[TCP]: add tcp_slow_start helper

Move all the code that does linear TCP slowstart to one
inline function to ease later patch to add ABC support.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c
index 404a326..3284cfb 100644
--- a/net/ipv4/tcp_htcp.c
+++ b/net/ipv4/tcp_htcp.c
@@ -210,11 +210,10 @@
 	if (!tcp_is_cwnd_limited(sk, in_flight))
 		return;
 
-        if (tp->snd_cwnd <= tp->snd_ssthresh) {
-                /* In "safe" area, increase. */
-		if (tp->snd_cwnd < tp->snd_cwnd_clamp)
-			tp->snd_cwnd++;
-	} else {
+        if (tp->snd_cwnd <= tp->snd_ssthresh)
+		tcp_slow_start(tp);
+	else {
+
 		measure_rtt(sk);
 
 		/* keep track of number of round-trip times since last backoff event */
@@ -224,7 +223,7 @@
 			htcp_alpha_update(ca);
 		}
 
-                /* In dangerous area, increase slowly.
+		/* In dangerous area, increase slowly.
 		 * In theory this is tp->snd_cwnd += alpha / tp->snd_cwnd
 		 */
 		if ((tp->snd_cwnd_cnt++ * ca->alpha)>>7 >= tp->snd_cwnd) {