1 files changed, 26 insertions, 19 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index cd52ce0a2a85..7d5e59f688de 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2816,8 +2816,17 @@ static void tcp_process_loss(struct sock *sk, int flag, int num_dupack,
 	*rexmit = REXMIT_LOST;
 }
 
+static bool tcp_force_fast_retransmit(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	return after(tcp_highest_sack_seq(tp),
+		     tp->snd_una + tp->reordering * tp->mss_cache);
+}
+
 /* Undo during fast recovery after partial ACK. */
-static bool tcp_try_undo_partial(struct sock *sk, u32 prior_snd_una)
+static bool tcp_try_undo_partial(struct sock *sk, u32 prior_snd_una,
+				 bool *do_lost)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
@@ -2842,7 +2851,9 @@ static bool tcp_try_undo_partial(struct sock *sk, u32 prior_snd_una)
 		tcp_undo_cwnd_reduction(sk, true);
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);
 		tcp_try_keep_open(sk);
-		return true;
+	} else {
+		/* Partial ACK arrived. Force fast retransmit. */
+		*do_lost = tcp_force_fast_retransmit(sk);
 	}
 	return false;
 }
@@ -2866,14 +2877,6 @@ static void tcp_identify_packet_loss(struct sock *sk, int *ack_flag)
 	}
 }
 
-static bool tcp_force_fast_retransmit(struct sock *sk)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-
-	return after(tcp_highest_sack_seq(tp),
-		     tp->snd_una + tp->reordering * tp->mss_cache);
-}
-
 /* Process an event, which can update packets-in-flight not trivially.
  * Main goal of this function is to calculate new estimate for left_out,
  * taking into account both packets sitting in receiver's buffer and
@@ -2943,17 +2946,21 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
 		if (!(flag & FLAG_SND_UNA_ADVANCED)) {
 			if (tcp_is_reno(tp))
 				tcp_add_reno_sack(sk, num_dupack, ece_ack);
-		} else {
-			if (tcp_try_undo_partial(sk, prior_snd_una))
-				return;
-			/* Partial ACK arrived. Force fast retransmit. */
-			do_lost = tcp_force_fast_retransmit(sk);
-		}
-		if (tcp_try_undo_dsack(sk)) {
-			tcp_try_keep_open(sk);
+		} else if (tcp_try_undo_partial(sk, prior_snd_una, &do_lost))
 			return;
-		}
+
+		if (tcp_try_undo_dsack(sk))
+			tcp_try_keep_open(sk);
+
 		tcp_identify_packet_loss(sk, ack_flag);
+		if (icsk->icsk_ca_state != TCP_CA_Recovery) {
+			if (!tcp_time_to_recover(sk, flag))
+				return;
+			/* Undo reverts the recovery state. If loss is evident,
+			 * starts a new recovery (e.g. reordering then loss);
+			 */
+			tcp_enter_recovery(sk, ece_ack);
+		}
 		break;
 	case TCP_CA_Loss:
 		tcp_process_loss(sk, flag, num_dupack, rexmit);