648 lines
21 KiB
Groff
648 lines
21 KiB
Groff
.\" $NetBSD: ip6.4,v 1.1 1999/12/20 05:50:49 itojun Exp $
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.\"
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.\" Copyright (C) 1999 WIDE Project.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the project nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" KAME Id: ip6.4,v 1.3 1999/12/20 01:53:35 jinmei Exp
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.\"
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.Dd December 17, 1999
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.Dt IP6 4
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.Os
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.\"
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.Sh NAME
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.Nm ip6
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.Nd Internet Protocol version 6 (IPv6)
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.\"
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.Sh SYNOPSIS
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.Fd #include <sys/socket.h>
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.Fd #include <netinet/in.h>
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.Ft int
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.Fn socket AF_INET6 SOCK_RAW proto
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.\"
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.Sh DESCRIPTION
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.Tn IPv6
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is the network layer protocol used by the Internet protocol version 6 family
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.Pq Dv AF_INET6 .
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Options may be set at the
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.Tn IPv6
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level when using higher-level protocols that are based on
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.Tn IPv6
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(such as
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.Tn TCP
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and
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.Tn UDP ) .
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It may also be accessed through a
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.Dq raw socket
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when developing new protocols, or special-purpose applications.
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.Pp
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There are several
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.Tn IPv6-level
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.Xr setsockopt 2 / Ns Xr getsockopt 2
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options.
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They are be separated into the basic IPv6 sockets API
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.Pq defined in RFC2553 ,
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and the advanced API
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.Pq defined in RFC2292 .
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The basic API looks very similar to the API presented in
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.Xr ip 4 .
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Advanced API uses ancillary data and can handle more complex cases.
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.Pp
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To specify some of socket options, certain privilege
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(i.e. root privilege) is required.
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.\"
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.Ss Basic IPv6 sockets API
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.Dv IPV6_UNICAST_HOPS
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may be used to set the hoplimit field in the
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.Tn IPv6
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header.
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As symbol name suggests, the option controls hoplimit field on unicast packets.
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If -1 is specified, the kernel will use a default value.
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If a value of 0 to 255 is specified, the packet will have the specified
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value as hoplimit.
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Other values are considered invalid, and
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.Dv EINVAL
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will be returned.
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For example:
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.Bd -literal -offset indent
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int hlim = 60; /* max = 255 */
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setsockopt(s, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &hlim, sizeof(hlim));
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.Ed
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.Pp
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.Tn IPv6
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multicasting is supported only on
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.Dv AF_INET6
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sockets of type
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.Dv SOCK_DGRAM
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and
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.Dv SOCK_RAW,
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and only on networks where the interface driver supports multicasting.
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.Pp
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The
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.Dv IPV6_MULTICAST_HOPS
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option changes the hoplimit for outgoing multicast datagrams
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in order to control the scope of the multicasts:
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.Bd -literal -offset indent
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unsigned int hlim; /* range: 0 to 255, default = 1 */
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setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &hlim, sizeof(hlim));
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.Ed
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.Pp
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Datagrams with a hoplimit of 1 are not forwarded beyond the local network.
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Multicast datagrams with a hoplimit of 0 will not be transmitted on any network,
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but may be delivered locally if the sending host belongs to the destination
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group and if multicast loopback has not been disabled on the sending socket
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(see below).
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Multicast datagrams with hoplimit greater than 1 may be forwarded
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to other networks if a multicast router is attached to the local network.
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.Pp
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For hosts with multiple interfaces, each multicast transmission is
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sent from the primary network interface.
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The
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.Dv IPV6_MULTICAST_IF
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option overrides the default for
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subsequent transmissions from a given socket:
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.Bd -literal -offset indent
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unsigned int outif;
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outif = if_nametoindex("ne0");
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setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_IF, &outif, sizeof(outif));
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.Ed
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.Pp
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where "outif" is an interface index of the desired interface,
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or 0 to specify the default interface.
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.Pp
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If a multicast datagram is sent to a group to which the sending host itself
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belongs (on the outgoing interface), a copy of the datagram is, by default,
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looped back by the IPv6 layer for local delivery.
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The
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.Dv IPV6_MULTICAST_LOOP
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option gives the sender explicit control
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over whether or not subsequent datagrams are looped back:
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.Bd -literal -offset indent
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u_char loop; /* 0 = disable, 1 = enable (default) */
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setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &loop, sizeof(loop));
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.Ed
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.Pp
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This option
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improves performance for applications that may have no more than one
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instance on a single host (such as a router demon), by eliminating
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the overhead of receiving their own transmissions.
