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From "Bill Kuker (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SSHD-85) Port Forward closes connection before all bytes are sent
Date Tue, 13 Jun 2017 19:08:01 GMT

    [ https://issues.apache.org/jira/browse/SSHD-85?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16048266#comment-16048266
] 

Bill Kuker commented on SSHD-85:
--------------------------------

Here is a more minimal reproduction...

https://github.com/bkuker/sshd-85

It creates an SSH Server, an SSH Client, and a Test Server.

The Test server writes a known string to the client and closes the connection.

There are 3 tests:

readFastPF: Connects to the test server via a port forward and reads everything at once. Always
works.
readSlowDirect: Connects to the test server directly (NO port forward) and reads the data
in two smaller buffers with a 50ms delay in between. Always works.
readSlowPF: Connects to the test server via a port forward and reads the data in two smaller
buffers with a 50ms delay in between. (Nearly) always fails.

The problem is that the when the test server closes the socket Apache SSH closes the port
forward *despite there being data left to send to the client*.

> Port Forward closes connection before all bytes are sent
> --------------------------------------------------------
>
>                 Key: SSHD-85
>                 URL: https://issues.apache.org/jira/browse/SSHD-85
>             Project: MINA SSHD
>          Issue Type: Bug
>    Affects Versions: 0.2.0
>         Environment: Windows or Linux, JSCH Client
>            Reporter: Bill Kuker
>            Assignee: Guillaume Nodet
>         Attachments: MINA-Port-Forward.txt, SSHD-85_testcase.txt
>
>
> When I am forwarding connections from a Client to a port on the SSH Server through the
SSH Client to a Remote Server on the SSH Client network:
> Client --(a)---> SSH Server <===[ssh]===> SSH Client --(b)--> Remote Server
>  if the Remote Server sends some bytes and immediately closes the connection (b) to the
SSH Client the SSH Server will close the connection (a) to the client before all of those
bytes are sent to the SSH Client.
> This is probably a race condition. If I run one connection at a time it works 99% of
the time, but if I use a load generator (a completely separate process) to max out all 4 cores
I can make it fail (I do not get all the bytes from Remote Server at Client) 99% of the time.
Also by running about 100 simultaneous requests I get maybe a 20% failure rate.
> If the Remote Server is something like Telnet (Open for a while, user closes connection)
everything seems fine, but the the Remote Server is a web server with keep alive disabled,
and many small requests are made, many images, htmls, css are truncated.
> Sorry I can't be more precise with this, but I hope anyone else having a similar trouble
can help fill out this bug with details.



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