1 files changed, 19 insertions, 28 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 730bc44dbad9..6527f61f59ff 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -980,7 +980,6 @@ static void tcp_update_skb_after_send(struct sock *sk, struct sk_buff *skb,
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
-	skb->skb_mstamp_ns = tp->tcp_wstamp_ns;
 	if (sk->sk_pacing_status != SK_PACING_NONE) {
 		unsigned long rate = sk->sk_pacing_rate;
 
@@ -1028,7 +1027,9 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
 
 	BUG_ON(!skb || !tcp_skb_pcount(skb));
 	tp = tcp_sk(sk);
-
+	prior_wstamp = tp->tcp_wstamp_ns;
+	tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache);
+	skb->skb_mstamp_ns = tp->tcp_wstamp_ns;
 	if (clone_it) {
 		TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
 			- tp->snd_una;
@@ -1045,11 +1046,6 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
 			return -ENOBUFS;
 	}
 
-	prior_wstamp = tp->tcp_wstamp_ns;
-	tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache);
-
-	skb->skb_mstamp_ns = tp->tcp_wstamp_ns;
-
 	inet = inet_sk(sk);
 	tcb = TCP_SKB_CB(skb);
 	memset(&opts, 0, sizeof(opts));
@@ -2937,12 +2933,16 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
 		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
 	}
 
+	/* To avoid taking spuriously low RTT samples based on a timestamp
+	 * for a transmit that never happened, always mark EVER_RETRANS
+	 */
+	TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
+
 	if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
 		tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
 				  TCP_SKB_CB(skb)->seq, segs, err);
 
 	if (likely(!err)) {
-		TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
 		trace_tcp_retransmit_skb(sk, skb);
 	} else if (err != -EBUSY) {
 		NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs);
@@ -2963,13 +2963,12 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
 #endif
 		TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
 		tp->retrans_out += tcp_skb_pcount(skb);
-
-		/* Save stamp of the first retransmit. */
-		if (!tp->retrans_stamp)
-			tp->retrans_stamp = tcp_skb_timestamp(skb);
-
 	}
 
+	/* Save stamp of the first (attempted) retransmit. */
+	if (!tp->retrans_stamp)
+		tp->retrans_stamp = tcp_skb_timestamp(skb);
+
 	if (tp->undo_retrans < 0)
 		tp->undo_retrans = 0;
 	tp->undo_retrans += tcp_skb_pcount(skb);
@@ -3750,7 +3749,7 @@ void tcp_send_probe0(struct sock *sk)
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct net *net = sock_net(sk);
-	unsigned long probe_max;
+	unsigned long timeout;
 	int err;
 
 	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
@@ -3762,26 +3761,18 @@ void tcp_send_probe0(struct sock *sk)
 		return;
 	}
 
+	icsk->icsk_probes_out++;
 	if (err <= 0) {
 		if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
 			icsk->icsk_backoff++;
-		icsk->icsk_probes_out++;
-		probe_max = TCP_RTO_MAX;
+		timeout = tcp_probe0_when(sk, TCP_RTO_MAX);
 	} else {
 		/* If packet was not sent due to local congestion,
-		 * do not backoff and do not remember icsk_probes_out.
-		 * Let local senders to fight for local resources.
-		 *
-		 * Use accumulated backoff yet.
+		 * Let senders fight for local resources conservatively.
 		 */
-		if (!icsk->icsk_probes_out)
-			icsk->icsk_probes_out = 1;
-		probe_max = TCP_RESOURCE_PROBE_INTERVAL;
-	}
-	tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
-			     tcp_probe0_when(sk, probe_max),
-			     TCP_RTO_MAX,
-			     NULL);
+		timeout = TCP_RESOURCE_PROBE_INTERVAL;
+	}
+	tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, TCP_RTO_MAX, NULL);
 }
 
 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)