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.\" Copyright (c) 1990, 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: (1) source code distributions
.\" retain the above copyright notice and this paragraph in its entirety, (2)
.\" distributions including binary code include the above copyright notice and
.\" this paragraph in its entirety in the documentation or other materials
.\" provided with the distribution. 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
.\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
.\"
.\" $FreeBSD$
.\"
.Dd July 9, 2012
.Dt RARPD 8
.Os
.Sh NAME
.Nm rarpd
.Nd reverse ARP daemon
.Sh SYNOPSIS
.Nm
.Fl a
.Op Fl dfsv
.Op Fl t Ar directory
.Op Fl P Ar pidfile
.Nm
.Op Fl dfsv
.Op Fl t Ar directory
.Op Fl P Ar pidfile
.Ar interface
.Sh DESCRIPTION
The
.Nm
utility services Reverse ARP requests on the Ethernet connected to
.Ar interface .
Upon receiving a request,
.Nm
maps the target hardware address to an IP address via its name, which
must be present in both the
.Xr ethers 5
and
.Xr hosts 5
databases.
If a host does not exist in both databases, the translation cannot
proceed and a reply will not be sent.
.Pp
By default, a request is honored only if the server
(i.e., the host that
.Nm
is running on)
can "boot" the target; that is, a file or directory matching the glob
.Pa /tftpboot/\fIipaddr\fP*
exists, where
.Em ipaddr
is the target IP address in hex.
For example, the IP address 204.216.27.18 will be replied to if any of
.Pa /tftpboot/CCD81B12 ,
.Pa /tftpboot/CCD81B12.SUN3 ,
or
.Pa /tftpboot/CCD81B12-boot
exist.
This requirement can be overridden with the
.Fl s
flag (see below).
.Pp
In normal operation,
.Nm
forks a copy of itself and runs in the background.
Anomalies and errors are reported via
.Xr syslog 3 .
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl a
Listen on all the Ethernets attached to the system.
If
.Fl a
is omitted, an interface must be specified.
.It Fl d
If
.Fl f
is also specified,
.Nm
logs messages to
.Em stdout
and
.Em stderr
instead of via
.Xr syslog 3 .
.It Fl f
Run in the foreground.
.It Fl P
Specify the pathname of the PID file.
If not specified,
.Pa /var/run/rarpd.pid
or
.Pa /var/run/rarpd.ifname.pid
will be used depending on the
.Fl a
flag or the specified interface name.
.It Fl s
Supply a response to any RARP request for which an ethernet to IP address
mapping exists; do not depend on the existence of
.Pa /tftpboot/\fIipaddr\fP* .
.It Fl t
Supply an alternate tftp root directory to
.Pa /tftpboot ,
similar to the
.Fl s
option of
.Xr tftpd 8 .
This permits
.Nm
to selectively respond to RARP requests, but use an alternate directory
for IP checking.
.It Fl v
Enable verbose syslogging.
.El
.Sh FILES
.Bl -tag -width /etc/ethers -compact
.It Pa /etc/ethers
.It Pa /etc/hosts
.It Pa /tftpboot
.It Pa /var/run/rarpd.pid
.El
.Sh SEE ALSO
.Xr bpf 4
.Rs
.%A "Finlayson, R."
.%A "Mann, T."
.%A "Mogul, J.C."
.%A "Theimer, M."
.%T "RFC 903: Reverse Address Resolution Protocol"
.%D "June 1984"
.%O "4 p"
.Re
.Sh AUTHORS
.An -nosplit
.An Craig Leres Aq leres@ee.lbl.gov
and
.An Steven McCanne Aq mccanne@ee.lbl.gov .
Lawrence Berkeley Laboratory, University of California, Berkeley, CA.
.Sh BUGS
The
.Nm
utility can depend on the DNS to resolve the name discovered from
.Pa /etc/ethers .
If this name is not in the DNS but is in
.Pa /etc/hosts ,
the DNS lookup can cause a delayed RARP response, so in this situation
it is recommended to configure
.Xr nsswitch.conf 5
to read
.Pa /etc/hosts
first.
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