ICMP6(4)                  OpenBSD Programmer's Manual                 ICMP6(4)

NAME
     icmp6 - Internet Control Message Protocol for IPv6

SYNOPSIS
     #include <sys/socket.h>
     #include <netinet/in.h>
     #include <netinet/icmp6.h>

     int
     socket(AF_INET6, SOCK_RAW, proto);

DESCRIPTION
     ICMPv6 is the error and control message protocol used by IPv6 and the In-
     ternet protocol family.  It may be accessed through a ``raw socket'' for
     network monitoring and diagnostic functions.  The proto parameter to the
     socket call to create an ICMPv6 socket is obtained from
     getprotobyname(3), or you can use IPPROTO_ICMPV6. ICMPv6 sockets are con-
     nectionless, and are normally used with the sendto(2) and recvfrom(2)
     calls, though the connect(2) call may also be used to fix the destination
     for future packets (in which case the read(2) or recv(2) and write(2) or
     send(2) system calls may be used).

     Outgoing packets automatically have an IPv6 header prepended to them
     (based on the destination address). ICMPv6 pseudo header checksum field
     (icmp6_cksum) will be filled automatically by the kernel.  Incoming pack-
     ets are received without the IPv6 header nor IPv6 extension headers.  No-
     tice that this behavior is opposite from IPv4 raw sockets and.  ICMPv4
     sockets.

   ICMPv6 type/code filter
     Each ICMPv6 raw socket has an associated filter whose datatype is defined
     as struct icmp6_filter;

     This structure, along with the macros and constants defined later in this
     section, are defined as a result of including the <netinet/icmp6.h> head-
     er.

     The current filter is fetched and stored using getsockopt(2) and setsock-
     opt(2) with a level of IPPROTO_ICMPV6 and an option name of ICMP6_FILTER.

     Six macros operate on an icmp6_filter structure:
           ICMP6_FILTER_SETPASSALL(struct icmp6_filter *)
           ICMP6_FILTER_SETBLOCKALL(struct icmp6_filter *)
           ICMP6_FILTER_SETPASS(int, struct icmp6_filter *)
           ICMP6_FILTER_SETBLOCK(int, struct icmp6_filter *)
           ICMP6_FILTER_WILLPASS(int, const struct icmp6_filter *)
           ICMP6_FILTER_WILLBLOCK(int, const struct icmp6_filter *)

     The first argument to the last four macros (an integer) is an ICMPv6 mes-
     sage 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.

     The first two macros, SETPASSALL and SETBLOCKALL, let us specify that all
     ICMPv6 messages are passed to the application or that ICMPv6 messages are
     blocked from being passed to the application.

     The next two macros, SETPASS and SETBLOCK, let us specify that messages
     of a given ICMPv6 type should be passed to the application or not passed
     to the application (blocked).

     The final two macros, WILLPASS and WILLBLOCK, return true or false de-
     pending 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.

     When an ICMPv6 raw socket is created, it will by default pass all ICMPv6
     message types to the application.

     For further discussions see RFC2292.

DIAGNOSTICS
     A socket operation may fail with one of the following errors returned:

     [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 al-
                      ready connected;

     [ENOTCONN]       when trying to send a datagram, but no destination ad-
                      dress is specified, and the socket hasn't been connect-
                      ed;

     [ENOBUFS]        when the system runs out of memory for an internal data
                      structure;

     [EADDRNOTAVAIL]  when an attempt is made to create a socket with a net-
                      work address for which no network interface exists.

SEE ALSO
     send(2), recv(2), intro(4), inet6(4), ip6(4)

     W. Stevens, and M. Thomas, Advanced Sockets API for IPv6, RFC, 2292,
     February 1998.

     A. Conta, and S. Deering, Internet Control Message Protocol (ICMPv6) for
     the Internet Protocol Version 6 (IPv6) Specification, RFC, 2463, December
     1998.

HISTORY
     The implementation is based on KAME stack (which is descendant of WIDE
     hydrangea IPv6 stack kit).

     Part of the document was shamelessly copied from RFC2292.

OpenBSD 2.9                    December 17, 1999                             2
