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 diagnos
tic functions.
The proto parameter to the socket(2) call to create an ICM
Pv6 socket may be obtained from getprotobyname(3). ICMPv6 sockets are con
nectionless, 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 re
moved.
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 de; fined:

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 destina

tion
1 admin-unr unreach Administratively pro

hibited
2 beyond-unr unreach Beyond scope of

source address
2 notnbr-unr unreach Not a neighbor (obse

lete)
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 re

assembly
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 corresponds 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 re

quest/reply */
#define icmp6_seq icmp6_data16[1] /* echo re

quest/reply */
#define icmp6_maxdelay icmp6_data16[0] /* mcast group

membership*/; icmp6_type describes the type of the message. Suitable val; ues 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 mes; sages. 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 in; put to a subset of the incoming ICMPv6 messages so only interesting mes; sages 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 ob
tain and install the filter on ICMPv6 sockets at option level IPPRO
TO_ICMPV6 and
name ICMPV6_FILTER with a pointer to the icmp6_filter struc
ture as the option value.

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comprehensive documentation repository

See also

icmp6(4)

NAME

SYNOPSIS

DESCRIPTION

SEE ALSO