3 files changed, 23 insertions, 6 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 7de4ea3a04d9..4fd3eb2f8ec2 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -752,6 +752,8 @@ static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
         return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
 }
 
+extern int tcp_limit_reno_sacked(struct tcp_sock *tp);
+
 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
  * The exception is rate halving phase, when cwnd is decreasing towards
  * ssthresh.
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 7d0958785bfb..b4812c3cbbcf 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1625,13 +1625,11 @@ out:
         return flag;
 }
 
-/* If we receive more dupacks than we expected counting segments
- * in assumption of absent reordering, interpret this as reordering.
- * The only another reason could be bug in receiver TCP.
+/* Limits sacked_out so that sum with lost_out isn't ever larger than
+ * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
  */
-static void tcp_check_reno_reordering(struct sock *sk, const int addend)
+int tcp_limit_reno_sacked(struct tcp_sock *tp)
 {
-        struct tcp_sock *tp = tcp_sk(sk);
         u32 holes;
 
         holes = max(tp->lost_out, 1U);
@@ -1639,8 +1637,20 @@ static void tcp_check_reno_reordering(struct sock *sk, const int addend)
 
         if ((tp->sacked_out + holes) > tp->packets_out) {
                 tp->sacked_out = tp->packets_out - holes;
-                tcp_update_reordering(sk, tp->packets_out + addend, 0);
+                return 1;
         }
+        return 0;
+}
+
+/* If we receive more dupacks than we expected counting segments
+ * in assumption of absent reordering, interpret this as reordering.
+ * The only another reason could be bug in receiver TCP.
+ */
+static void tcp_check_reno_reordering(struct sock *sk, const int addend)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        if (tcp_limit_reno_sacked(tp))
+                tcp_update_reordering(sk, tp->packets_out + addend, 0);
 }
 
 /* Emulate SACKs for SACKless connection: account for a new dupack. */
@@ -2600,6 +2610,8 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
         case TCP_CA_Loss:
                 if (flag & FLAG_DATA_ACKED)
                         icsk->icsk_retransmits = 0;
+                if (tcp_is_reno(tp) && flag & FLAG_SND_UNA_ADVANCED)
+                        tcp_reset_reno_sack(tp);
                 if (!tcp_try_undo_loss(sk)) {
                         tcp_moderate_cwnd(tp);
                         tcp_xmit_retransmit_queue(sk);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 72b9350006fe..d29ef79c00ca 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1808,6 +1808,9 @@ void tcp_simple_retransmit(struct sock *sk)
         if (!lost)
                 return;
 
+        if (tcp_is_reno(tp))
+                tcp_limit_reno_sacked(tp);
+
         tcp_verify_left_out(tp);
 
         /* Don't muck with the congestion window here.