RE: ssh works, scp stalls

From: Zieg, Mark (mark.zieg_at_lmco.com)
Date: 09/15/03

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    Date: Mon, 15 Sep 2003 13:29:52 -0400
    To: Phil Moors <pmoors@greenbelt.com>, secureshell@securityfocus.com
    
    

    I don't have a technical explanation for what's happening, but I used to
    get that same error when downloading very large files from a remote
    FreeBSD server to my home FreeBSD box over RoadRunner.

    It only happened between those particular two hosts, so at the time, I
    just kludged a lame workaround rather than figuring out the underlying
    problem.

    I found that by using "rsync --rsh=ssh --bwlimit=18" (ie, limiting the
    transfer bandwidth to 15-18K/sec) the problem went away. If I jacked up
    the bandwidth much higher, I would get those stall conditions again.

    -MZ

    -----Original Message-----
    From: Phil Moors [mailto:pmoors@greenbelt.com]
    Sent: Friday, September 12, 2003 5:56 PM
    To: secureshell@securityfocus.com
    Subject: ssh works, scp stalls

    Just the past week, I can no longer scp to my remote sites with either
    scp or sftp. The ssh utility works just as usual. I've seen only one
    other post with this problem on the dev list and there was no
    resolution. I've noticed some unusual things going on at my ISP like
    whether I can ping hosts on the internet depends on which dial up number
    I use. So they are clearly filtering ICMP on parts of their network.

    When I start scp everything goes as normal until after authentication.
    Then:

    debug1: ssh-userauth2 successful: method password
    debug1: fd 4 setting O_NONBLOCK
    debug1: fd 5 setting O_NONBLOCK
    debug1: channel 0: new [client-session]
    debug1: send channel open 0
    debug1: Entering interactive session.
    debug2: callback start
    debug1: ssh_session2_setup: id 0
    debug1: Sending command: scp -v -t .
    debug1: channel request 0: exec
    debug2: callback done
    debug1: channel 0: open confirm rwindow 0 rmax 32768
    debug2: channel 0: rcvd adjust 131072
    Sending file modes: C0664 7383040 ptdoc.tar
    ptdoc.tar 1% | | 132 KB -
    stalled -debug2: channel 0: rcvd adjust 65560
    ptdoc.tar 2% | | 196 KB -
    stalled -d

    I'll keep getting 'stalled' messages until the file is transferred,
    though it takes a very long time. While this is going on, the modem
    lights flash in a way I'm not used to seeing. In particular, the SD and
    CS leds flash on and off together.

    I've read posts about MTU and TCPMSS. The MTU for my 56k modem dial up
    shows up as 1500 in ifconfig. I've tweaked it to 576 and 1492 with no
    real change in behaviour.

    Has anyone seen this before??

    TIA,

    Phil


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