[PATCH net-next] tcp: fix tcp_should_expand_sndbuf() to use tcp_packets_in_flight()

tcp_should_expand_sndbuf() does not expand the send buffer if we have
filled the congestion window.

However, it should use tcp_packets_in_flight() instead of
tp->packets_out to make this check.

Testing has established that the difference matters a lot if there are
many SACKed packets, causing a needless performance shortfall.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <redacted>
Signed-off-by: Eric Dumazet <redacted>
Signed-off-by: Nandita Dukkipati <redacted>
---
 net/ipv4/tcp_input.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 8fdd27b..fb4cf8b 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c

@@ -4770,7 +4770,7 @@ static bool tcp_should_expand_sndbuf(const struct sock *sk)
 		return false;
 
 	/* If we filled the congestion window, do not expand.  */
-	if (tp->packets_out >= tp->snd_cwnd)
+	if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
 		return false;
 
 	return true;

-- 
2.2.0.rc0.207.ga3a616c