tcp: sack lost marking fixes

When only fast rexmit should be done, tcp_mark_head_lost marks
L too far. Also, sacked_upto below 1 is perfectly valid number,
the packets == 0 then needs to be trapped elsewhere.

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

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index e4fbdae..ee0df48 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2495,7 +2495,7 @@ static void tcp_timeout_skbs(struct sock *sk)
 /* Mark head of queue up as lost. With RFC3517 SACK, the packets is
  * is against sacked "cnt", otherwise it's against facked "cnt"
  */
-static void tcp_mark_head_lost(struct sock *sk, int packets)
+static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
 {
        struct tcp_sock *tp = tcp_sk(sk);
        struct sk_buff *skb;
@@ -2503,13 +2503,13 @@ static void tcp_mark_head_lost(struct sock *sk, int packets)
        int err;
        unsigned int mss;
 
-       if (packets == 0)
-               return;
-
        WARN_ON(packets > tp->packets_out);
        if (tp->lost_skb_hint) {
                skb = tp->lost_skb_hint;
                cnt = tp->lost_cnt_hint;
+               /* Head already handled? */
+               if (mark_head && skb != tcp_write_queue_head(sk))
+                       return;
        } else {
                skb = tcp_write_queue_head(sk);
                cnt = 0;
@@ -2544,6 +2544,9 @@ static void tcp_mark_head_lost(struct sock *sk, int packets)
                }
 
                tcp_skb_mark_lost(tp, skb);
+
+               if (mark_head)
+                       break;
        }
        tcp_verify_left_out(tp);
 }
@@ -2555,17 +2558,18 @@ static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
        struct tcp_sock *tp = tcp_sk(sk);
 
        if (tcp_is_reno(tp)) {
-               tcp_mark_head_lost(sk, 1);
+               tcp_mark_head_lost(sk, 1, 1);
        } else if (tcp_is_fack(tp)) {
                int lost = tp->fackets_out - tp->reordering;
                if (lost <= 0)
                        lost = 1;
-               tcp_mark_head_lost(sk, lost);
+               tcp_mark_head_lost(sk, lost, 0);
        } else {
                int sacked_upto = tp->sacked_out - tp->reordering;
-               if (sacked_upto < fast_rexmit)
-                       sacked_upto = fast_rexmit;
-               tcp_mark_head_lost(sk, sacked_upto);
+               if (sacked_upto >= 0)
+                       tcp_mark_head_lost(sk, sacked_upto, 0);
+               else if (fast_rexmit)
+                       tcp_mark_head_lost(sk, 1, 1);
        }
 
        tcp_timeout_skbs(sk);
@@ -2971,7 +2975,7 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
            before(tp->snd_una, tp->high_seq) &&
            icsk->icsk_ca_state != TCP_CA_Open &&
            tp->fackets_out > tp->reordering) {
-               tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering);
+               tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering, 0);
                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSS);
        }