path: root/share/man/man4/inet6.4

.\"	$OpenBSD: inet6.4,v 1.8 2000/03/28 23:46:31 deraadt Exp $
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.\"	KAME Id: inet6.4,v 1.7 2000/03/22 07:59:10 jinmei Exp
.\"
.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.
.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 , 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.
.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. 
The address in a
.Xr connect 2
or
.Xr sendto 2
call may be given as
.Dq Dv ::
to mean
.Dq this host .
.Dq Dv ::
can be obtained by setting
.Dv sin6_addr
field into 0, or by using the address contained in variable
.Dv in6addr_any .
.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 8 ,
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 kenrel 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 sys/netinet6/IMPLEMENTATION .
.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.
.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 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.
.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 .
.Sh STANDARDS
.Rs
.%A Tatsuya Jinmei
.%A Atsushi Onoe
.%T "An Extension of Format for IPv6 Scoped Addresses"
.%R internet draft
.%D March 2000
.%N draft-ietf-ipngwg-scopedaddr-format-01.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.