[apple/xnu.git] / bsd / man / man4 / icmp6.4

.\"	$NetBSD: icmp6.4,v 1.13 2005/01/11 06:01:41 itojun Exp $
.\"	$KAME: icmp6.4,v 1.6 2004/12/27 05:30:56 itojun Exp $
.\"	$OpenBSD: icmp6.4,v 1.19 2004/12/23 20:33:03 jaredy Exp $
.\"
.\" Copyright (c) 1986, 1991, 1993
.\"     The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.Dd December 20, 2004
.Dt ICMP6 4
.Os
.Sh NAME
.Nm icmp6
.Nd Internet Control Message Protocol for IPv6
.Sh SYNOPSIS
.In sys/socket.h
.In netinet/in.h
.In netinet/icmp6.h
.Ft int
.Fn socket AF_INET6 SOCK_RAW IPPROTO_ICMPV6
.Sh DESCRIPTION
ICMPv6 is the error and control message protocol used by IPv6 and the
IPv6 protocol family (see
.Xr ip6 4
and
.Xr inet6 4 ) .
It may be accessed through a
.Dq raw socket
for network monitoring and diagnostic functions.
.Pp
The
.Fa proto
parameter to the
.Xr socket 2
call to create an ICMPv6 socket may be obtained from
.Xr getprotobyname 3 .
ICMPv6 sockets are connectionless, and are normally used with the
.Xr sendto 2
and
.Xr recvfrom 2
calls, though the
.Xr connect 2
call may also be used to fix the destination for future packets
(in which case
.Xr read 2
or
.Xr recv 2
and
.Xr write 2
or
.Xr send 2
system calls may be used).
.Pp
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.
.Ss 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
.Xr pf.conf 5 .
The following types are defined:
.Bl -column x xxxxxxxxxxxx -offset indent
.It Sy Num Ta Sy Abbrev. Ta Sy Description
.It 1 Ta unreach Ta "Destination unreachable"
.It 2 Ta toobig Ta "Packet too big"
.It 3 Ta timex Ta "Time exceeded"
.It 4 Ta paramprob Ta "Invalid IPv6 header"
.It 128 Ta echoreq Ta "Echo service request"
.It 129 Ta echorep Ta "Echo service reply"
.It 130 Ta groupqry Ta "Group membership query"
.It 130 Ta listqry Ta "Multicast listener query"
.It 131 Ta grouprep Ta "Group membership report"
.It 131 Ta listenrep Ta "Multicast listener report"
.It 132 Ta groupterm Ta "Group membership termination"
.It 132 Ta listendone Ta "Multicast listerner done"
.It 133 Ta routersol Ta "Router solicitation"
.It 134 Ta routeradv Ta "Router advertisement"
.It 135 Ta neighbrsol Ta "Neighbor solicitation"
.It 136 Ta neighbradv Ta "Neighbor advertisement"
.It 137 Ta redir Ta "Shorter route exists"
.It 138 Ta routrrenum Ta "Route renumbering"
.It 139 Ta fqdnreq Ta "FQDN query"
.It 139 Ta niqry Ta "Node information query"
.It 139 Ta wrureq Ta "Who-are-you request"
.It 140 Ta fqdnrep Ta "FQDN reply"
.It 140 Ta nirep Ta "Node information reply"
.It 140 Ta wrurep Ta "Who-are-you reply"
.It 200 Ta mtraceresp Ta "mtrace response"
.It 201 Ta mtrace Ta "mtrace messages"
.El
.Pp
The following codes are defined:
.Bl -column x xxxxxxxxxxxx xxxxxxxx -offset indent
.It Sy Num Ta Sy Abbrev. Ta Sy Type Ta
.Sy Description
.It 0 Ta noroute-unr Ta unreach Ta "No route to destination"
.It 1 Ta admin-unr Ta unreach Ta "Administratively prohibited"
.It 2 Ta beyond-unr Ta unreach Ta "Beyond scope of source address"
.It 2 Ta notnbr-unr Ta unreach Ta "Not a neighbor (obselete)"
.It 3 Ta addr-unr Ta unreach Ta "Address unreachable"
.It 4 Ta port-unr Ta unreach Ta "Port unreachable"
.It 0 Ta transit Ta timex Ta "Time exceeded in transit"
.It 1 Ta reassemb Ta timex Ta "Time exceeded in reassembly"
.It 0 Ta badhead Ta paramprob Ta "Erroneous header field"
.It 1 Ta nxthdr Ta paramprob Ta "Unrecognized next header"
.It 2 Ta "" Ta redir Ta "Unrecognized option"
.It 0 Ta redironlink Ta redir Ta "Redirection to on-link node"
.It 1 Ta redirrouter Ta redir Ta "Redirection to better router"
.El
.Ss Headers
All ICMPv6 messages are prefixed with an ICMPv6 header.
