question

Ed Sutter ed.sutter at alcatel-lucent.com
Fri Apr 26 02:57:53 WST 2013


Hi,
I have a modified version of the dropbear ssh server running in
a multitasking RTOS environment that is not POSIX compliant.
In almost all cases it is running perfectly...
I run load tests on it by just using a simple expect script
that spawns an ssh client and sends commands and expects
responses (in a loop).
If, within that loop, I occasionally (every ~30 minutes)
disconnect and reconnect then I can let that run *forever*
(haven't fully tested that).  :-(

The problem I run into is if I just make an initial connection
and put the script in a loop that simply keeps issuing commands
and responses (I never disconnect; just maintain the initial session).
After some unpredictable amount of time (usually it takes an hour or
more); having invoked a few thousand commands, suddenly everything
just stops.  The server is sitting in the select of the session_loop,
and the client (in the expect script) is just waiting for a response.

It seems like everything is where its supposed to be, but the client
is not able to send any characters to the server.  It appears that the
connection dropped; however, I'm fairly certain that it has not.

So, I apparently broke something; hence my question...

After the client/server transactions for key exchange, login/password etc..
are complete and basically both sides are just passing encrypted data back
and forth, is there any other periodic responsibility (on the servers' part)
to issue any "keep-alive" type of commands (or something similar) that I
have not implemented?

Thanks,
Ed


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