TCP: Increase the max_burst threshold from 3 to tp->reordering.

[ Upstream commit: dd9e0dda66ba38a2ddd1405ac279894260dc5c36 ]

This change is necessary to allow cwnd to grow during persistent
reordering.  Cwnd moderation is applied when in the disorder state
and an ack that fills the hole comes in.  If the hole was greater
than 3 packets, but less than tp->reordering, cwnd will shrink when
it should not have.

Signed-off-by: John Heffner <jheffner@napa.none>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4fd3eb2f8ec2c4bef73eab8ebe9866301e00832e..d69d12e3c0421356a097a22c0cfb00c70ed39508 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -776,11 +776,14 @@ extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
 extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);
 
 /* Slow start with delack produces 3 packets of burst, so that
- * it is safe "de facto".
+ * it is safe "de facto".  This will be the default - same as
+ * the default reordering threshold - but if reordering increases,
+ * we must be able to allow cwnd to burst at least this much in order
+ * to not pull it back when holes are filled.
  */
 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
 {
-       return 3;
+       return tp->reordering;
 }
 
 /* Returns end sequence number of the receiver's advertised window */