I'm having a puzzling issue with X11.
I am running Ubuntu 19.10 on a desktop, from which I can ssh to Server A where X11 forwarding works nicely (i.e. X11 on my client side works), but on the other hand if I try to use X11 to another Server B then it does not work.
But it happens that X11 on Server B is fine because it works when I connect to it via my laptop (with Ubuntu 18.04)!
This is what I get from ssh -v -X :
debug1: Requesting X11 forwarding with authentication spoofing.
debug1: Sending environment.
....
debug1: client_input_channel_open: ctype x11 rchan 2 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 49834
debug1: channel 1: new [x11]
debug1: confirm x11
debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 49860
debug1: channel 2: new [x11]
debug1: confirm x11
debug1: client_input_channel_open: ctype x11 rchan 4 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 49878
debug1: channel 3: new [x11]
debug1: confirm x11
debug1: channel 1: FORCE input drain
This is very strange, because the usual solutions (edit /etc/ssh/ssh_config) do not work. And with Ubuntu 18.04 everything works out of the box!
I compared the outputs of both the successful case w/Ubuntu18.04@laptop and the unsuccessful case w/Ubuntu19.10@desktop and the only significant difference is the message FORCE input drain.
A more complete output with ssh -vvv -X gives me this (note that I am trying to open a gnuplot window to test the X11):
gnuplot> p x w l
debug3: receive packet: type 90
debug1: client_input_channel_open: ctype x11 rchan 2 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 52382
debug2: fd 7 setting O_NONBLOCK
debug3: fd 7 is O_NONBLOCK
debug1: channel 1: new [x11]
debug1: confirm x11
debug3: send packet: type 91
debug2: channel 1: rcvd adjust 34784
debug3: receive packet: type 90
debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 52394
debug2: fd 8 setting O_NONBLOCK
debug3: fd 8 is O_NONBLOCK
debug1: channel 2: new [x11]
debug1: confirm x11
debug3: send packet: type 91
debug3: receive packet: type 90
debug1: client_input_channel_open: ctype x11 rchan 4 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 52398
debug2: fd 9 setting O_NONBLOCK
debug3: fd 9 is O_NONBLOCK
debug1: channel 3: new [x11]
debug1: confirm x11
debug3: send packet: type 91
debug2: channel 1: rcvd adjust 33588
debug2: channel 1: rcvd adjust 46612
debug2: channel 1: rcvd adjust 37976
debug2: channel 1: rcvd adjust 45940
debug2: channel 1: rcvd adjust 33144
debug3: receive packet: type 96
debug2: channel 1: rcvd eof
debug2: channel 1: output open -> drain
debug2: channel 1: obuf empty
debug2: channel 1: chan_shutdown_write (i0 o1 sock 7 wfd 7 efd -1 [closed])
debug2: channel 1: output drain -> closed
debug1: channel 1: FORCE input drain
debug2: channel 1: ibuf empty
debug2: channel 1: send eof
debug3: send packet: type 96
debug2: channel 1: input drain -> closed
debug2: channel 1: send close
debug3: send packet: type 97
debug3: channel 1: will not send data after close
debug3: channel 1: will not send data after close
Warning: slow font initialization
debug3: channel 1: will not send data after close
debug3: channel 1: will not send data after close
gnuplot>
debug3: channel 1: will not send data after close
Does anyone have any idea of what is this? Maybe some bug in Ubuntu 19.10?
0 Answers