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

     tftp-proxy - Internet Trivial File Transfer Protocol proxy

     tftp-proxy [-v] [-w transwait]

     tftp-proxy is a proxy for the Internet Trivial File Transfer Protocol
     invoked by the inetd(8) internet server.  TFTP connections should be
     redirected to the proxy using the pf(4) rdr command, after which the
     proxy connects to the server on behalf of the client.

     The proxy establishes a pf(4) rdr rule using the anchor facility to
     rewrite packets between the client and the server.  Once the rule is
     established, tftp-proxy forwards the initial request from the client to
     the server to begin the transfer.  After transwait seconds, the pf(4) NAT
     state is assumed to have been established and the rdr rule is deleted and
     the program exits.  Once the transfer between the client and the server
     is completed, the NAT state will naturally expire.

     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, tftp-proxy adds the following rule to the anchor:

           rdr proto udp from $server to $proxy port $port -> $client

     The options are as follows:

     -v      Log the connection and request information to syslogd(8).

     -w transwait
             Number of seconds to wait for the data transmission to begin
             before removing the pf(4) rdr rule.  The default is 2 seconds.

     To make use of the proxy, pf.conf(5) needs the following rules.  The
     anchors are mandatory.  Adjust the rules as needed for your

     In the NAT section:

           nat on $ext_if from $int_if -> ($ext_if:0)

           no nat on $ext_if to port tftp

           rdr-anchor "tftp-proxy/*"
           rdr on $int_if proto udp from $lan to any port tftp -> \
      port 6969

     In the filter section, an anchor must be added to hold the pass rules:

           anchor "tftp-proxy/*"

     inetd(8) must be configured to spawn the proxy on the port that packets
     are being forwarded to by pf(4).  An example inetd.conf(5) entry follows:

   dgram   udp     wait    root \
                   /usr/libexec/tftp-proxy tftp-proxy

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

     tftp-proxy chroots to /var/chroot/tftp-proxy and changes to user "_proxy"
     to drop privileges.

NetBSD 9.99                      May 31, 2007                      NetBSD 9.99