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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, 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 listerner 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
	   2	beyond-unr	unreach     Beyond scope of source address
	   2	notnbr-unr	unreach     Not a neighbor (obselete)
	   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			redir	    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_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)

     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.

FreeBSD 5.4		       December 20, 2004		   FreeBSD 5.4

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