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Posted to user@guacamole.apache.org by Dilip Modi <dm...@zscaler.com.INVALID> on 2025/09/18 16:11:08 UTC
Regarding drdynvc RDP crash
Hello Guacamole Community,
We are experiencing a crash in guacd in our production environment and
would appreciate any insights you might have. The crash appears to be
related to the RDP protocol, specifically when loading a Dynamic Virtual
Channel (DVC).
*Summary of the Issue:*
The guacd process crashes during an RDP connection. The last log message
from the crashing process indicates it was attempting to load the disp DVC.
The backtrace confirms the crash occurs within the FreeRDP
library's drdynvc handling thread.
*Logs:*
Here is the relevant log snippet from guacd just before it crashed. The
process ID is 1432425.
plaintext
Sep 16 12:47:23 guacd[1432425]: 2025-09-16 12:47:23.368484 guacd[1432425]:
DEBUG:#011Loading Dynamic Virtual Channel disp
Sep 16 12:47:26 guacd[1565]: 2025-09-16 12:47:26.274395 guacd[1565]:
DEBUG:#011shutdown is sent successfully [1432425]
*Backtrace:*
The backtrace of the crashing thread (LWP 1432468) points directly
to drdynvc_virtual_channel_client_thread.
plaintext
#0 0x00007ff54031da31 in StreamPool_Take () from
/opt/zscaler/lib64/libwinpr2.so.2
#1 0x00007ff54041be5c in drdynvc_virtual_channel_client_thread () from
/opt/zscaler/lib64/libfreerdp-client2.so.2
#2 0x00007ff54034aa75 in thread_launcher () from
/opt/zscaler/lib64/libwinpr2.so.2
#3 0x00007ff544e8a19a in start_thread () from /usr/lib64/libc.so.6
#4 0x00007ff544f0f240 in clone3 () from /usr/lib64/libc.so.6
*Our Analysis:*
The crash seems to stem from a bug or race condition within the FreeRDP
library (libfreerdp-client2.so.2) when it handles the drdynvc plugin, which
is responsible for DVCs like disp. Our guacd is using FreeRDP libraries
from a standard path.
Has anyone in the community encountered similar crashes with drdynvc? Any
suggestions on how to further debug this or potential workarounds would be
greatly appreciated.
Thank you for your time and help.
Thanks,
Dilip
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Re: [External⚠️] Re: Regarding drdynvc RDP crash
Posted by Nick Couchman <vn...@apache.org>.
On Thu, Sep 18, 2025 at 11:55 PM Dilip Modi <dm...@zscaler.com.invalid>
wrote:
> Thanks Nick for your response.
>
> This is not always reproducible but yes we get into this crash sometimes.
> Also, yes crash is from freerdp library. Currently I am using freerdp
> 2.11.0.
> Any insight would be appreciated.
>
>
If the crash is happening in FreeRDP, then we're not likely to be able to
give you much help in diagnosing the issue. You might want to try the
FreeRDP mailing list or Github Issues page; however, I would imagine the
first response you're going to get on there to to upgrade past the 2.11
version to something more recent - the 2.x series has up to 2.11.7, and the
3.x series is up to 3.17.2.
Beyond that, you'll need to come up with some more definitive information
around the circumstances that lead to the crash.
-Nick
Re: [External⚠️] Re: Regarding drdynvc RDP crash
Posted by Dilip Modi <dm...@zscaler.com.INVALID>.
Thanks Nick for your response.
This is not always reproducible but yes we get into this crash sometimes.
Also, yes crash is from freerdp library. Currently I am using freerdp
2.11.0.
Any insight would be appreciated.
On Thu, Sep 18, 2025 at 11:18 PM Nick Couchman <vn...@apache.org> wrote:
> On Thu, Sep 18, 2025 at 12:12 PM Dilip Modi <dm...@zscaler.com.invalid>
> wrote:
>
>> Hello Guacamole Community,
>>
>> We are experiencing a crash in guacd in our production environment and
>> would appreciate any insights you might have. The crash appears to be
>> related to the RDP protocol, specifically when loading a Dynamic Virtual
>> Channel (DVC).
>>
>> *Summary of the Issue:*
>>
>> The guacd process crashes during an RDP connection. The last log message
>> from the crashing process indicates it was attempting to load the disp DVC.
>> The backtrace confirms the crash occurs within the FreeRDP
>> library's drdynvc handling thread.
