TCP: avoid to send keepalive probes if receiving data

RFC 1122 says the following:
...
  Keep-alive packets MUST only be sent when no data or
  acknowledgement packets have been received for the
  connection within an interval.
...

The acknowledgement packet is reseting the keepalive
timer but the data packet isn't. This patch fixes it by
checking the timestamp of the last received data packet
too when the keepalive timer expires.

Signed-off-by: Flavio Leitner <fleitner@redhat.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index c732be00606b..440a5c6004f6 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -517,7 +517,7 @@ static void tcp_keepalive_timer (unsigned long data)
         struct sock *sk = (struct sock *) data;
         struct inet_connection_sock *icsk = inet_csk(sk);
         struct tcp_sock *tp = tcp_sk(sk);
-        __u32 elapsed;
+        u32 elapsed;
 
         /* Only process if socket is not in use. */
         bh_lock_sock(sk);
@@ -554,7 +554,7 @@ static void tcp_keepalive_timer (unsigned long data)
         if (tp->packets_out || tcp_send_head(sk))
                 goto resched;
 
-        elapsed = tcp_time_stamp - tp->rcv_tstamp;
+        elapsed = keepalive_time_elapsed(tp);
 
         if (elapsed >= keepalive_time_when(tp)) {
                 if (icsk->icsk_probes_out >= keepalive_probes(tp)) {