netdev - Re: [PATCH net-next] tcp: be more strict before accepting ECN negociation

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Date:	Fri, 04 May 2012 22:49:06 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Rick Jones <rick.jones2@...com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Perry Lorier <perryl@...gle.com>,
	Matt Mathis <mattmathis@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	Tom Herbert <therbert@...gle.com>,
	Wilmer van der Gaast <wilmer@...gle.com>,
	Dave Täht <dave.taht@...ferbloat.net>,
	Ankur Jain <jankur@...gle.com>
Subject: Re: [PATCH net-next] tcp: be more strict before accepting ECN
 negociation

On Fri, 2012-05-04 at 13:36 -0700, Rick Jones wrote:
> On 05/04/2012 01:20 PM, Rick Jones wrote:
> > True, I'm looking at more than the ECN bits, but in the 90 minutes the
> > tcpdump has been running there have been no packets with the any of the
> > 8 bits at ip[1] being 1 anyway :) Netperf.org doesn't get a massive
> > quantity of traffic. It may go the entire week-end or longer without
> > seeing such a packet.
> 
> I see fate is working as intended, or someone decided to try to feed me 
> my words :) for within 6 minutes of my sending the above I got:
> 
> 13:26:16.866007 IP (tos 0x3,CE, ttl 41, id 28850, offset 0, flags [DF], 
> proto TCP (6), length 64)
>      somesystemin.de.55363 > www.netperf.org.www: Flags [S], cksum 
> 0x4cfc (correct), seq 304457158, win 65535, options [mss 1460,nop,wscale 
> 3,nop,nop,TS val 288116308 ecr 0,sackOK,eol], length 0
> 13:26:17.831880 IP (tos 0x3,CE, ttl 41, id 6911, offset 0, flags [DF], 
> proto TCP (6), length 64)
>      somesystemin.de.55367 > www.netperf.org.www: Flags [S], cksum 
> 0x17aa (correct), seq 586073737, win 65535, options [mss 1460,nop,wscale 
> 3,nop,nop,TS val 288117270 ecr 0,sackOK,eol], length 0
> 13:26:17.831929 IP (tos 0x3,CE, ttl 41, id 28924, offset 0, flags [DF], 
> proto TCP (6), length 64)
>      somesystemin.de.55368 > www.netperf.org.www: Flags [S], cksum 
> 0x07cc (correct), seq 1513398047, win 65535, options [mss 
> 1460,nop,wscale 3,nop,nop,TS val 288117271 ecr 0,sackOK,eol], length 0
> 13:26:17.831952 IP (tos 0x3,CE, ttl 41, id 2494, offset 0, flags [DF], 
> proto TCP (6), length 64)
>      somesystemin.de.55366 > www.netperf.org.www: Flags [S], cksum 
> 0x75f4 (correct), seq 1153058420, win 65535, options [mss 
> 1460,nop,wscale 3,nop,nop,TS val 288117270 ecr 0,sackOK,eol], length 0
> 13:26:17.832177 IP (tos 0x3,CE, ttl 41, id 6854, offset 0, flags [DF], 
> proto TCP (6), length 64)
>      somesystemin.de.55365 > www.netperf.org.www: Flags [S], cksum 
> 0xfca0 (correct), seq 2332522875, win 65535, options [mss 
> 1460,nop,wscale 3,nop,nop,TS val 288117270 ecr 0,sackOK,eol], length 0
> 13:26:17.832239 IP (tos 0x3,CE, ttl 41, id 64733, offset 0, flags [DF], 
> proto TCP (6), length 64)
>      somesystemin.de.55364 > www.netperf.org.www: Flags [S], cksum 
> 0x7414 (correct), seq 1544827132, win 65535, options [mss 
> 1460,nop,wscale 3,nop,nop,TS val 288117270 ecr 0,sackOK,eol], length 0
> 13:26:38.649126 IP (tos 0x3,CE, ttl 41, id 9860, offset 0, flags [DF], 
> proto TCP (6), length 64)
>      somesystemin.de.55369 > www.netperf.org.www: Flags [S], cksum 
> 0x6270 (correct), seq 683091230, win 65535, options [mss 1460,nop,wscale 
> 3,nop,nop,TS val 288137968 ecr 0,sackOK,eol], length 0
> 13:26:39.417589 IP (tos 0x3,CE, ttl 41, id 13478, offset 0, flags [DF], 
> proto TCP (6), length 64)
>      somesystemin.de.55370 > www.netperf.org.www: Flags [S], cksum 
> 0x2862 (correct), seq 3168323595, win 65535, options [mss 
> 1460,nop,wscale 3,nop,nop,TS val 288138734 ecr 0,sackOK,eol], length 0
> 
> rick

Interesting indeed ;)

Did you check if it was spoofed ?

(did the 3WHS really completed)



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