Subject: [Isms] properly closing an ssh session

From: Juergen Schoenwaelder <[email-masked]>
Date: Tue, 18 Sep 2007 18:05:05 +0200

Hi,

I have a question for SSH experts (hope there are some on this list).
I am wondering what the proper way of closing the SSH session is in
our case. Note that we run a single SSH channel over the SSH transport
and there are several options now.

a) Be brutal and simply close the underlying TCP connection.

b) Be a bit less brutal and send an SSH_DISCONNECT with say a
   reason code of SSH_DISCONNECT_BY_APPLICATION and be done.

c) Be friendly and play the game of doing an SSH_CHANNEL_CLOSE
   exchange followed by SSH_DISCONNECT.

d) Be overly friendly by exchanging SSH_CHANNEL_EOF before
   exchanging SSH_CHANNEL_CLOSE and doing an SSH_DISCONNECT.

My reading of the RFCs indicates that d) is not really required and of
course a) will always work. There might be reasons to do b) although
it is not clear which benefit one would get (since my understanding is
that SSH_DISCONNECT does not impact who is closing the TCP connection
and who has to go into wait state).

Any suggestions what should be done to play the SSH game nicely?

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1, 28759 Bremen, Germany
Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>

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