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Date:	Mon, 17 Dec 2007 13:00:16 -0200
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, dccp@...r.kernel.org,
	Gerrit Renker <gerrit@....abdn.ac.uk>,
	Ian McDonald <ian.mcdonald@...di.co.nz>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 2/5] [CCID3]: Remove two irrelevant states in TX feedback handling

From: Gerrit Renker <gerrit@....abdn.ac.uk>

 * the NO_SENT state is only triggered in bidirectional mode,
   costing unnecessary processing.
 * the TERM (terminating) state is irrelevant.

Signed-off-by: Gerrit Renker <gerrit@....abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@...di.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 net/dccp/ccids/ccid3.c |  173 +++++++++++++++++++++++-------------------------
 1 files changed, 84 insertions(+), 89 deletions(-)

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 90e0454..1b1cb74 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -402,112 +402,107 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 	if (!(DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK ||
 	      DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_DATAACK))
 		return;
+	/* ... and only in the established state */
+	if (hctx->ccid3hctx_state != TFRC_SSTATE_FBACK &&
+	    hctx->ccid3hctx_state != TFRC_SSTATE_NO_FBACK)
+		return;
 
 	opt_recv = &hctx->ccid3hctx_options_received;
+	now = ktime_get_real();
 
-	switch (hctx->ccid3hctx_state) {
-	case TFRC_SSTATE_NO_FBACK:
-	case TFRC_SSTATE_FBACK:
-		now = ktime_get_real();
-
-		/* estimate RTT from history if ACK number is valid */
-		r_sample = tfrc_tx_hist_rtt(hctx->ccid3hctx_hist,
-					    DCCP_SKB_CB(skb)->dccpd_ack_seq, now);
-		if (r_sample == 0) {
-			DCCP_WARN("%s(%p): %s with bogus ACK-%llu\n", dccp_role(sk), sk,
-				  dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type),
-				  (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq);
-			return;
-		}
+	/* Estimate RTT from history if ACK number is valid */
+	r_sample = tfrc_tx_hist_rtt(hctx->ccid3hctx_hist,
+				    DCCP_SKB_CB(skb)->dccpd_ack_seq, now);
+	if (r_sample == 0) {
+		DCCP_WARN("%s(%p): %s with bogus ACK-%llu\n", dccp_role(sk), sk,
+			  dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type),
+			  (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq);
+		return;
+	}
+
+	/* Update receive rate in units of 64 * bytes/second */
+	hctx->ccid3hctx_x_recv = opt_recv->ccid3or_receive_rate;
+	hctx->ccid3hctx_x_recv <<= 6;
 
-		/* Update receive rate in units of 64 * bytes/second */
-		hctx->ccid3hctx_x_recv = opt_recv->ccid3or_receive_rate;
-		hctx->ccid3hctx_x_recv <<= 6;
+	/* Update loss event rate (which is scaled by 1e6) */
+	pinv = opt_recv->ccid3or_loss_event_rate;
+	if (pinv == ~0U || pinv == 0)	       /* see RFC 4342, 8.5   */
+		hctx->ccid3hctx_p = 0;
+	else				       /* can not exceed 100% */
+		hctx->ccid3hctx_p = 1000000 / pinv;
+	/*
+	 * Validate new RTT sample and update moving average
+	 */
+	r_sample = dccp_sample_rtt(sk, r_sample);
+	hctx->ccid3hctx_rtt = tfrc_ewma(hctx->ccid3hctx_rtt, r_sample, 9);
 
-		/* Update loss event rate */
-		pinv = opt_recv->ccid3or_loss_event_rate;
-		if (pinv == ~0U || pinv == 0)	       /* see RFC 4342, 8.5   */
-			hctx->ccid3hctx_p = 0;
-		else				       /* can not exceed 100% */
-			hctx->ccid3hctx_p = 1000000 / pinv;
+	if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK) {
 		/*
-		 * Validate new RTT sample and update moving average
+		 * Larger Initial Windows [RFC 4342, sec. 5]
 		 */
-		r_sample = dccp_sample_rtt(sk, r_sample);
-		hctx->ccid3hctx_rtt = tfrc_ewma(hctx->ccid3hctx_rtt, r_sample, 9);
+		hctx->ccid3hctx_x    = rfc3390_initial_rate(sk);
+		hctx->ccid3hctx_t_ld = now;
 
-		if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK) {
-			/*
-			 * Larger Initial Windows [RFC 4342, sec. 5]
-			 */
-			hctx->ccid3hctx_x    = rfc3390_initial_rate(sk);
-			hctx->ccid3hctx_t_ld = now;
+		ccid3_update_send_interval(hctx);
 
-			ccid3_update_send_interval(hctx);
+		ccid3_pr_debug("%s(%p), s=%u, MSS=%u, "
+			       "R_sample=%uus, X=%u\n", dccp_role(sk),
+			       sk, hctx->ccid3hctx_s,
+			       dccp_sk(sk)->dccps_mss_cache, r_sample,
+			       (unsigned)(hctx->ccid3hctx_x >> 6));
 
