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ICMP6(4)	       FreeBSD 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 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
	   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

     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 ICMP6_FILTER with a pointer to the icmp6_filter structure as the op-
     tion value.

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

     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.

FreeBSD	13.0			August 3, 2017			  FreeBSD 13.0


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