPv4 traffic should be routed to that .Dv AF_INET6 socket. IPv4 traffic should be seen as if it came from IPv6 address like .Li ::ffff:10.1.1.1 . This is called IPv4 mapped address. .It If there are both wildcard bind .Dv AF_INET socket and wildcard bind .Dv AF_INET6 socket on one TCP/UDP port, they should behave separately. IPv4 traffic should be routed to .Dv AF_INET socket and IPv6 should be routed to .Dv AF_INET6 socket. .El .Pp However, RFC2553 does not define the constraint between the order of .Xr bind 2 , nor how IPv4 TCP/UDP port number and IPv6 TCP/UDP port number relate each other .Po should they be integrated or separated .Pc . Implemented behavior is very different across kernel to kernel. Therefore, it is unwise to rely too much upon the behavior of .Dv AF_INET6 wildcard bind socket. It is recommended to listen to two sockets, one for .Dv AF_INET and another for .Dv AF_INET6 , when you would like to accept both IPv4 and IPv6 traffic. .Pp It should also be noted that malicious parties can take advantage of the complexity presented above, and are able to bypass access control, if the target node routes IPv4 traffic to .Dv AF_INET6 socket. Users are advised to take caution handling connections from IPv4 mapped address to .Dv AF_INET6 sockets. .Pp Because of the above, .Ox does not route IPv4 traffic to .Dv AF_INET6 socket. The particular behavior in RFC2553 is intentionally omitted for security reasons presented above. If you need to accept both IPv4 and IPv6 traffic, listen to two sockets. .Sh SEE ALSO .Xr ioctl 2 , .Xr socket 2 , .Xr sysctl 3 , .Xr icmp6 4 , .Xr intro 4 , .Xr ip6 4 , .Xr tcp 4 , .Xr udp 4 .Sh STANDARDS .Rs .%A Tatsuya Jinmei .%A Atsushi Onoe .%T "An Extension of Format for IPv6 Scoped Addresses" .%R internet draft .%D June 2000 .%N draft-ietf-ipngwg-scopedaddr-format-02.txt .%O work in progress material .Re .Sh HISTORY The .Nm protocol interface are defined in RFC2553 and RFC2292. The implementation described herein appeared in WIDE/KAME project. .Sh BUGS The IPv6 support is subject to change as the Internet protocols develop. Users should not depend on details of the current implementation, but rather the services exported. .Pp Users are suggested to implement .Dq version independent code as much as possible, as you will need to support both .Xr inet 4 and .Nm inet6 .