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 From:  Manuel Kasper <mk at neon1 dot net>
 To:  m0n0wall at lists dot m0n0 dot ch
 Subject:  Re: [m0n0wall] how to set up a the PPTP server with firewall rules
 Date:  Mon, 7 Jul 2003 09:27:45 +0200 (CEST)
On Sun, 6 Jul 2003, Fred Wright wrote:

> Only the GRE traffic is a problem, since there's no conflict with the
> control connection (as long as you don't need simultaneous client and
> server operation with respect to a single remote system).  So the PPTP
> code should be able to use the local IP address of the already-established
> control connection socket to bind() the (presumably raw) GRE socket.  It
> could even bind to the remote IP by using connect(), which also improves
> efficiency.

Interestingly, the reason for the "Address already in use" message is not
GRE, but the TCP port 1723 server socket. I sent Michiel a slightly
modified version of m0n0wall where the PPTP server uses "set pptp self"
(to 127.0.0.1) like the PPTP client does (which uses the pseudo WAN IP
address assigned on the WAN->PPTP setup page). Still - the same message...
Looking at MPD's source code, it's clear that the message originates from
the bind() on the TCP server socket. I don't quite understand why two
different processes cannot bind to the same port but on different IP
addresses... I thought that was possible. MPD even uses setsockopt(...
SO_REUSEADDR ...) before the bind() - don't know what effect that has,
though.

Some more debugging may be in order, I guess. Maybe we have to check if
MPD really supplies the IP address given in "set pptp self" to bind().

- Manuel