[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>

1 files changed, 11 insertions, 31 deletions

diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
index 93c5f92070f..4376814d29f 100644
--- a/net/ipv4/tcp_vegas.c
+++ b/net/ipv4/tcp_vegas.c
@@ -236,8 +236,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack,
                         /* We don't have enough RTT samples to do the Vegas
                          * calculation, so we'll behave like Reno.
                          */
-                        if (tp->snd_cwnd > tp->snd_ssthresh)
-                                tp->snd_cwnd++;
+                        tcp_reno_cong_avoid(sk, ack, seq_rtt, in_flight, cnt);
                 } else {
                         u32 rtt, target_cwnd, diff;
 
@@ -275,7 +274,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack,
                          */
                         diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd;
 
-                        if (tp->snd_cwnd < tp->snd_ssthresh) {
+                        if (tp->snd_cwnd <= tp->snd_ssthresh) {
                                 /* Slow start.  */
                                 if (diff > gamma) {
                                         /* Going too fast. Time to slow down
@@ -295,6 +294,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack,
                                                             V_PARAM_SHIFT)+1);
 
                                 }
+                                tcp_slow_start(tp);
                         } else {
                                 /* Congestion avoidance. */
                                 u32 next_snd_cwnd;
@@ -327,37 +327,17 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack,
                                 else if (next_snd_cwnd < tp->snd_cwnd)
                                         tp->snd_cwnd--;
                         }
-                }
 
-                /* Wipe the slate clean for the next RTT. */
-                vegas->cntRTT = 0;
-                vegas->minRTT = 0x7fffffff;
+                        if (tp->snd_cwnd < 2)
+                                tp->snd_cwnd = 2;
+                        else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
+                                tp->snd_cwnd = tp->snd_cwnd_clamp;
+                }
         }
 
-        /* The following code is executed for every ack we receive,
-         * except for conditions checked in should_advance_cwnd()
-         * before the call to tcp_cong_avoid(). Mainly this means that
-         * we only execute this code if the ack actually acked some
-         * data.
-         */
-
-        /* If we are in slow start, increase our cwnd in response to this ACK.
-         * (If we are not in slow start then we are in congestion avoidance,
-         * and adjust our congestion window only once per RTT. See the code
-         * above.)
-         */
-        if (tp->snd_cwnd <= tp->snd_ssthresh)
-                tp->snd_cwnd++;
-
-        /* to keep cwnd from growing without bound */
-        tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
-
-        /* Make sure that we are never so timid as to reduce our cwnd below
-         * 2 MSS.
-         *
-         * Going below 2 MSS would risk huge delayed ACKs from our receiver.
-         */
-        tp->snd_cwnd = max(tp->snd_cwnd, 2U);
+        /* Wipe the slate clean for the next RTT. */
+        vegas->cntRTT = 0;
+        vegas->minRTT = 0x7fffffff;
 }
 
 /* Extract info for Tcp socket info provided via netlink. */