1 files changed, 32 insertions, 15 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fec8a7a4dbaf..378ca8a086a3 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1851,19 +1851,22 @@ static inline u32 tcp_cwnd_min(const struct sock *sk)
 }
 
 /* Decrease cwnd each second ack. */
-static void tcp_cwnd_down(struct sock *sk)
+static void tcp_cwnd_down(struct sock *sk, int flag)
 {
         struct tcp_sock *tp = tcp_sk(sk);
         int decr = tp->snd_cwnd_cnt + 1;
 
-        tp->snd_cwnd_cnt = decr&1;
-        decr >>= 1;
+        if ((flag&FLAG_FORWARD_PROGRESS) ||
+            (IsReno(tp) && !(flag&FLAG_NOT_DUP))) {
+                tp->snd_cwnd_cnt = decr&1;
+                decr >>= 1;
 
-        if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
-                tp->snd_cwnd -= decr;
+                if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
+                        tp->snd_cwnd -= decr;
 
-        tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
-        tp->snd_cwnd_stamp = tcp_time_stamp;
+                tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
+                tp->snd_cwnd_stamp = tcp_time_stamp;
+        }
 }
 
 /* Nothing was retransmitted or returned timestamp is less
@@ -2060,7 +2063,7 @@ static void tcp_try_to_open(struct sock *sk, int flag)
                 }
                 tcp_moderate_cwnd(tp);
         } else {
-                tcp_cwnd_down(sk);
+                tcp_cwnd_down(sk, flag);
         }
 }
 
@@ -2109,7 +2112,10 @@ tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
 {
         struct inet_connection_sock *icsk = inet_csk(sk);
         struct tcp_sock *tp = tcp_sk(sk);
-        int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
+        int is_dupack = (tp->snd_una == prior_snd_una &&
+                         (!(flag&FLAG_NOT_DUP) ||
+                          ((flag&FLAG_DATA_SACKED) &&
+                           (tp->fackets_out > tp->reordering))));
 
         /* Some technical things:
          * 1. Reno does not count dupacks (sacked_out) automatically. */
@@ -2260,7 +2266,7 @@ tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
 
         if (is_dupack || tcp_head_timedout(sk))
                 tcp_update_scoreboard(sk);
-        tcp_cwnd_down(sk);
+        tcp_cwnd_down(sk, flag);
         tcp_xmit_retransmit_queue(sk);
 }
 
@@ -2490,12 +2496,23 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
                 tcp_ack_update_rtt(sk, acked, seq_rtt);
                 tcp_ack_packets_out(sk);
 
-                /* Is the ACK triggering packet unambiguous? */
-                if (acked & FLAG_RETRANS_DATA_ACKED)
-                        last_ackt = net_invalid_timestamp();
+                if (ca_ops->pkts_acked) {
+                        s32 rtt_us = -1;
+
+                        /* Is the ACK triggering packet unambiguous? */
+                        if (!(acked & FLAG_RETRANS_DATA_ACKED)) {
+                                /* High resolution needed and available? */
+                                if (ca_ops->flags & TCP_CONG_RTT_STAMP &&
+                                    !ktime_equal(last_ackt,
+                                                 net_invalid_timestamp()))
+                                        rtt_us = ktime_us_delta(ktime_get_real(),
+                                                                last_ackt);
+                                else if (seq_rtt > 0)
+                                        rtt_us = jiffies_to_usecs(seq_rtt);
+                        }
 
-                if (ca_ops->pkts_acked)
-                        ca_ops->pkts_acked(sk, pkts_acked, last_ackt);
+                        ca_ops->pkts_acked(sk, pkts_acked, rtt_us);
+                }
         }
 
 #if FASTRETRANS_DEBUG > 0