[PATCH 3.16 152/212] tcp: account for ts offset only if tsecr not zero

[Ben Hutchings]

3.16.44-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Alexey Kodanev <alexey.kodanev@xxxxxxxxxx>

commit eee2faabc63d863a129000b698a2bca54dff643d upstream.

We can get SYN with zero tsecr, don't apply offset in this case.

Fixes: ee684b6f2830 ("tcp: send packets with a socket timestamp")
Signed-off-by: Alexey Kodanev <alexey.kodanev@xxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/ipv4/tcp_minisocks.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -101,7 +101,8 @@ tcp_timewait_state_process(struct inet_t
 		tcp_parse_options(skb, &tmp_opt, 0, NULL);
 
 		if (tmp_opt.saw_tstamp) {
-			tmp_opt.rcv_tsecr	-= tcptw->tw_ts_offset;
+			if (tmp_opt.rcv_tsecr)
+				tmp_opt.rcv_tsecr -= tcptw->tw_ts_offset;
 			tmp_opt.ts_recent	= tcptw->tw_ts_recent;
 			tmp_opt.ts_recent_stamp	= tcptw->tw_ts_recent_stamp;
 			paws_reject = tcp_paws_reject(&tmp_opt, th->rst);