[PATH net 2/4] tcp: always evaluate losses in RACK upon undo

[Yuchung Cheng]

When sender detects spurious retransmission, all packets
marked lost are remarked to be in-flight. However some may
be considered lost based on its timestamps in RACK. This patch
forces RACK to re-evaluate, which may be skipped previously if
the ACK does not advance RACK timestamp.

Signed-off-by: Yuchung Cheng <ych...@google.com>
Reviewed-by: Neal Cardwell <ncardw...@google.com>
Reviewed-by: Priyaranjan Jha <priyar...@google.com>
Reviewed-by: Eric Dumazet <eduma...@google.com>
---
 net/ipv4/tcp_input.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 734cfc8ff76e..5a240f9d208b 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2326,6 +2326,7 @@ static void tcp_undo_cwnd_reduction(struct sock *sk, bool 
unmark_loss)
        }
        tp->snd_cwnd_stamp = tcp_jiffies32;
        tp->undo_marker = 0;
+       tp->rack.advanced = 1; /* Force RACK to re-exam losses */
 }
 
 static inline bool tcp_may_undo(const struct tcp_sock *tp)
-- 
2.15.1.424.g9478a66081-goog