Re: ssh X11forwarding won't work, please help

From: Vincent Zweije (vzweije_at_sense.znet)
Date: 08/02/04

  • Next message: Nils Gorges: "Re: ssh X11forwarding won't work, please help" 
    Date: Mon, 2 Aug 2004 22:52:10 +0200 (CEST)

    In article <celd3e$907$05$1@news.t-online.com>, Nils Gorges
    <noctamid@gmx.de> wrote:

    || [user@machine3:~]$ xterm &
    || [1] 10273
    ||
    || debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
    || debug1: client_request_x11: request from 127.0.0.1 34196
    || debug1: fd 7 setting O_NONBLOCK
    || debug1: channel 1: new [x11]
    || debug1: confirm x11
    || debug1: channel request 0: window-change
    || debug1: channel request 0: window-change
    || debug1: channel request 0: window-change
    || debug1: channel request 0: window-change
    || debug1: channel_free: channel 0: client-session, nchannels 2
    || debug1: channel_free: channel 1: x11, nchannels 1
    ||
    || ---
    || At this point the shell freezes......
    || ---
    ||
    || After a while at machine1:
    ||
    || Read from remote host 192.168.1.3: Connection timed out
    || Connection to 192.168.1.3 closed.

    This must be the ssh connection timing out while trying to read data.
    This is strange.

    || debug1: Transferred: stdin 0, stdout 0, stderr 96 bytes in 1058.2 seconds
    || debug1: Bytes per second: stdin 0.0, stdout 0.0, stderr 0.1
    || debug1: Exit status -1

    The strace you posted in an earlier message showed xterm falling silent
    in a select() system call, meaning it is also waiting for input from
    localhost:6010 (file descriptor 3) which is never coming.

    I'd have a look at the network connections in between. I'm suspecting
    an ssh bug, because of the connection timeout, the apparent dealock,
    and the shell freezing.

    What versions of ssh are you using? I'd try and see if there are any
    old versions of ssh that might freeze up in some situations.

    Are there any firewall rules on machine 1 and machine 3? Particularly
    with respect to localhost traffic?

    Try with two simultaneous ssh connections: the first with X forwarding,
    print its DISPLAY, start the second without X forwarding, but use the
    DISPLAY of the first to start the xterm. Then your second shell will
    not freeze, but the first shell might.

    Ciao. Vincent. 

    -- 
Vincent Zweije <zweije@xs4all.nl>    | "If you're flamed in a group you
<http://www.xs4all.nl/~zweije/>      | don't read, does anybody get burnt?"
[Xhost should be taken out and shot] |            -- Paul Tomblin on a.s.r.
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