Commit af772144 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: introduce TCP_PAWS_WRAP 



tcp_paws_check() uses TCP_PAWS_24DAYS constant to detect if TCP TS
values might have wrapped after a long idle period.

This mechanism is described in RFC 7323 5.5 (Outdated Timestamps)

TCP_PAWS_24DAYS value was based on the assumption of a clock
of 1 Khz.

As we want to adopt a 1 Mhz clock in the future, we reduce
this constant.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3d44de9a

include/net/tcp.h

+7 −2
Original line number Diff line number Diff line
@@ -166,7 +166,12 @@ static_assert((1 << ATO_BITS) > TCP_DELACK_MAX); 
#define MAX_TCP_KEEPCNT		127

#define MAX_TCP_SYNCNT		127



#define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)

/* Ensure that TCP PAWS checks are relaxed after ~2147 seconds

 * to avoid overflows. This assumes a clock smaller than 1 Mhz.

 * Default clock is 1 Khz, tcp_usec_ts uses 1 Mhz.

 */

#define TCP_PAWS_WRAP (INT_MAX / USEC_PER_SEC)



#define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated

					 * after this time. It should be equal

					 * (or greater than) TCP_TIMEWAIT_LEN
@@ -1619,7 +1624,7 @@ static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt, 
	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)

		return true;

	if (unlikely(!time_before32(ktime_get_seconds(),

				    rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS)))

				    rx_opt->ts_recent_stamp + TCP_PAWS_WRAP)))

		return true;

	/*

	 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,