Commit bc2ce894 authored Dec 16, 2010 by Eric Dumazet Committed by David S. Miller Dec 16, 2010

tcp: relax tcp_paws_check()

Some windows versions have wrong RFC1323 implementations, with SYN and
SYNACKS messages containing zero tcp timestamps.

We relaxed in commit fc1ad92d the passive connection case
(Windows connects to a linux machine), but the reverse case (linux
connects to a Windows machine) has an analogue problem when tsvals from
windows machine are 'negative' (high order bit set) : PAWS triggers and
we drops incoming messages.

Fix this by making zero ts_recent value special, allowing frame to be
processed.

Based on a report and initial patch from Dmitiy Balakin

Bugzilla reference : https://bugzilla.kernel.org/show_bug.cgi?id=24842



Reported-by:  <dmitriy.balakin@nicneiron.ru>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 44345724

include/net/tcp.h

+7 −1

Original line number	Diff line number	Diff line
		@@ -1038,7 +1038,13 @@ static inline int tcp_paws_check(const struct tcp_options_received *rx_opt,
		return 1;
		if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
		return 1;

		/*
		* Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
		* then following tcp messages have valid values. Ignore 0 value,
		* or else 'negative' tsval might forbid us to accept their packets.
		*/
		if (!rx_opt->ts_recent)
		return 1;
		return 0;
		}

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