tcp: convert retransmit_cnt_hint to seqno

Main benefit in this is that we can then freely point
the retransmit_skb_hint to anywhere we want to because
there's no longer need to know what would be the count
changes involve, and since this is really used only as a
terminator, unnecessary work is one time walk at most,
and if some retransmissions are necessary after that
point later on, the walk is not full waste of time
anyway.

Since retransmit_high must be kept valid, all lost
markers must ensure that.

Now I also have learned how those "holes" in the
rexmittable skbs can appear, mtu probe does them. So
I removed the misleading comment as well.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 18 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 11490958a096..cfae61b40c44 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1838,7 +1838,7 @@ void tcp_simple_retransmit(struct sock *sk)
         struct tcp_sock *tp = tcp_sk(sk);
         struct sk_buff *skb;
         unsigned int mss = tcp_current_mss(sk, 0);
-        int lost = 0;
+        u32 prior_lost = tp->lost_out;
 
         tcp_for_write_queue(skb, sk) {
                 if (skb == tcp_send_head(sk))
@@ -1849,17 +1849,13 @@ void tcp_simple_retransmit(struct sock *sk)
                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
                                 tp->retrans_out -= tcp_skb_pcount(skb);
                         }
-                        if (!(TCP_SKB_CB(skb)->sacked & TCPCB_LOST)) {
-                                TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
-                                tp->lost_out += tcp_skb_pcount(skb);
-                                lost = 1;
-                        }
+                        tcp_skb_mark_lost_uncond_verify(tp, skb);
                 }
         }
 
         tcp_clear_all_retrans_hints(tp);
 
-        if (!lost)
+        if (prior_lost == tp->lost_out)
                 return;
 
         if (tcp_is_reno(tp))
@@ -2009,15 +2005,11 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
         const struct inet_connection_sock *icsk = inet_csk(sk);
         struct tcp_sock *tp = tcp_sk(sk);
         struct sk_buff *skb;
-        int packet_cnt;
 
-        if (tp->retransmit_skb_hint) {
+        if (tp->retransmit_skb_hint)
                 skb = tp->retransmit_skb_hint;
-                packet_cnt = tp->retransmit_cnt_hint;
-        } else {
+        else
                 skb = tcp_write_queue_head(sk);
-                packet_cnt = 0;
-        }
 
         /* First pass: retransmit lost packets. */
         if (tp->lost_out) {
@@ -2028,7 +2020,6 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
                                 break;
                         /* we could do better than to assign each time */
                         tp->retransmit_skb_hint = skb;
-                        tp->retransmit_cnt_hint = packet_cnt;
 
                         /* Assume this retransmit will generate
                          * only one packet for congestion window
@@ -2039,6 +2030,8 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
                          */
                         if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
                                 return;
+                        if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high))
+                                break;
 
                         if (sacked & TCPCB_LOST) {
                                 if (!(sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) {
@@ -2059,10 +2052,6 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
                                                                           inet_csk(sk)->icsk_rto,
                                                                           TCP_RTO_MAX);
                                 }
-
-                                packet_cnt += tcp_skb_pcount(skb);
-                                if (packet_cnt >= tp->lost_out)
-                                        break;
                         }
                 }
         }