[prev in list] [next in list] [prev in thread] [next in thread] 

List:       mina-dev
Subject:    [jira] [Comment Edited] (SSHD-720) SSHD does not always detect remote closure in time.
From:       "Claude Warren (JIRA)" <jira () apache ! org>
Date:       2016-11-29 7:27:58
Message-ID: JIRA.13023790.1480352841000.386606.1480404478513 () Atlassian ! JIRA
[Download RAW message or body]


    [ https://issues.apache.org/jira/browse/SSHD-720?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15703148#comment-15703148 \
] 

Claude Warren edited comment on SSHD-720 at 11/29/16 7:27 AM:
--------------------------------------------------------------

I updated the example code to use threads as requested.  However, I point out that \
the issue is on the client side code.

The point is that the server I am trying to talk to in production if paranoid.  So if \
I hit it with any sort of incorrect command it shuts down the -connection- +session+. \
My example code simulates this by calling sshd.close();  The result is exactly the \
result I see in my production code.

I test to see if the session is open before calling createChannel() as shown below in \
an extract from the interactWithServer() method. {code}
    if ( !session.isOpen() ) {
        System.err.println( "Session invalid on "+command);
        throw new SessionInvalidException();
    }
    System.out.println( "Sending "+command);
    channel = session.createChannel(Channel.CHANNEL_EXEC, command);
{code}

I don't see any way to accurately check that the server connection still exists \
before making the call.  What I have not been able to verify is that the \
session.isOpen() checks the service status.  As the session says it is OK but the \
createExecChannel() fails at service.registerChannel() because the ConnectionService \
is closing.

{code}
@Override
    public ChannelExec createExecChannel(String command) throws IOException {
        ChannelExec channel = new ChannelExec(command);
        ConnectionService service = getConnectionService();
        int id = service.registerChannel(channel);
        if (log.isDebugEnabled()) {
            log.debug("createExecChannel({})[{}] created id={}", this, command, id);
        }
        return channel;
    }
{code}

By way of a qualification for {{not always}} it means that the example code will \
sometimes detect that the server has gone away, however the code usually fails as \
expected.

In short, what I am looking for is a way to detect that the remote server has gone \
away before I call session.createChannel().

I will go back and review the example code to see where else I have made errors.  \
However, I believe that I found the run the command directly from start in one of the \
examples.  If I find that I will point it out.  I would hasten to point out that the \
test code ran and failed as expected on 2 different systems, so while it may be \
poorly coded it fails.  Thank you for taking the time to look at this report.


was (Author: claudenw):
I updated the example code to use threads as requested.  However, I point out that \
the issue is on the client side code.

The point is that the server I am trying to talk to in production if paranoid.  So if \
I hit it with any sort of incorrect command it shuts down the connection.  My example \
code simulates this by calling sshd.close();  The result is exactly the result I see \
in my production code.

I test to see if the session is open before calling createChannel() as shown below in \
an extract from the interactWithServer() method. {code}
    if ( !session.isOpen() ) {
        System.err.println( "Session invalid on "+command);
        throw new SessionInvalidException();
    }
    System.out.println( "Sending "+command);
    channel = session.createChannel(Channel.CHANNEL_EXEC, command);
{code}

I don't see any way to accurately check that the server connection still exists \
before making the call.  What I have not been able to verify is that the \
session.isOpen() checks the service status.  As the session says it is OK but the \
createExecChannel() fails at service.registerChannel() because the ConnectionService \
is closing.

{code}
@Override
    public ChannelExec createExecChannel(String command) throws IOException {
        ChannelExec channel = new ChannelExec(command);
        ConnectionService service = getConnectionService();
        int id = service.registerChannel(channel);
        if (log.isDebugEnabled()) {
            log.debug("createExecChannel({})[{}] created id={}", this, command, id);
        }
        return channel;
    }
{code}

By way of a qualification for {{not always}} it means that the example code will \
sometimes detect that the server has gone away, however the code usually fails as \
expected.

In short, what I am looking for is a way to detect that the remote server has gone \
away before I call session.createChannel().

I will go back and review the example code to see where else I have made errors.  \
However, I believe that I found the run the command directly from start in one of the \
examples.  If I find that I will point it out.  I would hasten to point out that the \
test code ran and failed as expected on 2 different systems, so while it may be \
poorly coded it fails.  Thank you for taking the time to look at this report.

> SSHD does not always detect remote closure in time.
> ---------------------------------------------------
> 
> Key: SSHD-720
> URL: https://issues.apache.org/jira/browse/SSHD-720
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 1.4.0
> Reporter: Claude Warren
> Priority: Minor
> Attachments: CommsTest2.java, CommsTest2a.java
> 
> 
> I am attempting to use a device that will close the connection if there are any \
> invalid commands.  The client side does not detect this condition and I don't see \
> any way to check for it. Example code is attached



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)


[prev in list] [next in list] [prev in thread] [next in thread]