[PATCH] [TCP]: Bind fackets_out state to highest_sack more tightly

[Ilpo Järvinen]

Added checks will catch most of the errors if the current
complex fack_count counting logic is flawed somewhere.

Fackets_out should always be advancable if highest_sack is too
because the fackets_out is nowadays accurate (and obviously it
must be smaller than packets_out).

Signed-off-by: Ilpo Järvinen <[EMAIL PROTECTED]>
---
 net/ipv4/tcp_input.c |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9499a12..23b2a34 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1270,24 +1270,28 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct 
sock *sk,
                        }
                }
 
-               if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
+               fack_count += tcp_skb_pcount(skb);
+               if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp))) {
+                       WARN_ON((fack_count <= tp->fackets_out) ||
+                               (fack_count > tp->packets_out));
+
                        tcp_advance_highest_sack(sk, skb);
+                       tp->fackets_out = fack_count;
+               } else
+                       WARN_ON(fack_count > tp->fackets_out);
+
                tcp_write_queue_requeue(skb, sk, TCP_WQ_SACKED);
 
                TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
                flag |= FLAG_DATA_SACKED;
                tp->sacked_out += tcp_skb_pcount(skb);
 
-               fack_count += tcp_skb_pcount(skb);
-
                /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
                if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
                    before(TCP_SKB_CB(skb)->seq,
                           TCP_SKB_CB(tp->lost_skb_hint)->seq))
                        tp->lost_cnt_hint += tcp_skb_pcount(skb);
 
-               if (fack_count > tp->fackets_out)
-                       tp->fackets_out = fack_count;
        }
 
        /* D-SACK. We can detect redundant retransmission in S|R and plain R
-- 
1.5.0.6