On Wed, 24 Apr 2024 at 16:32:09 +0200, Lee Garrett wrote: > Although the dropbear man page is not explicit, I'm assuming it refers to > TCP keepalive.
I think this assumption is incorrect: https://sources.debian.org/src/dropbear/2024.84-1/src/common-session.c/#L497 > It should be trivially reproducible by running `ssh -o ServerAliveCountMax=3 > -o ServerAliveInterval=1 root@yourdropbearserver`. The client should then > disconnect after 3 seconds. Seems to work as expected for me: $ ssh -oLogLevel=DEBUG3 \ -oServerAliveCountMax=3 -oServerAliveInterval=1 \ -oUserKnownHostsFile=/tmp/known_hosts \ -i /tmp/test.key \ -l user -p 10022 127.0.0.1 sleep 300 […] debug1: Sending command: sleep 300 debug2: channel 0: request exec confirm 1 debug3: send packet: type 98 debug3: client_repledge: enter debug2: channel_input_open_confirmation: channel 0: callback done debug2: channel 0: open confirm rwindow 65536 rmax 32759 debug3: receive packet: type 99 debug2: channel_input_status_confirm: type 99 id 0 debug2: exec request accepted on channel 0 debug3: send packet: type 80 debug3: receive packet: type 82 debug3: send packet: type 80 debug3: receive packet: type 82 debug3: send packet: type 80 debug3: receive packet: type 82 debug3: send packet: type 80 debug3: receive packet: type 82 […] debug3: send packet: type 80 debug3: receive packet: type 82 debug3: receive packet: type 96 debug2: channel 0: rcvd eof debug2: channel 0: output open -> drain debug2: channel 0: obuf empty debug2: chan_shutdown_write: channel 0: (i0 o1 sock -1 wfd 5 efd 6 [write]) debug2: channel 0: output drain -> closed debug3: receive packet: type 98 debug1: client_input_channel_req: channel 0 rtype exit-status reply 0 debug3: receive packet: type 97 debug2: channel 0: rcvd close debug2: chan_shutdown_read: channel 0: (i0 o3 sock -1 wfd 4 efd 6 [write]) debug2: channel 0: input open -> closed debug3: channel 0: will not send data after close debug2: channel 0: almost dead debug2: channel 0: gc: notify user debug2: channel 0: gc: user detached debug2: channel 0: send close debug3: send packet: type 97 debug2: channel 0: is dead debug2: channel 0: garbage collecting debug1: channel 0: free: client-session, nchannels 1 debug3: channel 0: status: The following connections are open: #0 client-session (t4 [session] r0 i3/0 o3/0 e[write]/0 fd -1/-1/6 sock -1 cc -1 io 0x00/0x00) debug3: send packet: type 1 Transferred: sent 15360, received 7448 bytes, in 300.0 seconds Bytes per second: sent 51.2, received 24.8 debug1: Exit status 0 There is one packet 80/82 exchange per second until the `sleep 300` terminates. The output is similar with OpenSSH's sshd. -- Guilhem.
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