How to debug VPN Connection Issues (13.10)

Question

I'm trying to connect to a work VPN, but every time I attempt to connect it fails. The VPN has been configured in the Network Manager UI and the connection is being started from there too. I have checked the system logs and see the following:

Jan 28 08:29:09 cwlt NetworkManager[751]: <info> Starting VPN service 'pptp'...
Jan 28 08:29:09 cwlt NetworkManager[751]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 6383
Jan 28 08:29:09 cwlt NetworkManager[751]: <info> VPN service 'pptp' appeared; activating connections
Jan 28 08:29:09 cwlt NetworkManager[751]: <info> VPN plugin state changed: starting (3)
Jan 28 08:29:09 cwlt NetworkManager[751]: <info> VPN connection 'VPN' (Connect) reply received.
Jan 28 08:29:09 cwlt pppd[6387]: Plugin /usr/lib/pppd/2.4.5/nm-pptp-pppd-plugin.so loaded.
Jan 28 08:29:09 cwlt pppd[6387]: pppd 2.4.5 started by root, uid 0
Jan 28 08:29:09 cwlt pppd[6387]: using channel 10
Jan 28 08:29:09 cwlt pppd[6387]: Using interface ppp0
Jan 28 08:29:09 cwlt pppd[6387]: Connect: ppp0 <--> /dev/pts/4
Jan 28 08:29:09 cwlt NetworkManager[751]:    SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Jan 28 08:29:09 cwlt NetworkManager[751]:    SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/ppp0, iface: ppp0): no ifupdown configuration found.
Jan 28 08:29:09 cwlt NetworkManager[751]: <warn> /sys/devices/virtual/net/ppp0: couldn't determine device driver; ignoring...
Jan 28 08:29:09 cwlt pptp[6391]: nm-pptp-service-6383 log[main:pptp.c:314]: The synchronous pptp option is NOT activated
Jan 28 08:29:09 cwlt whoopsie[1138]: online
Jan 28 08:29:09 cwlt pptp[6405]: nm-pptp-service-6383 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 1 'Start-Control-Connection-Request'
Jan 28 08:29:09 cwlt pptp[6405]: nm-pptp-service-6383 log[ctrlp_disp:pptp_ctrl.c:739]: Received Start Control Connection Reply
Jan 28 08:29:09 cwlt pptp[6405]: nm-pptp-service-6383 log[ctrlp_disp:pptp_ctrl.c:773]: Client connection established.
Jan 28 08:29:10 cwlt pptp[6405]: nm-pptp-service-6383 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 7 'Outgoing-Call-Request'
Jan 28 08:29:10 cwlt whoopsie[1138]: online
Jan 28 08:29:10 cwlt pptp[6405]: nm-pptp-service-6383 log[ctrlp_disp:pptp_ctrl.c:858]: Received Outgoing Call Reply.
Jan 28 08:29:10 cwlt pptp[6405]: nm-pptp-service-6383 log[ctrlp_disp:pptp_ctrl.c:897]: Outgoing call established (call ID 0, peer's call ID 42341).
Jan 28 08:29:49 cwlt NetworkManager[751]: <warn> VPN connection 'Fluency Labs VPN' (IP Config Get) timeout exceeded.
Jan 28 08:29:49 cwlt NetworkManager[751]: <info> Policy set 'VM529841-5G' (eth1) as default for IPv4 routing and DNS.
Jan 28 08:29:49 cwlt pppd[6387]: Terminating on signal 15
Jan 28 08:29:49 cwlt pppd[6387]: Connection terminated.
Jan 28 08:29:49 cwlt avahi-daemon[709]: Withdrawing workstation service for ppp0.
Jan 28 08:29:49 cwlt NetworkManager[751]:    SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Jan 28 08:29:49 cwlt pppd[6387]: Child process /usr/sbin/pptp xxx.xxx.xxx.xxx --nolaunchpppd --loglevel 0 --logstring nm-pptp-service-6383 (pid 6389) terminated with signal 15
Jan 28 08:29:49 cwlt pppd[6387]: Exit.
Jan 28 08:29:49 cwlt pptp[6391]: nm-pptp-service-6383 warn[decaps_hdlc:pptp_gre.c:204]: short read (-1): Input/output error
Jan 28 08:29:49 cwlt pptp[6391]: nm-pptp-service-6383 warn[decaps_hdlc:pptp_gre.c:216]: pppd may have shutdown, see pppd log
Jan 28 08:29:49 cwlt pptp[6405]: nm-pptp-service-6383 log[callmgr_main:pptp_callmgr.c:234]: Closing connection (unhandled)
Jan 28 08:29:49 cwlt pptp[6405]: nm-pptp-service-6383 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request'
Jan 28 08:29:49 cwlt pptp[6405]: nm-pptp-service-6383 log[call_callback:pptp_callmgr.c:79]: Closing connection (call state)
Jan 28 08:29:54 cwlt NetworkManager[751]: <info> VPN service 'pptp' disappeared

I've deliberately hidden the ip-address here so don't worry about that. I don't really know what is going wrong here, so if someone could point me in the right direction that would be great.

Answer 1

Answering your question title is a bit different from your specific problem. I will start by answering the question title: how to debug vpn connection issues?

1. First You need to run pppd in debug mode by passing debug option.

sudo grep debug /etc/rsyslog.d/*

the output might be something like this:

 /etc/rsyslog.d/50-default.conf:#*.=debug;\
 /etc/rsyslog.d/50-default.conf:#   news.none;mail.none -/var/log/debug
 /etc/rsyslog.d/50-default.conf:#   *.=debug;*.=info;\
 /etc/rsyslog.d/50-default.conf:    *.=debug;*.=info;\

so /var/log/debug is your debug file.

1. Start pppd with debug option

sudo pppd debug call /path/to/yourvpn.vpn

1. Watch Debug Log

tail -f /var/log/debug

Answer 2

Now let me answer your specific problem.

as it seems there are some warnings in your log. I will try to investigate them one by one.

1. You have a line saying:

NetworkManager[751]: Policy set 'VM529841-5G' (eth1) as default for IPv4 routing and DNS.

I assume that VPN should use tunnel interface instead of ethernet1. so please try unticking "use this connection only for resources on its network" in Network Connections -> VPN -> edit -> Ipv4 settings tab -> Routes.

2. Another line says:

VPN connection 'Fluency Labs VPN' (IP Config Get) timeout exceeded

remove the wins entry from /etc/nsswitch.conf hosts line

1. Another line says:

/sys/devices/virtual/net/ppp0: couldn't determine device driver; ignoring...

following this question It Looks like there must be a bug in libgcrypt11=1.5.0-3ubuntu2.2. After rolling back to libgcrypt11=1.5.0-3ubuntu2.1 things are working again...

sudo apt-get install libgcrypt11=1.5.0-3ubuntu2.1

I hope that saves you