SSH sometimes screws up connection when terminal overflows?

Posted by SeveQ on Server Fault See other posts from Server Fault or by SeveQ
Published on 2010-02-28T23:16:51Z Indexed on 2010/04/14 0:03 UTC
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I've got a problem with SSH on a Debian Lenny based server (it's a vHost within a Xen environment, booted on a Xen kernel). I hope someone can help me with this.

The SSH connection seems somehow getting screwed up frequently when the terminal overflows (new lines beyond the bottom of the terminal, usually forcing it to scroll). The connection gets lost but not regularly disconnected. It nearly always happens when I do the following:

  • an existing SSH connection gets disconnected (regularly)
  • I order putty to reestablish the connection
  • login-prompt appears at the very bottom of the putty terminal window
  • I enter my login-name, press the enter key
  • I'm asked for the password, I enter it, press the enter key and BOOM! Nothing more happens. I have to reconnect again.

So it is reproducable.

I'm not totally sure if the connection crashes before or after I enter the password.

Furthermore it also happens when there is much text to be displayed (for example when I compile something or do an ls -l on a directory with many entries).

Using 'screen', however, helps to reduces the frequency of occurence but doesn't solve the problem completely.

It's occurence is independent from which terminal software I use. I mostly use putty but it also happens with other clients.

I certainly hope somebody can help me solving this problem.

Thanks in advance!

//edit: I've just made a Wireshark trace of the ssh connection and there is nothing, I repeat, nothing different between the working and the failing connection (at least aside from frame numbers, ports and times that obviously can't be equal). This leads me to the assumption that the error has to happen on the server's side.

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