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ICMP6(4)                 BSD Kernel Interfaces Manual                 ICMP6(4)

NAME
     icmp6 -- Internet Control Message Protocol for IPv6

SYNOPSIS
     #include <&lt;sys/socket.h>&gt;
     #include <&lt;netinet/in.h>&gt;
     #include <&lt;netinet/icmp6.h>&gt;

     int
     socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);

DESCRIPTION
     ICMPv6 is the error and control message protocol used by IPv6 and the
     IPv6 protocol family (see ip6(4) and inet6(4)).  It may be accessed
     through a ``raw socket'' for network monitoring and diagnostic functions.

     The proto parameter to the socket(2) call to create an ICMPv6 socket may
     be obtained from getprotobyname(3).  ICMPv6 sockets are connectionless,
     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 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).  Incoming packets on the socket are
     received with the IPv6 header and any extension headers removed.

   Types
     ICMPv6 messages are classified according to the type and code fields
     present in the ICMPv6 header.  The abbreviations for the types and codes
     may be used in rules in pf.conf(5).  The following types are defined:

           Num    Abbrev.       Description
           1      unreach       Destination unreachable
           2      toobig        Packet too big
           3      timex         Time exceeded
           4      paramprob     Invalid IPv6 header
           128    echoreq       Echo service request
           129    echorep       Echo service reply
           130    groupqry      Group membership query
           130    listqry       Multicast listener query
           131    grouprep      Group membership report
           131    listenrep     Multicast listener report
           132    groupterm     Group membership termination
           132    listendone    Multicast listener done
           133    routersol     Router solicitation
           134    routeradv     Router advertisement
           135    neighbrsol    Neighbor solicitation
           136    neighbradv    Neighbor advertisement
           137    redir         Shorter route exists
           138    routrrenum    Route renumbering
           139    fqdnreq       FQDN query
           139    niqry         Node information query
           139    wrureq        Who-are-you request
           140    fqdnrep       FQDN reply
           140    nirep         Node information reply
           140    wrurep        Who-are-you reply
           200    mtraceresp    mtrace response
           201    mtrace        mtrace messages

     The following codes are defined:

           Num    Abbrev.        Type         Description
           0      noroute-unr    unreach      No route to destination
           1      admin-unr      unreach      Administratively prohibited
           2      beyond-unr     unreach      Beyond scope of source address
           2      notnbr-unr     unreach      Not a neighbor (obsolete)
           3      addr-unr       unreach      Address unreachable
           4      port-unr       unreach      Port unreachable
           0      transit        timex        Time exceeded in transit
           1      reassemb       timex        Time exceeded in reassembly
           0      badhead        paramprob    Erroneous header field
           1      nxthdr         paramprob    Unrecognized next header
           2                     paramprob    Unrecognized option
           0      redironlink    redir        Redirection to on-link node
           1      redirrouter    redir        Redirection to better router

   Headers
     All ICMPv6 messages are prefixed with an ICMPv6 header.  This header cor-
     responds to the icmp6_hdr structure and has the following definition:

           struct icmp6_hdr {
                   u_int8_t        icmp6_type;     /* type field */
                   u_int8_t        icmp6_code;     /* code field */
                   u_int16_t       icmp6_cksum;    /* checksum field */
                   union {
                           u_int32_t icmp6_un_data32[1]; /* type-specific */
                           u_int16_t icmp6_un_data16[2]; /* type-specific */
                           u_int8_t  icmp6_un_data8[4];  /* type-specific */
                   } icmp6_dataun;
           } __packed;

           #define icmp6_data32    icmp6_dataun.icmp6_un_data32
           #define icmp6_data16    icmp6_dataun.icmp6_un_data16
           #define icmp6_data8     icmp6_dataun.icmp6_un_data8
           #define icmp6_pptr      icmp6_data32[0] /* parameter prob */
           #define icmp6_mtu       icmp6_data32[0] /* packet too big */
           #define icmp6_id        icmp6_data16[0] /* echo request/reply */
           #define icmp6_seq       icmp6_data16[1] /* echo request/reply */
           #define icmp6_maxdelay  icmp6_data16[0] /* mcast group membership*/

     icmp6_type describes the type of the message.  Suitable values are
     defined in <netinet/icmp6.h>.  icmp6_code describes the sub-type of the
     message and depends on icmp6_type.  icmp6_cksum contains the checksum for
     the message and is filled in by the kernel on outgoing messages.  The
     other fields are used for type-specific purposes.

   Filters
     Because of the extra functionality of ICMPv6 in comparison to ICMPv4, a
     larger number of messages may be potentially received on an ICMPv6
     socket.  Input filters may therefore be used to restrict input to a sub-
     set of the incoming ICMPv6 messages so only interesting messages are
     returned by the recv(2) family of calls to an application.

     The icmp6_filter structure may be used to refine the input message set
     according to the ICMPv6 type.  By default, all messages types are allowed
     on newly created raw ICMPv6 sockets.  The following macros may be used to
     refine the input set:

     void ICMP6_FILTER_SETPASSALL(struct icmp6_filter *filterp)
             Allow all incoming messages.  filterp is modified to allow all
             message types.

     void ICMP6_FILTER_SETBLOCKALL(struct icmp6_filter *filterp)
             Ignore all incoming messages.  filterp is modified to ignore all
             message types.

     void ICMP6_FILTER_SETPASS(int type, struct icmp6_filter *filterp)
             Allow ICMPv6 messages with the given type.  filterp is modified
             to allow such messages.

     void ICMP6_FILTER_SETBLOCK(int type, struct icmp6_filter *filterp)
             Ignore ICMPv6 messages with the given type.  filterp is modified
             to ignore such messages.

     int ICMP6_FILTER_WILLPASS(int type, const struct icmp6_filter *filterp)
             Determine if the given filter will allow an ICMPv6 message of the
             given type.

     int ICMP6_FILTER_WILLBLOCK(int type, const struct icmp6_filter *filterp)
             Determine if the given filter will ignore an ICMPv6 message of
             the given type.

     The getsockopt(2) and setsockopt(2) calls may be used to obtain and
     install the filter on ICMPv6 sockets at option level IPPROTO_ICMPV6 and
     name ICMPV6_FILTER with a pointer to the icmp6_filter structure as the
     option value.

SEE ALSO
     getsockopt(2), recv(2), send(2), setsockopt(2), socket(2),
     getprotobyname(3), inet6(4), ip6(4), netintro(4)

STANDARDS
     W. Stevens, M. Thomas, E. Nordmark, and T. Jinmei, Advanced Sockets
     Application Program Interface (API) for IPv6, RFC 3542, May 2003.

     A. Conta, S. Deering, and M. Gupta, Internet Control Message Protocol
     (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification, RFC
     4443, March 2006.

BSD                             March 26, 2017                             BSD