[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/include/net/tcp.h b/include/net/tcp.h
index c6ecd45..ef8f9d4 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1199,9 +1199,14 @@
static inline void tcp_advance_send_head(struct sock *sk, struct sk_buff *skb)
{
+ struct tcp_sock *tp = tcp_sk(sk);
+
sk->sk_send_head = skb->next;
if (sk->sk_send_head == (struct sk_buff *)&sk->sk_write_queue)
sk->sk_send_head = NULL;
+ /* Don't override Nagle indefinately with F-RTO */
+ if (tp->frto_counter == 2)
+ tp->frto_counter = 3;
}
static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)