icmp6(4) BSD Kernel Interfaces Manual 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
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 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_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
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.
Non-privileged ICMPv6
ICMPv6 sockets can be opened with the SOCK_DGRAM socket type without
requiring root privileges. The synopsis is the following:
socket(AF_INET6, SOCK_DGRAM, IPPROTO_ICMPV6)
This can only be used to send ICMPv6 echo requests to gauge the quality
of the connectivity to a host, to receive destination unreachable message
for path MTU discovery, or to receveive time exceeded message for tracer-
oute.
A socket opened with superuser privileges can send any kind of ICMPv6
message and can also use the ip6(4) options that require superuser privi-
leges.
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
Mac OS X 10.9 - Generated Tue Oct 15 20:58:06 CDT 2013