Re: SSH Hangs in 2.5.59 and 2.5.55 (TCP_NODELAY?)

[Christopher Faylor <cgf@redhat.com>]

On Fri, Jan 24, 2003 at 04:15:23PM -0500, Christopher Faylor wrote:
>On Fri, Jan 24, 2003 at 01:46:10PM -0700, lost@l-w.net wrote:
>>On Fri, 24 Jan 2003, David C Niemi wrote:
>>
>>> I have been experiencing some baffling SSH client hangs under 2.5.59 (and
>>> 55) in which the session totally hangs up after I have typed (typically)
>>> 10-100 characters.  Right before it hangs permanently, a character is
>>> echo'd back to the screen several seconds late.  Interestingly, data due
>>> back for my client which is initiated by the server side does make it, I
>>> just can't type anything further.
>>
>><snip>
>>
>>> Neither "ifconfig" nor dmesg show *any* errors whatsoever.
>>>
>>> Anyone else seeing SSH client hangs to nonlocal hosts under 2.5.59?
>>
>>I'm seeing the same problem with a D-Link NIC (8139too driver). Exact same
>>symptoms - a delayed echo followed by no further echos. Checking netstat
>>shows an output queue for the socket but it never transmits anything.
>>Messages echoed by the remote server also make it through the connection.
>
>I hate "me toos" but maybe this will provide some useful data.
>
>I'm seeing the same thing with a 3c59x driver.  I couldn't reproduce the
>problem with a tulip driver when I connect my laptop directly to my
>cable modem.  The problem only occurs when going through the laptop
>(which acts as a firewall, running netfilter) to a remote site, in my
>case the site is sources.redhat.com.

Checking the strace log between telnet and ssh, I noticed that ssh does this:
  setsockopt(3, SOL_TCP, TCP_NODELAY, [1], 4) = 0

while telnet doesn't.

If I introduce that call into telnet, it seems to hang eventually too in the
same way as ssh.

cgf