From 86791bbfe5ed7b275be040cfeff049a1624af1b7 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 17 Jul 2012 10:13:05 +0200 Subject: 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 Cc: Kiran Kumar Kella Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- Documentation/networking/ip-sysctl.txt | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'Documentation') diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 7d4ecaa..890fce9 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -534,6 +534,11 @@ tcp_thin_dupack - BOOLEAN Documentation/networking/tcp-thin.txt Default: 0 +tcp_challenge_ack_limit - INTEGER + Limits number of Challenge ACK sent per second, as recommended + in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks) + Default: 100 + UDP variables: udp_mem - vector of 3 INTEGERs: min, pressure, max -- cgit v1.1