[
https://issues.apache.org/jira/browse/SSHD-557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17081569#comment-17081569
]
Guillaume Nodet commented on SSHD-557:
--------------------------------------
As indicated by the comment at
[https://github.com/apache/mina-sshd/blob/master/sshd-core/src/main/java/org/apache/sshd/server/forward/TcpipServerChannel.java#L197
|https://github.com/apache/mina-sshd/blob/master/sshd-core/src/main/java/org/apache/sshd/server/forward/TcpipServerChannel.java#L197]the
logic should be rewritten with an {{ChannelAsyncOutputStream}} so that no
thread would be blocked by a call to {{waitForSpace}}.
> MINA SSHD deadlocks upon multiple concurrent HTTP downloads over
> locally-forwarded ports
> ----------------------------------------------------------------------------------------
>
> Key: SSHD-557
> URL: https://issues.apache.org/jira/browse/SSHD-557
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 0.14.0, 1.0.0
> Environment: Fedora 21, kernel 3.17.4-301, OpenJDK 1.8.0_51-b16
> Reporter: Sam Gardner
> Assignee: Lyor Goldstein
> Priority: Major
> Labels: sshd
> Fix For: 1.1.0
>
> Attachments: AbstractUserAuth.java, setup-tunnels-remote.sh,
> setup-tunnels.sh, ssh-load-remote.sh, ssh-load.sh,
> sshd-core-0.14.0-jar-with-dependencies.jar,
> sshd-core-1.0.0-jar-with-dependencies.jar
>
>
> SSHD-Core 1.0.0 deadlocks when multiple concurrent downloads are in progress
> over ChannelOutputStreams
> In both Mina-SSHD 0.14.0 and 1.0.0 the server will become deadlocked if
> multiple concurrent downloads are started over a locally-forwarded TCP
> socket. In this state the process is still alive and client connections stay
> open, but no data can be transmitted and new connections will not be accepted
> - when inspected via telnet, the SSH port will not even return a banner.
> Inspection of the hung process using the {{jstack}} tool shows that each NIO
> worker thread is in the following state: {noformat}
> "sshd-SshServer[36f6e879]-nio2-thread-4" #14 daemon prio=5 os_prio=0
> tid=0x00007f219c009000 nid=0x34c6 in Object.wait() [0x00007f21c8439000]
> java.lang.Thread.State: WAITING (on object monitor)
> at java.lang.Object.wait(Native Method)
> - waiting on <0x00000000d799f9b0> (a
> org.apache.sshd.common.channel.Window)
> at java.lang.Object.wait(Object.java:502)
> at org.apache.sshd.common.channel.Window.waitForSpace(Window.java:175)
> - locked <0x00000000d799f9b0> (a
> org.apache.sshd.common.channel.Window)
> at
> org.apache.sshd.common.channel.ChannelOutputStream.flush(ChannelOutputStream.java:126)
> - locked <0x00000000d799fa68> (a
> org.apache.sshd.common.channel.ChannelOutputStream)
> at
> org.apache.sshd.server.forward.TcpipServerChannel$1.messageReceived(TcpipServerChannel.java:156)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:220)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker$2.run(Invoker.java:218)
> at
> sun.nio.ch.AsynchronousChannelGroupImpl$1.run(AsynchronousChannelGroupImpl.java:112)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> These are the steps to reproduce:
> # Start up approximately 200 separate SSH sessions with one local forward to
> an HTTP server:
> {{ssh -N -LXXXXX:<HTTP_SERVER>:80 account@<MINA_SSHD_SERVER>}}
> ## To simplify this process, I modified
> [org.apache.sshd.server.auth.AbstractUserAuth|^AbstractUserAuth.java] to
> always accept requests - this makes it possible to create the sessions on the
> same client (though I've also reproduced this on separate clients as well).
> ## This [script|^setup-tunnels.sh] will setup the client sessions as
> background processes
> # With the above sessions alive and backgrounded, fetch large files
> concurrently from the HTTP server over multiple forwarded ports:
> {{wget http://localhost:XXXXX/hugefile}}
> ## This [script|^ssh-load.sh] will start {{wget}} downloads in the above
> manner.
> # After a time, the {{wget}} downloads will stop progressing, and inspection
> of the SSH server process via {{jstack <PID>}} will show each of the
> {{nio2-thread-[0-9]}} threads in the deadlocked state.
> Note: I previously filed SSHD-539 on this, and have since reproduced it on
> vanilla MINA SSHD-Core without our proprietary modifications and running
> outside of Tomcat.
> The JAR files I used to reproduce are attached to this ticket as well.
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