710 lines
22 KiB
Groff
710 lines
22 KiB
Groff
.\" $KAME: ip6.4,v 1.14 2001/02/26 09:31:39 itojun Exp $
|
|
.\"
|
|
.\" Copyright (C) 1999 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.
|
|
.\"
|
|
.\" Copyright (c) 1983, 1991, 1993
|
|
.\" The Regents of the University of California. 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. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd March 13, 2000
|
|
.Dt IP6 4
|
|
.Os
|
|
.\"
|
|
.Sh NAME
|
|
.Nm ip6
|
|
.Nd Internet Protocol version 6 (IPv6)
|
|
.\"
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/types.h>
|
|
.Fd #include <sys/socket.h>
|
|
.Fd #include <netinet/in.h>
|
|
.Ft int
|
|
.Fn socket AF_INET6 SOCK_RAW proto
|
|
.\"
|
|
.Sh DESCRIPTION
|
|
.Tn IPv6
|
|
is the network layer protocol used by the Internet protocol version 6 family
|
|
.Pq Dv AF_INET6 .
|
|
Options may be set at the
|
|
.Tn IPv6
|
|
level when using higher-level protocols that are based on
|
|
.Tn IPv6
|
|
(such as
|
|
.Tn TCP
|
|
and
|
|
.Tn UDP ) .
|
|
It may also be accessed through a
|
|
.Dq raw socket
|
|
when developing new protocols, or special-purpose applications.
|
|
.Pp
|
|
There are several
|
|
.Tn IPv6-level
|
|
.Xr setsockopt 2 Ns / Ns Xr getsockopt 2
|
|
options.
|
|
They are separated into the basic IPv6 sockets API
|
|
.Pq defined in RFC2553 ,
|
|
and the advanced API
|
|
.Pq defined in RFC2292 .
|
|
The basic API looks very similar to the API presented in
|
|
.Xr ip 4 .
|
|
Advanced API uses ancillary data and can handle more complex cases.
|
|
.Pp
|
|
To specify some of socket options, certain privilege
|
|
(i.e. root privilege) is required.
|
|
.\"
|
|
.Ss Basic IPv6 sockets API
|
|
.Dv IPV6_UNICAST_HOPS
|
|
may be used to set the hoplimit field in the
|
|
.Tn IPv6
|
|
header.
|
|
As symbol name suggests, the option controls hoplimit field on unicast packets.
|
|
If -1 is specified, the kernel will use a default value.
|
|
If a value of 0 to 255 is specified, the packet will have the specified
|
|
value as hoplimit.
|
|
Other values are considered invalid, and
|
|
.Er EINVAL
|
|
will be returned.
|
|
For example:
|
|
.Bd -literal -offset indent
|
|
int hlim = 60; /* max = 255 */
|
|
setsockopt(s, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &hlim, sizeof(hlim));
|
|
.Ed
|
|
.Pp
|
|
.Tn IPv6
|
|
multicasting is supported only on
|
|
.Dv AF_INET6
|
|
sockets of type
|
|
.Dv SOCK_DGRAM
|
|
and
|
|
.Dv SOCK_RAW,
|
|
and only on networks where the interface driver supports multicasting.
|
|
.Pp
|
|
The
|
|
.Dv IPV6_MULTICAST_HOPS
|
|
option changes the hoplimit for outgoing multicast datagrams
|
|
in order to control the scope of the multicasts:
|
|
.Bd -literal -offset indent
|
|
unsigned int hlim; /* range: 0 to 255, default = 1 */
|
|
setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &hlim, sizeof(hlim));
|
|
.Ed
|
|
.Pp
|
|
Datagrams with a hoplimit of 1 are not forwarded beyond the local network.
|
|
Multicast datagrams with a hoplimit of 0 will not be transmitted on any network,
|
|
but may be delivered locally if the sending host belongs to the destination
|
|
group and if multicast loopback has not been disabled on the sending socket
|
|
(see below).
|
|
Multicast datagrams with hoplimit greater than 1 may be forwarded
|
|
to other networks if a multicast router is attached to the local network.
|
|
.Pp
|
|
For hosts with multiple interfaces, each multicast transmission is
|
|
sent from the primary network interface.