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It should generally not be used by applications for which there
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may be more than one instance on a single host (such as a conferencing
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program) or for which the sender does not belong to the destination
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group (such as a time querying program).
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.Pp
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A multicast datagram sent with an initial hoplimit greater than 1 may be delivered
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to the sending host on a different interface from that on which it was sent,
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if the host belongs to the destination group on that other interface.
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The loopback control option has no effect on such delivery.
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.Pp
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A host must become a member of a multicast group before it can receive
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datagrams sent to the group.
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To join a multicast group, use the
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.Dv IPV6_JOIN_GROUP
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option:
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.Bd -literal -offset indent
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struct ipv6_mreq mreq6;
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setsockopt(s, IPPROTO_IPV6, IPV6_JOIN_GROUP, &mreq6, sizeof(mreq6));
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.Ed
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.Pp
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where
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.Fa mreq6
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is the following structure:
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.Bd -literal -offset indent
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struct ipv6_mreq {
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struct in6_addr ipv6mr_multiaddr;
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u_int ipv6mr_interface;
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};
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.Ed
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.Pp
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.Dv ipv6mr_interface
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should be 0 to choose the default multicast interface, or the
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interface index of a particular multicast-capable interface if
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the host is multihomed.
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Membership is associated with a single interface;
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programs running on multihomed hosts may need to
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join the same group on more than one interface.
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.Pp
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To drop a membership, use:
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.Bd -literal -offset indent
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struct ipv6_mreq mreq6;
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setsockopt(s, IPPROTO_IPV6, IPV6_LEAVE_GROUP, &mreq6, sizeof(mreq6));
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.Ed
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.Pp
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where
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.Fa mreq6
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contains the same values as used to add the membership.
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Memberships are dropped when the socket is closed or the process exits.
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.Pp
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.Dv IPV6_PORTRANGE
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controls how ephemeral ports are allocated for
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.Dv SOCK_STREAM
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and
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.Dv SOCK_DGRAM
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sockets.
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For example,
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.Bd -literal -offset indent
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int range = IPV6_PORTRANGE_LOW; /* see <netinet/in.h> */
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setsockopt(s, IPPROTO_IPV6, IPV6_PORTRANGE, &range, sizeof(range));
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.Ed
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.\"
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.Ss Advanced IPv6 sockets API
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The advanced IPv6 sockets API lets userland programs to specify, or obtain,
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details about the IPv6 header and the IPv6 extension headers on packets.
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The advanced API uses ancillary data for passing data from/to the kernel.
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.Pp
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There are
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.Xr setsockopt 2 / Ns Xr getsockopt 2
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flags to get optional information on packets for incoming packets.
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They are
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.Dv IPV6_PKTINFO ,
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.Dv IPV6_HOPLIMIT ,
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.Dv IPV6_HOPOPTS ,
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.Dv IPV6_DSTOPTS ,
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and
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.Dv IPV6_RTHDR .
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.Bd -literal -offset indent
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int on = 1;
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setsockopt(fd, IPPROTO_IPV6, IPV6_PKTINFO, &on, sizeof(on));
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setsockopt(fd, IPPROTO_IPV6, IPV6_HOPLIMIT, &on, sizeof(on));
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setsockopt(fd, IPPROTO_IPV6, IPV6_HOPOPTS, &on, sizeof(on));
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setsockopt(fd, IPPROTO_IPV6, IPV6_DSTOPTS, &on, sizeof(on));
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setsockopt(fd, IPPROTO_IPV6, IPV6_RTHDR, &on, sizeof(on));
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.Ed
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.Pp
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When any of these options are enabled, the corresponding data is
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returned as control information by
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.Xr recvmsg2 ,
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as one or more ancillary data objects.
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.Pp
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If
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.Dv IPV6_PKTINFO
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is enabled, destination IPv6 address and arriving interface index
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will be made available via
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.Li struct in6_pktinfo
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on ancillary data stream.
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You can pick the structure by checking for an ancillary data item with
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.Li cmsg_level
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equals to
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.Dv IPPROTO_IPV6 ,
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and
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.Li cmsg_type
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equals to
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.Dv IPV6_PKTINFO .
