1 files changed, 27 insertions, 15 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 8fe754be8076..0feb10935be1 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -104,6 +104,7 @@ int sysctl_tcp_abc __read_mostly;
 #define FLAG_ONLY_ORIG_SACKED   0x200 /* SACKs only non-rexmit sent before RTO */
 #define FLAG_SND_UNA_ADVANCED   0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
 #define FLAG_DSACKING_ACK       0x800 /* SACK blocks contained DSACK info */
+#define FLAG_NONHEAD_RETRANS_ACKED      0x1000 /* Non-head rexmitted data was ACKed */
 
 #define FLAG_ACKED              (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
 #define FLAG_NOT_DUP            (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
@@ -1594,6 +1595,8 @@ void tcp_enter_frto(struct sock *sk)
         tp->undo_retrans = 0;
 
         skb = tcp_write_queue_head(sk);
+        if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
+                tp->undo_marker = 0;
         if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
                 tp->retrans_out -= tcp_skb_pcount(skb);
@@ -1643,6 +1646,8 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
                         /* ...enter this if branch just for the first segment */
                         flag |= FLAG_DATA_ACKED;
                 } else {
+                        if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
+                                tp->undo_marker = 0;
                         TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
                 }
 
@@ -1658,7 +1663,6 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
         tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments;
         tp->snd_cwnd_cnt = 0;
         tp->snd_cwnd_stamp = tcp_time_stamp;
-        tp->undo_marker = 0;
         tp->frto_counter = 0;
 
         tp->reordering = min_t(unsigned int, tp->reordering,
@@ -2584,20 +2588,6 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p)
                         end_seq = scb->end_seq;
                 }
 
-                /* Initial outgoing SYN's get put onto the write_queue
-                 * just like anything else we transmit.  It is not
-                 * true data, and if we misinform our callers that
-                 * this ACK acks real data, we will erroneously exit
-                 * connection startup slow start one packet too
-                 * quickly.  This is severely frowned upon behavior.
-                 */
-                if (!(scb->flags & TCPCB_FLAG_SYN)) {
-                        flag |= FLAG_DATA_ACKED;
-                } else {
-                        flag |= FLAG_SYN_ACKED;
-                        tp->retrans_stamp = 0;
-                }
-
                 /* MTU probing checks */
                 if (fully_acked && icsk->icsk_mtup.probe_size &&
                     !after(tp->mtu_probe.probe_seq_end, scb->end_seq)) {
@@ -2610,6 +2600,9 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p)
                                         tp->retrans_out -= packets_acked;
                                 flag |= FLAG_RETRANS_DATA_ACKED;
                                 seq_rtt = -1;
+                                if ((flag & FLAG_DATA_ACKED) ||
+                                    (packets_acked > 1))
+                                        flag |= FLAG_NONHEAD_RETRANS_ACKED;
                         } else if (seq_rtt < 0) {
                                 seq_rtt = now - scb->when;
                                 if (fully_acked)
@@ -2631,6 +2624,20 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p)
                 }
                 tp->packets_out -= packets_acked;
 
+                /* Initial outgoing SYN's get put onto the write_queue
+                 * just like anything else we transmit.  It is not
+                 * true data, and if we misinform our callers that
+                 * this ACK acks real data, we will erroneously exit
+                 * connection startup slow start one packet too
+                 * quickly.  This is severely frowned upon behavior.
+                 */
+                if (!(scb->flags & TCPCB_FLAG_SYN)) {
+                        flag |= FLAG_DATA_ACKED;
+                } else {
+                        flag |= FLAG_SYN_ACKED;
+                        tp->retrans_stamp = 0;
+                }
+
                 if (!fully_acked)
                         break;
 
@@ -2852,6 +2859,10 @@ static int tcp_process_frto(struct sock *sk, int flag)
         if (flag&FLAG_DATA_ACKED)
                 inet_csk(sk)->icsk_retransmits = 0;
 
+        if ((flag & FLAG_NONHEAD_RETRANS_ACKED) ||
+            ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED)))
+                tp->undo_marker = 0;
+
         if (!before(tp->snd_una, tp->frto_highmark)) {
                 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag);
                 return 1;
@@ -2916,6 +2927,7 @@ static int tcp_process_frto(struct sock *sk, int flag)
                         break;
                 }
                 tp->frto_counter = 0;
+                tp->undo_marker = 0;
         }
         return 0;
 }