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>

1 files changed, 14 insertions, 10 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index e4fbdae066d5..ee0df4817498 100644
--- 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);
         }