1 files changed, 12 insertions, 4 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3f2f09091bc..125b4517f36 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1178,10 +1178,18 @@ static void tcp_mark_lost_retrans(struct sock *sk)
                 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
                         continue;
 
-                if (after(received_upto, ack_seq) &&
-                    (tcp_is_fack(tp) ||
-                     !before(received_upto,
-                             ack_seq + tp->reordering * tp->mss_cache))) {
+                /* TODO: We would like to get rid of tcp_is_fack(tp) only
+                 * constraint here (see above) but figuring out that at
+                 * least tp->reordering SACK blocks reside between ack_seq
+                 * and received_upto is not easy task to do cheaply with
+                 * the available datastructures.
+                 *
+                 * Whether FACK should check here for tp->reordering segs
+                 * in-between one could argue for either way (it would be
+                 * rather simple to implement as we could count fack_count
+                 * during the walk and do tp->fackets_out - fack_count).
+                 */
+                if (after(received_upto, ack_seq)) {
                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
                         tp->retrans_out -= tcp_skb_pcount(skb);