|
|
The
|
|
.Dv IPV6_MULTICAST_IF
|
|
option overrides the default for
|
|
subsequent transmissions from a given socket:
|
|
.Bd -literal -offset indent
|
|
unsigned int outif;
|
|
outif = if_nametoindex("ne0");
|
|
setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_IF, &outif, sizeof(outif));
|
|
.Ed
|
|
.Pp
|
|
where "outif" is an interface index of the desired interface,
|
|
or 0 to specify the default interface.
|
|
.Pp
|
|
If a multicast datagram is sent to a group to which the sending host itself
|
|
belongs (on the outgoing interface), a copy of the datagram is, by default,
|
|
looped back by the IPv6 layer for local delivery.
|
|
The
|
|
.Dv IPV6_MULTICAST_LOOP
|
|
option gives the sender explicit control
|
|
over whether or not subsequent datagrams are looped back:
|
|
.Bd -literal -offset indent
|
|
u_char loop; /* 0 = disable, 1 = enable (default) */
|
|
setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &loop, sizeof(loop));
|
|
.Ed
|
|
.Pp
|
|
This option
|
|
improves performance for applications that may have no more than one
|
|
instance on a single host (such as a router daemon), by eliminating
|
|
the overhead of receiving their own transmissions.
|
|
It should generally not be used by applications for which there
|
|
may be more than one instance on a single host (such as a conferencing
|
|
program) or for which the sender does not belong to the destination
|
|
group (such as a time querying program).
|
|
.Pp
|
|
A multicast datagram sent with an initial hoplimit greater than 1 may be delivered
|
|
to the sending host on a different interface from that on which it was sent,
|
|
if the host belongs to the destination group on that other interface.
|
|
The loopback control option has no effect on such delivery.
|
|
.Pp
|
|
A host must become a member of a multicast group before it can receive
|
|
datagrams sent to the group.
|
|
To join a multicast group, use the
|
|
.Dv IPV6_JOIN_GROUP
|
|
option:
|
|
.Bd -literal -offset indent
|
|
struct ipv6_mreq mreq6;
|
|
setsockopt(s, IPPROTO_IPV6, IPV6_JOIN_GROUP, &mreq6, sizeof(mreq6));
|
|
.Ed
|
|
.Pp
|
|
where
|
|
.Fa mreq6
|
|
is the following structure:
|
|
.Bd -literal -offset indent
|
|
struct ipv6_mreq {
|
|
struct in6_addr ipv6mr_multiaddr;
|
|
u_int ipv6mr_interface;
|
|
};
|
|
.Ed
|
|
.Pp
|
|
.Dv ipv6mr_interface
|
|
should be 0 to choose the default multicast interface, or the
|
|
interface index of a particular multicast-capable interface if
|
|
the host is multihomed.
|
|
Membership is associated with a single interface;
|
|
programs running on multihomed hosts may need to
|
|
join the same group on more than one interface.
|
|
.Pp
|
|
To drop a membership, use:
|
|
.Bd -literal -offset indent
|
|
struct ipv6_mreq mreq6;
|
|
setsockopt(s, IPPROTO_IPV6, IPV6_LEAVE_GROUP, &mreq6, sizeof(mreq6));
|
|
.Ed
|
|
.Pp
|
|
where
|
|
.Fa mreq6
|
|
contains the same values as used to add the membership.
|
|
Memberships are dropped when the socket is closed or the process exits.
|
|
.Pp
|
|
.Dv IPV6_PORTRANGE
|
|
controls how ephemeral ports are allocated for
|
|
.Dv SOCK_STREAM
|
|
and
|
|
.Dv SOCK_DGRAM
|
|
sockets.
|
|
For example,
|
|
.Bd -literal -offset indent
|
|
int range = IPV6_PORTRANGE_LOW; /* see <netinet/in.h> */
|
|
setsockopt(s, IPPROTO_IPV6, IPV6_PORTRANGE, &range, sizeof(range));
|
|
.Ed
|
|
.Pp
|
|
.Dv IPV6_V6ONLY
|
|
controls behavior of
|
|
.Dv AF_INET6
|
|
wildcard listening socket.
|
|
The following example sets the option to 1:
|
|
.Bd -literal -offset indent
|
|
int on = 1;
|
|
setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &on, sizeof(on));
|
|
.Ed
|
|
.Pp
|
|
If set to 1,
|
|
.Dv AF_INET6
|
|
wildcard listening socket will accept IPv6 traffic only.
