[TCP]: Two fixes to new sacktag code

1) Skip condition used to be wrong way around which made SACK
processing very broken, missed many blocks because of that.

2) Use highest_sack advancement only if some skbs are already
sacked because otherwise tcp_write_queue_next may move things
too far (occurs mainly with GSO). The other similar advancement
is not problem because highest_sack was previosly put to point
a sacked skb.

These problems were located because of problem report from Matt
Mathis <mathis@psc.edu>.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 97ea3eda206dfb0b33996470942533259215c04f..33d284e3f7f5680f9edde1dfd88039af3234b648 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1384,7 +1384,7 @@ static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
                if (skb == tcp_send_head(sk))
                        break;
 
-               if (before(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
+               if (!before(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
                        break;
        }
        return skb;
@@ -1575,7 +1575,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
                        continue;
                }
 
-               if (!before(start_seq, tcp_highest_sack_seq(tp))) {
+               if (tp->sacked_out && !before(start_seq, tcp_highest_sack_seq(tp))) {
                        skb = tcp_write_queue_next(sk, tp->highest_sack);
                        fack_count = tp->fackets_out;
                }