From: Eric Dumazet Date: Thu, 16 Dec 2010 22:08:34 +0000 (-0800) Subject: tcp: relax tcp_paws_check() X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=bc2ce894e113ed95b92541134b002fdc641e8080;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git 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 fc1ad92dfc4e363 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 Signed-off-by: David S. Miller --- diff --git a/include/net/tcp.h b/include/net/tcp.h index 3f227baee4be..2ab6c9c1c53a 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -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; }