X2Go Bug report logs - #495
failure to reconnect after abrupt (CTRL-C / SIGINT) termination of x2goclient, corrupt x2go_sessions file?

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Subject: Bug#495: [X2Go-Dev] Bug#495: failure to reconnect after abrupt (CTRL-C / SIGINT) termination of x2goclient, corrupt x2go_sessions file?
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Date: Fri, 09 May 2014 15:03:12 +0000
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From: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>
To: Robert Izzard <izzard@astro.uni-bonn.de>, 495@bugs.x2go.org
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Hi Robert,

On  Fr 09 Mai 2014 15:24:10 CEST, Robert Izzard wrote:

> Package: x2goserver
> Version: 4.0.15-0~847
>
> (x2goserver: 4.0.15-0~847~~ubuntu12.04.1 on Ubuntu Linux 12.04.4 LTS  
> kernel 3.8.0-39-generic,
>  x2goclient: 4.0.15-0~847~ubuntu14.04.1 on Ubuntu Linux 14.04 LTS  
> kernel 3.14.3-031403-generic)
>  
> Please note: I have labelled package x2goserver, but the bug is  
> displayed on x2goclient even though I *think* the bug is in the  
> server somewhere (see below).
>
> Sometimes after an abrupt (e.g. CTRL-C, probably also network
> failure or laptop sleep/wake cycle) termination of x2goclient, I
> cannot reconnect to the server. I get errors such as the dreaded
> "Failure negotiating the session in stage '7'." and "Error: Wrong
> version or invalid session authentication cookie." instead.
>
> I am connecting through a proxy using ssh key-based
> authentication (using "Try auto-login" with "ssh-agent or default
> ssh key" on the proxy, although switching to password made no
> difference). I can connect with ssh through the proxy with no
> problem. I can *start* an x2go session with no problem. I can
> restart a session with no problem *provided I cleanly exit
> x2goclient* (e.g. by clicking on the close button on the window).
> If I exit x2goclient with a CTRL-C in the terminal, I cannot
> connect again. Note that I can connect to an NX session through
> the proxy without any problem and this does not have the same
> problem when CTRL-C.
>
> Steps to repeat:
> 1) On the client, open a new desktop on the server using
> x2goclient. (I am running KDE but I doubt it matters).
> 2) On the client, press CTRL-C to stop x2goclient.
> 3) On the client, try to reconnect -- it fails with errors (which
> are very hard to copy-paste as they go so fast, this is a bug in
> the GUI):
>
> ------------------------
> NXPROXY - Version 3.5.0
>
> Copyright (C) 2001, 2010 NoMachine.
>
> See http://www.nomachine.com/ for more information.
> Info: Proxy running in client mode with pid '7219'.
> Session: Starting session at 'Thu May 8 17:33:51 2014'.
> Info: Connecting to remote host 'localhost:31007'.
> Info: Connection to remote proxy 'localhost:31007' established.
> Error: The remote NX proxy closed the connection.
> Error: Failure negotiating the session in stage '7'.
> Error: Wrong version or invalid session authentication cookie.
> Session: Terminating session at 'Thu May 8 17:33:51 2014'.
> Session: Session terminated at 'Thu May 8 17:33:51 2014'.
> ------------------------
>
> At this point the CPU usage of x2goclient jumps to 100% and I
> have to kill it (although the GUI continues to respond). This is
> just a minor annoyance at the moment.
>
> And in .x2go/SESSION_ID/sessions on the client, similar warnings:
>
> ------------------------
>
> Loop: PANIC! No shutdown of proxy link performed by remote proxy.
> Loop: PANIC! The remote NX proxy closed the connection.
> Loop: PANIC! Failure negotiating the session in stage '7'.
> Loop: PANIC! Wrong version or invalid session authentication cookie.
> ------------------------
>
> The server clearly detects the disconnect in its session.log,
> followed by “Display failure detected” errors on attempted
> reconnect:
>
> -----------------------
> running as X2Go Agent
>
> NXAGENT - Version 3.5.0
>
> Copyright (C) 2001, 2011 NoMachine.
>
> See http://www.nomachine.com/ for more information.
>
> Info: Agent running with pid '17414'.
> Session: Starting session at 'Fri May 9 14:44:26 2014'.
> Info: Proxy running in server mode with pid '17414'.
