NAME
iiccmmpp66 - Internet Control Message Protocol for IPv6
SYNOPSIS
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int ssoocckkeett(AFINET6, SOCKRAW, IPPROTOICMPV6);> 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. TTyyppeess 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: NNuumm AAbbbbrreevv.. DDeessccrriippttiioonn 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 query139 wrureq Who-are-you request
140 fqdnrep FQDN reply 140 nirep Node information reply140 wrurep Who-are-you reply
200 mtraceresp mtrace response 201 mtrace mtrace messages The following codes are defined: NNuumm AAbbbbrreevv.. TTyyppee DDeessccrriippttiioonn0 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 option0 redironlink redir Redirection to on-link node
1 redirrouter redir Redirection to better router HHeeaaddeerrssAll ICMPv6 messages are prefixed with an ICMPv6 header. This header cor-
responds to the icmp6hdr structure and has the following definition:
struct icmp6hdr {
uint8t icmp6type; /* type field */
uint8t icmp6code; /* code field */
uint16t icmp6cksum; /* checksum field */
union {uint32t icmp6undata32[1]; /* type-specific */
uint16t icmp6undata16[2]; /* type-specific */
uint8t icmp6undata8[4]; /* type-specific */
} icmp6dataun;
} packed;#define icmp6data32 icmp6dataun.icmp6undata32
#define icmp6data16 icmp6dataun.icmp6undata16
#define icmp6data8 icmp6dataun.icmp6undata8
#define icmp6pptr icmp6data32[0] /* parameter prob */
#define icmp6mtu icmp6data32[0] /* packet too big */
#define icmp6id icmp6data16[0] /* echo request/reply */
#define icmp6seq icmp6data16[1] /* echo request/reply */
#define icmp6maxdelay icmp6data16[0] /* mcast group membership*/
icmp6type describes the type of the message. Suitable values are
defined in
. icmp6code describes the sub-type of the message and depends on icmp6type. icmp6cksum contains the checksum for
the message and is filled in by the kernel on outgoing messages. Theother fields are used for type-specific purposes.
FFiilltteerrss Because of the extra functionality of ICMPv6 in comparison to ICMPv4, a larger number of messages may be potentially received on an ICMPv6socket. 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 icmp6filter 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:vvooiidd IICCMMPP66FFIILLTTEERRSSEETTPPAASSSSAALLLL(struct icmp6filter *filterp)
Allow all incoming messages. filterp is modified to allow all message types.vvooiidd IICCMMPP66FFIILLTTEERRSSEETTBBLLOOCCKKAALLLL(struct icmp6filter *filterp)
Ignore all incoming messages. filterp is modified to ignore all message types.vvooiidd IICCMMPP66FFIILLTTEERRSSEETTPPAASSSS(int type, struct icmp6filter *filterp)
Allow ICMPv6 messages with the given type. filterp is modified to allow such messages.vvooiidd IICCMMPP66FFIILLTTEERRSSEETTBBLLOOCCKK(int type, struct icmp6filter *filterp)
Ignore ICMPv6 messages with the given type. filterp is modified to ignore such messages.iinntt IICCMMPP66FFIILLTTEERRWWIILLLLPPAASSSS(int type, const struct icmp6filter *filterp)
Determine if the given filter will allow an ICMPv6 message of the given type.iinntt IICCMMPP66FFIILLTTEERRWWIILLLLBBLLOOCCKK(int type, const struct icmp6filter *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 IPPROTOICMPV6 andname ICMPV6FILTER with a pointer to the icmp6filter 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. BSD December 20, 2004 BSD