1 files changed, 26 insertions, 10 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e65c211d3f4b..17388adedc7d 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -710,8 +710,9 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
 			min_t(unsigned int, eff_sacks,
 			      (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
 			      TCPOLEN_SACK_PERBLOCK);
-		size += TCPOLEN_SACK_BASE_ALIGNED +
-			opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
+		if (likely(opts->num_sack_blocks))
+			size += TCPOLEN_SACK_BASE_ALIGNED +
+				opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
 	}
 
 	return size;
@@ -1352,6 +1353,7 @@ int tcp_mtu_to_mss(struct sock *sk, int pmtu)
 	return __tcp_mtu_to_mss(sk, pmtu) -
 	       (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
 }
+EXPORT_SYMBOL(tcp_mtu_to_mss);
 
 /* Inverse of above */
 int tcp_mss_to_mtu(struct sock *sk, int mss)
@@ -1500,7 +1502,8 @@ static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
 	 * window, and remember whether we were cwnd-limited then.
 	 */
 	if (!before(tp->snd_una, tp->max_packets_seq) ||
-	    tp->packets_out > tp->max_packets_out) {
+	    tp->packets_out > tp->max_packets_out ||
+	    is_cwnd_limited) {
 		tp->max_packets_out = tp->packets_out;
 		tp->max_packets_seq = tp->snd_nxt;
 		tp->is_cwnd_limited = is_cwnd_limited;
@@ -2147,6 +2150,14 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 				break;
 		}
 
+		/* Argh, we hit an empty skb(), presumably a thread
+		 * is sleeping in sendmsg()/sk_stream_wait_memory().
+		 * We do not want to send a pure-ack packet and have
+		 * a strange looking rtx queue with empty packet(s).
+		 */
+		if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq)
+			break;
+
 		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
 			break;
 
@@ -2163,6 +2174,10 @@ repair:
 			break;
 	}
 
+	is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
+	if (likely(sent_pkts || is_cwnd_limited))
+		tcp_cwnd_validate(sk, is_cwnd_limited);
+
 	if (likely(sent_pkts)) {
 		if (tcp_in_cwnd_reduction(sk))
 			tp->prr_out += sent_pkts;
@@ -2170,8 +2185,6 @@ repair:
 		/* Send one loss probe per tail loss episode. */
 		if (push_one != 2)
 			tcp_schedule_loss_probe(sk);
-		is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
-		tcp_cwnd_validate(sk, is_cwnd_limited);
 		return false;
 	}
 	return !tp->packets_out && tcp_send_head(sk);
@@ -2262,6 +2275,11 @@ void tcp_send_loss_probe(struct sock *sk)
 	int pcount;
 	int mss = tcp_current_mss(sk);
 
+	/* At most one outstanding TLP */
+	if (tp->tlp_high_seq)
+		goto rearm_timer;
+
+	tp->tlp_retrans = 0;
 	skb = tcp_send_head(sk);
 	if (skb) {
 		if (tcp_snd_wnd_test(tp, skb, mss)) {
@@ -2284,10 +2302,6 @@ void tcp_send_loss_probe(struct sock *sk)
 		return;
 	}
 
-	/* At most one outstanding TLP retransmission. */
-	if (tp->tlp_high_seq)
-		goto rearm_timer;
-
 	if (skb_still_in_host_queue(sk, skb))
 		goto rearm_timer;
 
@@ -2308,10 +2322,12 @@ void tcp_send_loss_probe(struct sock *sk)
 	if (__tcp_retransmit_skb(sk, skb))
 		goto rearm_timer;
 
+	tp->tlp_retrans = 1;
+
+probe_sent:
 	/* Record snd_nxt for loss detection. */
 	tp->tlp_high_seq = tp->snd_nxt;
 
-probe_sent:
 	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
 	/* Reset s.t. tcp_rearm_rto will restart timer from now */
 	inet_csk(sk)->icsk_pending = 0;