tcp: Revert "tcp: remove CA_ACK_SLOWPATH"

This change was a followup to the header prediction removal,
so first revert this as a prerequisite to back out hp removal.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 27 insertions, 4 deletions

diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c
index e5de84310949..bec9cafbe3f9 100644
--- a/net/ipv4/tcp_westwood.c
+++ b/net/ipv4/tcp_westwood.c
@@ -154,6 +154,24 @@ static inline void update_rtt_min(struct westwood *w)
 }
 
 /*
+ * @westwood_fast_bw
+ * It is called when we are in fast path. In particular it is called when
+ * header prediction is successful. In such case in fact update is
+ * straight forward and doesn't need any particular care.
+ */
+static inline void westwood_fast_bw(struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct westwood *w = inet_csk_ca(sk);
+
+	westwood_update_window(sk);
+
+	w->bk += tp->snd_una - w->snd_una;
+	w->snd_una = tp->snd_una;
+	update_rtt_min(w);
+}
+
+/*
  * @westwood_acked_count
  * This function evaluates cumul_ack for evaluating bk in case of
  * delayed or partial acks.
@@ -205,12 +223,17 @@ static u32 tcp_westwood_bw_rttmin(const struct sock *sk)
 
 static void tcp_westwood_ack(struct sock *sk, u32 ack_flags)
 {
-	struct westwood *w = inet_csk_ca(sk);
+	if (ack_flags & CA_ACK_SLOWPATH) {
+		struct westwood *w = inet_csk_ca(sk);
 
-	westwood_update_window(sk);
-	w->bk += westwood_acked_count(sk);
+		westwood_update_window(sk);
+		w->bk += westwood_acked_count(sk);
 
-	update_rtt_min(w);
+		update_rtt_min(w);
+		return;
+	}
+
+	westwood_fast_bw(sk);
 }
 
 static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)