This header corresponds to the
.Vt icmp6_hdr
structure and has the following definition:
.Bd -literal -offset indent
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*/
.Ed
.Pp
.Va icmp6_type
describes the type of the message.
Suitable values are defined in
.Aq Pa netinet/icmp6.h .
.Va icmp6_code
describes the sub-type of the message and depends on
.Va icmp6_type .
.Va 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.
.Ss 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 subset of the
incoming ICMPv6 messages so only interesting messages are returned by the
.Xr recv 2
family of calls to an application.
.Pp
The
.Vt 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:
.Bl -tag -width Ds
.It Fn "void ICMP6_FILTER_SETPASSALL" "struct icmp6_filter *filterp"
Allow all incoming messages.
.Va filterp
is modified to allow all message types.
.It Fn "void ICMP6_FILTER_SETBLOCKALL" "struct icmp6_filter *filterp"
Ignore all incoming messages.
.Va filterp
is modified to ignore all message types.
.It Fn "void ICMP6_FILTER_SETPASS" "int type" \
    "struct icmp6_filter *filterp"
Allow ICMPv6 messages with the given
.Fa type .
.Va filterp
is modified to allow such messages.
.It Fn "void ICMP6_FILTER_SETBLOCK" "int type" \
    "struct icmp6_filter *filterp"
Ignore ICMPv6 messages with the given
.Fa type .
.Va filterp
is modified to ignore such messages.
.It Fn "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.
.It Fn "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.
.El
.Pp
The
.Xr getsockopt 2
and
.Xr setsockopt 2
calls may be used to obtain and install the filter on ICMPv6 sockets at
option level
.Dv IPPROTO_ICMPV6
and name
.Dv ICMPV6_FILTER
with a pointer to the
.Vt icmp6_filter
structure as the option value.
.Ss "Non-privileged ICMPv6"
.Pp
.Tn ICMPv6
sockets can be opened with the 
.Dv SOCK_DGRAM
socket type without requiring root privileges. The synopsis is the following:
.Pp
.Fn socket AF_INET6 SOCK_DGRAM IPPROTO_ICMP6
.Pp
This can only be used to send 
.Tn 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 traceroute. 
.Pp
A socket opened with superuser privileges can send any kind of 
.Tn ICMPv6 
message and can also use the 
.Xr ip6 4
options that require superuser privileges.
.Sh SEE ALSO
.Xr getsockopt 2 ,
.Xr recv 2 ,
.Xr send 2 ,
.Xr setsockopt 2 ,
.Xr socket 2 ,
.Xr getprotobyname 3 ,
.Xr inet6 4 ,
.Xr ip6 4 ,
.Xr netintro 4
.Rs
.%A W. Stevens
.%A M. Thomas
.%T Advanced Sockets API for IPv6
.%N RFC 2292
.%D February 1998
.Re
.Rs
.%A A. Conta
.%A S. Deering
.%T "Internet Control Message Protocol (ICMPv6) for the Internet" \
    "Protocol Version 6 (IPv6) Specification"
.%N RFC 2463
.%D December 1998
.Re
Commit	Line	Data
91447636 A	1	.\" $NetBSD: icmp6.4,v 1.13 2005/01/11 06:01:41 itojun Exp $
	2	.\" $KAME: icmp6.4,v 1.6 2004/12/27 05:30:56 itojun Exp $
	3	.\" $OpenBSD: icmp6.4,v 1.19 2004/12/23 20:33:03 jaredy Exp $
9bccf70c A	4	.\"
9bccf70c A	5	.\" Copyright (c) 1986, 1991, 1993
91447636	6	.\" The Regents of the University of California. All rights reserved.
