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  2. SSHD-151

Direct TCP/IP Port Forward sends EOF to client after closing channel


    • Type: Bug
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 0.6.0
    • Fix Version/s: 0.7.0
    • Labels:


      While testing port forwarding from an OpenSSH_5.8p2 client to a MINA SSHD server, I noticed that after the first disconnection of a client from the forwarded port, the entire SSH session would be disconnected. The client command I ran was:

      ssh -N -L 60443:<target>:443 -p 50022 tester@<minasshd>

      Looking at the traces, I saw the following from SSHD:

      13:54:12.823 [NioProcessor-1] DEBUG o.a.s.server.session.ServerSession - Received packet SSH_MSG_CHANNEL_OPEN
      13:54:12.823 [NioProcessor-1] INFO o.a.s.server.session.ServerSession - Received SSH_MSG_CHANNEL_OPEN direct-tcpip
      13:54:12.826 [NioProcessor-1] INFO o.a.s.s.channel.ChannelDirectTcpip - Receiving request for direct tcpip: hostToConnect=<target>, portToConnect=443, originatorIpAddress=, originatorPort=54145
      13:54:15.588 [NioProcessor-1] DEBUG o.a.s.server.session.ServerSession - Received packet SSH_MSG_CHANNEL_EOF
      13:54:15.589 [NioProcessor-1] INFO o.a.s.s.channel.ChannelDirectTcpip - Received SSH_MSG_CHANNEL_EOF on channel 0
      13:54:15.589 [NioProcessor-1] INFO o.a.s.s.channel.ChannelDirectTcpip - Send SSH_MSG_CHANNEL_CLOSE on channel 0
      13:54:15.590 [NioProcessor-1] DEBUG o.a.s.server.session.ServerSession - Received packet SSH_MSG_CHANNEL_CLOSE
      13:54:15.590 [NioProcessor-1] INFO o.a.s.s.channel.ChannelDirectTcpip - Received SSH_MSG_CHANNEL_CLOSE on channel 0
      13:54:15.590 [NioProcessor-1] INFO o.a.s.s.channel.ChannelDirectTcpip - Closing channel 0 immediately
      13:54:15.591 [NioProcessor-1] INFO o.a.s.s.channel.ChannelDirectTcpip - Closing channel 0 immediately
      13:54:15.593 [NioProcessor-26] INFO o.a.s.s.channel.ChannelDirectTcpip - Send SSH_MSG_CHANNEL_EOF on channel 0
      13:54:15.595 [NioProcessor-1] DEBUG o.a.s.server.session.ServerSession - Received packet SSH_MSG_DISCONNECT
      13:54:15.595 [NioProcessor-1] INFO o.a.s.server.session.ServerSession - Received SSH_MSG_DISCONNECT (reason=2, msg=Received ieof for nonexistent channel 2.)
      13:54:15.595 [NioProcessor-1] INFO o.a.s.server.session.ServerSession - Closing session
      13:54:15.595 [NioProcessor-1] DEBUG o.a.s.server.session.ServerSession - Closing IoSession
      13:54:15.596 [NioProcessor-1] DEBUG o.a.s.server.session.ServerSession - IoSession closed

      So if I read this right, the client sends an EOF, then the server sends a CLOSE, then the client sends a CLOSE. After all of this, the server sends back an EOF, but the channel no longer exists at the client, which causes a disconnection.

      I looked into the source code, and figured the following change might correct the issue:

      Index: sshd-core/src/main/java/org/apache/sshd/server/channel/ChannelDirectTcpip.java
      — sshd-core/src/main/java/org/apache/sshd/server/channel/ChannelDirectTcpip.java (revision 1207930)
      +++ sshd-core/src/main/java/org/apache/sshd/server/channel/ChannelDirectTcpip.java (working copy)
      @@ -109,7 +109,9 @@

      public void sessionClosed(IoSession session) throws Exception {
      + if (!closing)

      { sendEof(); + }


      It appears to work, but I do not know if it is correct, or if it will break other situations. Can anyone comment on it?


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              • Assignee:
                gnt Guillaume Nodet
                kwinchester Kevin Winchester
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                • Created: