[TCP]: BIC tcp congestion calculation timestamp

Small change to bictcp based on the BIC 1.1 patches for web100.
Keep track of last time congestion was computed, and recompute
if cwnd changes or every 1/32 of a second.

Also changes the initialization location for the parameters.
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@redhat.com>

include/linux/tcp.h

@@ -420,6 +420,7 @@ struct tcp_opt {
 		__u32	cnt;		/* increase cwnd by 1 after this number of ACKs */
 		__u32 	last_max_cwnd;	/* last maximium snd_cwnd */
 		__u32	last_cwnd;	/* the last snd_cwnd */
+		__u32   last_stamp;     /* time when updated last_cwnd */
 	} bictcp;
 };
 

net/ipv4/tcp_input.c

@@ -330,6 +330,15 @@ static void tcp_init_buffer_space(struct sock *sk)
 	tp->snd_cwnd_stamp = tcp_time_stamp;
 }
 
+static void init_bictcp(struct tcp_opt *tp)
+{
+	tp->bictcp.cnt = 0;
+
+	tp->bictcp.last_max_cwnd = 0;
+	tp->bictcp.last_cwnd = 0;
+	tp->bictcp.last_stamp = 0;
+}
+
 /* 5. Recalculate window clamp after socket hit its memory bounds. */
 static void tcp_clamp_window(struct sock *sk, struct tcp_opt *tp)
 {
@@ -1233,6 +1242,8 @@ static void tcp_enter_frto_loss(struct sock *sk)
 	tcp_set_ca_state(tp, TCP_CA_Loss);
 	tp->high_seq = tp->frto_highmark;
 	TCP_ECN_queue_cwr(tp);
+
+	init_bictcp(tp);
 }
 
 void tcp_clear_retrans(struct tcp_opt *tp)
@@ -2011,10 +2022,12 @@ static inline __u32 bictcp_cwnd(struct tcp_opt *tp)
 	if (!sysctl_tcp_bic)
 		return tp->snd_cwnd;
 
-	if (tp->bictcp.last_cwnd == tp->snd_cwnd)
-		return tp->bictcp.cnt; /*  same cwnd, no update */
-      
+	if (tp->bictcp.last_cwnd == tp->snd_cwnd &&
+	   (s32)(tcp_time_stamp - tp->bictcp.last_stamp) <= (HZ>>5))
+		return tp->bictcp.cnt;
+
 	tp->bictcp.last_cwnd = tp->snd_cwnd;
+	tp->bictcp.last_stamp = tcp_time_stamp;
       
 	/* start off normal */
 	if (tp->snd_cwnd <= sysctl_tcp_bic_low_window)
@@ -4612,6 +4625,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 				return 1;
 
 			init_westwood(sk);
+			init_bictcp(tp);
 
 			/* Now we have several options: In theory there is 
 			 * nothing else in the frame. KA9Q has an option to 
@@ -4635,6 +4649,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 
 	case TCP_SYN_SENT:
 		init_westwood(sk);
+		init_bictcp(tp);
 
 		queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
 		if (queued >= 0)

net/ipv4/tcp_minisocks.c

@@ -767,9 +767,6 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct open_request *req,
 		newtp->snd_cwnd = 2;
 		newtp->snd_cwnd_cnt = 0;
 
-		newtp->bictcp.cnt = 0;
-		newtp->bictcp.last_max_cwnd = newtp->bictcp.last_cwnd = 0;
-
 		newtp->frto_counter = 0;
 		newtp->frto_highmark = 0;