[PKT_SCHED]: RED: Use new generic red interface

Simplifies code a lot by separating the red algorithm and the
queueing logic. We now differentiate between probability marks
and forced marks but sum them together again to not break
backwards compatibility.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

net/sched/sch_red.c

@@ -41,44 +41,10 @@
 #include <net/pkt_sched.h>
 #include <net/inet_ecn.h>
 #include <net/dsfield.h>
+#include <net/red.h>
 
 
-/*	Random Early Detection (RED) algorithm.
-	=======================================
-
-	Source: Sally Floyd and Van Jacobson, "Random Early Detection Gateways
-	for Congestion Avoidance", 1993, IEEE/ACM Transactions on Networking.
-
-	This file codes a "divisionless" version of RED algorithm
-	as written down in Fig.17 of the paper.
-
-Short description.
-------------------
-
-	When a new packet arrives we calculate the average queue length:
-
-	avg = (1-W)*avg + W*current_queue_len,
-
-	W is the filter time constant (chosen as 2^(-Wlog)), it controls
-	the inertia of the algorithm. To allow larger bursts, W should be
-	decreased.
-
-	if (avg > th_max) -> packet marked (dropped).
-	if (avg < th_min) -> packet passes.
-	if (th_min < avg < th_max) we calculate probability:
-
-	Pb = max_P * (avg - th_min)/(th_max-th_min)
-
-	and mark (drop) packet with this probability.
-	Pb changes from 0 (at avg==th_min) to max_P (avg==th_max).
-	max_P should be small (not 1), usually 0.01..0.02 is good value.
-
-	max_P is chosen as a number, so that max_P/(th_max-th_min)
-	is a negative power of two in order arithmetics to contain
-	only shifts.
-
-
-	Parameters, settable by user:
+/*	Parameters, settable by user:
 	-----------------------------
 
 	limit		- bytes (must be > qth_max + burst)
@@ -89,92 +55,19 @@ Short description.
 	arbitrarily high (well, less than ram size)
 	Really, this limit will never be reached
 	if RED works correctly.
-
-	qth_min		- bytes (should be < qth_max/2)
-	qth_max		- bytes (should be at least 2*qth_min and less limit)
-	Wlog	       	- bits (<32) log(1/W).
-	Plog	       	- bits (<32)
-
-	Plog is related to max_P by formula:
-
-	max_P = (qth_max-qth_min)/2^Plog;
-
-	F.e. if qth_max=128K and qth_min=32K, then Plog=22
-	corresponds to max_P=0.02
-
-	Scell_log
-	Stab
-
-	Lookup table for log((1-W)^(t/t_ave).
-
-
-NOTES:
-
-Upper bound on W.
------------------
-
-	If you want to allow bursts of L packets of size S,
-	you should choose W:
-
-	L + 1 - th_min/S < (1-(1-W)^L)/W
-
-	th_min/S = 32         th_min/S = 4
-			                       
-	log(W)	L
-	-1	33
-	-2	35
-	-3	39
-	-4	46
-	-5	57
-	-6	75
-	-7	101
-	-8	135
-	-9	190
-	etc.
  */
 
 struct red_sched_data
 {
-/* Parameters */
-	u32		limit;		/* HARD maximal queue length	*/
-	u32		qth_min;	/* Min average length threshold: A scaled */
-	u32		qth_max;	/* Max average length threshold: A scaled */
-	u32		Rmask;
-	u32		Scell_max;
-	unsigned char	flags;
-	char		Wlog;		/* log(W)		*/
-	char		Plog;		/* random number bits	*/
-	char		Scell_log;
-	u8		Stab[256];
-
-/* Variables */
-	unsigned long	qave;		/* Average queue length: A scaled */
-	int		qcount;		/* Packets since last random number generation */
-	u32		qR;		/* Cached random number */
-
-	psched_time_t	qidlestart;	/* Start of idle period		*/
-	struct tc_red_xstats st;
+	u32			limit;		/* HARD maximal queue length */
+	unsigned char		flags;
+	struct red_parms	parms;
+	struct red_stats	stats;
 };
 
-static int red_ecn_mark(struct sk_buff *skb)
+static inline int red_use_ecn(struct red_sched_data *q)
 {
-	if (skb->nh.raw + 20 > skb->tail)
-		return 0;
-
-	switch (skb->protocol) {
-	case __constant_htons(ETH_P_IP):
-		if (INET_ECN_is_not_ect(skb->nh.iph->tos))
-			return 0;
-		IP_ECN_set_ce(skb->nh.iph);
-		return 1;
-	case __constant_htons(ETH_P_IPV6):
-		if (INET_ECN_is_not_ect(ipv6_get_dsfield(skb->nh.ipv6h)))
-			return 0;
-		IP6_ECN_set_ce(skb->nh.ipv6h);
-		return 1;
-	default:
-		return 0;
-	}
+	return q->flags & TC_RED_ECN;
 }
 
 static int
@@ -182,119 +75,50 @@ red_enqueue(struct sk_buff *skb, struct Qdisc* sch)
 {
 	struct red_sched_data *q = qdisc_priv(sch);
 
