pptp vpn connection drops out

[JazzyPenguin]

I use pptp vpn to connect to our office network. Under Hardy using Network Manager (NM 0.6.6) this worked very well and was stable. Under Intrepid NM0.7 the same connection is unstable. While it connects without a problem and i can initiate Remote Desktop Protocols etc... eventually the connection drops out with the error VPN connection failed. I can usually reconnect immediately, but not always, if not a restart is usually required. Reconnected VPN connectiions continue to be unstable and fail frequently thereafter. Interestingly, opening pidgin precipitates this connection failure (not sure about other applications).

[Cyril Lavier (davromaniak)]

Thank you for reporting this bug.

I didn't experience a number of unstabilities as you, but I can confirm NM0.7 is not stable as NM0.6.6.

[Cyril Lavier (davromaniak)]

Sorry, I forgot to confirm this bug.

[Jonathan Prior (behe)]

I am receiving this problem with SwissVPN. A workaround is detailed here: http://blog.scopeport.org/internet/vpn-connection-ubuntu-intrepid-fails/ (setting the MTU to 1412 before the connection drops). Unfortunately this must be done every time I connect.

You may be able to reproduce this by using SwissVPN's demo account: http://www.swissvpn.net/index.php?cot=faq#selected
and connecting to SwissVPN using these instructions: http://www.swissvpn.net/sub.html

[Alex Valavanis (valavanisalex)]

You can set the mtu permanently by adding the line:

mtu 1412

to /etc/ppp/options

If you like, just run the following command to add the line:

sudo echo mtu 1412 >> /etc/ppp/options

[Scott Deagan (scott-deagan)]

I'm having the same issue. I can connect, but sooner or later (usually sooner) the connection will drop. I have tried adjusting my MTU to various sizes, but this doesn't help. I have Windows 7 and Mac OSX running on the same computer, and the VPN connection within those operating systems is stable and reliable (stays connected for weeks).

Here is my /var/log/syslog report of the disconnection:

Oct 10 05:44:27 iMac-Ubuntu pptp[11871]: nm-pptp-service-11745 log[pptp_read_some:pptp_ctrl.c:544]: read returned zero, peer has closed
Oct 10 05:44:27 iMac-Ubuntu pptp[11871]: nm-pptp-service-11745 log[callmgr_main:pptp_callmgr.c:258]: Closing connection (shutdown)
Oct 10 05:44:27 iMac-Ubuntu pptp[11871]: nm-pptp-service-11745 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request'
Oct 10 05:44:27 iMac-Ubuntu pptp[11871]: nm-pptp-service-11745 log[pptp_read_some:pptp_ctrl.c:544]: read returned zero, peer has closed
Oct 10 05:44:27 iMac-Ubuntu pptp[11871]: nm-pptp-service-11745 log[call_callback:pptp_callmgr.c:79]: Closing connection (call state)
Oct 10 05:44:27 iMac-Ubuntu pppd[11861]: Modem hangup
Oct 10 05:44:27 iMac-Ubuntu pppd[11861]: Connect time 22.6 minutes.
Oct 10 05:44:27 iMac-Ubuntu pppd[11861]: Sent 36219320 bytes, received 1371467319 bytes.
Oct 10 05:44:27 iMac-Ubuntu pppd[11861]: MPPE disabled
Oct 10 05:44:27 iMac-Ubuntu pppd[11861]: Connection terminated.
Oct 10 05:44:27 iMac-Ubuntu NetworkManager[806]: <info> VPN plugin state changed: 5
Oct 10 05:44:27 iMac-Ubuntu NetworkManager[806]: <info> VPN plugin state changed: 6
Oct 10 05:44:27 iMac-Ubuntu NetworkManager[806]: <info> VPN plugin state change reason: 0
Oct 10 05:44:27 iMac-Ubuntu NetworkManager[806]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active.
Oct 10 05:44:27 iMac-Ubuntu pppd[11861]: Terminating on signal 15
Oct 10 05:44:27 iMac-Ubuntu pppd[11861]: Exit.
Oct 10 05:44:28 iMac-Ubuntu NetworkManager[806]: <info> Policy set 'Auto eth0' (eth0) as default for IPv4 routing and DNS.
Oct 10 05:44:28 iMac-Ubuntu NetworkManager[806]: SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Oct 10 05:44:33 iMac-Ubuntu NetworkManager[806]: <info> VPN service 'pptp' disappeared

I have spoken to my systems administrator, and he says:

"According to our debug log the disconnections are caused by malformed GRE packets. We have a lot of bad checksums on your connection."

The connection is a PPTP, configured via Network Manager.

[Hercules (sithiraklis)]

I experience the same problem in Ubuntu 12.04 LTS (Precise Pangolin). While I have experienced this also in previous versions of Ubuntu too the connection drops happen frequently. In this Ubuntu version, I've also had the pptp crash and prompt me to send an error report. This has happened 3 times(!). I don't know which files to look that relate to VPN connections (log maybe) but I'd be glad to help if you wish to see those :)

[Hercules (sithiraklis)]

I'm attaching a syslog file for inspection if anyone desires so.

[postadelmaga (postadelmaga)]

Same Issue here in 12.10:

i have created a pptp VPN connection, I can connect but after a minute or two it freeze ( ping, svn, navigation all freeze ) and the only way to re-enable it is to reconnect.

It is very frustrating because I need it to work with svn and I'm not able to checkout a repository.

[postadelmaga (postadelmaga)]

Sorry I have changed the status to 'confirmed' but I guess the previous one 'Triaged' was better.

[postadelmaga (postadelmaga)]

I have just checked the `/val/log/syslog` ( see also comment #8 ) and I have noticed that when the issue start I got this messages:

 pppd[8268]: Protocol-Reject for unsupported protocol 'IP6 Header Compression' (0x4f)
 pppd[8268]: Protocol-Reject for unsupported protocol 0x1c18
 pppd[8268]: Protocol-Reject for unsupported protocol 0xb9
 pppd[8268]: Protocol-Reject for unsupported protocol 'RTP IPHC Full Header' (0x61)
 pppd[8268]: Protocol-Reject for unsupported protocol 'KNX Bridging Control Protocol' (0x8051)
 pppd[8268]: Protocol-Reject for unsupported protocol 'DECnet Phase IV' (0x27)

A lot of them ( 3 every second )

[postadelmaga (postadelmaga)]

I have done some research and I have end up with this:
http://pptpclient.sourceforge.net/howto-diagnosis.phtml#lcp_protrej_1

According with pptpclient documentation the "unsupported protocol" error is caused by "the MPPC patch to pppd is not compatible with kernel * MPPE kernel module"

Can anyone confirm if this could be the cause ?

[postadelmaga (postadelmaga)]

Same bug on 13.04 this is shame !