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https://issues.apache.org/jira/browse/SSHD-942?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16934471#comment-16934471
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Goldstein Lyor commented on SSHD-942:
-------------------------------------
I thought some more about this and what I have suggested might "mask" out
protocol problems that are not related to latency or out-of-order messages -
e.g. a client that does not adhere to the protocol 100% and is indeed sending
messages when they are not expected. If you have implemented some logging then
at least you can take notice of this by enabling the log and examining the
issued messages.
If you really want to make the code robust, the handler should be combined
with a channel listener that tracks the identifiers of the established channels
so far as a session attribute. The listeners updates the relevant session
attribute every time a channel is established while the handler examines this
attribute and ignores unexpected messages for referenced channels whose
identifier is a tracked one and optionally warns or throws an exception for
others.
> SSH session crashes on high latency network
> -------------------------------------------
>
> Key: SSHD-942
> URL: https://issues.apache.org/jira/browse/SSHD-942
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 1.7.0, 2.0.0, 2.3.0
> Reporter: David Ostrovsky
> Priority: Major
>
> Gerrit users report problem: [1] with {{git clone/fetch/pull}} operations on
> high latency network, after upgrading Gerrit to 2.16.x from 2.15.x that
> effectively means upgrade of SSHD from 1.6.0 to 1.7.0 and to 2.0.0.
> The error on SSHD 2.0.0 (Gerrit 2.16) is:
> {noformat}
> [2019-09-16 10:27:14,256] [sshd-SshServer[24facb47]-nio2-thread-8] WARN
> org.apache.sshd.server.session.ServerSessionImpl :
> exceptionCaught(ServerSessionImpl[usexxx@/172.x.x.1:63306])[state=Opened]
> SshChannelNotFoundException: Received SSH_MSG_CHANNEL_WINDOW_ADJUST on
> unknown channel 0
> {noformat}
> Note that the attempt to upgrade SSHD in Gerrit to 2.3.0 in this CL: [2],
> didn't fix the problem:
> {noformat}
> [2019-09-17 14:05:27,923] [sshd-SshDaemon[189c6683](port=22)-nio2-thread-4]
> WARN org.apache.sshd.server.session.ServerSessionImpl :
> exceptionCaught(ServerSessionImpl[<username>@/<ip>:55212])[state=Opened]
> SshChannelNotFoundException: Received SSH_MSG_CHANNEL_WINDOW_ADJUST on
> unknown channel 3
> [2019-09-17 14:05:27,924] [SSH git-upload-pack <repo> (<username>)] ERROR
> com.google.gerrit.sshd.BaseCommand : Internal server error (user <username>
> account 1000190) during git-upload-pack '<repo path>'
> org.apache.sshd.common.channel.WindowClosedException: Already closed:
> Window[server/remote](ChannelSession[id=2,
> recipient=6]-ServerSessionImpl[<username>@/<ip>:55212])
> at org.apache.sshd.common.channel.Window.waitForCondition(Window.java:302)
> at org.apache.sshd.common.channel.Window.waitForSpace(Window.java:252)
> {noformat}
> Also note, that downgrade to 1.7.0: [3] didn't fix the problem either. Only
> after downgrade to SSH 1.6.0: [4] the problem disappeared, and only warnings
> left in the log:
> {noformat}
> [2019-09-18 09:24:52,755] [NioProcessor-2] WARN
> org.apache.sshd.server.session.ServerConnectionService : Received
> SSH_MSG_CHANNEL_CLOSE on unknown channel 12
> [2019-09-18 09:24:52,756] [NioProcessor-2] WARN
> org.apache.sshd.server.session.ServerConnectionService : Received
> SSH_MSG_CHANNEL_CLOSE on unknown channel 13
> [2019-09-18 09:25:02,576] [NioProcessor-2] WARN
> org.apache.sshd.server.session.ServerConnectionService : Received
> SSH_MSG_CHANNEL_CLOSE on unknown channel 15
> [2019-09-18 09:25:36,508] [NioProcessor-2] WARN
> org.apache.sshd.server.session.ServerConnectionService : Received
> SSH_MSG_CHANNEL_CLOSE on unknown channel 18
> [2019-09-18 09:25:57,527] [NioProcessor-2] WARN
> org.apache.sshd.server.session.ServerConnectionService : Received
> SSH_MSG_CHANNEL_CLOSE on unknown channel 19
> [2019-09-18 09:30:16,488] [NioProcessor-2] WARN
> org.apache.sshd.server.session.ServerConnectionService : Received
> SSH_MSG_CHANNEL_CLOSE on unknown channel 21
> {noformat}
> [1]
> [https://bugs.chromium.org/p/gerrit/issues/detail?id=11491|https://bugs.chromium.org/p/gerrit/issues/detail?id=11491&;]
> [2] [https://gerrit-review.googlesource.com/c/gerrit/+/207752]
> [3] [https://gerrit-review.googlesource.com/c/gerrit/+/237730]
> [4] [https://gerrit-review.googlesource.com/c/gerrit/+/237731]
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