tcp: add tp->tcp_mstamp field

We want to use precise timestamps in TCP stack, but we do not
want to call possibly expensive kernel time services too often.

tp->tcp_mstamp is guaranteed to be updated once per incoming packet.

We will use it in the following patches, removing specific
skb_mstamp_get() calls, and removing ack_time from
struct tcp_sacktag_state.

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

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index cbe5b602a2d3..99a22f44c32e 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -240,6 +240,7 @@ struct tcp_sock {
         u32     tlp_high_seq;   /* snd_nxt at the time of TLP retransmit. */
 
 /* RTT measurement */
+        struct skb_mstamp tcp_mstamp; /* most recent packet received/sent */
         u32     srtt_us;        /* smoothed round trip time << 3 in usecs */
         u32     mdev_us;        /* medium deviation                     */
         u32     mdev_max_us;    /* maximal mdev for the last rtt period */