[DCCP] CCID2: Add helper functions for changing important CCID2 state

Introduce methods which manipulate interesting congestion control
state such as pipe and rtt estimate.  This is useful for people
wishing to monitor the variables of CCID and instrument the code
[perhaps using Kprobes].  Personally, I am a fan of
encapsulation---that justifies this change =D.

Signed-off-by: Andrea Bittau <a.bittau@cs.ucl.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dccp/ccids/ccid2.c

@@ -199,6 +199,17 @@ static void ccid2_change_cwnd(struct ccid2_hc_tx_sock *hctx, int val)
 	hctx->ccid2hctx_cwnd = val;
 }
 
+static void ccid2_change_srtt(struct ccid2_hc_tx_sock *hctx, long val)
+{
+	ccid2_pr_debug("change SRTT to %ld\n", val);
+	hctx->ccid2hctx_srtt = val;
+}
+
+static void ccid2_change_pipe(struct ccid2_hc_tx_sock *hctx, long val)
+{
+	hctx->ccid2hctx_pipe = val;
+}
+
 static void ccid2_start_rto_timer(struct sock *sk);
 
 static void ccid2_hc_tx_rto_expire(unsigned long data)
@@ -228,7 +239,7 @@ static void ccid2_hc_tx_rto_expire(unsigned long data)
 	ccid2_start_rto_timer(sk);
 
 	/* adjust pipe, cwnd etc */
-	hctx->ccid2hctx_pipe = 0;
+	ccid2_change_pipe(hctx, 0);
 	hctx->ccid2hctx_ssthresh = hctx->ccid2hctx_cwnd >> 1;
 	if (hctx->ccid2hctx_ssthresh < 2)
 		hctx->ccid2hctx_ssthresh = 2;
@@ -274,7 +285,7 @@ static void ccid2_hc_tx_packet_sent(struct sock *sk, int more, int len)
 
 	BUG_ON(!hctx->ccid2hctx_sendwait);
 	hctx->ccid2hctx_sendwait = 0;
-	hctx->ccid2hctx_pipe++;
+	ccid2_change_pipe(hctx, hctx->ccid2hctx_pipe + 1);
 	BUG_ON(hctx->ccid2hctx_pipe < 0);
 
 	/* There is an issue.  What if another packet is sent between
@@ -470,11 +481,13 @@ static inline void ccid2_new_ack(struct sock *sk,
 		if (hctx->ccid2hctx_srtt == -1) {
 			ccid2_pr_debug("R: %lu Time=%lu seq=%llu\n",
 			       	       r, jiffies, seqp->ccid2s_seq);
-			hctx->ccid2hctx_srtt = r;
+			ccid2_change_srtt(hctx, r);
 			hctx->ccid2hctx_rttvar = r >> 1;
 		} else {
 			/* RTTVAR */
 			long tmp = hctx->ccid2hctx_srtt - r;
+			long srtt;
+
 			if (tmp < 0)
 				tmp *= -1;
 
@@ -484,10 +497,12 @@ static inline void ccid2_new_ack(struct sock *sk,
 			hctx->ccid2hctx_rttvar += tmp;
 
 			/* SRTT */
-			hctx->ccid2hctx_srtt *= 7;
-			hctx->ccid2hctx_srtt >>= 3;
+			srtt = hctx->ccid2hctx_srtt;
+			srtt *= 7;
+			srtt >>= 3;
 			tmp = r >> 3;
-			hctx->ccid2hctx_srtt += tmp;
+			srtt += tmp;
+			ccid2_change_srtt(hctx, srtt);
 		}
 		s = hctx->ccid2hctx_rttvar << 2;
 		/* clock granularity is 1 when based on jiffies */
@@ -523,7 +538,7 @@ static void ccid2_hc_tx_dec_pipe(struct sock *sk)
 {
 	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
 
-	hctx->ccid2hctx_pipe--;
+	ccid2_change_pipe(hctx, hctx->ccid2hctx_pipe-1);
 	BUG_ON(hctx->ccid2hctx_pipe < 0);
 
 	if (hctx->ccid2hctx_pipe == 0)
@@ -749,7 +764,7 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
 
 	hctx->ccid2hctx_sent	 = 0;
 	hctx->ccid2hctx_rto	 = 3 * HZ;
-	hctx->ccid2hctx_srtt	 = -1;
+	ccid2_change_srtt(hctx, -1);
 	hctx->ccid2hctx_rttvar	 = -1;
 	hctx->ccid2hctx_lastrtt  = 0;
 	hctx->ccid2hctx_rpdupack = -1;