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

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

From: Andrew Vagin <[email protected]>

[ 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 <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Alexey Kuznetsov <[email protected]>
Cc: James Morris <[email protected]>
Cc: Hideaki YOSHIFUJI <[email protected]>
Cc: Patrick McHardy <[email protected]>
Signed-off-by: Andrey Vagin <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 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) {


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