[pptp-server] PPTP behind a Firewall

[Robert Dege]

Thanks for the reply.  Unfortunately, I am not using the PPTP client at 
the moment.  I am using a Win98 box.

Here's what happens:

1.  Win98 box tries to make a PPTP connection.
2.  For some odd reason, ip_masq_pptp module does not load by default. 
I have to manually insmod it.  Once I do that, I start to receive the 
ip_masq_gre errors.  Yet, lsmod claims that ip_masq_pptp is unused:

Module                  Size  Used by
ip_masq_pptp            6848   0 (unused)
ip_masq_ftp             2656   1

(Do I possibly have to add something to the modules.conf file???)

3.  Debugging info shows:

Apr 16 13:22:47 odo kernel: ip_masq_gre(): creating GRE masq for 
172.28.254.46 -> 12.19.228.58 CID=0 MCID=643A
Apr 16 13:22:47 odo kernel: ip_demasq_gre(): 12.19.228.58 -> 
12.19.228.52 CID=0 no masq table, discarding

This occurs during the inital handshake.  Doing a tcpdump on IP 47 shows 
that the packets are still being passed to the pptp server & received 
back despite the debugging messages.

4.  PPTP on the Win98 box finally fails due to timeout.


I can post the PPTP server debugging info if anybody thinks it will help.

Any response is appreciated.

-Rob

>>  You should be seeing ip_<masq|demasq>_pptp() messages. Are you using the Linux
>> PPTP client? I found that the commonly available Linux client uses the
>> wrong CallID once a PPTP session is established, and it causes the
>> sort of symptom you're seeing - masquerading doesn't recognize the
>> traffic as PPTP and tries to handle it as plain GRE.
> 
> 
> I have a patch to pptp-linux that corrects that problem:
> 
> 	ftp://seattlefirewall.dyndns.org/pub/patches/callid.patch
> 
> -Tom