[
https://issues.apache.org/jira/browse/SSHD-85?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16052705#comment-16052705
]
Goldstein Lyor commented on SSHD-85:
------------------------------------
I have been looking over the test code and have a few concerns - the main one
is that the server that sends the payload does not wait to make sure that the
bytes have been sent and successfully acknowledged by the receiver - it simply
writes the payload and then closes the socket, AFAIK this does not guarantee
that all the written bytes have been sent and successfully acknowledged by the
receiver. Assuming this is the case, no wonder bytes are getting lost since it
becomes a *race* condition. This can also explain why using a tunnel, a large
buffer or having a long enough pause in read fails - the receiver/reader side
eventually attempts to read from a closed socket. In order to avod that, I
would recommend using an {{AsynchronousSocketChannel}} at the server code that
writes the payload and wait for the write completion - e.g. [this example
code|https://gist.github.com/ochinchina/72cc23220dc8a933fc46].
> 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, 1.4.0, 1.6.0
> 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.
> *Update in 2017*
> I have provided a maven project with a unit test that has a 100% failure rate
> on my desktop without resorting to creating artificial load. It is a lot
> simpler:
> https://github.com/bkuker/sshd-85
> https://github.com/bkuker/sshd-85/blob/master/src/main/java/com/billkuker/sshd/sshd85/TheTest.java
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
