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

.\"	$NetBSD: icmp.4,v 1.3 1994/11/30 16:22:14 jtc 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. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. 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.
.\"
.\"     @(#)icmp.4	8.1 (Berkeley) 6/5/93
.\"
.Dd June 19, 2002
.Dt ICMP 4
.Os BSD 4.3
.Sh NAME
.Nm icmp
.Nd Internet Control Message Protocol
.Sh SYNOPSIS
.Fd #include <sys/socket.h>
.Fd #include <netinet/in.h>
.Ft int
.Fn socket AF_INET SOCK_RAW proto
.Sh DESCRIPTION
.Tn ICMP
is the error and control message protocol used
by
.Tn IP
and the Internet protocol family.  It may be accessed
through a
.Dq raw socket
for network monitoring
and diagnostic functions.
The
.Fa proto
parameter to the socket call to create an
.Tn ICMP
socket
is obtained from
.Xr getprotobyname 3 .
.Tn ICMP
sockets are connectionless,
and are normally used with the
.Xr sendto
and
.Xr recvfrom
calls, though the
.Xr connect 2
call may also be used to fix the destination for future
packets (in which case the 
.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
.Tn IP
header prepended to
them (based on the destination address).
Incoming packets are received with the
.Tn IP
header and options intact.
Note that the ip_off and ip_len fields are in host byte order.
For more information about the IP header structure, see 
.Xr ip 4 .
.Ss "Non-privileged ICMP"
.Pp
.Tn ICMP
sockets can be opened with the 
.Dv SOCK_DGRAM
socket type without requiring root privileges. The synopsis is the following:
.Pp
.Fn socket AF_INET SOCK_DGRAM IPPROTO_ICMP
.Pp
Datagram oriented
.Tn ICMP
sockets offer a subset of the functionality available to raw 
.Tn ICMP
sockets. Only
.Tn IMCP
request messages of the following types can be sent: 
ICMP_ECHO, ICMP_TSTAMP or ICMP_MASKREQ. 
The code field must be the value zero (0). 
The minimal length of an 
.Tn ICMP 
message request is eight (8) octets.
.Pp
The advantage of using datagram oriented
.Tn ICMP
sockets is that even a non-privileged process can use 
.Tn ICMP
echo requests to gauge the quality of the connectivity to a host, 
or to receive 
.Tn ICMP
destination unreachable message for path MTU discovery, or to receive 
time exceeded messages for traceroute. 
.Pp
The following 
.Tn IP
level option can be used with datagram oriented 
.Tn ICMP
sockets:
.Bl -column ip_opts -offset 4n
.It IP_OPTIONS
.It IP_HDRINCL
.It IP_TOS
.It IP_TTL
.It IP_RECVOPTS
.It IP_RECVRETOPTS
.It IP_RECVDSTADDR
.It IP_RETOPTS
.It IP_MULTICAST_IF
.It IP_MULTICAST_TTL
.It IP_MULTICAST_LOOP
.It IP_ADD_MEMBERSHIP
.It IP_DROP_MEMBERSHIP
.It IP_MULTICAST_VIF
.It IP_PORTRANGE
.It IP_RECVIF
.It IP_IPSEC_POLICY
.It IP_STRIPHDR
.El
.Pp
When the  
.Tn IP
option IP_HDRINCL is used, the provided 
.Tn IP 
header must obey the following rules:
.Bl -column ip_opts -offset 4n
.It ip_v Ta Must be IPVERSION (4);
.It ip_hl Ta Between 5 and 10 (inclusive);
.It ip_tos Ta Any value;
.It ip_len Ta Must be the total length of IP datagram (IP header + ICMP message);
.It ip_id Ta Must be zero, will be automatically set;
.It ip_off Ta Must be zero, will be automatically set;
.It ip_ttl Ta Any value;
.It ip_p Ta Must be IPPROTO_IP;
.It ip_sum Ta Value ignored, will be automatically set;
.It ip_src Ta Must be an 
.Tn IP
address currently assigned to one of the local interface or INADDR_ANY;
.It ip_dst Ta Any address;
.It ip_opts Ta Any option.
.El
.Pp
The maximum length of a IMCP message that can be sent is controlled 
by the sysctl 
variable net.inet.raw.maxdgram.
