On Sat, Jul 5, 2025 at 9:27 AM Horváth Csaba <[email protected]>
wrote:

> Hi,
>
> The previous log was written by guacd with parameter -L debug, i only
> copied from syslog.
>
> Now i tried again. In the below log i first connected to a VNC server
> (so you can see the server is basically working) and then tried SSH,
> but this time i got the message "Connected to Guacamole" and right
> after the red ribbon with "Error occurred within the Guacamole
> server..."
>
> # /usr/local/sbin/guacd -f -b 127.0.0.1 -L debug -l 4822 -p /tmp/guacd.pid
> guacd[2658943]: INFO:    Guacamole proxy daemon (guacd) version 1.6.0
> started
> guacd[2658943]: DEBUG:    Successfully bound AF_INET socket to host
> 127.0.0.1, port 4822
> guacd[2658943]: INFO:    Listening on host 127.0.0.1, port 4822
> ...
> guacd[2658943]: INFO:    Creating new client for protocol "ssh"
> guacd[2658943]: INFO:    Connection ID is
> "$0eb617c4-ec41-46a0-9be9-7d0705aea227"
> guacd[2659316]: DEBUG:    Processing instruction: size
> guacd[2659316]: DEBUG:    Processing instruction: audio
> guacd[2659316]: DEBUG:    Processing instruction: video
> guacd[2659316]: DEBUG:    Processing instruction: image
> guacd[2659316]: DEBUG:    Processing instruction: timezone
> guacd[2659316]: DEBUG:    Processing instruction: name
> guacd[2659316]: INFO:    User "@04f87cbf-6f45-4785-897f-5df0cdfd8fbc"
> joined connection "�!A�" (1 users now present)
> guacd[2659316]: DEBUG:    Client is using protocol version "VERSION_1_5_0"
> guacd[2658943]: INFO:    Creating new client for protocol "ssh"
> guacd[2658943]: INFO:    Connection ID is
> "$ad924c87-097e-4f1b-b0ab-8e3788c0a7ab"
> guacd[2659508]: DEBUG:    Processing instruction: size
> guacd[2659508]: DEBUG:    Processing instruction: audio
> guacd[2659508]: DEBUG:    Processing instruction: video
> guacd[2659508]: DEBUG:    Processing instruction: image
> guacd[2659508]: DEBUG:    Processing instruction: timezone
> guacd[2659508]: DEBUG:    Processing instruction: name
> guacd[2659508]: INFO:    User "@ca7f6e87-53c6-4b6b-be2c-9e28255a04d9"
> joined connection "�@�" (1 users now present)
> guacd[2659508]: DEBUG:    Client is using protocol version "VERSION_1_5_0"
> guacd[2659316]: ERROR:    User is not responding.
> guacd[2659316]: INFO:    User "@04f87cbf-6f45-4785-897f-5df0cdfd8fbc"
> disconnected (0 users remain)
> guacd[2659316]: INFO:    Last user of connection "�!A�" disconnected
> guacd[2659316]: DEBUG:    Requesting termination of client...
> double free or corruption (out)
>
guacd[2658943]: INFO:    Connection
> "$0eb617c4-ec41-46a0-9be9-7d0705aea227" removed.
> guacd[2658943]: DEBUG:    Unable to request termination of client
> process: No such process
> guacd[2658943]: DEBUG:    All child processes for connection
> "$0eb617c4-ec41-46a0-9be9-7d0705aea227" have been terminated.
> guacd[2659508]: ERROR:    User is not responding.
> guacd[2659508]: INFO:    User "@ca7f6e87-53c6-4b6b-be2c-9e28255a04d9"
> disconnected (0 users remain)
> guacd[2659508]: INFO:    Last user of connection "�@�" disconnected
> guacd[2659508]: DEBUG:    Requesting termination of client...
> double free or corruption (out)
> guacd[2658943]: INFO:    Connection
> "$ad924c87-097e-4f1b-b0ab-8e3788c0a7ab" removed.
> guacd[2658943]: DEBUG:    Unable to request termination of client
> process: No such process
> guacd[2658943]: DEBUG:    All child processes for connection
> "$ad924c87-097e-4f1b-b0ab-8e3788c0a7ab" have been terminated.
>
>
There are a few things that jump out to me here:
* First, the connection name or UUID appears to be mangled, as if something
is getting messed up with that. I'm not sure if this is an artifact of
copy/paste in e-mail, or if it really shows up that way in the log?
* Second, something is stopping traffic between Guacamole Client and guacd.
It's not entirely clear what, but the "User is not responding" message
indicates that guacd has stopped receiving its regular pings from the
client-side. This is likely related to the next issue (the double-free or
corruption) in some way or another, though it isn't exactly clear why.
* Finally, the double free or corruption message is interesting as it
indicates that we've a bug somewhere in the code that is trying to free
something that has already been freed. Whether this is causing the issues
you're seeing or is just a byproduct or unrelated bug is unclear.

The next things I'd suggest are:
* Look for indications that you're getting a segfault in the guacd process
somewhere - any message in dmesg or other log facilities that indicate that
the guacd process is crashing? If so, get a stack trace of that crash and
see if you can post the contents of the stack back here.
* Look at network traffic between Guacamole Client and guacd, and between
guacd and the SSH server, and see if something is shutting down the
connection for some reason. The fact that guacd is saying the client
stopped responding indicates the potential that something network-related
may be amiss.
* Look at the Guacamole Client logs (Tomcat) and see if there's anything in
those logs that indicates a reason why the conversation between the browser
and guacd is getting shut down. You may also need to put Guacamole Client
into debug mode to see better messages related to that.

-Nick

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