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.Pp
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If
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.Dv IPV6_HOPLIMIT
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is enabled, hoplimit value on the packet will be made available to the
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userland program.
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ancillary data stream will contain an integer data item with
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.Li cmsg_level
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equals to
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.Dv IPPROTO_IPV6 ,
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and
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.Li cmsg_type
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equals to
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.Dv IPV6_HOPLIMIT .
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.Pp
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.Xr inet6_option_space 3
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and friends will help you parse ancillary data items for
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.Dv IPV6_HOPOPTS
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and
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.Dv IPV6_DSTOPTS .
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Similarly,
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.Xr inet6_rthdr_space 3
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and friends will help you parse ancillary data items for
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.Dv IPV6_RTHDR .
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.Pp
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.Dv IPV6_HOPOPTS
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and
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.Dv IPV6_DSTOPTS
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may appear multiple times on an ancillary data stream.
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Other ancillary data item will appear no more than once.
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.Pp
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For outgoing direction,
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you can pass ancillary data items with normal payload data, using
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.Xr sendmsg 2 .
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Ancillary data items will be parsed by the kernel, and used to construct
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the IPv6 header and extension headers.
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For the 5
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.Li cmsg_level
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values listed above, ancillary data format is the same as inbound case.
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Additionally, you can specify
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.Dv IPV6_NEXTHOP
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data object.
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The
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.Dv IPV6_NEXTHOP
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ancillary data object specifies the next hop for the
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datagram as a socket address structure.
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In the
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.Li cmsghdr
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structure
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containing this ancillary data, the
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.Li cmsg_level
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member will be
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.Dv IPPROTO_IPV6 ,
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the
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.Li cmsg_type
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member will be
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.Dv IPV6_NEXTHOP ,
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and the first byte of
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.Li cmsg_data[]
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will be the first byte of the socket address structure.
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.Pp
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If the socket address structure contains an IPv6 address (e.g., the
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sin6_family member is
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.Dv AF_INET6
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), then the node identified by that
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address must be a neighbor of the sending host.
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If that address
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equals the destination IPv6 address of the datagram, then this is
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equivalent to the existing
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.Dv SO_DONTROUTE
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socket option.
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.Pp
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For applications that do not, or unable to use
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.Xr sendmsg 2
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or
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.Xr recvmsg 2 ,
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.Dv IPV6_PKTOPTIONS
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socket option is defined.
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Setting the socket option specifies any of the optional output fields:
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.Bd -literal -offset indent
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setsockopt(fd, IPPROTO_IPV6, IPV6_PKTOPTIONS, &buf, len);
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.Ed
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.Pp
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The fourth argument points to a buffer containing one or more
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ancillary data objects, and the fifth argument is the total length of
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all these objects.
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The application fills in this buffer exactly as
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if the buffer were being passed to
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.Xr sendmsg 2
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as control information.
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.Pp
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The options set by calling
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.Xr setsockopt 2
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for
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.Dv IPV6_PKTOPTIONS
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are
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called "sticky" options because once set they apply to all packets
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sent on that socket.
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The application can call
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.Xr setsockopt 2
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again to
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change all the sticky options, or it can call
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.Xr setsockopt 2
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with a
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length of 0 to remove all the sticky options for the socket.
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.Pp
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The corresponding receive option
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.Bd -literal -offset indent
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getsockopt(fd, IPPROTO_IPV6, IPV6_PKTOPTIONS, &buf, &len);
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.Ed
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.Pp
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returns a buffer with one or more ancillary data objects for all the
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optional receive information that the application has previously
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specified that it wants to receive.
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The fourth argument points to
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the buffer that is filled in by the call.
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The fifth argument is a
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pointer to a value-result integer: when the function is called the
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integer specifies the size of the buffer pointed to by the fourth
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argument, and on return this integer contains the actual number of
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bytes that were returned.
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The application processes this buffer
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exactly as if the buffer were returned by
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.Xr recvmsg 2
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as control information.
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.\"
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.Ss Advanced API and TCP sockets
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When using
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.Xr getsockopt 2
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with the
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.Dv IPV6_PKTOPTIONS
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option and a
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.Tn TCP
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socket, only the options from the most recently received segment are
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retained and returned to the caller, and only after the socket option
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has been set.
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.\" That is,
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.\" .Tn TCP
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.\" need not start saving a copy of the options until the application says
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.\" to do so.
