[pptp-server] Connection is on, communication is off: "no masq table" in the log

[Vlad Strezhnev]

Our corporate pptpd server is behind a firewall.

It looks like everything is configured properly and connections are smooth both from DMZ and from outside.
The problem is the persistent complete losses of communication after random periods of time (say 10 min to 1 hour) when the client is connected from outside (eg from home DSL). The connections from DMZ do not have this problem.

The worst thing is that since no disconnection is reported to the client, the auto reconnect option does not work. 
The only way to restore the communication is to manually stop and restart the VPN client. 

The log shows a lot of " ip_demasq_gre() ... no masq table" errors  but no preceeding "ip_masq_in_get_gre(): lookup ... FAIL" errors.
 So the previous discussion of this problem in this mailing list might not be not applicable. 

Following is the log of the last minutes of the recent unattended session that "theoretically" lasted for more then 6 hours but died somewhere in the middle of the night :-( 
(PS The real IPs were removed from the log.)

Any hits on what's happening will be much appreciated.

###Start of the log #####

Dec 18 05:27:52 [ Firewall IP (internal) ] kernel: ip_demasq_gre(): [ DSL router IP ] -> [ Firewall IP (external) ] CID=0 no masq table, discarding 
Dec 18 05:30:12 [ Firewall IP (internal) ] last message repeated 3 times
Dec 18 05:32:49 [ Firewall IP (internal) ] last message repeated 12 times
Dec 18 05:34:21 [ Firewall IP (internal) ] last message repeated 3 times
Dec 18 05:34:25 [ Firewall IP (internal) ] last message repeated 3 times
Dec 18 05:37:28 [ Firewall IP (internal) ] kernel: ip_demasq_gre(): [ DSL router IP ] -> [ Firewall IP (external) ] CID=0 no masq table, discarding 
Dec 18 05:39:56 [ Firewall IP (internal) ] kernel: ip_demasq_gre(): [ DSL router IP ] -> [ Firewall IP (external) ] CID=0 no masq table, discarding 
Dec 18 05:39:58 [ Firewall IP (internal) ] last message repeated 2 times
Dec 18 05:47:54 [ Firewall IP (internal) ] kernel: ip_demasq_gre(): [ DSL router IP ] -> [ Firewall IP (external) ] CID=0 no masq table, discarding 
Dec 18 05:49:26 [ Firewall IP (internal) ] last message repeated 3 times
Dec 18 05:52:01 [ Firewall IP (internal) ] kernel: ip_demasq_gre(): [ DSL router IP ] -> [ Firewall IP (external) ] CID=0 no masq table, discarding 
Dec 18 05:52:02 [ Firewall IP (internal) ] last message repeated 2 times
Dec 18 05:56:16 [ Firewall IP (internal) ] kernel: ip_demasq_gre(): [ DSL router IP ] -> [ Firewall IP (external) ] CID=0 no masq table, discarding 
Dec 18 05:56:52 [ Firewall IP (internal) ] last message repeated 10 times
Dec 18 05:56:53 [ Firewall IP (internal) ] last message repeated 2 times
Dec 18 05:57:06 [ PPTPD Server IP ] pptpd[27407]: CTRL: Ignored a SET LINK INFO packet with real ACCMs!
Dec 18 05:57:06 [ Firewall IP (internal) ] kernel: ip_demasq_gre(): [ DSL router IP ] -> [ Firewall IP (external) ] CID=0 no masq table, discarding 
Dec 18 05:57:08 [ Firewall IP (internal) ] kernel: ip_demasq_gre(): [ DSL router IP ] -> [ Firewall IP (external) ] CID=0 no masq table, discarding 
Dec 18 05:57:12 [ PPTPD Server IP ] pppd[27408]: Modem hangup
Dec 18 05:57:12 [ PPTPD Server IP ] pppd[27408]: Connection terminated. 

Dec 18 05:57:12 [ PPTPD Server IP ] pppd[27408]: Connect time 414.4 minutes. 

Dec 18 05:57:12 [ PPTPD Server IP ] pppd[27408]: Sent 1631331 bytes, received 345410 bytes.
Dec 18 05:57:12 [ PPTPD Server IP ] pptpd[27407]: CTRL: Error with select(), quitting
Dec 18 05:57:12 [ PPTPD Server IP ] pptpd[27407]: CTRL: Client [ DSL router IP ] control connection finished
Dec 18 05:57:12 [ PPTPD Server IP ] pppd[27408]: Exit.


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