I was posting about problems with TCP lately.
It might still be a problem with the kernel and not the firewall.
I am having problems with machines on the same LAN.
Here is what I do to reproduce (sometimes works, sometimes not)
# ssh user@xxxxxxxxxxx
# su -
[choosing detailed interface statistics on a busy interface]
It shows the statistics nice, but after a few seconds it
gets seriously lagged, even my keystrokes to exit work with a lag.
It also happens eg. when removing a lot of files in midnight
commander via ssh. FTP transfers also suffer
I am not doing andy filtering or mangling on the way between the
I have this behaviour with a 2.6.8-rc1 kernel and 2.6.7+ kernels
and alos with 2.6.8-rc1 and 2.4.26 kernel.
I suspect changes in 2.6.7-8 devel cycle to have changed something
I made a tcpdump -v (human readable) of the problematic connection:
It is a connection between 22.214.171.124 (2.6.8-rc1) and 126.96.36.199
(2.4.26) Same effects are seen between 188.8.131.52 and 184.108.40.206
so it is not a router issue. Follow what's below:
16:17:01.669931: logging on with ssh, typing commands, waiting for
the problem to appear.
Notice tcpdump's bad tcp checksums at the beginning!
16:17:19.195772: 2.6.8-rc1 kernel sends the first packet with a very
small win and we have a problem. (is it SWS?)
in the mean time i am trying to get out of iptraf and log out
16:17:40.372086: closing the connection, notice the tcp bad checksums
2.4.26 sysctls are as default
2.6.8 sysctls are as default except that:
tcp_windows_scaling is 0
tcp_bic is 0
tcp_sack is 0
tcp_fack is 0
I tried to zero these options to fix the problem, although with these
enabled the problems still exists.
What would you suggest?