[net-next,01/15] 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>
---
 net/ipv4/tcp_ipv4.c     |  1 +
 net/ipv4/tcp_output.c   | 21 +++++++++++----------
 net/ipv4/tcp_recovery.c |  1 -
 net/ipv4/tcp_timer.c    |  3 ++-
 4 files changed, 14 insertions(+), 12 deletions(-)

On Tue, May 16, 2017 at 5:00 PM, Eric Dumazet <edumazet@google.com> wrote:
> 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>

> ---
>  net/ipv4/tcp_ipv4.c     |  1 +
>  net/ipv4/tcp_output.c   | 21 +++++++++++----------
>  net/ipv4/tcp_recovery.c |  1 -
>  net/ipv4/tcp_timer.c    |  3 ++-
>  4 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index 5ab2aac5ca191075383fc75214da816873bb222c..d8fe25db79f223e3fde85882effd2ac6ec15f8ca 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -483,6 +483,7 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
>                 skb = tcp_write_queue_head(sk);
>                 BUG_ON(!skb);
>
> +               skb_mstamp_get(&tp->tcp_mstamp);
>                 remaining = icsk->icsk_rto -
>                             min(icsk->icsk_rto,
>                                 tcp_time_stamp - tcp_skb_timestamp(skb));
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index a32172d69a03cbe76b45ec3094222f6c3a73e27d..4c8a6eaba6b39a2aea061dd6857ed8df954c5ca2 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);
>         }
>  }
> diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c
> index 362b8c75bfab44cf87c2a01398a146a271bc1119..cd72b3d3879e88181c8a4639f0334a24e4cda852 100644
> --- a/net/ipv4/tcp_recovery.c
> +++ b/net/ipv4/tcp_recovery.c
> @@ -166,7 +166,6 @@ void tcp_rack_reo_timeout(struct sock *sk)
>         u32 timeout, prior_inflight;
>
>         prior_inflight = tcp_packets_in_flight(tp);
> -       skb_mstamp_get(&tp->tcp_mstamp);
>         tcp_rack_detect_loss(sk, &timeout);
>         if (prior_inflight != tcp_packets_in_flight(tp)) {
>                 if (inet_csk(sk)->icsk_ca_state != TCP_CA_Recovery) {
> diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
> index 86934bcf685a65ec3af3d22f1801ffa33eea76e2..ec7c5473c788d77ae459b38492f2f2606d00d1ba 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) {
> --
> 2.13.0.303.g4ebf302169-goog
>