tcp: use tp->tcp_mstamp in output path

Idea is to later convert tp->tcp_mstamp to a full u64 counter
using usec resolution, so that we can later have fine
grained TCP TS clock (RFC 7323), regardless of HZ value.

We try to refresh tp->tcp_mstamp only when necessary.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 86934bcf685a..ec7c5473c788 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -339,7 +339,7 @@ static void tcp_probe_timer(struct sock *sk)
          */
         start_ts = tcp_skb_timestamp(tcp_send_head(sk));
         if (!start_ts)
-                skb_mstamp_get(&tcp_send_head(sk)->skb_mstamp);
+                tcp_send_head(sk)->skb_mstamp = tp->tcp_mstamp;
         else if (icsk->icsk_user_timeout &&
                  (s32)(tcp_time_stamp - start_ts) > icsk->icsk_user_timeout)
                 goto abort;
@@ -561,6 +561,7 @@ void tcp_write_timer_handler(struct sock *sk)
                 goto out;
         }
 
+        skb_mstamp_get(&tcp_sk(sk)->tcp_mstamp);
         event = icsk->icsk_pending;
 
         switch (event) {