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>

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index cbe5b602a2d349fdeb1e878305f37b4da1e6cc86..99a22f44c32e1587a6bf4835b65c7a4314807aa8 100644 (file)
--- 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 */

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 5af2f04f885914491a7116c20056b3d2188d2d7d..bd18c65df4a9d9c2b66d8005f2cc4ff468140a73 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5362,6 +5362,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 {
        struct tcp_sock *tp = tcp_sk(sk);
 
+       skb_mstamp_get(&tp->tcp_mstamp);
        if (unlikely(!sk->sk_rx_dst))
                inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb);
        /*
@@ -5922,6 +5923,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 
        case TCP_SYN_SENT:
                tp->rx_opt.saw_tstamp = 0;
+               skb_mstamp_get(&tp->tcp_mstamp);
                queued = tcp_rcv_synsent_state_process(sk, skb, th);
                if (queued >= 0)
                        return queued;
@@ -5933,6 +5935,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
                return 0;
        }
 
+       skb_mstamp_get(&tp->tcp_mstamp);
        tp->rx_opt.saw_tstamp = 0;
        req = tp->fastopen_rsk;
        if (req) {