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, 11 insertions, 10 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index a32172d69a03..4c8a6eaba6b3 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -997,8 +997,8 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
         BUG_ON(!skb || !tcp_skb_pcount(skb));
         tp = tcp_sk(sk);
 
+        skb->skb_mstamp = tp->tcp_mstamp;
         if (clone_it) {
-                skb_mstamp_get(&skb->skb_mstamp);
                 TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
                         - tp->snd_una;
                 tcp_rate_skb_sent(sk, skb);
@@ -1906,7 +1906,6 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
         const struct inet_connection_sock *icsk = inet_csk(sk);
         u32 age, send_win, cong_win, limit, in_flight;
         struct tcp_sock *tp = tcp_sk(sk);
-        struct skb_mstamp now;
         struct sk_buff *head;
         int win_divisor;
 
@@ -1962,8 +1961,8 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
         }
 
         head = tcp_write_queue_head(sk);
-        skb_mstamp_get(&now);
-        age = skb_mstamp_us_delta(&now, &head->skb_mstamp);
+
+        age = skb_mstamp_us_delta(&tp->tcp_mstamp, &head->skb_mstamp);
         /* If next ACK is likely to come too late (half srtt), do not defer */
         if (age < (tp->srtt_us >> 4))
                 goto send_now;
@@ -2280,6 +2279,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
         }
 
         max_segs = tcp_tso_segs(sk, mss_now);
+        skb_mstamp_get(&tp->tcp_mstamp);
         while ((skb = tcp_send_head(sk))) {
                 unsigned int limit;
 
@@ -2291,7 +2291,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 
                 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
                         /* "skb_mstamp" is used as a start point for the retransmit timer */
-                        skb_mstamp_get(&skb->skb_mstamp);
+                        skb->skb_mstamp = tp->tcp_mstamp;
                         goto repair; /* Skip network transmission */
                 }
 
@@ -2879,7 +2879,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
                      skb_headroom(skb) >= 0xFFFF)) {
                 struct sk_buff *nskb;
 
-                skb_mstamp_get(&skb->skb_mstamp);
+                skb->skb_mstamp = tp->tcp_mstamp;
                 nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
                 err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
                              -ENOBUFS;
@@ -3095,7 +3095,7 @@ void tcp_send_active_reset(struct sock *sk, gfp_t priority)
         skb_reserve(skb, MAX_TCP_HEADER);
         tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
                              TCPHDR_ACK | TCPHDR_RST);
-        skb_mstamp_get(&skb->skb_mstamp);
+        skb_mstamp_get(&tcp_sk(sk)->tcp_mstamp);
         /* Send it off. */
         if (tcp_transmit_skb(sk, skb, 0, priority))
                 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
@@ -3453,7 +3453,8 @@ int tcp_connect(struct sock *sk)
                 return -ENOBUFS;
 
         tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
-        tp->retrans_stamp = tcp_time_stamp;
+        skb_mstamp_get(&tp->tcp_mstamp);
+        tp->retrans_stamp = tp->tcp_mstamp.stamp_jiffies;
         tcp_connect_queue_skb(sk, buff);
         tcp_ecn_send_syn(sk, buff);
 
@@ -3572,7 +3573,6 @@ void tcp_send_ack(struct sock *sk)
         skb_set_tcp_pure_ack(buff);
 
         /* Send it off, this clears delayed acks for us. */
-        skb_mstamp_get(&buff->skb_mstamp);
         tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
 }
 EXPORT_SYMBOL_GPL(tcp_send_ack);
@@ -3606,15 +3606,16 @@ static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
          * send it.
          */
         tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
-        skb_mstamp_get(&skb->skb_mstamp);
         NET_INC_STATS(sock_net(sk), mib);
         return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
 }
 
+/* Called from setsockopt( ... TCP_REPAIR ) */
 void tcp_send_window_probe(struct sock *sk)
 {
         if (sk->sk_state == TCP_ESTABLISHED) {
                 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
+                skb_mstamp_get(&tcp_sk(sk)->tcp_mstamp);
                 tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
         }
 }