[TCP] FRTO: RFC4138 allows Nagle override when new data must be sent
This is a corner case where less than MSS sized new data thingie
is awaiting in the send queue. For F-RTO to work correctly, a
new data segment must be sent at certain point or F-RTO cannot
be used at all. RFC4138 allows overriding of Nagle at that
point.
Implementation uses frto_counter states 2 and 3 to distinguish
when Nagle override is needed.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index b5fa3c1..0faacf9 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1035,8 +1035,10 @@
if (nonagle & TCP_NAGLE_PUSH)
return 1;
- /* Don't use the nagle rule for urgent data (or for the final FIN). */
- if (tp->urg_mode ||
+ /* Don't use the nagle rule for urgent data (or for the final FIN).
+ * Nagle can be ignored during F-RTO too (see RFC4138).
+ */
+ if (tp->urg_mode || (tp->frto_counter == 2) ||
(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN))
return 1;