tcp: Fix tcp_mark_head_lost() with packets == 0

[ Upstream commit 6830c25b7d08fbbd922959425193791bc42079f2 ]

A packet is marked as lost in case packets == 0, although nothing should be done.
This results in a too early retransmitted packet during recovery in some cases.
This small patch fixes this issue by returning immediately.

Signed-off-by: Lennart Schulte <lennart.schulte@nets.rwth-aachen.de>
Signed-off-by: Arnd Hannemann <hannemann@nets.rwth-aachen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3fddc69ccccc..b347d3c46b1a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2499,6 +2499,9 @@ static void tcp_mark_head_lost(struct sock *sk, int packets)
         int err;
         unsigned int mss;
 
+        if (packets == 0)
+                return;
+
         WARN_ON(packets > tp->packets_out);
         if (tp->lost_skb_hint) {
                 skb = tp->lost_skb_hint;