openssh unix dev - Dec 2008 - Port forwarding using the client of a multiplexed connection.

I am trying to set up port forwarding using the client of a multiplexed
connection, but the client is dying.

The connection paramaters I am using are as follows:
for the master: /usr/bin/ssh -T -n -N -o ControlMaster=yes -o
ControlPath=/var/run/autossh/control-%r@%h-%p.sock -o ConnectionAttempts=3
-o BatchMode=yes -o EscapeChar=none -o ExitOnForwardFailure=yes -o
ServerAliveInterval=15 -o ForwardAgent=no -c arcfour -2 -x user at host.com
for the client: /usr/bin/ssh -T -n -N -o ControlMaster=no -o
ControlPath=/var/run/autossh/control-%r@%h-%p.sock -o ConnectionAttempts=3
-o BatchMode=yes -o EscapeChar=none -o ExitOnForwardFailure=yes -o
ServerAliveInterval=15 -o ForwardAgent=no -R 5900:address:5900 -R
5901:address:5901 -c arcfour -2 -x user at host.com

The master (this is only the part output when I start the client):
debug3: fd 6 is not O_NONBLOCK
debug3: ssh_msg_recv entering
debug3: ssh_msg_send: type 2
debug3: ssh_msg_recv entering
debug3: muxserver_accept_control: receiving 0 env vars
debug2: muxserver_accept_control: accepted tty 0, subsys 0, cmd
debug2: muxserver_accept_control: got fds stdin 7, stdout 8, stderr 9
debug3: ssh_msg_send: type 2
debug2: fd 7 setting O_NONBLOCK
debug2: fd 8 setting O_NONBLOCK
debug2: fd 9 setting O_NONBLOCK
debug2: fd 6 setting O_NONBLOCK
debug1: channel 0: new [client-session]
debug3: muxserver_accept_control: channel_new: 0
debug2: channel 0: send open
debug2: callback start
debug2: client_session2_setup: id 0
debug2: channel 0: request shell confirm 1
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel 0: rcvd adjust 2097152
debug2: channel_input_confirm: type 99 id 0
debug2: shell request accepted on channel 0
debug2: channel 0: read<=0 rfd 7 len 0
debug2: channel 0: read failed
debug2: channel 0: close_read
debug2: channel 0: input open -> drain
debug2: channel 0: ibuf empty
debug2: channel 0: send eof
debug2: channel 0: input drain -> closed
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug2: channel 0: rcvd eof
debug2: channel 0: output open -> drain
debug2: channel 0: obuf empty
debug2: channel 0: close_write
debug2: channel 0: output drain -> closed
debug2: channel 0: rcvd close
debug3: channel 0: will not send data after close
debug2: channel 0: send close
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 r0 i3/0 o3/0 fd -1/-1 cfd 6)

debug3: channel 0: close_fds r -1 w -1 e 9 c 6


The client:
debug1: Reading configuration data /etc/ssh/ssh_config
debug3: ssh_msg_send: type 2
debug3: ssh_msg_recv entering
debug3: ssh_msg_send: type 2
debug3: ssh_msg_recv entering
debug2: Received EOF from master
debug2: Received exit status from master 0

Thanks for any help
-Russell Harmon

Hi Russell,

Russell Harmon wrote:
> I am trying to set up port forwarding using the client of a
> multiplexed connection, but the client is dying.
> 
> The connection paramaters I am using are as follows:
> for the master: /usr/bin/ssh -T -n -N ..
> for the client: /usr/bin/ssh -T -n -N ..
..
> The master (this is only the part output when I start the client):
..
> debug2: muxserver_accept_control: got fds stdin 7, stdout 8, stderr 9
..
> debug2: shell request accepted on channel 0
> debug2: channel 0: read<=0 rfd 7 len 0
> debug2: channel 0: read failed
> debug2: channel 0: close_read
> debug2: channel 0: input open -> drain
> debug2: channel 0: ibuf empty
> debug2: channel 0: send eof
> debug2: channel 0: input drain -> closed
..
> The client:
..
> debug2: Received EOF from master
> debug2: Received exit status from master 0
This is a bit of a wild guess, but does it work if you run the client
without -T -N ?

It seems the server is trying to read from the client stdin even
though -T -N is given, and whey they don't return data the server
closes down the client.

I'm not sure there should be a shell request when using -T -N..


//Peter