[TCP]: Correct DSACK check placing

Previously one of the in-block skip branches was missing it.

Also, drop it from tail-fully-processed case because the next
iteration will do exactly the same thing, i.e., process the
SACK block that contains the DSACK information.

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

1 files changed, 5 insertions, 10 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3ad6a19ad30f..79996b16b942 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1554,20 +1554,15 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
                         }
 
                         /* Rest of the block already fully processed? */
-                        if (!after(end_seq, cache->end_seq)) {
-                                skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, cache->end_seq,
-                                                               &fack_count, &reord, &flag);
+                        if (!after(end_seq, cache->end_seq))
                                 goto advance_sp;
-                        }
+
+                        skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, cache->end_seq,
+                                                       &fack_count, &reord, &flag);
 
                         /* ...tail remains todo... */
                         if (TCP_SKB_CB(tp->highest_sack)->end_seq == cache->end_seq) {
-                                /* ...but better entrypoint exists! Check that DSACKs are
-                                 * properly accounted while skipping here
-                                 */
-                                tcp_maybe_skipping_dsack(skb, sk, next_dup, cache->end_seq,
-                                                         &fack_count, &reord, &flag);
-
+                                /* ...but better entrypoint exists! */
                                 skb = tcp_write_queue_next(sk, tp->highest_sack);
                                 fack_count = tp->fackets_out;
                                 cache++;