Created attachment 3193 [details] Update last_client_time on timeout I've discovered a bug in serverloop.c(function=wait_until_can_do_something)! With latest openssh (7.8p1 as well as current master) sshd disconnects a non-responding client after approximately: ((ClientAliveCountMax / 2) * ClientAliveInterval) seconds I did a bisect which showed that the fix introduced for bz#2756 causes this behavior: https://bugzilla.mindrot.org/show_bug.cgi?id=2756 How to reproduce: 1. server #> /sbin/sshd -p 2020 -ddd -f ${sshd_config} 2>&1 | ts 2. client $> ssh $IP -p2020 3. close e.g. notebook of the client connection and wait for the timeout to happen (maybe killing the client process is already enough, didn't test it). ${sshd_config} ---- TCPKeepAlive no ClientAliveInterval 15 ClientAliveCountMax 8 ---- The debug log of sshd shows: ---- ... [2018-04-26 11:59:35] debug3: /tmp/sshd_config:94 setting TCPKeepAlive no [2018-04-26 11:59:35] debug3: /tmp/sshd_config:98 setting ClientAliveInterval 15 [2018-04-26 11:59:35] debug3: /tmp/sshd_config:99 setting ClientAliveCountMax 8 ... [2018-04-26 12:00:16] debug2: channel 0: request keepalive@openssh.com confirm 1 [2018-04-26 12:00:16] debug2: channel 0: request keepalive@openssh.com confirm 1 [2018-04-26 12:00:31] debug2: channel 0: request keepalive@openssh.com confirm 1 [2018-04-26 12:00:31] debug2: channel 0: request keepalive@openssh.com confirm 1 [2018-04-26 12:00:46] debug2: channel 0: request keepalive@openssh.com confirm 1 [2018-04-26 12:00:46] debug2: channel 0: request keepalive@openssh.com confirm 1 [2018-04-26 12:01:01] debug2: channel 0: request keepalive@openssh.com confirm 1 [2018-04-26 12:01:01] debug2: channel 0: request keepalive@openssh.com confirm 1 [2018-04-26 12:01:16] Timeout, client not responding from user $USER x.x.x.x port xxxxx ---- keepalive packets are sent twice on every interval. I think the problem is that if a timeout of the select call in function=wait_until_can_do_something happens the next select call will return immediately with data contained in 'writesetp' which causes to send another keepalive packet since variable=last_client_time wasn't updated. A very naive patch which solves the problem for me is attached. However, there might a better solution for this problem!