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Date:	Fri, 04 May 2012 14:01:42 -0700
From:	Rick Jones <>
To:	Eric Dumazet <>
CC:	David Miller <>,
	netdev <>,
	Perry Lorier <>,
	Matt Mathis <>,
	Yuchung Cheng <>,
	Neal Cardwell <>,
	Tom Herbert <>,
	Wilmer van der Gaast <>,
	Dave Täht <>,
	Ankur Jain <>
Subject: Re: [PATCH net-next] tcp: be more strict before accepting ECN negociation

> Interesting indeed ;)
> Did you check if it was spoofed ?
> (did the 3WHS really completed)

Well, the tcpdump command was still:

tcpdump -i eth0 -vvv '(tcp[tcpflags]&  tcp-syn != 0)&&  (ip[1] != 0x0)'

I didn't see any SYN|ACKs go out, but would have had to set 
ECT for me to see a SYN|ACK going out.   FWIW, this is on a 2.6.31-15 
(Ubuntu) kernel with net.ipv4.tcp_ecn = 2 and I don't think the SYNs 
themselves were negotiating ECN:

13:26:16.866007 IP (tos 0x3,CE, ttl 41, id 28850, offset 0, flags [DF], 
proto TCP (6), length 64) > Flags [S], cksum 
0x4cfc (correct), seq 304457158, win 65535, options [mss 1460,nop,wscale

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