tcp: Do not underestimate rwnd_limited

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 <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 68b5326f7321..318690234758 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2356,8 +2356,11 @@ 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;