.Sh DIAGNOSTICS
A socket operation may fail with one of the following errors returned:
.Bl -tag -width [EADDRNOTAVAIL]
.It Bq Er EISCONN
when trying to establish a connection on a socket which
already has one, or when trying to send a datagram with the destination
address specified and the socket is already connected;
.It Bq Er ENOTCONN
when trying to send a datagram, but
no destination address is specified, and the socket hasn't been
connected;
.It Bq Er ENOBUFS
when the system runs out of memory for
an internal data structure;
.It Bq Er EADDRNOTAVAIL
when an attempt is made to create a 
socket with a network address for which no network interface
exists;
.It Bq Er EINVAL
when an invalid value is used with
.Tn IMCP
datagram socket for a field of the  
.Tn IP
or
.Tn ICMP
header.
.El
.Sh SEE ALSO
.Xr recv 2 ,
.Xr send 2 ,
.Xr inet 4 ,
.Xr intro 4 ,
.Xr ip 4
.Sh HISTORY
The
.Nm
protocol appeared in
.Bx 4.3 .
Commit	Line	Data
9bccf70c A	1	.\" $NetBSD: icmp.4,v 1.3 1994/11/30 16:22:14 jtc Exp $
	2	.\"
	3	.\" Copyright (c) 1986, 1991, 1993
	4	.\" The Regents of the University of California. All rights reserved.
	5	.\"
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 3. All advertising materials mentioning features or use of this software
	15	.\" must display the following acknowledgement:
	16	.\" This product includes software developed by the University of
	17	.\" California, Berkeley and its contributors.
	18	.\" 4. Neither the name of the University nor the names of its contributors
	19	.\" may be used to endorse or promote products derived from this software
	20	.\" without specific prior written permission.
	21	.\"
	22	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	34	.\" @(#)icmp.4 8.1 (Berkeley) 6/5/93
	35	.\"
	36	.Dd June 19, 2002
	37	.Dt ICMP 4
	38	.Os BSD 4.3
	39	.Sh NAME
	40	.Nm icmp
	41	.Nd Internet Control Message Protocol
	42	.Sh SYNOPSIS
	43	.Fd #include <sys/socket.h>
	44	.Fd #include <netinet/in.h>
	45	.Ft int
	46	.Fn socket AF_INET SOCK_RAW proto
	47	.Sh DESCRIPTION
	48	.Tn ICMP
	49	is the error and control message protocol used
	50	by
	51	.Tn IP
	52	and the Internet protocol family. It may be accessed
	53	through a
	54	.Dq raw socket
	55	for network monitoring
	56	and diagnostic functions.
	57	The
	58	.Fa proto
	59	parameter to the socket call to create an
	60	.Tn ICMP
	61	socket
	62	is obtained from
	63	.Xr getprotobyname 3 .
	64	.Tn ICMP
65	sockets are connectionless,
66	and are normally used with the
67	.Xr sendto
68	and
69	.Xr recvfrom
70	calls, though the
71	.Xr connect 2
72	call may also be used to fix the destination for future
73	packets (in which case the
74	.Xr read 2
75	or
76	.Xr recv 2
77	and
78	.Xr write 2
79	or
80	.Xr send 2
81	system calls may be used).
82	.Pp
83	Outgoing packets automatically have an
84	.Tn IP
85	header prepended to
86	them (based on the destination address).
87	Incoming packets are received with the
88	.Tn IP
89	header and options intact.
2d21ac55 A	90	Note that the ip_off and ip_len fields are in host byte order.
	91	For more information about the IP header structure, see
	92	.Xr ip 4 .
9bccf70c A	93	.Ss "Non-privileged ICMP"
	94	.Pp
	95	.Tn ICMP
	96	sockets can be opened with the
	97	.Dv SOCK_DGRAM
	98	socket type without requiring root privileges. The synopsis is the following:
	99	.Pp
55e303ae	100	.Fn socket AF_INET SOCK_DGRAM IPPROTO_ICMP
9bccf70c	101	.Pp
9bccf70c A	102	Datagram oriented
	103	.Tn ICMP
	104	sockets offer a subset of the functionality available to raw
	105	.Tn ICMP
	106	sockets. Only
	107	.Tn IMCP
	108	request messages of the following types can be sent:
	109	ICMP_ECHO, ICMP_TSTAMP or ICMP_MASKREQ.
	110	The code field must be the value zero (0).
	111	The minimal length of an
	112	.Tn ICMP
	113	message request is eight (8) octets.