9bccf70c A	7	.\"
	8	.\" Redistribution and use in source and binary forms, with or without
	9	.\" modification, are permitted provided that the following conditions
	10	.\" are met:
	11	.\" 1. Redistributions of source code must retain the above copyright
	12	.\" notice, this list of conditions and the following disclaimer.
	13	.\" 2. Redistributions in binary form must reproduce the above copyright
	14	.\" notice, this list of conditions and the following disclaimer in the
	15	.\" documentation and/or other materials provided with the distribution.
91447636	16	.\" 3. Neither the name of the University nor the names of its contributors
9bccf70c A	17	.\" may be used to endorse or promote products derived from this software
	18	.\" without specific prior written permission.
	19	.\"
	20	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	21	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	24	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	.\" SUCH DAMAGE.
91447636	31	.Dd December 20, 2004
9bccf70c A	32	.Dt ICMP6 4
9bccf70c A	33	.Os
9bccf70c A	34	.Sh NAME
	35	.Nm icmp6
	36	.Nd Internet Control Message Protocol for IPv6
9bccf70c	37	.Sh SYNOPSIS
9bccf70c A	38	.In sys/socket.h
	39	.In netinet/in.h
	40	.In netinet/icmp6.h
	41	.Ft int
91447636	42	.Fn socket AF_INET6 SOCK_RAW IPPROTO_ICMPV6
9bccf70c	43	.Sh DESCRIPTION
91447636 A	44	ICMPv6 is the error and control message protocol used by IPv6 and the
	45	IPv6 protocol family (see
	46	.Xr ip6 4
	47	and
	48	.Xr inet6 4 ) .
9bccf70c A	49	It may be accessed through a
	50	.Dq raw socket
	51	for network monitoring and diagnostic functions.
91447636	52	.Pp
9bccf70c A	53	The
9bccf70c A	54	.Fa proto
91447636 A	55	parameter to the
	56	.Xr socket 2
	57	call to create an ICMPv6 socket may be obtained from
	58	.Xr getprotobyname 3 .
	59	ICMPv6 sockets are connectionless, and are normally used with the
9bccf70c A	60	.Xr sendto 2
	61	and
	62	.Xr recvfrom 2
	63	calls, though the
	64	.Xr connect 2
	65	call may also be used to fix the destination for future packets
91447636	66	(in which case
9bccf70c A	67	.Xr read 2
	68	or
	69	.Xr recv 2
	70	and
	71	.Xr write 2
	72	or
	73	.Xr send 2
	74	system calls may be used).
	75	.Pp
91447636	76	Outgoing packets automatically have an IPv6 header prepended to them
9bccf70c	77	(based on the destination address).
91447636 A	78	Incoming packets on the socket are received with the IPv6 header and any
	79	extension headers removed.
	80	.Ss Types
	81	ICMPv6 messages are classified according to the type and code fields
	82	present in the ICMPv6 header.
	83	The abbreviations for the types and codes may be used in rules in
	84	.Xr pf.conf 5 .
	85	The following types are defined:
	86	.Bl -column x xxxxxxxxxxxx -offset indent
	87	.It Sy Num Ta Sy Abbrev. Ta Sy Description
	88	.It 1 Ta unreach Ta "Destination unreachable"
	89	.It 2 Ta toobig Ta "Packet too big"
	90	.It 3 Ta timex Ta "Time exceeded"
	91	.It 4 Ta paramprob Ta "Invalid IPv6 header"
	92	.It 128 Ta echoreq Ta "Echo service request"
	93	.It 129 Ta echorep Ta "Echo service reply"
	94	.It 130 Ta groupqry Ta "Group membership query"
	95	.It 130 Ta listqry Ta "Multicast listener query"
	96	.It 131 Ta grouprep Ta "Group membership report"
	97	.It 131 Ta listenrep Ta "Multicast listener report"
	98	.It 132 Ta groupterm Ta "Group membership termination"
	99	.It 132 Ta listendone Ta "Multicast listerner done"
	100	.It 133 Ta routersol Ta "Router solicitation"
	101	.It 134 Ta routeradv Ta "Router advertisement"
