Bug#407735: 2.6.18-3-686 tcp_window_scaling serious problem

[prosolutions@gmx.net]

> 
> tags 407735 wontfix
> severity 407735 minor
> thanks
> 

I've been googling about this problem.  It could be a problem with the
way many routers around the world are configured, yet only manifests
with particular Linux kernel versions.  It may be that many network
admins need to change their configuration, but this would be a political
issue, not something end-users should be forced to bear the brunt of.

Once again, this problem has nothing to do with my local hardware, and
occurs consistently with the same exact sites on the Internet (one
example: slashdot.org).  Doing  echo "0" >
/proc/sys/net/ipv4/tcp_window_scaling  fixes the issue completely.



http://en.opensuse.org/SDB:Problem_with_establishing_TCP/IP_connection_in_openSUSE_10.2

http://www.mail-archive.com/debian-doc@lists.debian.org/msg09314.html

http://www.penlug.org/twiki/bin/view/Main/CiscoVpn

"The recent 2.6.7 kernel's TCP changes are only exposing a pre-existing
problem with a large number of poor/broken firewall implementations.
These are clueless firewall implementations that strip or alter the TCP
options. When the options are modified, TCP gets busted. The reason this
matters now, is that when the linux kernel proposes a new window
scaling, it quite sensibly expects that the other side will receive the
same initial SYN request that it actually sent. If there is a clueless
firewall in the middle that corrupts or strips it, then the window we
send is not correctly scaled, and the result is that the other side
thinks that there is not really enough space to send. The current
proliferation of these clueless firewall implementations resulted in a
proposal on the linux kernel mailing list by Stephen Hemminger, where he
proposes a patch that will avoid sending window scaling that is big
enough to break in these cases unless the tcp_rmem has already been
increased. The aim is to keep the default configuration from blowing in
a corrupt world. For more details on the lively ensuing discussion of
Stephen's patch, search for the following string in the archive pages
listed below: 

  "[PATCH] fix tcp_default_win_scale." 

  See the Jul 1 to Jul 7, 2004 lkml archives. Also the Jul 8 to Jul 15,
  2004 lkml archives 

  There's also an entertaining explanation from James Janssen, a Gentoo
  user, here.
"