	114	.Pp
2d21ac55 A	115	The advantage of using datagram oriented
	116	.Tn ICMP
	117	sockets is that even a non-privileged process can use
	118	.Tn ICMP
	119	echo requests to gauge the quality of the connectivity to a host,
	120	or to receive
	121	.Tn ICMP
	122	destination unreachable message for path MTU discovery, or to receive
	123	time exceeded messages for traceroute.
	124	.Pp
9bccf70c A	125	The following
	126	.Tn IP
	127	level option can be used with datagram oriented
	128	.Tn ICMP
	129	sockets:
	130	.Bl -column ip_opts -offset 4n
	131	.It IP_OPTIONS
	132	.It IP_HDRINCL
	133	.It IP_TOS
	134	.It IP_TTL
	135	.It IP_RECVOPTS
	136	.It IP_RECVRETOPTS
	137	.It IP_RECVDSTADDR
	138	.It IP_RETOPTS
	139	.It IP_MULTICAST_IF
	140	.It IP_MULTICAST_TTL
	141	.It IP_MULTICAST_LOOP
	142	.It IP_ADD_MEMBERSHIP
	143	.It IP_DROP_MEMBERSHIP
	144	.It IP_MULTICAST_VIF
	145	.It IP_PORTRANGE
	146	.It IP_RECVIF
	147	.It IP_IPSEC_POLICY
	148	.It IP_STRIPHDR
	149	.El
	150	.Pp
	151	When the
	152	.Tn IP
	153	option IP_HDRINCL is used, the provided
	154	.Tn IP
	155	header must obey the following rules:
	156	.Bl -column ip_opts -offset 4n
	157	.It ip_v Ta Must be IPVERSION (4);
	158	.It ip_hl Ta Between 5 and 10 (inclusive);
	159	.It ip_tos Ta Any value;
	160	.It ip_len Ta Must be the total length of IP datagram (IP header + ICMP message);
	161	.It ip_id Ta Must be zero, will be automatically set;
	162	.It ip_off Ta Must be zero, will be automatically set;
	163	.It ip_ttl Ta Any value;
	164	.It ip_p Ta Must be IPPROTO_IP;
	165	.It ip_sum Ta Value ignored, will be automatically set;
	166	.It ip_src Ta Must be an
	167	.Tn IP
	168	address currently assigned to one of the local interface or INADDR_ANY;
	169	.It ip_dst Ta Any address;
	170	.It ip_opts Ta Any option.
	171	.El
	172	.Pp
	173	The maximum length of a IMCP message that can be sent is controlled
	174	by the sysctl
	175	variable net.inet.raw.maxdgram.
	176	.Sh DIAGNOSTICS
	177	A socket operation may fail with one of the following errors returned:
	178	.Bl -tag -width [EADDRNOTAVAIL]
	179	.It Bq Er EISCONN
	180	when trying to establish a connection on a socket which
	181	already has one, or when trying to send a datagram with the destination
	182	address specified and the socket is already connected;
	183	.It Bq Er ENOTCONN
	184	when trying to send a datagram, but
	185	no destination address is specified, and the socket hasn't been
	186	connected;
	187	.It Bq Er ENOBUFS
	188	when the system runs out of memory for
189	an internal data structure;
190	.It Bq Er EADDRNOTAVAIL
191	when an attempt is made to create a
192	socket with a network address for which no network interface
193	exists;
194	.It Bq Er EINVAL
195	when an invalid value is used with
196	.Tn IMCP
197	datagram socket for a field of the
198	.Tn IP
199	or
200	.Tn ICMP
201	header.
202	.El
203	.Sh SEE ALSO
9bccf70c	204	.Xr recv 2 ,
2d21ac55	205	.Xr send 2 ,
9bccf70c	206	.Xr inet 4 ,
2d21ac55	207	.Xr intro 4 ,
9bccf70c A	208	.Xr ip 4
	209	.Sh HISTORY
	210	The
	211	.Nm
	212	protocol appeared in
	213	.Bx 4.3 .