tcp: new helper for RACK to detect loss

Create a new helper tcp_rack_detect_loss to prepare the upcoming
RACK reordering timer patch.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 4 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index ec6d84363024..bb24b93e64bc 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2865,10 +2865,14 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
         }
 
         /* Use RACK to detect loss */
-        if (sysctl_tcp_recovery & TCP_RACK_LOST_RETRANS &&
-            tcp_rack_mark_lost(sk)) {
-                flag |= FLAG_LOST_RETRANS;
-                *ack_flag |= FLAG_LOST_RETRANS;
+        if (sysctl_tcp_recovery & TCP_RACK_LOST_RETRANS) {
+                u32 prior_retrans = tp->retrans_out;
+
+                tcp_rack_mark_lost(sk);
+                if (prior_retrans > tp->retrans_out) {
+                        flag |= FLAG_LOST_RETRANS;
+                        *ack_flag |= FLAG_LOST_RETRANS;
+                }
         }
 
         /* E. Process state. */