-	psched_time_t now;
+	q->parms.qavg = red_calc_qavg(&q->parms, sch->qstats.backlog);
 
-	if (!PSCHED_IS_PASTPERFECT(q->qidlestart)) {
-		long us_idle;
-		int  shift;
+	if (red_is_idling(&q->parms))
+		red_end_of_idle_period(&q->parms);
 
-		PSCHED_GET_TIME(now);
-		us_idle = PSCHED_TDIFF_SAFE(now, q->qidlestart, q->Scell_max);
-		PSCHED_SET_PASTPERFECT(q->qidlestart);
+	switch (red_action(&q->parms, q->parms.qavg)) {
+		case RED_DONT_MARK:
+			break;
 
-/*
-   The problem: ideally, average length queue recalcultion should
-   be done over constant clock intervals. This is too expensive, so that
-   the calculation is driven by outgoing packets.
-   When the queue is idle we have to model this clock by hand.
-
-   SF+VJ proposed to "generate" m = idletime/(average_pkt_size/bandwidth)
-   dummy packets as a burst after idle time, i.e.
-
-          q->qave *= (1-W)^m
-
-   This is an apparently overcomplicated solution (f.e. we have to precompute
-   a table to make this calculation in reasonable time)
-   I believe that a simpler model may be used here,
-   but it is field for experiments.
-*/
-		shift = q->Stab[us_idle>>q->Scell_log];
-
-		if (shift) {
-			q->qave >>= shift;
-		} else {
-			/* Approximate initial part of exponent
-			   with linear function:
-			   (1-W)^m ~= 1-mW + ...
-
-			   Seems, it is the best solution to
-			   problem of too coarce exponent tabulation.
-			 */
-
-			us_idle = (q->qave * us_idle)>>q->Scell_log;
-			if (us_idle < q->qave/2)
-				q->qave -= us_idle;
-			else
-				q->qave >>= 1;
-		}
-	} else {
-		q->qave += sch->qstats.backlog - (q->qave >> q->Wlog);
-		/* NOTE:
-		   q->qave is fixed point number with point at Wlog.
-		   The formulae above is equvalent to floating point
-		   version:
-
-		   qave = qave*(1-W) + sch->qstats.backlog*W;
-		                                           --ANK (980924)
-		 */
-	}
+		case RED_PROB_MARK:
+			sch->qstats.overlimits++;
+			if (!red_use_ecn(q) || !INET_ECN_set_ce(skb)) {
+				q->stats.prob_drop++;
+				goto congestion_drop;
+			}
 
-	if (q->qave < q->qth_min) {
-		q->qcount = -1;
-enqueue:
-		if (sch->qstats.backlog + skb->len <= q->limit) {
-			__skb_queue_tail(&sch->q, skb);
-			sch->qstats.backlog += skb->len;
-			sch->bstats.bytes += skb->len;
-			sch->bstats.packets++;
-			return NET_XMIT_SUCCESS;
-		} else {
-			q->st.pdrop++;
-		}
-		kfree_skb(skb);
-		sch->qstats.drops++;
-		return NET_XMIT_DROP;
-	}
-	if (q->qave >= q->qth_max) {
-		q->qcount = -1;
-		sch->qstats.overlimits++;
-mark:
-		if  (!(q->flags&TC_RED_ECN) || !red_ecn_mark(skb)) {
-			q->st.early++;
-			goto drop;
-		}
-		q->st.marked++;
-		goto enqueue;
+			q->stats.prob_mark++;
+			break;
+
+		case RED_HARD_MARK:
+			sch->qstats.overlimits++;
+			if (!red_use_ecn(q) || !INET_ECN_set_ce(skb)) {
+				q->stats.forced_drop++;
+				goto congestion_drop;
+			}
+
+			q->stats.forced_mark++;
+			break;
 	}
 
-	if (++q->qcount) {
-		/* The formula used below causes questions.
-
-		   OK. qR is random number in the interval 0..Rmask
-		   i.e. 0..(2^Plog). If we used floating point
-		   arithmetics, it would be: (2^Plog)*rnd_num,
-		   where rnd_num is less 1.
-
-		   Taking into account, that qave have fixed
-		   point at Wlog, and Plog is related to max_P by
-		   max_P = (qth_max-qth_min)/2^Plog; two lines
-		   below have the following floating point equivalent:
-		   
-		   max_P*(qave - qth_min)/(qth_max-qth_min) < rnd/qcount
-
-		   Any questions? --ANK (980924)
-		 */
-		if (((q->qave - q->qth_min)>>q->Wlog)*q->qcount < q->qR)
-			goto enqueue;
-		q->qcount = 0;
-		q->qR = net_random()&q->Rmask;
-		sch->qstats.overlimits++;
-		goto mark;
+	if (sch->qstats.backlog + skb->len <= q->limit) {
+		__skb_queue_tail(&sch->q, skb);
+		sch->qstats.backlog += skb->len;
+		sch->bstats.bytes += skb->len;
+		sch->bstats.packets++;
+		return NET_XMIT_SUCCESS;
 	}
-	q->qR = net_random()&q->Rmask;
-	goto enqueue;
 
