Dropbear timeout?

[mokkurkalve]

Sorry if this been answered before. I didn't find any search function on this forum.
I recently purchased an RT-AC68U and installed asuswrt-merlin 378.50_beta2. It seems to work great but one thing is a bit odd. I enabled dropbear ssh server login with only key login. This works fine but I get logged out after less than a minute of inactivity every time (Timeout, server not responding are the feedback). This is a bit quick I think. Using ordinary OpenSSH ssh program as client. Setting "ServerAliveInterval 10" in /etc/ssh/ssh_config didn't help one bit. Anybody knows how come?

 

[mokkurkalve]

Strange. When disabling "ServerAliveInterval" on the client side dropbear seems NOT to timeout..!?!
Does this mean that sending keepalives to the dropbear server makes it disconnect the connection? The disconnect seems actually to happen at ServerAliveInterval intervals. Very strange indeed...

And BTW. The dropbear on the router side per "ps" runs:
dropbear -p 22 -s -j -k

 

[mattiL]

Search tool:

 

[mokkurkalve]

Seems I found some sort of answer to this puzzling question:
http://permalink.gmane.org/gmane.network.ssh.dropbear/936

Seems that unless activated (with something like "-K 60" to the program, not -A as in the proposed patch in the mail) dropbear will ignore ServerAlive messages, thus making an OpenSSH ssh client detach after the default ServerAliveCountMax (which defaults to 3 x ServerAliveInterval). So the only way to not be atomatically detached from the dropbear server is to not send ServerAlive messages (set ServerAliveInterval to default 0).

If i understood this correctly that is.....

 

[mokkurkalve]

BTW (and probably OT) - Dropbear updated:
https://matt.ucc.asn.au/dropbear/CHANGES

 

[Nullity]

My operating system is ArchLinux (and frequently test other distros) and I have never encountered this problem with OpenSSH's ssh client. I often leave the terminal open for over an hour with no disconnects. I am using a RT-N66U.

Are you using a modified ssh_config?
What operating system are you using?

You might benefit from running "ssh" with the "-v" option to see more information. If you want even more verbosity you can try "-vv" or even "-vvv".

 

[mokkurkalve]

Yes. The problem was that I had ServerAliveInterval activated in ssh_config. Does not work with Dropbear it seems....

 

[Nullity]

Yes. The problem was that I had ServerAliveInterval activated in ssh_config. Does not work with Dropbear it seems....

When I encounter bugs or quirks with embedded systems I usually just deal with it.

 

[mokkurkalve]

Problem solved. I just reused (misused?) my old thread to give a heads up on software update. In case it would be of any interest....

 

[mystical]

Changing ServerAliveInterval to 0 in /etc/ssh/ssh_config did not stop the timeouts for my Mac OSX clients.
However, "ssh -o "ServerAliveInterval 0" admin@IP_ADDR" never times out, so that is my suggested work around for Apple OSX clients.

 

[Nullity]

Changing ServerAliveInterval to 0 in /etc/ssh/ssh_config did not stop the timeouts for my Mac OSX clients.
However, "ssh -o "ServerAliveInterval 0" admin@IP_ADDR" never times out, so that is my suggested work around for Apple OSX clients.

Strange. Have you tried putting the option into ~/.ssh/config?

 

[mystical]

Strange. Have you tried putting the option into ~/.ssh/config?

nevermind ;=)
I didn't recall doing it, but I found I had set ServerAliveInterval 60 in my ~/.ssh/config
thanks to all for this thread which led me to my problem.

 

[Nullity]

nevermind ;=)
I didn't recall doing it, but I found I had set ServerAliveInterval 60 in my ~/.ssh/config
thanks to all for this thread which led me to my problem.

Yeah, I often look at my config files and think "what the hell was I thinking?".