Subject: [PATCH 14/21] tcp: Do not underestimate rwnd_limited

From: Eric Dumazet <[email-masked]>
Date: Wed, 5 Dec 2018 14:24:31 -0800

[ Upstream commit 41727549de3e7281feb174d568c6e46823db8684 ]

If available rwnd is too small, tcp_tso_should_defer()
can decide it is worth waiting before splitting a TSO packet.

This really means we are rwnd limited.

Fixes: 5615f88614a4 ("tcp: instrument how long TCP is limited by receive window")
Signed-off-by: Eric Dumazet <[email-masked]>
Acked-by: Soheil Hassas Yeganeh <[email-masked]>
Reviewed-by: Yuchung Cheng <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/ipv4/tcp_output.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 68f65ddf9e3c..97e8aea4ac71 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2338,8 +2338,11 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 		} else {
 			if (!push_one &&
 			    tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
-						 max_segs))
+						 max_segs)) {
+				if (!is_cwnd_limited)
+					is_rwnd_limited = true;
 				break;
+			}
 		}
 
 		limit = mss_now;
-- 
2.19.2