.\"	$NetBSD: icmp6.4,v 1.6 2002/02/13 08:17:35 ross Exp $
.\"	$KAME: icmp6.4,v 1.3 2000/11/24 08:44:40 itojun Exp $
.\"
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.Dd December 17, 1999
.Dt ICMP6 4
.Os
.Sh NAME
.Nm icmp6
.Nd Internet Control Message Protocol for IPv6
.Sh SYNOPSIS
.Fd #include \*[Lt]sys/socket.h\*[Gt]
.Fd #include \*[Lt]netinet/in.h\*[Gt]
.Fd #include \*[Lt]netinet/icmp6.h\*[Gt]
.Ft int
.Fn socket AF_INET6 SOCK_RAW proto
.Sh DESCRIPTION
.Tn ICMPv6
is the error and control message protocol used
by
.Tn IPv6
and the Internet protocol family.
It may be accessed through a
.Dq raw socket
for network monitoring and diagnostic functions.
The
.Fa proto
parameter to the socket call to create an
.Tn ICMPv6
socket is obtained from
.Xr getprotobyname 3 ,
or you can use
.Dv IPPROTO_ICMPV6 .
.Tn ICMPv6
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
Outgoing packets automatically have an
.Tn IPv6
header prepended to them
.Pq based on the destination address .
.Tn ICMPv6
pseudo header checksum field
.Pq Li icmp6_cksum
will be filled automatically by the kernel.
Incoming packets are received without the
.Tn IPv6
header nor IPv6 extension headers.
Notice that this behavior is opposite from
.Tn IPv4
raw sockets and.
.Tn ICMPv4
sockets.
.Ss ICMPv6 type/code filter
Each
.Tn ICMPv6
raw socket has an associated filter whose datatype is defined as
.Li struct icmp6_filter ;
.Pp
This structure, along with the macros and constants defined later in
this section, are defined as a result of including the
.Aq Li netinet/icmp6.h
header.
.Pp
The current filter is fetched and stored using
.Xr getsockopt 2
and
.Xr setsockopt 2
with a level of
.Dv IPPROTO_ICMPV6
and an option name of
.Dv ICMP6_FILTER .
.Pp
Six macros operate on an icmp6_filter structure:
.\" is "Fn" legal for macros?
.Bl -item -compact -offset indent
.It Ft void
.Fn ICMP6_FILTER_SETPASSALL "struct icmp6_filter *"
.It Ft void
.Fn ICMP6_FILTER_SETBLOCKALL "struct icmp6_filter *"
.It Ft void
.Fn ICMP6_FILTER_SETPASS "int" "struct icmp6_filter *"
.It Ft void
.Fn ICMP6_FILTER_SETBLOCK "int" "struct icmp6_filter *"
.It Ft int
.Fn ICMP6_FILTER_WILLPASS "int" "const struct icmp6_filter *"
.It Ft int
.Fn ICMP6_FILTER_WILLBLOCK "int" "const struct icmp6_filter *"
.El
.Pp
The first argument to the last four macros
.Pq an integer
is an
.Tn ICMPv6
message type, between 0 and 255.
The pointer argument to all six
macros is a pointer to a filter that is modified by the first four
macros examined by the last two macros.
.Pp
The first two macros,
.Dv SETPASSALL
and
.Dv SETBLOCKALL ,
let us specify that
all
.Tn ICMPv6 messages are passed to the application or that all
.Tn ICMPv6
messages are blocked from being passed to the application.
.Pp
The next two macros,
.Dv SETPASS
and
.Dv SETBLOCK ,
let us specify that
messages of a given
.Tn ICMPv6
type should be passed to the application
or not passed to the application
.Pq blocked .
.Pp
The final two macros,
.Dv WILLPASS
and
.Dv WILLBLOCK ,
return true or false
depending whether the specified message type is passed to the
application or blocked from being passed to the application by the
filter pointed to by the second argument.
.Pp
When an
.Tn ICMPv6
raw socket is created, it will by default pass all
.Tn ICMPv6
message types to the application.
.Pp
For further discussions see RFC2292.
.\"
.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.
.El
.Sh SEE ALSO
.Xr recv 2 ,
.Xr send 2 ,
.Xr inet6 4 ,
.Xr intro 4 ,
.Xr ip6 4
.Rs
.%A W. Stevens
.%A M. Thomas
.%R RFC
.%N 2292
.%D February 1998
.%T "Advanced Sockets API for IPv6"
.Re
.Rs
.%A A. Conta
.%A S. Deering
.%R RFC
.%N 2463
.%D December 1998
.%T "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification"
.Re
.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 RFC2292.