Paramiko SSH Tunnel Shutdown Issue

Question

I\'m working on a python script to query a few remote databases over an established ssh tunnel every so often. I\'m fairly familiar with the paramiko library, so that was my cho

Answer 1

You may want to add some synchronization between the spawned thread and the caller so that you don't try to use the tunnel before it is ready. Something like:

    from threading import Event   
    def startTunnel(self):
        class SubHandler(Handler):
            chain_host = '127.0.0.1'
            chain_port = 5432
            ssh_transport = self.c.get_transport()
        mysignal = Event()
        mysignal.clear()
        def ThreadTunnel():
            global t
            t = ForwardServer(('', 3333), SubHandler)
            mysignal.set() 
            t.serve_forever()
        Thread(target=ThreadTunnel).start()
        mysignal.wait()

Answer 2

You can also try sshtunnel it has two cases to close tunnel .stop() if you want to wait until the end of all active connections or .stop(force=True) to close all active connections.

If you don't want to use it you can check the source code for this logic here: https://github.com/pahaz/sshtunnel/blob/090a1c1/sshtunnel.py#L1423-L1456

Answer 3

It appears the SocketServer's shutdown method isn't properly shutting down/closing the socket. With the below changes in my code, I retain access to the SocketServer object and access the socket directly to close it. Note that socket.close() works in my case, but others might be interested in socket.shutdown() followed by a socket.close() if other resources are accessing that socket.

[Ref: socket.shutdown vs socket.close

def ThreadTunnel():
    self.t = ForwardServer(('127.0.0.1', 3333), SubHandler)
    self.t.serve_forever()
Thread(target=ThreadTunnel).start()

def stopTunnel(self):
    self.t.shutdown()
    self.trans.close()
    self.c.close()
    self.t.socket.close()

Answer 4

Note that you don't have do the Subhandler hack as shown in the demo code. The comment is wrong. Handlers do have access to their Server's data. Inside a handler you can use self.server.instance_data.

If you use the following code, in your Handler, you would use

• self.server.chain_host
• self.server.chain_port
• self.server.ssh_transport

---

class ForwardServer(SocketServer.ThreadingTCPServer):
    daemon_threads = True
    allow_reuse_address = True

    def __init__(
          self, connection, handler, chain_host, chain_port, ssh_transport):
        SocketServer.ThreadingTCPServer.__init__(self, connection, handler)
        self.chain_host = chain_host
        self.chain_port = chain_port
        self.ssh_transport = ssh_transport
...

server = ForwardServer(('', local_port), Handler, 
                       remote_host, remote_port, transport)
server.serve_forever()