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The application is not allowed to specify ancillary data in a call to
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.Xr sendmsg 2
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on a
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.Tn TCP
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socket, and none of the ancillary data that we
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described above is ever returned as control information by
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.Xr recvmsg 2
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on a
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.Tn TCP
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socket.
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.\"
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.Ss Conflict resolution
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In some cases, there are multiple APIs defined for manipulating
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a IPv6 header field.
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A good example is the outgoing interface for multicast datagrams:
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it can be manipulated by
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.Dv IPV6_MULTICAST_IF
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in basic API,
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.Dv IPV6_PKTINFO
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in advanced API, and
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.Li sin6_scope_id
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field of the socket address passed to
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.Xr sendto 2 .
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.Pp
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When conflicting options are given to the kernel,
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the kernel will get the value in the following preference:
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(1) options specified by using advanced API,
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(2) options specified by socket address, and lastly
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(3) options specified by using basic API.
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.\"
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.Ss "Raw IPv6 Sockets"
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Raw
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.Tn IPv6
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sockets are connectionless, and are normally used with the
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.Xr sendto 2
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and
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.Xr recvfrom 2
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calls, though the
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.Xr connect 2
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call may also be used to fix the destination for future
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packets (in which case the
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.Xr read 2
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or
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.Xr recv 2
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and
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.Xr write 2
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or
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.Xr send 2
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system calls may be used).
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.Pp
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If
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.Fa proto
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is 0, the default protocol
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.Dv IPPROTO_RAW
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is used for outgoing packets, and only incoming packets destined
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for that protocol are received.
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If
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.Fa proto
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is non-zero, that protocol number will be used on outgoing packets
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and to filter incoming packets.
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.Pp
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Outgoing packets automatically have an
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.Tn IPv6
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header prepended to them (based on the destination address and the
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protocol number the socket is created with).
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Incoming packets are received without
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.Tn IPv6
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header nor extension headers.
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.Pp
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All data sent via raw sockets MUST be in network byte order and all
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data received via raw sockets will be in network byte order.
|
|
This differs from the IPv4 raw sockets, which did not specify a byte
|
|
ordering and typically used the host's byte order.
|
|
.Pp
|
|
Another difference from IPv4 raw sockets is that complete packets
|
|
(that is, IPv6 packets with extension headers) cannot be read or
|
|
written using the IPv6 raw sockets API.
|
|
Instead, ancillary data
|
|
objects are used to transfer the extension headers, as described above.
|
|
Should an application need access to the
|
|
complete IPv6 packet, some other technique, such as the datalink
|
|
interfaces, such as
|
|
.Xr bpf 4 ,
|
|
must be used.
|
|
.Pp
|
|
All fields in the IPv6 header that an application might want to
|
|
change (i.e., everything other than the version number) can be
|
|
modified using ancillary data and/or socket options by the
|
|
application for output.
|
|
All fields in a received IPv6 header (other
|
|
than the version number and Next Header fields) and all extension
|
|
headers are also made available to the application as ancillary data
|
|
on input.
|
|
Hence there is no need for a socket option similar to the
|
|
IPv4
|
|
.Dv IP_HDRINCL
|
|
socket option.
|
|
.Pp
|
|
When writing to a raw socket the kernel will automatically fragment
|
|
the packet if its size exceeds the path MTU, inserting the required
|
|
fragmentation headers. On input the kernel reassembles received
|
|
fragments, so the reader of a raw socket never sees any fragment
|
|
headers.
|
|
.Pp
|
|
Most IPv4 implementations give special treatment to a raw socket
|
|
created with a third argument to
|
|
.Xr socket 2
|
|
of
|
|
.Dv IPPROTO_RAW ,
|
|
whose value is normally 255.
|
|
We note that this value has no special meaning to
|
|
an IPv6 raw socket (and the IANA currently reserves the value of 255
|
|
when used as a next-header field).
|
|
.\" Note: This feature was added to
|
|
.\" IPv4 in 1988 by Van Jacobson to support traceroute, allowing a
|
|
.\" complete IP header to be passed by the application, before the
|
|
.\" .Dv IP_HDRINCL
|
|
.\" socket option was added.
|
|
.Pp
|
|
For ICMPv6 raw sockets,
|
|
the kernel will calculate and insert the ICMPv6 checksum for
|
|
since this checksum is mandatory.
