Re: Weird IP options

From: David Ford (david@kalifornia.com)
Date: Mon Oct 09 2000 - 14:05:08 EST


Known FAQ, not a problem.

You compiled ECN into your kernel and a lot of sites out on the internet have a
broken stack implementation.

echo 0 > /proc/sys/net/ipv4/tcp_ecn

-d

BERNARD Sebastien wrote:

> Near the test3-4 kernel, I was not able to reach www.linuxtoday.com.
> After some debug, I find that is because my linux box is emitting syn packet
> with some really strange options (description of packet follows).
> Can anyone tell me if this behaviour is normal or not ?
>
> Here is the dialog from linuxtoday.
>
> 18:55:09.979659 eth0 > x.x.x.5.45762 > 63.236.72.248.www: S [ECN-Echo,CWR]
> 40
> 82580514:4082580514(0) win 5840 <mss 1460,sackOK,timestamp 27634996
> 0,nop,wscale
> 0> (DF)
> 18:55:10.166933 eth0 < 63.236.72.248.www > x.x.x.5.45762: R 0:0(0) ack
> 408258
> 0515 win 5840 <mss 1460,sackOK,timestamp 27634996 0,nop,wscale 0>
>
> It goes on like this a few times but it's not really useful.
>
> The packet is syn and the response is rst.
> I suspect the server/firewall/router to dislike the option of the packet.
> By the way this connection works perfectly with a windows server and a
> linux2.2 box.
> This problem is happening with other sites like www.sun.com, www.ibm.com,
> www.intel.com.
>
> PLEASE HELP !!!
> -
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