165 lines
4.7 KiB
Groff
165 lines
4.7 KiB
Groff
.\" 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
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd March 21, 2003
|
|
.Dt ICMP 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm icmp
|
|
.Nd Internet Control Message Protocol
|
|
.Sh SYNOPSIS
|
|
.In sys/types.h
|
|
.In sys/socket.h
|
|
.In 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 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 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.
|
|
.Ss MIB Variables
|
|
The
|
|
.Tn ICMP
|
|
protocol implements a number of variables in the
|
|
.Va net.inet.icmp
|
|
branch of the
|
|
.Xr sysctl 3
|
|
MIB.
|
|
.Bl -tag -width ".Va icmplim_output"
|
|
.It Va maskrepl
|
|
.Pq Vt boolean
|
|
Enable/disable replies to ICMP Address Mask Request packets.
|
|
Defaults to false.
|
|
.It Va maskfake
|
|
.Pq Vt "unsigned integer"
|
|
When
|
|
.Va maskrepl
|
|
is set and this value is non-zero,
|
|
it will be used instead of the real address mask when
|
|
the system replies to an ICMP Address Mask Request packet.
|
|
Defaults to 0.
|
|
.It Va icmplim
|
|
.Pq Vt integer
|
|
Bandwidth limit for ICMP replies in packets/second.
|
|
Used when
|
|
.Va icmplim_output
|
|
is non-zero.
|
|
Defaults to 200.
|
|
.It Va icmplim_output
|
|
.Pq Vt boolean
|
|
Enable/disable bandwidth limiting of ICMP replies.
|
|
Defaults to true.
|
|
.It Va drop_redirect
|
|
.Pq Vt boolean
|
|
Enable/disable dropping of ICMP Redirect packets.
|
|
Defaults to false.
|
|
.It Va log_redirect
|
|
.Pq Vt boolean
|
|
Enable/disable logging of ICMP Redirect packets.
|
|
Defaults to false.
|
|
.It Va bmcastecho
|
|
.Pq Vt boolean
|
|
Enable/disable ICMP replies received via broadcast or multicast.
|
|
Defaults to false.
|
|
.El
|
|
.Sh ERRORS
|
|
A socket operation may fail with one of the following errors returned:
|
|
.Bl -tag -width Er
|
|
.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.
|
|
.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 .
|