[ 30/46] tcp: dont apply tsoffset if rcv_tsecr is zero

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrew Vagin <avagin@openvz.org>

[ Upstream commit e3e12028315749b7fa2edbc37328e5847be9ede9 ]

The zero value means that tsecr is not valid, so it's a special case.

tsoffset is used to customize tcp_time_stamp for one socket.
tsoffset is usually zero, it's used when a socket was moved from one
host to another host.

Currently this issue affects logic of tcp_rcv_rtt_measure_ts. Due to
incorrect value of rcv_tsecr, tcp_rcv_rtt_measure_ts sets rto to
TCP_RTO_MAX.

Reported-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/tcp_input.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3598,7 +3598,10 @@ static bool tcp_parse_aligned_timestamp(
 		++ptr;
 		tp->rx_opt.rcv_tsval = ntohl(*ptr);
 		++ptr;
-		tp->rx_opt.rcv_tsecr = ntohl(*ptr) - tp->tsoffset;
+		if (*ptr)
+			tp->rx_opt.rcv_tsecr = ntohl(*ptr) - tp->tsoffset;
+		else
+			tp->rx_opt.rcv_tsecr = 0;
 		return true;
 	}
 	return false;
@@ -3623,7 +3626,7 @@ static bool tcp_fast_parse_options(const
 	}
 
 	tcp_parse_options(skb, &tp->rx_opt, 1, NULL);
-	if (tp->rx_opt.saw_tstamp)
+	if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
 		tp->rx_opt.rcv_tsecr -= tp->tsoffset;
 
 	return true;
@@ -5376,7 +5379,7 @@ static int tcp_rcv_synsent_state_process
 	int saved_clamp = tp->rx_opt.mss_clamp;
 
 	tcp_parse_options(skb, &tp->rx_opt, 0, &foc);
-	if (tp->rx_opt.saw_tstamp)
+	if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
 		tp->rx_opt.rcv_tsecr -= tp->tsoffset;
 
 	if (th->ack) {