> Info: Waiting for connection from 'localhost' on port '30004'.
> Info: Accepted connection from '127.0.0.1'.
> Info: Connection with remote proxy completed.
> Info: Using ADSL link parameters 512/24/1/0.
> Info: Using agent parameters 5000/10/50/0/0.
> Info: Using cache parameters 4/4096KB/8192KB/8192KB.
> Info: Using pack method '16m-png-9' with session
> 'unix-kde-depth_24'.
> Info: Using ZLIB data compression 1/1/32.
> Info: Using ZLIB stream compression 4/4.
> Info: No suitable cache file found.
> Info: Listening to X11 connections on display ':51'.
> Info: Established X client connection.
> Info: Using shared memory parameters 1/1/1/2048K.
> Info: Using alpha channel in render extension.
> Info: Not using local device configuration changes.
> keyboard file created
> SessionPath not defined
> Session: Session started at 'Fri May 9 14:44:27 2014'.
> Error: Failure reading from the peer proxy.
> Error: Connection with remote peer broken.
> Error: Please check the state of your network and retry.
> Session: Display failure detected at 'Fri May 9 14:44:44 2014'.
> Session: Suspending session at 'Fri May 9 14:44:44 2014'.
> Session: Session suspended at 'Fri May 9 14:44:44 2014'.
> Session: Resuming session at 'Fri May 9 14:45:11 2014'.
> Info: Proxy running in server mode with pid '17414'.
> Info: Waiting for connection from 'localhost' on port '30004'.
> Info: Aborting the procedure due to signal '1'.
> Session: Display failure detected at 'Fri May 9 14:45:27 2014'.
> Session: Suspending session at 'Fri May 9 14:45:27 2014'.
> Session: Session suspended at 'Fri May 9 14:45:27 2014'.
> --------------
>
> In .x2go/C-SESSION_ID/session.log on the server, I now have the
> following text repeated over and over:
>
> Session: Suspending session at 'Fri May 9 15:08:49 2014'.
> [then hundreds or thousands of times, with later timestamps]
>
>
>
> The problem appears to be with the file
> /var/lib/x2go/x2go_sessions on the server. If I back this up
> *before* hitting CTRL-C on the client, then do the CTRL-C, then
> reinstate the backup, I can restart the session with no problems.
> Clearly this is beyond the ability of a normal user (without root
> on the server) and is not really a fix, even if it does work.
>
>
>
> It seems that there is a problem with the x2go_sessions file on
> the server being corrupted in some way when the remote session is
> abruptly disconnected. This is a failure bad enough for me to
> stop using x2go and go back to NX.
>
> * Backing up this file all the time is not an option.
>
> * Deleting this file and continuing, as suggested at
> http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=323, is not an
> option.
>
> * Note that unlink suggested in
> http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=323, there is no
> *server* crash.
>
> * I have tried the other options at
> http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=323, none apply
> here (e.g. permissions are fine).
>
> * The action that precipitates the problem is on the *client*
> side.
>
> * Note also that the network itself is not at fault: I can
> connect from a laptop in the same office (but on a different
> subnet) as the server, or from home to the proxy server direct.
> Same problem.
>
> * This seems similar to
> http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=101 but the fixes
> are more than a year ago and presumably (?) are in the latest
> x2goclient already.
>
> * No amount of calls to x2gosuspend-session or x2goresume-session
> on the appropriate session makes any difference.
>
> * If I suspend the session with x2gosuspend-session, attempting
> to connect *does* set the session into the “Running” state (just
> as x2goresume-session). The error seems to occur after this.
>
> Thanks for all your help x2go team, I hope we can fix this
> because I'd like to recommend x2go for my colleagues.

This is all very interesting!!!!

Can you please check one more thing? If the connection failure occurs:  
leave the sessions db file as it is, but restart the server's SSH  
daemon and try to resume then.

Does that also solve the resumption problem?

Thanks,
Mike
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