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.
$Id: inet6.4,v 1.1.1.1 1999/08/08 23:30:37 itojun Exp $
$FreeBSD: head/share/man/man4/inet6.4 57636 2000-03-01 02:37:46Z gsutter $
.Dd January 29, 1999 .Dt INET6 4 .Os .Sh NAME .Nm inet6 .Nd Internet protocol version 6 family .Sh SYNOPSIS .Fd #include <sys/types.h> .Fd #include <netinet/in.h> .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.
p .Nm is a collection of protocols layered atop the .Em Internet Protocol version 6
q Tn IPv6 network layer, and utilizing the IPv6 address format. The .Nm family provides protocol support for the .Dv SOCK_STREAM , 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 format. The include file .Aq Pa netinet/in.h defines this address as a discriminated union.
p Sockets bound to the .Nm family utilize the following addressing structure, d -literal -offset indent struct sockaddr_in6 { u_char sin6_len; u_char sin6_family; u_int16_t sin6_port; u_int32_t sin6_flowinfo; struct in6_addr sin6_addr; u_int32_t sin6_scope_id; }; .Ed
p Sockets may be created with the local address .Dq Dv ::
o which is equal to IPv6 address .Dv 0:0:0:0:0:0:0:0
c to effect .Dq wildcard matching on incoming messages. The address in a .Xr connect 2 or .Xr sendto 2 call may be given as .Dq Dv :: to mean .Dq this host . The address .Dq Dv :: can be obtained by setting the .Dv sin6_addr field to 0, or by using the address contained in the variable .Dv in6addr_any .
p IPv6 defines scoped addresses such as link-local or site-local addresses. To manipulate link-local addresses properly from the userland, programs must use the advanced API defined in RFC2292. Otherwise, the address is ambiguous to the kernel and an error will be generated. Scoped addressing is not for daily use at this time, and is discouraged both by the specifications and specific implementations.
p FreeBSD's IPv6 implementation supports extended numeric IPv6 address notation for link-local addresses, like .Dq Li fe80::1%de0 to specify .Do .Li fe80::1 on the .Li de0 interface .Dc . This notation is supported by .Xr getaddrinfo 3 and .Xr getnameinfo 3 . Some of the normal userland programs, such as .Xr telnet 1 or .Xr ftp 8 , are able to use this notation. With some special programs such as .Xr ping6 8 , you can specify an outgoing interface by an extra command line option to disambiguate scoped addresses.
p Scoped addresses are handled specially in the kernel. Scoped addresses will have their interface indices embedded into the address, in the routing table or interface structures. Therefore, a scoped address may have a different representation in the kernel than on the wire. The embedded index will be visible in .Dv PF_ROUTE sockets, kernel memory accesses via .Xr kvm 3 and some other occasions. HOWEVER, users should never use the embedded form. For details, please consult
a IMPLEMENTATION supplied with the KAME kit. .Sh PROTOCOLS The .Nm family is comprised of the .Tn IPv6 network protocol, Internet Control Message Protocol version 6
q Tn ICMPv6 , Transmission Control Protocol
q Tn TCP , and User Datagram Protocol
q 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.
.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 ttcp 4 ,
.Xr udp 4
.Sh CAVEAT
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.
p 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 . .Sh HISTORY The .Nm IPv6 APIs are defined in RFC2553 and RFC2292. The implementation described herein appeared in WIDE/KAME project.