X2Go Bug report logs - #1421
journalctl flooded with ssh_channel_accept: No channel request of this type from server

version graph

Package: x2goclient; Maintainer for x2goclient is X2Go Developers <x2go-dev@lists.x2go.org>; Source for x2goclient is src:x2goclient.

Reported by: Sorin T <sorintsl@protonmail.com>

Date: Thu, 5 Dec 2019 12:05:02 UTC

Severity: normal

Found in version 4.1.2.1

Full log

Message #15 received at 1421@bugs.x2go.org (full text, mbox, reply):

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Subject: Re: [X2Go-Dev] Bug#1421: Bug#1421: journalctl flooded with
 ssh_channel_accept: No channel request of this type from server
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[Message part 1 (text/plain, inline)]
On 4/10/23 12:09, Orion Poplawski wrote:
> On 12/5/19 05:02, Sorin T wrote:
>> Package: x2goclient
>> Version: 4.1.2.1
>>
>>
>> This output is shown continuously. I have also disabled the Media and the Shared folders options.
>>
>> [2019/12/05 12:21:49.755356, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:49.844514, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:49.844968, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:50.345651, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:50.846330, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:51.347011, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:51.354536, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:51.355837, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:51.358011, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:51.858687, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:52.359381, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:52.860074, 1] ssh_channel_accept: No channel request of this
>> type from server
>> [2019/12/05 12:21:53.360787, 1] ssh_channel_accept: No channel request of this
>> type from server
>>
>> It could be a ssh config problem ? I am using on client machine:
>> OpenSSH_8.1p1, OpenSSL 1.1.1d  10 Sep 2019
>>
>> Guest OS: Debian based
>> Guest ssh version: OpenSSH_7.9p1 Debian-10, OpenSSL 1.1.1d  10 Sep 2019
>> Guest x2goserver: 4.1.0.3-4
> 
> 
> I'm seeing the same thing.
> 
> Client:
> AlmaLinux 8.7
> x2goclient-4.1.2.2-1.el8.x86_64
> libssh-0.9.6-3.el8.x86_64
> 
> Server:
> Either EL7/8
> openssh-7.4p1-22.el7_9.x86_64
> x2goserver-4.1.0.3-9.el7.x86_64
> 
> openssh-8.0p1-17.el8_7.x86_64
> x2goserver-4.1.0.3-17.el8.1.x86_64
> 
> x2goclient --debug --libssh-debug doesn't yield any more info.
> 
> [2023/04/10 12:02:04.013887, 1] ssh_config_parse_line:  Unsupported option:
> PreferredAuthentications, line: 60
> [2023/04/10 12:02:04.013984, 1] ssh_config_parse_line:  Unsupported option:
> ForwardAgent, line: 64
> [2023/04/10 12:02:04.014018, 1] ssh_config_parse_line:  Unsupported option:
> ForwardAgent, line: 67
> [2023/04/10 12:02:04.014049, 1] ssh_config_parse_line:  Unsupported option:
> ForwardAgent, line: 71
> [2023/04/10 12:02:04.014088, 1] ssh_config_parse_line:  Unsupported option:
> TCPKeepAlive, line: 77
> [2023/04/10 12:02:04.025702, 1] socket_callback_connected:  Socket connection
> callback: 1 (0)
> [2023/04/10 12:02:04.588049, 1] ssh_key_cmp:  key types don't match!
> [2023/04/10 12:02:04.588326, 1] ssh_key_cmp:  key types don't match!
> [2023/04/10 12:02:04.588388, 1] ssh_key_cmp:  key types don't match!
> [2023/04/10 12:02:04.694913, 1] ssh_config_parse_line:  Unsupported option:
> ForwardAgent, line: 4
> [2023/04/10 12:02:04.695018, 1] ssh_config_parse_line:  Unsupported option:
> ForwardAgent, line: 7
> [2023/04/10 12:02:04.695062, 1] ssh_config_parse_line:  Unsupported option:
> ForwardAgent, line: 14
> [2023/04/10 12:02:04.695093, 1] ssh_config_parse_line:  Unsupported option:
> HostKeyAlias, line: 19
> [2023/04/10 12:02:04.716659, 1] ssh_config_parse_line:  Unsupported option:
> PreferredAuthentications, line: 60
> [2023/04/10 12:02:04.716761, 1] ssh_config_parse_line:  Unsupported option:
> ForwardAgent, line: 64
> [2023/04/10 12:02:04.716811, 1] ssh_config_parse_line:  Unsupported option:
> ForwardAgent, line: 67
> [2023/04/10 12:02:04.716862, 1] ssh_config_parse_line:  Unsupported option:
> ForwardAgent, line: 71
> [2023/04/10 12:02:04.716904, 1] ssh_config_parse_line:  Unsupported option:
> TCPKeepAlive, line: 77
> [2023/04/10 12:02:08.024493, 1] ssh_channel_accept:  No channel request of
> this type from server
> [2023/04/10 12:02:08.027575, 1] ssh_channel_accept:  No channel request of
> this type from server
> [2023/04/10 12:02:08.029534, 1] ssh_channel_accept:  No channel request of
> this type from server
> [2023/04/10 12:02:08.030156, 1] ssh_channel_accept:  No channel request of
> this type from server
> [2023/04/10 12:02:08.030814, 1] ssh_channel_accept:  No channel request of
> this type from server
> [2023/04/10 12:02:08.031476, 1] ssh_channel_accept:  No channel request of
> this type from server
> ....


Seems like this issue may have been around nearly forever, but I guess
something changed at some point in the x2go or libssh logging setup that
allowed the ssh errors to get printed.  Basically, x2goclient loops forever
doing (among other things):

        addReverseTunnelConnections();
        checkReverseTunnelConnections();


checkReverseTunnelConnections() calls ssh_channel_accept_forward() which sets
an error if no channel request exists.

Now normally this doesn't get logged because x2goclient sets the libssh log
level to LOG_SSH_NOLOG (quite likely for this very reason).  However, I'm setting:

   LogLevel ERROR

in my ~/.ssh/config file - which has the effect of setting the libssh log
level to 1 and so the errors are printed.

Now, it does seem incredibly inefficient for x2goclient to repeatedly call
ssh_channel_accept_forward() if there are no forwarded connections to accept.
Is there any other way to do what is needed here?



-- 
Orion Poplawski
IT Systems Manager                         720-772-5637
NWRA, Boulder/CoRA Office             FAX: 303-415-9702
3380 Mitchell Lane                       orion@nwra.com
Boulder, CO 80301                 https://www.nwra.com/


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