1 files changed, 32 insertions, 3 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 57ae96a04220..12cab7d74dba 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2717,6 +2717,35 @@ static void tcp_try_undo_dsack(struct sock *sk)
         }
 }
 
+/* We can clear retrans_stamp when there are no retransmissions in the
+ * window. It would seem that it is trivially available for us in
+ * tp->retrans_out, however, that kind of assumptions doesn't consider
+ * what will happen if errors occur when sending retransmission for the
+ * second time. ...It could the that such segment has only
+ * TCPCB_EVER_RETRANS set at the present time. It seems that checking
+ * the head skb is enough except for some reneging corner cases that
+ * are not worth the effort.
+ *
+ * Main reason for all this complexity is the fact that connection dying
+ * time now depends on the validity of the retrans_stamp, in particular,
+ * that successive retransmissions of a segment must not advance
+ * retrans_stamp under any conditions.
+ */
+static int tcp_any_retrans_done(struct sock *sk)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        struct sk_buff *skb;
+
+        if (tp->retrans_out)
+                return 1;
+
+        skb = tcp_write_queue_head(sk);
+        if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS))
+                return 1;
+
+        return 0;
+}
+
 /* Undo during fast recovery after partial ACK. */
 
 static int tcp_try_undo_partial(struct sock *sk, int acked)
@@ -2729,7 +2758,7 @@ static int tcp_try_undo_partial(struct sock *sk, int acked)
                 /* Plain luck! Hole if filled with delayed
                  * packet, rather than with a retransmit.
                  */
-                if (tp->retrans_out == 0)
+                if (!tcp_any_retrans_done(sk))
                         tp->retrans_stamp = 0;
 
                 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
@@ -2788,7 +2817,7 @@ static void tcp_try_keep_open(struct sock *sk)
         struct tcp_sock *tp = tcp_sk(sk);
         int state = TCP_CA_Open;
 
-        if (tcp_left_out(tp) || tp->retrans_out || tp->undo_marker)
+        if (tcp_left_out(tp) || tcp_any_retrans_done(sk) || tp->undo_marker)
                 state = TCP_CA_Disorder;
 
         if (inet_csk(sk)->icsk_ca_state != state) {
@@ -2803,7 +2832,7 @@ static void tcp_try_to_open(struct sock *sk, int flag)
 
         tcp_verify_left_out(tp);
 
-        if (!tp->frto_counter && tp->retrans_out == 0)
+        if (!tp->frto_counter && !tcp_any_retrans_done(sk))
                 tp->retrans_stamp = 0;
 
         if (flag & FLAG_ECE)