>>
>
> Does it always crash? Or only under certain conditions? Is it random? Or
> easily reproducible?
>
>
>> *Logs:*
>>
>> Here is the relevant log snippet from guacd just before it crashed. The
>> process ID is 1432425.
>>
>> plaintext
>>
>>
>>
>> Sep 16 12:47:23 guacd[1432425]: 2025-09-16 12:47:23.368484
>> guacd[1432425]: DEBUG:#011Loading Dynamic Virtual Channel disp
>>
>> Sep 16 12:47:26 guacd[1565]: 2025-09-16 12:47:26.274395 guacd[1565]:
>> DEBUG:#011shutdown is sent successfully [1432425]
>>
>> *Backtrace:*
>>
>> The backtrace of the crashing thread (LWP 1432468) points directly
>> to drdynvc_virtual_channel_client_thread.
>>
>> plaintext
>>
>>
>>
>> #0 0x00007ff54031da31 in StreamPool_Take () from
>> /opt/zscaler/lib64/libwinpr2.so.2
>>
>> #1 0x00007ff54041be5c in drdynvc_virtual_channel_client_thread () from
>> /opt/zscaler/lib64/libfreerdp-client2.so.2
>>
>> #2 0x00007ff54034aa75 in thread_launcher () from
>> /opt/zscaler/lib64/libwinpr2.so.2
>>
>> #3 0x00007ff544e8a19a in start_thread () from /usr/lib64/libc.so.6
>>
>> #4 0x00007ff544f0f240 in clone3 () from /usr/lib64/libc.so.6
>>
>>
> Based on this backtrace, I'd say that the crash is happening entirely in
> the FreeRDP library and not in the guacd code, at all. I could well be
> mistaken about that, but all of the files referenced appear to be
> FreeRDP-related.
>
> -Nick
>
--
This communication (including any attachments) is intended for the sole
use of the intended recipient and may contain confidential, non-public,
and/or privileged material. Use, distribution, or reproduction of this
communication by unintended recipients is not authorized. If you received
this communication in error, please immediately notify the sender and then
delete all copies of this communication from your system.
Re: Regarding drdynvc RDP crash
Posted by Nick Couchman <vn...@apache.org>.
On Thu, Sep 18, 2025 at 12:12 PM Dilip Modi <dm...@zscaler.com.invalid>
wrote:
> Hello Guacamole Community,
>
> We are experiencing a crash in guacd in our production environment and
> would appreciate any insights you might have. The crash appears to be
> related to the RDP protocol, specifically when loading a Dynamic Virtual
> Channel (DVC).
>
> *Summary of the Issue:*
>
> The guacd process crashes during an RDP connection. The last log message
> from the crashing process indicates it was attempting to load the disp DVC.
> The backtrace confirms the crash occurs within the FreeRDP
> library's drdynvc handling thread.
>
Does it always crash? Or only under certain conditions? Is it random? Or
easily reproducible?
> *Logs:*
>
> Here is the relevant log snippet from guacd just before it crashed. The
> process ID is 1432425.
>
> plaintext
>
>
>
> Sep 16 12:47:23 guacd[1432425]: 2025-09-16 12:47:23.368484 guacd[1432425]:
> DEBUG:#011Loading Dynamic Virtual Channel disp
>
> Sep 16 12:47:26 guacd[1565]: 2025-09-16 12:47:26.274395 guacd[1565]:
> DEBUG:#011shutdown is sent successfully [1432425]
>
> *Backtrace:*
>
> The backtrace of the crashing thread (LWP 1432468) points directly
> to drdynvc_virtual_channel_client_thread.
>
> plaintext
>
>
>
> #0 0x00007ff54031da31 in StreamPool_Take () from
> /opt/zscaler/lib64/libwinpr2.so.2
>
> #1 0x00007ff54041be5c in drdynvc_virtual_channel_client_thread () from
> /opt/zscaler/lib64/libfreerdp-client2.so.2
>
> #2 0x00007ff54034aa75 in thread_launcher () from
> /opt/zscaler/lib64/libwinpr2.so.2
>
> #3 0x00007ff544e8a19a in start_thread () from /usr/lib64/libc.so.6
>
> #4 0x00007ff544f0f240 in clone3 () from /usr/lib64/libc.so.6
>
>
Based on this backtrace, I'd say that the crash is happening entirely in
the FreeRDP library and not in the guacd code, at all. I could well be
mistaken about that, but all of the files referenced appear to be
FreeRDP-related.
-Nick