tcp: export data delivery rate

This commit export two new fields in struct tcp_info:

  tcpi_delivery_rate: The most recent goodput, as measured by
    tcp_rate_gen(). If the socket is limited by the sending
    application (e.g., no data to send), it reports the highest
    measurement instead of the most recent. The unit is bytes per
    second (like other rate fields in tcp_info).

  tcpi_delivery_rate_app_limited: A boolean indicating if the goodput
    was measured when the socket's throughput was limited by the
    sending application.

This delivery rate information can be useful for applications that
want to know the current throughput the TCP connection is seeing,
e.g. adaptive bitrate video streaming. It can also be very useful for
debugging or troubleshooting.

Signed-off-by: Van Jacobson <vanj@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Nandita Dukkipati <nanditad@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 21 insertions, 2 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 2250f891f931..f253e5019d22 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2712,7 +2712,7 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info)
 {
         const struct tcp_sock *tp = tcp_sk(sk); /* iff sk_type == SOCK_STREAM */
         const struct inet_connection_sock *icsk = inet_csk(sk);
-        u32 now = tcp_time_stamp;
+        u32 now = tcp_time_stamp, intv;
         unsigned int start;
         int notsent_bytes;
         u64 rate64;
@@ -2802,6 +2802,15 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info)
         info->tcpi_min_rtt = tcp_min_rtt(tp);
         info->tcpi_data_segs_in = tp->data_segs_in;
         info->tcpi_data_segs_out = tp->data_segs_out;
+
+        info->tcpi_delivery_rate_app_limited = tp->rate_app_limited ? 1 : 0;
+        rate = READ_ONCE(tp->rate_delivered);
+        intv = READ_ONCE(tp->rate_interval_us);
+        if (rate && intv) {
+                rate64 = (u64)rate * tp->mss_cache * USEC_PER_SEC;
+                do_div(rate64, intv);
+                put_unaligned(rate64, &info->tcpi_delivery_rate);
+        }
 }
 EXPORT_SYMBOL_GPL(tcp_get_info);
 
diff --git a/net/ipv4/tcp_rate.c b/net/ipv4/tcp_rate.c
index 52ff84be59ab..9be1581a5a08 100644
--- a/net/ipv4/tcp_rate.c
+++ b/net/ipv4/tcp_rate.c
@@ -149,12 +149,22 @@ void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
          * for connections suffer heavy or prolonged losses.
          */
         if (unlikely(rs->interval_us < tcp_min_rtt(tp))) {
-                rs->interval_us = -1;
                 if (!rs->is_retrans)
                         pr_debug("tcp rate: %ld %d %u %u %u\n",
                                  rs->interval_us, rs->delivered,
                                  inet_csk(sk)->icsk_ca_state,
                                  tp->rx_opt.sack_ok, tcp_min_rtt(tp));
+                rs->interval_us = -1;
+                return;
+        }
+
+        /* Record the last non-app-limited or the highest app-limited bw */
+        if (!rs->is_app_limited ||
+            ((u64)rs->delivered * tp->rate_interval_us >=
+             (u64)tp->rate_delivered * rs->interval_us)) {
+                tp->rate_delivered = rs->delivered;
+                tp->rate_interval_us = rs->interval_us;
+                tp->rate_app_limited = rs->is_app_limited;
         }
 }