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171 lines
4.8 KiB
Groff
171 lines
4.8 KiB
Groff
.\" Copyright (c) 1986, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)icmp.4 8.1 (Berkeley) 6/5/93
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.\" $FreeBSD$
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.\"
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.Dd March 21, 2003
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.Dt ICMP 4
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.Os
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.Sh NAME
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.Nm icmp
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.Nd Internet Control Message Protocol
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/socket.h
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.In netinet/in.h
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.Ft int
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.Fn socket AF_INET SOCK_RAW proto
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.Sh DESCRIPTION
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.Tn ICMP
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is the error and control message protocol used
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by
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.Tn IP
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and the Internet protocol family.
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It may be accessed
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through a
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.Dq raw socket
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for network monitoring
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and diagnostic functions.
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The
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.Fa proto
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parameter to the socket call to create an
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.Tn ICMP
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socket
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is obtained from
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.Xr getprotobyname 3 .
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.Tn ICMP
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sockets are connectionless,
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and are normally used with the
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.Xr sendto 2
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and
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.Xr recvfrom 2
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calls, though the
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.Xr connect 2
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call may also be used to fix the destination for future
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packets (in which case the
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.Xr read 2
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or
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.Xr recv 2
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and
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.Xr write 2
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or
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.Xr send 2
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system calls may be used).
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.Pp
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Outgoing packets automatically have an
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.Tn IP
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header prepended to
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them (based on the destination address).
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Incoming packets are received with the
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.Tn IP
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header and options intact.
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.Ss MIB Variables
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The
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.Tn ICMP
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protocol implements a number of variables in the
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.Va net.inet.icmp
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branch of the
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.Xr sysctl 3
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MIB.
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.Bl -tag -width ".Va icmplim_output"
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.It Va maskrepl
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.Pq Vt boolean
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Enable/disable replies to ICMP Address Mask Request packets.
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Defaults to false.
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.It Va maskfake
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.Pq Vt "unsigned integer"
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When
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.Va maskrepl
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is set and this value is non-zero,
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it will be used instead of the real address mask when
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the system replies to an ICMP Address Mask Request packet.
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Defaults to 0.
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.It Va icmplim
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.Pq Vt integer
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Bandwidth limit for ICMP replies in packets/second.
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Used when
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.Va icmplim_output
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is non-zero.
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Defaults to 200.
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.It Va icmplim_output
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.Pq Vt boolean
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Enable/disable bandwidth limiting of ICMP replies.
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Defaults to true.
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.It Va drop_redirect
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.Pq Vt boolean
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Enable/disable dropping of ICMP Redirect packets.
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Defaults to false.
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.It Va log_redirect
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.Pq Vt boolean
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Enable/disable logging of ICMP Redirect packets.
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Defaults to false.
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.It Va bmcastecho
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.Pq Vt boolean
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Enable/disable ICMP replies received via broadcast or multicast.
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Defaults to false.
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.It Va reply_src
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.Pq Vt str
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An interface name used for the ICMP reply source in response to packets
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which are not directly addressed to us.
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By default continue with normal source selection.
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.El
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.Sh ERRORS
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A socket operation may fail with one of the following errors returned:
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.Bl -tag -width Er
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.It Bq Er EISCONN
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when trying to establish a connection on a socket which
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already has one, or when trying to send a datagram with the destination
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address specified and the socket is already connected;
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.It Bq Er ENOTCONN
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when trying to send a datagram, but
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no destination address is specified, and the socket hasn't been
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connected;
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.It Bq Er ENOBUFS
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when the system runs out of memory for
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an internal data structure;
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.It Bq Er EADDRNOTAVAIL
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when an attempt is made to create a
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socket with a network address for which no network interface
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exists.
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.El
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.Sh SEE ALSO
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.Xr recv 2 ,
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.Xr send 2 ,
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.Xr inet 4 ,
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.Xr intro 4 ,
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.Xr ip 4
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.Sh HISTORY
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The
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.Nm
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protocol appeared in
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.Bx 4.3 .
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