	102	.It 135 Ta neighbrsol Ta "Neighbor solicitation"
	103	.It 136 Ta neighbradv Ta "Neighbor advertisement"
	104	.It 137 Ta redir Ta "Shorter route exists"
	105	.It 138 Ta routrrenum Ta "Route renumbering"
	106	.It 139 Ta fqdnreq Ta "FQDN query"
	107	.It 139 Ta niqry Ta "Node information query"
	108	.It 139 Ta wrureq Ta "Who-are-you request"
	109	.It 140 Ta fqdnrep Ta "FQDN reply"
	110	.It 140 Ta nirep Ta "Node information reply"
	111	.It 140 Ta wrurep Ta "Who-are-you reply"
	112	.It 200 Ta mtraceresp Ta "mtrace response"
	113	.It 201 Ta mtrace Ta "mtrace messages"
	114	.El
	115	.Pp
	116	The following codes are defined:
	117	.Bl -column x xxxxxxxxxxxx xxxxxxxx -offset indent
	118	.It Sy Num Ta Sy Abbrev. Ta Sy Type Ta
	119	.Sy Description
	120	.It 0 Ta noroute-unr Ta unreach Ta "No route to destination"
	121	.It 1 Ta admin-unr Ta unreach Ta "Administratively prohibited"
	122	.It 2 Ta beyond-unr Ta unreach Ta "Beyond scope of source address"
	123	.It 2 Ta notnbr-unr Ta unreach Ta "Not a neighbor (obselete)"
	124	.It 3 Ta addr-unr Ta unreach Ta "Address unreachable"
	125	.It 4 Ta port-unr Ta unreach Ta "Port unreachable"
	126	.It 0 Ta transit Ta timex Ta "Time exceeded in transit"
	127	.It 1 Ta reassemb Ta timex Ta "Time exceeded in reassembly"
	128	.It 0 Ta badhead Ta paramprob Ta "Erroneous header field"
	129	.It 1 Ta nxthdr Ta paramprob Ta "Unrecognized next header"
	130	.It 2 Ta "" Ta redir Ta "Unrecognized option"
	131	.It 0 Ta redironlink Ta redir Ta "Redirection to on-link node"
	132	.It 1 Ta redirrouter Ta redir Ta "Redirection to better router"
	133	.El
	134	.Ss Headers
	135	All ICMPv6 messages are prefixed with an ICMPv6 header.
	136	This header corresponds to the
	137	.Vt icmp6_hdr
	138	structure and has the following definition:
	139	.Bd -literal -offset indent
	140	struct icmp6_hdr {
	141	u_int8_t icmp6_type; /* type field */
142	u_int8_t icmp6_code; /* code field */
143	u_int16_t icmp6_cksum; /* checksum field */
144	union {
145	u_int32_t icmp6_un_data32[1]; /* type-specific */
146	u_int16_t icmp6_un_data16[2]; /* type-specific */
147	u_int8_t icmp6_un_data8[4]; /* type-specific */
148	} icmp6_dataun;
149	} __packed;
150
151	#define icmp6_data32 icmp6_dataun.icmp6_un_data32
152	#define icmp6_data16 icmp6_dataun.icmp6_un_data16
153	#define icmp6_data8 icmp6_dataun.icmp6_un_data8
154	#define icmp6_pptr icmp6_data32[0] /* parameter prob */
155	#define icmp6_mtu icmp6_data32[0] /* packet too big */
156	#define icmp6_id icmp6_data16[0] /* echo request/reply */
157	#define icmp6_seq icmp6_data16[1] /* echo request/reply */
158	#define icmp6_maxdelay icmp6_data16[0] /* mcast group membership*/
159	.Ed
9bccf70c	160	.Pp
91447636 A	161	.Va icmp6_type
	162	describes the type of the message.
	163	Suitable values are defined in
	164	.Aq Pa netinet/icmp6.h .
	165	.Va icmp6_code
	166	describes the sub-type of the message and depends on
	167	.Va icmp6_type .
	168	.Va icmp6_cksum
	169	contains the checksum for the message and is filled in by the
	170	kernel on outgoing messages.
	171	The other fields are used for type-specific purposes.
	172	.Ss Filters
	173	Because of the extra functionality of ICMPv6 in comparison to ICMPv4,
	174	a larger number of messages may be potentially received on an ICMPv6
	175	socket.
	176	Input filters may therefore be used to restrict input to a subset of the
	177	incoming ICMPv6 messages so only interesting messages are returned by the
	178	.Xr recv 2
	179	family of calls to an application.
