ICMP6(4) BSD Kernel Interfaces Manual ICMP6(4)
NAME
icmp6 -- Internet Control Message Protocol for IPv6
SYNOPSIS
##include <>
##include <>
##include <>
int
socket(AFINET6, SOCKRAW, IPROTOICMPV6);
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
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
Headers
All 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. 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 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:
void ICMP6FILTERSETPASAL(struct icmp6filter *filterp)
Allow all incoming messages. filterp is modified to allow all
message types.
void ICMP6FILTERSETBLOCKAL(struct icmp6filter *filterp)
Ignore all incoming messages. filterp is modified to ignore all
message types.
void ICMP6FILTERSETPAS(int type, struct icmp6filter *filterp)
Allow ICMPv6 messages with the given type. filterp is modified
to allow such messages.
void ICMP6FILTERSETBLOCK(int type, struct icmp6filter *filterp)
Ignore ICMPv6 messages with the given type. filterp is modified
to ignore such messages.
int ICMP6FILTERWILPAS(int type, const struct icmp6filter *filterp)
Determine if the given filter will allow an ICMPv6 message of the
given type.
int ICMP6FILTERWILBLOCK(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 IPROTOICMPV6 and
name 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
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