Problems with ipv4 part of Kernels post-2.6.16

[Rogério Brito <rbrito@ime.usp.br>]

Hi, John, David and others developers.

I have been trying to keep up with the kernel releases (not only the
-rc ones, but also some -mm's) and I noticed something quite strange:
with some post 2.6.16 kernels (say, 2.6.17), I can't access (from where
I am) the site www.everymac.com, while I can access other sites.

This has made me quite curious, because just booting back with a
2.6.16.x kernel, I could access it, which, of course, led me to think
this was a problem with the networking part of the kernel.

Well, to cut a long story short, yesterday I decided to learn how to use
git, grabbed Linus's tree and started a bisection session.

After 12 recompilations, I found the following patch being the first
suspect (sorry for the line wrapping, but I copied this one from one
console to another, since I don't know how to generate it again with
git):

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
rbrito@dumont:/usr/local/media/progs/linux/kernel/linux-git$ git bisect
good
7b4f4b5ebceab67ce440a61081a69f0265e17c2a is first bad commit
commit 7b4f4b5ebceab67ce440a61081a69f0265e17c2a
Author: John Heffner <jheffner@psc.edu>
Date:   Sat Mar 25 01:34:07 2006 -0800

    [TCP]: Set default max buffers from memory pool size

    This patch sets the maximum TCP buffer sizes (available to automatic
    buffer tuning, not to setsockopt) based on the TCP memory pool size.
    The maximum sndbuf and rcvbuf each will be up to 4 MB, but no more
    than 1/128 of the memory pressure threshold.

    Signed-off-by: John Heffner <jheffner@psc.edu>
    Signed-off-by: David S. Miller <davem@davemloft.net>

:040000 040000 514849b6a38c5fb671f3aeae1c0108a0e8e897dc
3b912fd10db444b22262f995fac99f2851363531 M      net
rbrito@dumont:/usr/local/media/progs/linux/kernel/linux-git$
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

I'm currently connected to my provider via cable modem and I'm assigned
an IP address via DHCP (actually, I'm using a D-Link DI-524 router in
between, but I already tested *without* the router in the middle and the
problem remains). The contents of my /etc/sysctl.conf file are attached.

My userspace is Debian's testing/etch, regularly upgraded every day. My
system is a Duron 1.1GHz, with 512MB of RAM and a KT133 (VIA) chipset,
with the network card being a Realtek RTL8139.

I would like to point out that this has prevented me from using/testing
other newer kernels. :-(

If anything else is required, please, don't hesitate to ask. I will try
my best to use any patches that may seem relevant, until we can point
out what may be happening.


Thanks, Rogério Brito.

P.S.: Please, I'm not (currently) subscribed to any mailing list.  I'd
appreciate if the CCs weren't trimmed.
-- 
Rogério Brito : rbrito@ime.usp.br : http://www.ime.usp.br/~rbrito
Homepage of the algorithms package : http://algorithms.berlios.de
Homepage on freshmeat:  http://freshmeat.net/projects/algorithms/

#
# /etc/sysctl.conf - Configuration file for setting system variables
# See sysctl.conf (5) for information.
#

# Uncomment the following to stop low-level messages on console
#kernel.printk = 4 4 1 7

##############################################################3
# Functions previously found in netbase
#
#net.ipv4.conf.default.forwarding=1
#net.ipv6.conf.default.forwarding=1

dev.rtc.max-user-freq=1024
net.ipv4.conf.all.accept_redirects=0
net.ipv4.conf.all.accept_source_route=0
net.ipv4.conf.all.log_martians=1
net.ipv4.conf.all.rp_filter=1
net.ipv4.conf.default.accept_redirects=0
net.ipv4.conf.default.accept_source_route=0
net.ipv4.conf.default.log_martians=1
net.ipv4.conf.default.rp_filter=1
net.ipv4.icmp_echo_ignore_broadcasts=1
net.ipv4.tcp_syncookies=1