|
|
If set to 0, it will accept IPv4 traffic as well,
|
|
as if it was from IPv4 mapped address like
|
|
.Li ::ffff:10.1.1.1 .
|
|
.\" RFC2553 defines the behavior when the variable is set to 0.
|
|
Note that if you set it this to 0,
|
|
IPv4 access control gets much more complicated.
|
|
For example, even if you have no listening
|
|
.Dv AF_INET
|
|
listening socket on port
|
|
.Li X ,
|
|
you will end up accepting IPv4 traffic by
|
|
.Dv AF_INET6
|
|
listening socket on the same port.
|
|
The default value for this flag is copied at socket instantiation time,
|
|
from
|
|
.Li net.inet6.ip6.v6only
|
|
.Xr sysctl 3
|
|
variable.
|
|
The option affects
|
|
.Tn TCP
|
|
and
|
|
.Tn UDP
|
|
sockets only.
|
|
.\"
|
|
.Ss Advanced IPv6 sockets API
|
|
The advanced IPv6 sockets API lets userland programs specify or obtain
|
|
details about the IPv6 header and the IPv6 extension headers on packets.
|
|
The advanced API uses ancillary data for passing data from/to the kernel.
|
|
.Pp
|
|
There are
|
|
.Xr setsockopt 2 Ns / Ns Xr getsockopt 2
|
|
options to get optional information on incoming packets.
|
|
They are
|
|
.Dv IPV6_PKTINFO ,
|
|
.Dv IPV6_HOPLIMIT ,
|
|
.Dv IPV6_HOPOPTS ,
|
|
.Dv IPV6_DSTOPTS ,
|
|
and
|
|
.Dv IPV6_RTHDR .
|
|
.Bd -literal -offset indent
|
|
int on = 1;
|
|
|
|
setsockopt(fd, IPPROTO_IPV6, IPV6_PKTINFO, &on, sizeof(on));
|
|
setsockopt(fd, IPPROTO_IPV6, IPV6_HOPLIMIT, &on, sizeof(on));
|
|
setsockopt(fd, IPPROTO_IPV6, IPV6_HOPOPTS, &on, sizeof(on));
|
|
setsockopt(fd, IPPROTO_IPV6, IPV6_DSTOPTS, &on, sizeof(on));
|
|
setsockopt(fd, IPPROTO_IPV6, IPV6_RTHDR, &on, sizeof(on));
|
|
.Ed
|
|
.Pp
|
|
When any of these options are enabled, the corresponding data is
|
|
returned as control information by
|
|
.Xr recvmsg 2 ,
|
|
as one or more ancillary data objects.
|
|
.Pp
|
|
If
|
|
.Dv IPV6_PKTINFO
|
|
is enabled, the destination IPv6 address and the arriving interface index
|
|
will be available via
|
|
.Li struct in6_pktinfo
|
|
on ancillary data stream.
|
|
You can pick the structure by checking for an ancillary data item with
|
|
.Li cmsg_level
|
|
equals to
|
|
.Dv IPPROTO_IPV6 ,
|
|
and
|
|
.Li cmsg_type
|
|
equals to
|
|
.Dv IPV6_PKTINFO .
|
|
.Pp
|
|
If
|
|
.Dv IPV6_HOPLIMIT
|
|
is enabled, hoplimit value on the packet will be made available to the
|
|
userland program.
|
|
Ancillary data stream will contain an integer data item with
|
|
.Li cmsg_level
|
|
equals to
|
|
.Dv IPPROTO_IPV6 ,
|
|
and
|
|
.Li cmsg_type
|
|
equals to
|
|
.Dv IPV6_HOPLIMIT .
|
|
.Pp
|
|
.Xr inet6_option_space 3
|
|
and friends will help you parse ancillary data items for
|
|
.Dv IPV6_HOPOPTS
|
|
and
|
|
.Dv IPV6_DSTOPTS .
|
|
Similarly,
|
|
.Xr inet6_rthdr_space 3
|
|
and friends will help you parse ancillary data items for
|
|
.Dv IPV6_RTHDR .
|
|
.Pp
|
|
.Dv IPV6_HOPOPTS
|
|
and
|
|
.Dv IPV6_DSTOPTS
|
|
may appear multiple times on an ancillary data stream
|
|
(note that the behavior is slightly different than the specification).
|
|
Other ancillary data item will appear no more than once.