-			ccid3_pr_debug("%s(%p), s=%u, MSS=%u, "
-				       "R_sample=%uus, X=%u\n", dccp_role(sk),
-				       sk, hctx->ccid3hctx_s,
-				       dccp_sk(sk)->dccps_mss_cache, r_sample,
-				       (unsigned)(hctx->ccid3hctx_x >> 6));
+		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
+	} else {
 
-			ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
-		} else {
+		/* Update sending rate (step 4 of [RFC 3448, 4.3]) */
+		if (hctx->ccid3hctx_p > 0)
+			hctx->ccid3hctx_x_calc =
+				tfrc_calc_x(hctx->ccid3hctx_s,
+					    hctx->ccid3hctx_rtt,
+					    hctx->ccid3hctx_p);
+		ccid3_hc_tx_update_x(sk, &now);
 
-			/* Update sending rate (step 4 of [RFC 3448, 4.3]) */
-			if (hctx->ccid3hctx_p > 0)
-				hctx->ccid3hctx_x_calc =
-					tfrc_calc_x(hctx->ccid3hctx_s,
-						    hctx->ccid3hctx_rtt,
-						    hctx->ccid3hctx_p);
-			ccid3_hc_tx_update_x(sk, &now);
-
-			ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, "
-				       "p=%u, X_calc=%u, X_recv=%u, X=%u\n",
-				       dccp_role(sk),
-				       sk, hctx->ccid3hctx_rtt, r_sample,
-				       hctx->ccid3hctx_s, hctx->ccid3hctx_p,
-				       hctx->ccid3hctx_x_calc,
-				       (unsigned)(hctx->ccid3hctx_x_recv >> 6),
-				       (unsigned)(hctx->ccid3hctx_x >> 6));
-		}
+		ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, "
+			       "p=%u, X_calc=%u, X_recv=%u, X=%u\n",
+			       dccp_role(sk),
+			       sk, hctx->ccid3hctx_rtt, r_sample,
+			       hctx->ccid3hctx_s, hctx->ccid3hctx_p,
+			       hctx->ccid3hctx_x_calc,
+			       (unsigned)(hctx->ccid3hctx_x_recv >> 6),
+			       (unsigned)(hctx->ccid3hctx_x >> 6));
+	}
 
-		/* unschedule no feedback timer */
-		sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);
+	/* unschedule no feedback timer */
+	sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);
 
-		/*
-		 * As we have calculated new ipi, delta, t_nom it is possible
-		 * that we now can send a packet, so wake up dccp_wait_for_ccid
-		 */
-		sk->sk_write_space(sk);
+	/*
+	 * As we have calculated new ipi, delta, t_nom it is possible
+	 * that we now can send a packet, so wake up dccp_wait_for_ccid
+	 */
+	sk->sk_write_space(sk);
 
-		/*
-		 * Update timeout interval for the nofeedback timer.
-		 * We use a configuration option to increase the lower bound.
-		 * This can help avoid triggering the nofeedback timer too
-		 * often ('spinning') on LANs with small RTTs.
-		 */
-		hctx->ccid3hctx_t_rto = max_t(u32, 4 * hctx->ccid3hctx_rtt,
-						   CONFIG_IP_DCCP_CCID3_RTO *
-						   (USEC_PER_SEC/1000));
-		/*
-		 * Schedule no feedback timer to expire in
-		 * max(t_RTO, 2 * s/X)  =  max(t_RTO, 2 * t_ipi)
-		 */
-		t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
+	/*
+	 * Update timeout interval for the nofeedback timer.
+	 * We use a configuration option to increase the lower bound.
+	 * This can help avoid triggering the nofeedback timer too
+	 * often ('spinning') on LANs with small RTTs.
+	 */
+	hctx->ccid3hctx_t_rto = max_t(u32, 4 * hctx->ccid3hctx_rtt,
+					   (CONFIG_IP_DCCP_CCID3_RTO *
+					    (USEC_PER_SEC / 1000)));
+	/*
+	 * Schedule no feedback timer to expire in
+	 * max(t_RTO, 2 * s/X)  =  max(t_RTO, 2 * t_ipi)
+	 */
+	t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
 
-		ccid3_pr_debug("%s(%p), Scheduled no feedback timer to "
-			       "expire in %lu jiffies (%luus)\n",
-			       dccp_role(sk),
-			       sk, usecs_to_jiffies(t_nfb), t_nfb);
+	ccid3_pr_debug("%s(%p), Scheduled no feedback timer to "
+		       "expire in %lu jiffies (%luus)\n",
+		       dccp_role(sk),
+		       sk, usecs_to_jiffies(t_nfb), t_nfb);
 
-		sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
-				   jiffies + usecs_to_jiffies(t_nfb));
-		break;
-	case TFRC_SSTATE_NO_SENT:	/* fall through */
-	case TFRC_SSTATE_TERM:		/* ignore feedback when closing */
-		break;
-	}
+	sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
+			   jiffies + usecs_to_jiffies(t_nfb));
 }
 
 static int ccid3_hc_tx_parse_options(struct sock *sk, unsigned char option,
-- 
1.5.3.6

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