From 6e3521ef7b6243579e80428e87e29cae49922ecf Mon Sep 17 00:00:00 2001 From: mycroft Date: Fri, 13 May 1994 08:08:59 +0000 Subject: [PATCH] From 4.4-Lite. --- usr.sbin/arp/arp4.4 | 125 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 125 insertions(+) create mode 100644 usr.sbin/arp/arp4.4 diff --git a/usr.sbin/arp/arp4.4 b/usr.sbin/arp/arp4.4 new file mode 100644 index 000000000000..b418b9c602fa --- /dev/null +++ b/usr.sbin/arp/arp4.4 @@ -0,0 +1,125 @@ +.\" Copyright (c) 1985, 1986, 1988, 1994 +.\" 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. +.\" +.\" from: @(#)arp4.4 6.5 (Berkeley) 4/18/94 +.\" $Id: arp4.4,v 1.1.1.1 1994/05/13 08:08:59 mycroft Exp $ +.\" +.Dd April 18, 1994 +.Dt ARP 4 +.Os BSD 4 +.Sh NAME +.Nm arp +.Nd Address Resolution Protocol +.Sh SYNOPSIS +.Em "pseudo-device ether" +.Sh DESCRIPTION +The Address Resolution Protocol (ARP) is a protocol used to dynamically +map between Internet host addresses and 10Mb/s Ethernet addresses. +It is used by all the 10Mb/s Ethernet interface drivers. +It is not specific to Internet protocols or to 10Mb/s Ethernet, +but this implementation currently supports only that combination. +.Pp +ARP caches Internet-Ethernet address mappings. +When an interface requests a mapping for an address not in the cache, +ARP queues the message which requires the mapping and broadcasts +a message on the associated network requesting the address mapping. +If a response is provided, the new mapping is cached and any pending +message is transmitted. +ARP will queue at most one packet while waiting for a response to a +mapping request; +only the most recently ``transmitted'' packet is kept. +If the target host does not respond after several requests, +the host is considered to be down for a short period (normally 20 seconds), +allowing an error to be returned to transmission attempts during this +interval. +The error is +.Li EHOSTDOWN +for a non-responding destination host, and +.Li EHOSTUNREACH +for a non-responding router. +.Pp +The ARP cache is stored in the system routing table as +dynamically-created host routes. +The route to a directly-attached Ethernet network is installed as a +.Dq cloning +route (one with the +.Li RTF_CLONING +flag set), +causing routes to individual hosts on that network to be created on +demand. +These routes time out periodically (normally 20 minutes after validated; +entries are not validated when not in use). +An entry for a host which is not responding is a +.Dq reject +route (one with the +.Li RTF_REJECT +flag set). +.Pp +ARP entries may be added, deleted or changed with the +.Xr arp 8 +utility. +Manually-added entries may be temporary or permanent, +and may be +.Dq published , +in which case the system will respond to ARP requests for that host +as if it were the target of the request. +.Pp +In the past, +ARP was used to negotiate the use of a trailer encapsulation. +This is no longer supported. +.Pp +ARP watches passively for hosts impersonating the local host (i.e. a host +which responds to an ARP mapping request for the local host's address). +.Sh DIAGNOSTICS +.Em "duplicate IP address %x!! sent from ethernet address: %x:%x:%x:%x:%x:%x." +ARP has discovered another host on the local network which responds to +mapping requests for its own Internet address with a different Ethernet +address, generally indicating that two hosts are attempting to use the +same Internet address. +.Sh SEE ALSO +.Xr inet 4 , +.Xr route 4 , +.Xr arp 8 , +.Xr ifconfig 8 , +.Xr route 8 +.sp +.Rs +.%A Plummer, D. +.%B "An Ethernet Address Resolution Protocol" +.%T RFC826 +.Re +.Rs +.%A Leffler, S.J. +.%A Karels, M.J. +.%B "Trailer Encapsulations +.%T RFC893 +.Re +