|
|
.Pp
|
|
For outgoing direction,
|
|
you can pass ancillary data items with normal payload data, using
|
|
.Xr sendmsg 2 .
|
|
Ancillary data items will be parsed by the kernel, and used to construct
|
|
the IPv6 header and extension headers.
|
|
For the 5
|
|
.Li cmsg_level
|
|
values listed above, ancillary data format is the same as inbound case.
|
|
Additionally, you can specify
|
|
.Dv IPV6_NEXTHOP
|
|
data object.
|
|
The
|
|
.Dv IPV6_NEXTHOP
|
|
ancillary data object specifies the next hop for the
|
|
datagram as a socket address structure.
|
|
In the
|
|
.Li cmsghdr
|
|
structure
|
|
containing this ancillary data, the
|
|
.Li cmsg_level
|
|
member will be
|
|
.Dv IPPROTO_IPV6 ,
|
|
the
|
|
.Li cmsg_type
|
|
member will be
|
|
.Dv IPV6_NEXTHOP ,
|
|
and the first byte of
|
|
.Li cmsg_data[]
|
|
will be the first byte of the socket address structure.
|
|
.Pp
|
|
If the socket address structure contains an IPv6 address (e.g., the
|
|
sin6_family member is
|
|
.Dv AF_INET6
|
|
), then the node identified by that
|
|
address must be a neighbor of the sending host.
|
|
If that address
|
|
equals the destination IPv6 address of the datagram, then this is
|
|
equivalent to the existing
|
|
.Dv SO_DONTROUTE
|
|
socket option.
|
|
.Pp
|
|
For applications that do not, or unable to use
|
|
.Xr sendmsg 2
|
|
or
|
|
.Xr recvmsg 2 ,
|
|
.Dv IPV6_PKTOPTIONS
|
|
socket option is defined.
|
|
Setting the socket option specifies any of the optional output fields:
|
|
.Bd -literal -offset indent
|
|
setsockopt(fd, IPPROTO_IPV6, IPV6_PKTOPTIONS, &buf, len);
|
|
.Ed
|
|
.Pp
|
|
The fourth argument points to a buffer containing one or more
|
|
ancillary data objects, and the fifth argument is the total length of
|
|
all these objects.
|
|
The application fills in this buffer exactly as
|
|
if the buffer were being passed to
|
|
.Xr sendmsg 2
|
|
as control information.
|
|
.Pp
|
|
The options set by calling
|
|
.Xr setsockopt 2
|
|
for
|
|
.Dv IPV6_PKTOPTIONS
|
|
are
|
|
called "sticky" options because once set they apply to all packets
|
|
sent on that socket.
|
|
The application can call
|
|
.Xr setsockopt 2
|
|
again to
|
|
change all the sticky options, or it can call
|
|
.Xr setsockopt 2
|
|
with a
|
|
length of 0 to remove all the sticky options for the socket.
|
|
.Pp
|
|
The corresponding receive option
|
|
.Bd -literal -offset indent
|
|
getsockopt(fd, IPPROTO_IPV6, IPV6_PKTOPTIONS, &buf, &len);
|
|
.Ed
|
|
.Pp
|
|
returns a buffer with one or more ancillary data objects for all the
|
|
optional receive information that the application has previously
|
|
specified that it wants to receive.
|
|
The fourth argument points to
|
|
the buffer that is filled in by the call.
|
|
The fifth argument is a
|
|
pointer to a value-result integer: when the function is called the
|
|
integer specifies the size of the buffer pointed to by the fourth
|
|
argument, and on return this integer contains the actual number of
|
|
bytes that were returned.
|
|
The application processes this buffer
|
|
exactly as if the buffer were returned by
|
|
.Xr recvmsg 2
|
|
as control information.
|
|
.\"
|
|
.Ss Advanced API and TCP sockets
|
|
When using
|
|
.Xr getsockopt 2
|
|
with the
|
|
.Dv IPV6_PKTOPTIONS
|
|
option and a
|
|
.Tn TCP
|
|
socket, only the options from the most recently received segment are
|
|
retained and returned to the caller, and only after the socket option
|
|
has been set.
|
|
.\" That is,
|
|
.\" .Tn TCP
|
|
.\" need not start saving a copy of the options until the application says
|
|
.\" to do so.