9bccf70c	180	.Pp
91447636 A	181	The
	182	.Vt icmp6_filter
	183	structure may be used to refine the input message set according to the
	184	ICMPv6 type.
	185	By default, all messages types are allowed on newly created raw ICMPv6
	186	sockets.
	187	The following macros may be used to refine the input set:
	188	.Bl -tag -width Ds
	189	.It Fn "void ICMP6_FILTER_SETPASSALL" "struct icmp6_filter *filterp"
	190	Allow all incoming messages.
	191	.Va filterp
	192	is modified to allow all message types.
	193	.It Fn "void ICMP6_FILTER_SETBLOCKALL" "struct icmp6_filter *filterp"
	194	Ignore all incoming messages.
	195	.Va filterp
	196	is modified to ignore all message types.
	197	.It Fn "void ICMP6_FILTER_SETPASS" "int type" \
	198	"struct icmp6_filter *filterp"
	199	Allow ICMPv6 messages with the given
	200	.Fa type .
	201	.Va filterp
	202	is modified to allow such messages.
	203	.It Fn "void ICMP6_FILTER_SETBLOCK" "int type" \
	204	"struct icmp6_filter *filterp"
	205	Ignore ICMPv6 messages with the given
	206	.Fa type .
	207	.Va filterp
	208	is modified to ignore such messages.
	209	.It Fn "int ICMP6_FILTER_WILLPASS" "int type" \
	210	"const struct icmp6_filter *filterp"
	211	Determine if the given filter will allow an ICMPv6 message of the given
	212	type.
	213	.It Fn "int ICMP6_FILTER_WILLBLOCK" "int type" \
	214	"const struct icmp6_filter *filterp"
	215	Determine if the given filter will ignore an ICMPv6 message of the given
	216	type.
	217	.El
9bccf70c	218	.Pp
91447636	219	The
9bccf70c A	220	.Xr getsockopt 2
	221	and
	222	.Xr setsockopt 2
91447636 A	223	calls may be used to obtain and install the filter on ICMPv6 sockets at
91447636 A	224	option level
9bccf70c	225	.Dv IPPROTO_ICMPV6
91447636 A	226	and name
	227	.Dv ICMPV6_FILTER
	228	with a pointer to the
	229	.Vt icmp6_filter
	230	structure as the option value.
2d21ac55 A	231	.Ss "Non-privileged ICMPv6"
	232	.Pp
	233	.Tn ICMPv6
	234	sockets can be opened with the
	235	.Dv SOCK_DGRAM
	236	socket type without requiring root privileges. The synopsis is the following:
	237	.Pp
	238	.Fn socket AF_INET6 SOCK_DGRAM IPPROTO_ICMP6
	239	.Pp
	240	This can only be used to send
	241	.Tn ICMPv6
	242	echo requests to gauge the quality of the connectivity to a host, to receive
	243	destination unreachable message for path MTU discovery, or to receveive
	244	time exceeded message for traceroute.
	245	.Pp
	246	A socket opened with superuser privileges can send any kind of
	247	.Tn ICMPv6
	248	message and can also use the
	249	.Xr ip6 4
	250	options that require superuser privileges.
9bccf70c	251	.Sh SEE ALSO
91447636	252	.Xr getsockopt 2 ,
9bccf70c A	253	.Xr recv 2 ,
9bccf70c A	254	.Xr send 2 ,
91447636 A	255	.Xr setsockopt 2 ,
	256	.Xr socket 2 ,
	257	.Xr getprotobyname 3 ,
9bccf70c	258	.Xr inet6 4 ,
91447636 A	259	.Xr ip6 4 ,
91447636 A	260	.Xr netintro 4
9bccf70c A	261	.Rs
	262	.%A W. Stevens
	263	.%A M. Thomas
91447636 A	264	.%T Advanced Sockets API for IPv6
91447636 A	265	.%N RFC 2292
9bccf70c	266	.%D February 1998
9bccf70c A	267	.Re
	268	.Rs
	269	.%A A. Conta
	270	.%A S. Deering
91447636 A	271	.%T "Internet Control Message Protocol (ICMPv6) for the Internet" \
	272	"Protocol Version 6 (IPv6) Specification"
	273	.%N RFC 2463
9bccf70c	274	.%D December 1998
9bccf70c	275	.Re