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https://issues.apache.org/jira/browse/SSHD-968?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17042627#comment-17042627
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Lyor Goldstein commented on SSHD-968:
-------------------------------------
{quote}
According to RFC 4253 sect. 11.4
(https://tools.ietf.org/html/rfc4253#section-11.4) the SSH_MSG_UNIMPLEMENTED is
meant to be ignored, but this makes little sense for a heartbeat, as even
SSH_MSG_UNIMPLEMENTED is good enough to count as a reply for this. This is for
example the case in OpenSSH, where SSH_MSG_UNIMPLEMENTED replies for heartbeat,
does not lead to a termination of the SSH session.
{quote}
I am not comfortable with violating the standard - but on the other hand, we
have to practical - so I'll think about it.
{quote}
There is a workaround released in 2.1.1, to use ReservedSessionMessagesHandler
for handling replies, but this does not allow access to the method
AbstractSession.requestFailure() (without using reflection so to say).
{quote}
Perhaps this is a better solution - I have no problem making
{{AbstractSession#requestFailure}} publicly accessible.
{quote}
The reason for this is SSH_MSG_UNIMPLEMENTED is only logged in...Further, the
heartbeat is ongoing in the background, so there is no good solution to this
problem from outside of the framework.
{quote}
Perhaps the fix would be to consider {{SSH_MSG_UNIMPLEMENTED}} a valid response
for heartbeat, but it raises an important issue - how do we know that
{{SSH_MSG_UNIMPLEMENTED}} was received because of the heartbeat and not
something else ? How can we tell that the reason is
{quote}
In case SSH_MSG_GLOBAL_REQUEST is not supported by the remote SSH server, the
keep-alive heartbeat times out.
{quote}
To summarize - this raises an important question, but will have to think a bit
about possible answers...
> SshClient times out during keep-alive, when SSH_MSG_GLOBAL_REQUEST is replies
> with SSH_MSG_UNSUPPORTED
> ------------------------------------------------------------------------------------------------------
>
> Key: SSHD-968
> URL: https://issues.apache.org/jira/browse/SSHD-968
> Project: MINA SSHD
> Issue Type: Improvement
> Affects Versions: 2.3.0
> Environment: Windows 10
> Reporter: Patrik Ek
> Priority: Major
>
> In case SSH_MSG_GLOBAL_REQUEST is not supported by the remote SSH server, the
> keep-alive heartbeat times out. The reason for this is SSH_MSG_UNIMPLEMENTED
> is only logged in
> {color:#172b4d}org.apache.sshd.common.session.helpers{color}.AbstractSession
> The method identifying the SSH_MSG_UNIMPLEMENTED is called
> AbstractSession.doHandleMessage()
> The consequense is that no reply is received and the heartbeat times out
> instead of calling AbstractSession.requestFailure(). Which in turn leads to
> the session terminates.
> According to RFC 4253 sect. 11.4
> ({color:#004000}https://tools.ietf.org/html/rfc4253#section-11.4{color}) the
> SSH_MSG_UNIMPLEMENTED is meant to be ignored, but this makes little sense for
> a heartbeat, as even SSH_MSG_UNIMPLEMENTED is good enough to count as a reply
> for this. This is for example the case in OpenSSH, where
> SSH_MSG_UNIMPLEMENTED replies for heartbeat, does not lead to a termination
> of the SSH session.
> There is a workaround released in 2.1.1, to use
> ReservedSessionMessagesHandler for handling replies, but this does not allow
> access to the method AbstractSession.requestFailure() (without using
> reflection so to say). Further, the heartbeat is ongoing in the background,
> so there is no good solution to this problem from outside of the framework.
> https://issues.apache.org/jira/browse/SSHD-887?jql=project%20%3D%20SSHD%20AND%20fixVersion%20%3D%202.1.1
> Would this be possible to fix? The reason I write it here is because the bug
> seems to existing up to some version of libssh, even for the SSHv2 protocol,
> so just writing a bug report on the particular server will not solve the
> problems for already existing implementations using libssh.
> The following config is used,
> SshClient client =
> SshClient.setUpDefaultClient(){color:#cc7832};{color}{color:#808080}
> {color} {color:#172b4d}PropertyResolverUtils.updateProperty(client,
> ClientFactoryManager.HEARTBEAT_INTERVAL, 15000);
>
> PropertyResolverUtils.updateProperty(client,ClientFactoryManager.HEARTBEAT_REPLY_WAIT,
> 30000);
>
> PropertyResolverUtils.updateProperty(client,ClientFactoryManager.HEARTBEAT_REQUEST,
> "keepal...@openssh.com");{color}
> {color:#cc7832}{color:#172b4d}BR{color}
> {color:#172b4d}Patrik{color}
> {color}
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