Sam Gardner created SSHD-451:
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Summary: sshd-core DefaultTcpIpForwarder deadlocks on JRE 1.6.x
Key: SSHD-451
URL: https://issues.apache.org/jira/browse/SSHD-451
Project: MINA SSHD
Issue Type: Bug
Affects Versions: 0.14.0, 0.10.0
Environment: Java SE 6 [1.6.0_65-b14-466.1]
Reporter: Sam Gardner
I have a CentOS 6.4 system running {{httpd-2.4.9}} on port 8000.
>From this system, if I ssh to a {{MINA sshd-core 0.14.0}} server running on
>Java SE 6 {{1.6.0_65-b14-466.1}} using the following invocation {{/usr/bin/ssh
>-R *:8000:localhost:8000 -p 2000 -N username@local-mina-server
}}, I can reliably deadlock a remote forward channel after approximately five
requests to {{localhost:8000}} on the system running MINA.
After these requests I see one last line on the MINA server {noformat}
2015-04-22 10:11:10,406 | TRACE | NioProcessor-3 | TcpipClientChannel
| org.apache.sshd.client.channel.AbstractClientChannel 195 |
Waiting for lock on channel TcpipClientChannel[id=9, recipient=0], mask=130,
cond=0
{noformat}, and then I cease to be able to access the remotely forwarded port
until after the MINA server has been restarted.
I believe the issue is related to this method in {{DefaultTcpipForwarder.java}}:
{noformat}
public void messageReceived(IoSession session, Readable message) throws
Exception {
TcpipClientChannel channel = (TcpipClientChannel)
session.getAttribute(TcpipClientChannel.class);
Buffer buffer = new Buffer();
buffer.putBuffer(message);
channel.waitFor(ClientChannel.OPENED | ClientChannel.CLOSED,
Long.MAX_VALUE);
channel.getInvertedIn().write(buffer.array(), buffer.rpos(),
buffer.available());
channel.getInvertedIn().flush();
}
{noformat}
The channel lock {{wait}} request is given with a timeout of
{{Long.MAX_VALUE}}, which seems unlikely to ever return in a synchronous
environment like {{JRE 1.6.x}}. Initial testing indicates that a timeout of 5
seconds appears to fix the issue, but this may have unforeseen consequences
that I haven't run into yet.
I cannot reproduce the issue on MINA SSHD 0.8.0, or when using JRE 1.7.x.
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