|
|
.Pp
|
|
For other raw IPv6 sockets (that is, for raw IPv6 sockets created
|
|
with a third argument other than IPPROTO_ICMPV6), the application
|
|
must set the new IPV6_CHECKSUM socket option to have the kernel (1)
|
|
compute and store a psuedo header checksum for output,
|
|
and (2) verify the received
|
|
pseudo header checksum on input,
|
|
discarding the packet if the checksum is in error.
|
|
This option prevents applications from having to perform source
|
|
address selection on the packets they send.
|
|
The checksum will
|
|
incorporate the IPv6 pseudo-header, defined in Section 8.1 of RFC2460.
|
|
This new socket option also specifies an integer offset into
|
|
the user data of where the checksum is located.
|
|
.Bd -literal -offset indent
|
|
int offset = 2;
|
|
setsockopt(fd, IPPROTO_IPV6, IPV6_CHECKSUM, &offset, sizeof(offset));
|
|
.Ed
|
|
.Pp
|
|
By default, this socket option is disabled. Setting the offset to -1
|
|
also disables the option. By disabled we mean (1) the kernel will
|
|
not calculate and store a checksum for outgoing packets, and (2) the
|
|
kernel will not verify a checksum for received packets.
|
|
.Pp
|
|
Note: Since the checksum is always calculated by the kernel for an
|
|
ICMPv6 socket, applications are not able to generate ICMPv6 packets
|
|
with incorrect checksums (presumably for testing purposes) using this
|
|
API.
|
|
.\"
|
|
.Sh DIAGNOSTICS
|
|
A socket operation may fail with one of the following errors returned:
|
|
.Bl -tag -width [EADDRNOTAVAIL]
|
|
.It Bq Er EISCONN
|
|
when trying to establish a connection on a socket which already
|
|
has one, or when trying to send a datagram with the destination
|
|
address specified and the socket is already connected;
|
|
.It Bq Er ENOTCONN
|
|
when trying to send a datagram, but no destination address is
|
|
specified, and the socket hasn't been connected;
|
|
.It Bq Er ENOBUFS
|
|
when the system runs out of memory for an internal data structure;
|
|
.It Bq Er EADDRNOTAVAIL
|
|
when an attempt is made to create a socket with a network address
|
|
for which no network interface exists.
|
|
.It Bq Er EACCES
|
|
when an attempt is made to create a raw IPv6 socket by a non-privileged process.
|
|
.El
|
|
.Pp
|
|
The following errors specific to
|
|
.Tn IPv6
|
|
may occur:
|
|
.Bl -tag -width EADDRNOTAVAILxx
|
|
.It Bq Er EINVAL
|
|
An unknown socket option name was given.
|
|
.It Bq Er EINVAL
|
|
The ancillary data items were improperly formed, or option name was unknown.
|
|
.El
|
|
.\"
|
|
.Sh SEE ALSO
|
|
.Xr getsockopt 2 ,
|
|
.Xr send 2 ,
|
|
.Xr setsockopt 2 ,
|
|
.Xr recv 2 ,
|
|
.Xr inet6_option_space 3 ,
|
|
.Xr inet6_rthdr_space 3 ,
|
|
.Xr intro 4 ,
|
|
.Xr icmp6 4 ,
|
|
.Xr inet6 4
|
|
.Rs
|
|
.%A W. Stevens
|
|
.%A M. Thomas
|
|
.%R RFC
|
|
.%N 2292
|
|
.%D February 1998
|
|
.%T "Advanced Sockets API for IPv6"
|
|
.Re
|
|
.Rs
|
|
.%A S. Deering
|
|
.%A R. Hinden
|
|
.%R RFC
|
|
.%N 2460
|
|
.%D December 1998
|
|
.%T "Internet Protocol, Version 6 (IPv6) Specification"
|
|
.Re
|
|
.\"
|
|
.Sh STANDARDS
|
|
Most of the socket options are defined in
|
|
RFC2292 and/or RFC2553.
|
|
.Dv IPV6_PORTRANGE
|
|
and conflict resolution rule
|
|
is not defined in the RFCs and should be considered implementation dependent.
|
|
.\"
|
|
.Sh HISTORY
|
|
The implementation is based on KAME stack
|
|
.Po
|
|
which is decendant of WIDE hydrangea IPv6 stack kit
|
|
.Pc .
|
|
.Pp
|
|
Part of the document was shamelessly copied from RFC2553 and RFC2292.
|