|
|
The application is not allowed to specify ancillary data in a call to
|
|
.Xr sendmsg 2
|
|
on a
|
|
.Tn TCP
|
|
socket, and none of the ancillary data that we
|
|
described above is ever returned as control information by
|
|
.Xr recvmsg 2
|
|
on a
|
|
.Tn TCP
|
|
socket.
|
|
.\"
|
|
.Ss Conflict resolution
|
|
In some cases, there are multiple APIs defined for manipulating
|
|
a IPv6 header field.
|
|
A good example is the outgoing interface for multicast datagrams:
|
|
it can be manipulated by
|
|
.Dv IPV6_MULTICAST_IF
|
|
in basic API,
|
|
.Dv IPV6_PKTINFO
|
|
in advanced API, and
|
|
.Li sin6_scope_id
|
|
field of the socket address passed to
|
|
.Xr sendto 2 .
|
|
.Pp
|
|
When conflicting options are given to the kernel,
|
|
the kernel will get the value in the following preference:
|
|
(1) options specified by using ancillary data,
|
|
(2) options specified by a sticky option of the advanced API,
|
|
(3) options specified by using the basic API, and lastly
|
|
(4) options specified by a socket address.
|
|
Note that the conflict resolution is undefined in the API specifcation
|
|
and implementation dependent.
|
|
.\"
|
|
.Ss "Raw IPv6 Sockets"
|
|
Raw
|
|
.Tn IPv6
|
|
sockets are connectionless, and are normally used with the
|
|
.Xr sendto 2
|
|
and
|
|
.Xr recvfrom 2
|
|
calls, though the
|
|
.Xr connect 2
|
|
call may also be used to fix the destination for future
|
|
packets (in which case the
|
|
.Xr read 2
|
|
or
|
|
.Xr recv 2
|
|
and
|
|
.Xr write 2
|
|
or
|
|
.Xr send 2
|
|
system calls may be used).
|
|
.Pp
|
|
If
|
|
.Fa proto
|
|
is 0, the default protocol
|
|
.Dv IPPROTO_RAW
|
|
is used for outgoing packets, and only incoming packets destined
|
|
for that protocol are received.
|
|
If
|
|
.Fa proto
|
|
is non-zero, that protocol number will be used on outgoing packets
|
|
and to filter incoming packets.
|
|
.Pp
|
|
Outgoing packets automatically have an
|
|
.Tn IPv6
|
|
header prepended to them (based on the destination address and the
|
|
protocol number the socket is created with).
|
|
Incoming packets are received without
|
|
.Tn IPv6
|
|
header nor extension headers.
|
|
.Pp
|
|
All data sent via raw sockets MUST be in network byte order and all
|
|
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 ERRORS
|
|
A socket operation may fail with one of the following errors returned:
|
|
.Bl -tag -width Er
|
|
.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 recv 2 ,
|
|
.Xr send 2 ,
|
|
.Xr setsockopt 2 ,
|
|
.Xr inet6_option_space 3 ,
|
|
.Xr inet6_rthdr_space 3 ,
|
|
.Xr icmp6 4 ,
|
|
.Xr inet6 4 ,
|
|
.Xr intro 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
|
|
.Rs
|
|
.%A R. Gilligan
|
|
.%A S. Thomson
|
|
.%A J. Bound
|
|
.%A W. Stevens
|
|
.%R RFC
|
|
.%N 2553
|
|
.%D March 1999
|
|
.%T "Basic Socket Interface Extensions for IPv6"
|
|
.Re
|
|
.\"
|
|
.Sh STANDARDS
|
|
Most of the socket options are defined in
|
|
RFC2292 and/or RFC2553.
|
|
.Pp
|
|
.Dv IPV6_V6ONLY
|
|
socket option is defined in draft-ietf-ipngwg-rfc2553bis-03.
|
|
.Dv IPV6_PORTRANGE
|
|
socket option
|
|
and
|
|
conflict resolution rule
|
|
are not defined in the RFCs and should be considered implementation dependent.
|
|
.\"
|
|
.Sh HISTORY
|
|
The implementation is based on KAME stack
|
|
.Po
|
|
which is descendant of WIDE hydrangea IPv6 stack kit
|
|
.Pc .
|
|
.Pp
|
|
Part of the document was shamelessly copied from RFC2553 and RFC2292.
|
|
.\"
|
|
.Sh BUGS
|
|
The
|
|
.Dv IPV6_NEXTHOP
|
|
object/option is not fully implemented as of writing this.
|