TFTP-PROXY(8) System Manager's Manual TFTP-PROXY(8)

tftp-proxy — Internet Trivial File Transfer Protocol proxy

tftp-proxy [-46dv] [-a address] [-l address] [-p port] [-w transwait]

tftp-proxy is a proxy for the Internet Trivial File Transfer Protocol. TFTP connections should be redirected to the proxy using a pf(4) rule using the divert-to option, after which the proxy connects to the server on behalf of the client. The connection from the proxy to the server needs to be passed by a rule with divert-reply set.

The proxy inserts pf(4) pass and/or rdr rules using the anchor facility to allow payload packets between the client and the server. Once the rules are inserted, tftp-proxy forwards the initial request from the client to the server to begin the transfer. After transwait seconds, the states are assumed to have been established and the pf(4) rules are deleted and the program exits. Once the transfer between the client and the server is completed, the states will naturally expire.

The options are as follows:

Forces tftp-proxy to use IPv4 addresses only.
Forces tftp-proxy to use IPv6 addresses only.
address
The proxy will use address as the source address for the initial request from the client to the server for NAT traversal. Instead of a “pass in” rule an “rdr” rule will be generated. It is possible to have two -a options to specify both an IPv4 and an IPv6 address.
Do not daemonize. If this option is specified, tftp-proxy will run in the foreground and log the client IP, type of request, and filename to stderr.
address
Listen on the specified address. By default tftp-proxy listens on localhost addresses.
port
Listen on the specified port. By default tftp-proxy listens on port 6969.
Log the connection and request information to syslogd(8).
transwait
Number of seconds to wait for the data transmission to begin before removing the pf(4) rule. The default is 2 seconds.

To make use of the proxy, pf.conf(5) needs the following rules. The anchor is mandatory. Adjust the rule as needed for your configuration.

anchor "tftp-proxy/*"
pass in quick on $int_if inet proto udp from $lan to port tftp \
    divert-to 127.0.0.1 port 6969
pass out quick on $ext_if inet proto udp from $lan to port tftp \
    group _tftp_proxy divert-reply

tftp(1), pf(4), pf.conf(5), ftp-proxy(8), syslogd(8), tftpd(8)

The current stand-alone implementation first appeared in OpenBSD 5.3.

David Gwynne <dlg@openbsd.org>

March 31, 2022 Debian