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

     icmp6 -- Internet Control Message Protocol	for IPv6

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


     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.

     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
	   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 (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

     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	de-
     fined 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.

     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 re-
     turned 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 in-
     stall 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.

     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

BSD			       December	20, 2004			   BSD


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