[tor-talk] What is keeping the SSH connection alive?

Nurmi, Juha juha.nurmi at ahmia.fi
Tue Jul 8 04:08:50 UTC 2014


I have a Raspberry Pi as wireless router and Tor proxy. Everything from
wlan0 is directed to Tor. When I am taking SSH connection using this
wireless transparent proxy with my laptop the SSH connection is sometimes
left alive forever after the laptop is closed.

How it works:

1) I am taking SSH connection from my laptop to an SSH server.
2) I am walking away from my home with the laptop and the connection to the
wireless network is lost.
3) The SSH connection stays on (from the server point of view) forever.

The wireless router is keeping the SSH connection alive until I reboot it.

I don't understand how this is possible.

In the wireless router I am running the Tor software version
Moreover, there is nothing special in the SSH server.

It seems that the connection stays on until the router is rebooted. I see
the SSH connection coming from some exit node:

[juha at server ~]$ who
juha    pts/1        2014-07-07 13:04 (:pts/2:S.0)
juha    pts/0        2014-07-07 10:43 (h-

[juha at server ~]$ sudo netstat -tnpa | grep ESTABLISHED.*sshd
tcp        0      0 XXX.XXX.XXX.XXX:22
 ESTABLISHED 8743/sshd

The SSH server has the default settings (keep alive settings are commented

[juha at server ~]$ sudo grep -ni alive /etc/ssh/sshd_config
114:#TCPKeepAlive yes
119:#ClientAliveInterval 0
120:#ClientAliveCountMax 3

So, how does the SSH connection is kept alive forever without the client


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