[BUG?] sshd closes the connection after 2^16 bytes

Matthieu Moy <Matthieu.Moy@xxxxxxxxxxxxxxx> · Mon, 09 Nov 2009 15:26:23 +0100

Hi,

I'm having trouble with the sshd on one particular machine. In short:

$ head -c 196481 /dev/zero | ssh machine-name 'LANG=C wc'
      0       0   65536

(the 65536 here should have been a 196481 ...)

This happens whether I launch the command from the machine, or from
another remote machine. The OpenSSH version is:

OpenSSH_4.3p2, OpenSSL 0.9.8e-fips-rhel5 01 Jul 2008

with:

$ cat /etc/redhat-release 
Red Hat Enterprise Linux Server release 5.4 (Tikanga)
$ uname -a
Linux machine-name 2.6.18-128.7.1.el5 #1 SMP Wed Aug 19 04:08:13 EDT 2009 ppc64 ppc64 ppc64 GNU/Linux

One surprising thing:

$ head -c 196481 /dev/zero | ssh machine-name 'LANG=C wc'
      0       0   65536
$ head -c 196480 /dev/zero | ssh machine-name 'LANG=C wc'
      0       0  196480

So, the bug is triggered when sending 196481 bytes or more, but the
consequence is a truncation of the input at 65536=2^16 bytes.

Any idea what's going on?

Thanks,

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/