[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>

7 files changed, 43 insertions, 59 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 15bdbc6bd571..54c399886275 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -765,6 +765,16 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk)
                             (tp->snd_cwnd >> 2)));
 }
 
+/*
+ * Linear increase during slow start
+ */
+static inline void tcp_slow_start(struct tcp_sock *tp)
+{
+        if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+                tp->snd_cwnd++;
+}
+
+
 static inline void tcp_sync_left_out(struct tcp_sock *tp)
 {
         if (tp->rx_opt.sack_ok &&
diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c
index 5af99b3ef5d7..1d0cd86621b1 100644
--- a/net/ipv4/tcp_bic.c
+++ b/net/ipv4/tcp_bic.c
@@ -220,14 +220,12 @@ static void bictcp_cong_avoid(struct sock *sk, u32 ack,
         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 {
                 bictcp_update(ca, tp->snd_cwnd);
 
-                /* In dangerous area, increase slowly.
+                /* In dangerous area, increase slowly.
                  * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
                  */
                 if (tp->snd_cwnd_cnt >= ca->cnt) {
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 0705b496c6b3..6d3e883b48f6 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -189,12 +189,11 @@ void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 rtt, u32 in_flight,
         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 {
-                /* In dangerous area, increase slowly.
+        /* In "safe" area, increase. */
+        if (tp->snd_cwnd <= tp->snd_ssthresh)
+                tcp_slow_start(tp);
+        else {
+                /* In dangerous area, increase slowly.
                  * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
                  */
                 if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
diff --git a/net/ipv4/tcp_highspeed.c b/net/ipv4/tcp_highspeed.c
index 5e56ad368dd2..82b3c189bd7d 100644
--- a/net/ipv4/tcp_highspeed.c
+++ b/net/ipv4/tcp_highspeed.c
@@ -119,10 +119,9 @@ static void hstcp_cong_avoid(struct sock *sk, u32 adk, u32 rtt,
         if (!tcp_is_cwnd_limited(sk, in_flight))
                 return;
 
-        if (tp->snd_cwnd <= tp->snd_ssthresh) {
-                if (tp->snd_cwnd < tp->snd_cwnd_clamp)
-                        tp->snd_cwnd++;
-        } else {
+        if (tp->snd_cwnd <= tp->snd_ssthresh)
+                tcp_slow_start(tp);
+        else {
                 /* Update AIMD parameters */
                 if (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd) {
                         while (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd &&
diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c
index 404a326ba345..3284cfb993e6 100644
--- a/net/ipv4/tcp_htcp.c
+++ b/net/ipv4/tcp_htcp.c
@@ -210,11 +210,10 @@ static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
         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 @@ static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
                         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) {
diff --git a/net/ipv4/tcp_scalable.c b/net/ipv4/tcp_scalable.c
index a2fd25617d24..26d7486ee501 100644
--- a/net/ipv4/tcp_scalable.c
+++ b/net/ipv4/tcp_scalable.c
@@ -24,17 +24,16 @@ static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
         if (!tcp_is_cwnd_limited(sk, in_flight))
                 return;
 
-        if (tp->snd_cwnd <= tp->snd_ssthresh) {
-                tp->snd_cwnd++;
-        } else {
+        if (tp->snd_cwnd <= tp->snd_ssthresh)
+                tcp_slow_start(tp);
+        else {
                 tp->snd_cwnd_cnt++;
                 if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){
-                        tp->snd_cwnd++;
+                        if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+                                tp->snd_cwnd++;
                         tp->snd_cwnd_cnt = 0;
                 }
         }
-        tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
-        tp->snd_cwnd_stamp = tcp_time_stamp;
 }
 
 static u32 tcp_scalable_ssthresh(struct sock *sk)
diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
index 93c5f92070f9..4376814d29fb 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. */