1 files changed, 34 insertions, 63 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 26c936930e92..cad73b7dfef0 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1392,9 +1392,9 @@ static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
 
         if (before(next_dup->start_seq, skip_to_seq)) {
                 skb = tcp_sacktag_skip(skb, sk, next_dup->start_seq, fack_count);
-                tcp_sacktag_walk(skb, sk, NULL,
-                                 next_dup->start_seq, next_dup->end_seq,
-                                 1, fack_count, reord, flag);
+                skb = tcp_sacktag_walk(skb, sk, NULL,
+                                     next_dup->start_seq, next_dup->end_seq,
+                                     1, fack_count, reord, flag);
         }
 
         return skb;
@@ -1842,9 +1842,16 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
                 }
 
-                /* Don't lost mark skbs that were fwd transmitted after RTO */
-                if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) &&
-                    !after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark)) {
+                /* Marking forward transmissions that were made after RTO lost
+                 * can cause unnecessary retransmissions in some scenarios,
+                 * SACK blocks will mitigate that in some but not in all cases.
+                 * We used to not mark them but it was causing break-ups with
+                 * receivers that do only in-order receival.
+                 *
+                 * TODO: we could detect presence of such receiver and select
+                 * different behavior per flow.
+                 */
+                if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
                         tp->lost_out += tcp_skb_pcount(skb);
                 }
@@ -1860,7 +1867,7 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
         tp->reordering = min_t(unsigned int, tp->reordering,
                                sysctl_tcp_reordering);
         tcp_set_ca_state(sk, TCP_CA_Loss);
-        tp->high_seq = tp->frto_highmark;
+        tp->high_seq = tp->snd_nxt;
         TCP_ECN_queue_cwr(tp);
 
         tcp_clear_retrans_hints_partial(tp);
@@ -2476,28 +2483,34 @@ static inline void tcp_complete_cwr(struct sock *sk)
         tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
 }
 
+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)
+                state = TCP_CA_Disorder;
+
+        if (inet_csk(sk)->icsk_ca_state != state) {
+                tcp_set_ca_state(sk, state);
+                tp->high_seq = tp->snd_nxt;
+        }
+}
+
 static void tcp_try_to_open(struct sock *sk, int flag)
 {
         struct tcp_sock *tp = tcp_sk(sk);
 
         tcp_verify_left_out(tp);
 
-        if (tp->retrans_out == 0)
+        if (!tp->frto_counter && tp->retrans_out == 0)
                 tp->retrans_stamp = 0;
 
         if (flag & FLAG_ECE)
                 tcp_enter_cwr(sk, 1);
 
         if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
-                int state = TCP_CA_Open;
-
-                if (tcp_left_out(tp) || tp->retrans_out || tp->undo_marker)
-                        state = TCP_CA_Disorder;
-
-                if (inet_csk(sk)->icsk_ca_state != state) {
-                        tcp_set_ca_state(sk, state);
-                        tp->high_seq = tp->snd_nxt;
-                }
+                tcp_try_keep_open(sk);
                 tcp_moderate_cwnd(tp);
         } else {
                 tcp_cwnd_down(sk, flag);
@@ -3303,8 +3316,11 @@ no_queue:
         return 1;
 
 old_ack:
-        if (TCP_SKB_CB(skb)->sacked)
+        if (TCP_SKB_CB(skb)->sacked) {
                 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
+                if (icsk->icsk_ca_state == TCP_CA_Open)
+                        tcp_try_keep_open(sk);
+        }
 
 uninteresting_ack:
         SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
@@ -4525,49 +4541,6 @@ static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
         }
 }
 
-static int tcp_defer_accept_check(struct sock *sk)
-{
-        struct tcp_sock *tp = tcp_sk(sk);
-
-        if (tp->defer_tcp_accept.request) {
-                int queued_data =  tp->rcv_nxt - tp->copied_seq;
-                int hasfin =  !skb_queue_empty(&sk->sk_receive_queue) ?
-                        tcp_hdr((struct sk_buff *)
-                                sk->sk_receive_queue.prev)->fin : 0;
-
-                if (queued_data && hasfin)
-                        queued_data--;
-
-                if (queued_data &&
-                    tp->defer_tcp_accept.listen_sk->sk_state == TCP_LISTEN) {
-                        if (sock_flag(sk, SOCK_KEEPOPEN)) {
-                                inet_csk_reset_keepalive_timer(sk,
-                                                               keepalive_time_when(tp));
-                        } else {
-                                inet_csk_delete_keepalive_timer(sk);
-                        }
-
-                        inet_csk_reqsk_queue_add(
-                                tp->defer_tcp_accept.listen_sk,
-                                tp->defer_tcp_accept.request,
-                                sk);
-
-                        tp->defer_tcp_accept.listen_sk->sk_data_ready(
-                                tp->defer_tcp_accept.listen_sk, 0);
-
-                        sock_put(tp->defer_tcp_accept.listen_sk);
-                        sock_put(sk);
-                        tp->defer_tcp_accept.listen_sk = NULL;
-                        tp->defer_tcp_accept.request = NULL;
-                } else if (hasfin ||
-                           tp->defer_tcp_accept.listen_sk->sk_state != TCP_LISTEN) {
-                        tcp_reset(sk);
-                        return -1;
-                }
-        }
-        return 0;
-}
-
 static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
 {
         struct tcp_sock *tp = tcp_sk(sk);
@@ -4928,8 +4901,6 @@ step5:
 
         tcp_data_snd_check(sk);
         tcp_ack_snd_check(sk);
-
-        tcp_defer_accept_check(sk);
         return 0;
 
 csum_error: