.\"	$OpenBSD: tftp-proxy.8,v 1.5 2011/06/22 08:39:15 sthen Exp $
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.\" Copyright (c) 2005 joshua stein <jcs@openbsd.org>
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.Dd $Mdocdate: June 22 2011 $
.Dt TFTP-PROXY 8
.Os
.Sh NAME
.Nm tftp-proxy
.Nd Internet Trivial File Transfer Protocol proxy
.Sh SYNOPSIS
.Nm tftp-proxy
.Op Fl v
.Op Fl w Ar transwait
.Sh DESCRIPTION
.Nm
is a proxy for the Internet Trivial File Transfer Protocol invoked by
the
.Xr inetd 8
internet server.
TFTP connections should be redirected to the proxy using a
.Xr pf 4
rule using the
.Ar divert-to
option, after which the proxy connects to the server on behalf of
the client.
.Pp
The proxy establishes a
.Xr pf 4
.Ar rdr-to
pass rule using the
.Ar anchor
facility to rewrite packets between the client and the server.
Once the rule is established,
.Nm
forwards the initial request from the client to the server to begin the
transfer.
After
.Ar transwait
seconds, the NAT state is assumed to have been established and the
.Xr pf 4
rule is deleted and the program exits.
Once the transfer between the client and the server is completed, the
NAT state will naturally expire.
.Pp
Assuming the TFTP command request is from $client to $server, the
proxy connected to the server using the $proxy source address, and
$port is negotiated,
.Nm
adds the following rule to the anchor:
.Bd -literal -offset indent
pass in quick proto udp from $server to $proxy \e
    port $port rdr-to $client
.Ed
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl v
Log the connection and request information to
.Xr syslogd 8 .
.It Fl w Ar transwait
Number of seconds to wait for the data transmission to begin before
removing the
.Xr pf 4
rule.
The default is 2 seconds.
.El
.Sh CONFIGURATION
To make use of the proxy,
.Xr pf.conf 5
needs the following rules.
The anchor is mandatory.
Adjust the rule as needed for your configuration.
.Bd -literal -offset indent
anchor "tftp-proxy/*"
pass in quick on $int_if inet proto udp from $lan to any port tftp \e
    divert-to 127.0.0.1 port 6969
.Ed
.Pp
.Xr inetd 8
must be configured to spawn the proxy on the port that packets are
being forwarded to by
.Xr pf 4 .
An example
.Xr inetd.conf 5
entry follows:
.Bd -literal -offset indent
127.0.0.1:6969	dgram	udp	wait	root \e
	/usr/libexec/tftp-proxy	tftp-proxy
.Ed
.Sh SEE ALSO
.Xr tftp 1 ,
.Xr pf 4 ,
.Xr pf.conf 5 ,
.Xr ftp-proxy 8 ,
.Xr inetd 8 ,
.Xr syslogd 8 ,
.Xr tftpd 8
.Sh CAVEATS
.Nm
chroots to
.Pa /var/empty
and changes to user
.Dq proxy
to drop privileges.