1 files changed, 17 insertions, 14 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index eb7f82ebf4a..bef9f04c22b 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -817,7 +817,7 @@ __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
 	__u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
 
 	if (!cwnd)
-		cwnd = rfc3390_bytes_to_packets(tp->mss_cache);
+		cwnd = TCP_INIT_CWND;
 	return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
 }
 
@@ -1222,7 +1222,7 @@ static int tcp_check_dsack(struct sock *sk, struct sk_buff *ack_skb,
 	}
 
 	/* D-SACK for already forgotten data... Do dumb counting. */
-	if (dup_sack &&
+	if (dup_sack && tp->undo_marker && tp->undo_retrans &&
 	    !after(end_seq_0, prior_snd_una) &&
 	    after(end_seq_0, tp->undo_marker))
 		tp->undo_retrans--;
@@ -1299,7 +1299,8 @@ static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
 
 	/* Account D-SACK for retransmitted packet. */
 	if (dup_sack && (sacked & TCPCB_RETRANS)) {
-		if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
+		if (tp->undo_marker && tp->undo_retrans &&
+		    after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
 			tp->undo_retrans--;
 		if (sacked & TCPCB_SACKED_ACKED)
 			state->reord = min(fack_count, state->reord);
@@ -2658,7 +2659,7 @@ static void DBGUNDO(struct sock *sk, const char *msg)
 #define DBGUNDO(x...) do { } while (0)
 #endif
 
-static void tcp_undo_cwr(struct sock *sk, const int undo)
+static void tcp_undo_cwr(struct sock *sk, const bool undo_ssthresh)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
@@ -2670,14 +2671,13 @@ static void tcp_undo_cwr(struct sock *sk, const int undo)
 		else
 			tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1);
 
-		if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
+		if (undo_ssthresh && tp->prior_ssthresh > tp->snd_ssthresh) {
 			tp->snd_ssthresh = tp->prior_ssthresh;
 			TCP_ECN_withdraw_cwr(tp);
 		}
 	} else {
 		tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
 	}
-	tcp_moderate_cwnd(tp);
 	tp->snd_cwnd_stamp = tcp_time_stamp;
 }
 
@@ -2698,7 +2698,7 @@ static int tcp_try_undo_recovery(struct sock *sk)
 		 * or our original transmission succeeded.
 		 */
 		DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
-		tcp_undo_cwr(sk, 1);
+		tcp_undo_cwr(sk, true);
 		if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
 			mib_idx = LINUX_MIB_TCPLOSSUNDO;
 		else
@@ -2725,7 +2725,7 @@ static void tcp_try_undo_dsack(struct sock *sk)
 
 	if (tp->undo_marker && !tp->undo_retrans) {
 		DBGUNDO(sk, "D-SACK");
-		tcp_undo_cwr(sk, 1);
+		tcp_undo_cwr(sk, true);
 		tp->undo_marker = 0;
 		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO);
 	}
@@ -2778,7 +2778,7 @@ static int tcp_try_undo_partial(struct sock *sk, int acked)
 		tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
 
 		DBGUNDO(sk, "Hoe");
-		tcp_undo_cwr(sk, 0);
+		tcp_undo_cwr(sk, false);
 		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);
 
 		/* So... Do not make Hoe's retransmit yet.
@@ -2807,7 +2807,7 @@ static int tcp_try_undo_loss(struct sock *sk)
 
 		DBGUNDO(sk, "partial loss");
 		tp->lost_out = 0;
-		tcp_undo_cwr(sk, 1);
+		tcp_undo_cwr(sk, true);
 		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO);
 		inet_csk(sk)->icsk_retransmits = 0;
 		tp->undo_marker = 0;
@@ -2821,8 +2821,11 @@ static int tcp_try_undo_loss(struct sock *sk)
 static inline void tcp_complete_cwr(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
-	tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
-	tp->snd_cwnd_stamp = tcp_time_stamp;
+	/* Do not moderate cwnd if it's already undone in cwr or recovery */
+	if (tp->undo_marker && tp->snd_cwnd > tp->snd_ssthresh) {
+		tp->snd_cwnd = tp->snd_ssthresh;
+		tp->snd_cwnd_stamp = tcp_time_stamp;
+	}
 	tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
 }
 
@@ -3349,7 +3352,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 						 net_invalid_timestamp()))
 					rtt_us = ktime_us_delta(ktime_get_real(),
 								last_ackt);
-				else if (ca_seq_rtt > 0)
+				else if (ca_seq_rtt >= 0)
 					rtt_us = jiffies_to_usecs(ca_seq_rtt);
 			}
 
@@ -3493,7 +3496,7 @@ static void tcp_undo_spur_to_response(struct sock *sk, int flag)
 	if (flag & FLAG_ECE)
 		tcp_ratehalving_spur_to_response(sk);
 	else
-		tcp_undo_cwr(sk, 1);
+		tcp_undo_cwr(sk, true);
 }
 
 /* F-RTO spurious RTO detection algorithm (RFC4138)