From: Eric Dumazet <edumazet@google.com>
Date: Tue, 17 Jul 2012 08:13:05 +0000 (+0200)
Subject: tcp: implement RFC 5961 3.2
X-Git-Tag: v3.2.37~10
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=61f69dc4e40e41b0018f00fa4aeb23d3239556fb;p=pandora-kernel.git

tcp: implement RFC 5961 3.2

[ Upstream commit 282f23c6ee343126156dd41218b22ece96d747e3 ]

Implement the RFC 5691 mitigation against Blind
Reset attack using RST bit.

Idea is to validate incoming RST sequence,
to match RCV.NXT value, instead of previouly accepted
window : (RCV.NXT <= SEG.SEQ < RCV.NXT+RCV.WND)

If sequence is in window but not an exact match, send
a "challenge ACK", so that the other part can resend an
RST with the appropriate sequence.

Add a new sysctl, tcp_challenge_ack_limit, to limit
number of challenge ACK sent per second.

Add a new SNMP counter to count number of challenge acks sent.
(netstat -s | grep TCPChallengeACK)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Kiran Kumar Kella <kkiran@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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