-drop:
+	q->stats.pdrop++;
+	kfree_skb(skb);
+	sch->qstats.drops++;
+	return NET_XMIT_DROP;
+
+congestion_drop:
 	kfree_skb(skb);
 	sch->qstats.drops++;
 	return NET_XMIT_CN;
@@ -305,7 +129,8 @@ red_requeue(struct sk_buff *skb, struct Qdisc* sch)
 {
 	struct red_sched_data *q = qdisc_priv(sch);
 
-	PSCHED_SET_PASTPERFECT(q->qidlestart);
+	if (red_is_idling(&q->parms))
+		red_end_of_idle_period(&q->parms);
 
 	__skb_queue_head(&sch->q, skb);
 	sch->qstats.backlog += skb->len;
@@ -324,7 +149,8 @@ red_dequeue(struct Qdisc* sch)
 		sch->qstats.backlog -= skb->len;
 		return skb;
 	}
-	PSCHED_GET_TIME(q->qidlestart);
+
+	red_start_of_idle_period(&q->parms);
 	return NULL;
 }
 
@@ -338,11 +164,12 @@ static unsigned int red_drop(struct Qdisc* sch)
 		unsigned int len = skb->len;
 		sch->qstats.backlog -= len;
 		sch->qstats.drops++;
-		q->st.other++;
+		q->stats.other++;
 		kfree_skb(skb);
 		return len;
 	}
-	PSCHED_GET_TIME(q->qidlestart);
+
+	red_start_of_idle_period(&q->parms);
 	return 0;
 }
 
@@ -352,9 +179,7 @@ static void red_reset(struct Qdisc* sch)
 
 	__skb_queue_purge(&sch->q);
 	sch->qstats.backlog = 0;
-	PSCHED_SET_PASTPERFECT(q->qidlestart);
-	q->qave = 0;
-	q->qcount = -1;
+	red_restart(&q->parms);
 }
 
 static int red_change(struct Qdisc *sch, struct rtattr *opt)
@@ -374,19 +199,14 @@ static int red_change(struct Qdisc *sch, struct rtattr *opt)
 
 	sch_tree_lock(sch);
 	q->flags = ctl->flags;
-	q->Wlog = ctl->Wlog;
-	q->Plog = ctl->Plog;
-	q->Rmask = ctl->Plog < 32 ? ((1<<ctl->Plog) - 1) : ~0UL;
-	q->Scell_log = ctl->Scell_log;
-	q->Scell_max = (255<<q->Scell_log);
-	q->qth_min = ctl->qth_min<<ctl->Wlog;
-	q->qth_max = ctl->qth_max<<ctl->Wlog;
 	q->limit = ctl->limit;
-	memcpy(q->Stab, RTA_DATA(tb[TCA_RED_STAB-1]), 256);
 
-	q->qcount = -1;
+	red_set_parms(&q->parms, ctl->qth_min, ctl->qth_max, ctl->Wlog,
+				 ctl->Plog, ctl->Scell_log,
+				 RTA_DATA(tb[TCA_RED_STAB-1]));
+
 	if (skb_queue_empty(&sch->q))
-		PSCHED_SET_PASTPERFECT(q->qidlestart);
+		red_end_of_idle_period(&q->parms);
 	sch_tree_unlock(sch);
 	return 0;
 }
@@ -401,17 +221,18 @@ static int red_dump(struct Qdisc *sch, struct sk_buff *skb)
 	struct red_sched_data *q = qdisc_priv(sch);
 	unsigned char	 *b = skb->tail;
 	struct rtattr *rta;
-	struct tc_red_qopt opt;
+	struct tc_red_qopt opt = {
+		.limit		= q->limit,
+		.flags		= q->flags,
+		.qth_min	= q->parms.qth_min >> q->parms.Wlog,
+		.qth_max	= q->parms.qth_max >> q->parms.Wlog,
+		.Wlog		= q->parms.Wlog,
+		.Plog		= q->parms.Plog,
+		.Scell_log	= q->parms.Scell_log,
+	};
 
 	rta = (struct rtattr*)b;
 	RTA_PUT(skb, TCA_OPTIONS, 0, NULL);
-	opt.limit = q->limit;
-	opt.qth_min = q->qth_min>>q->Wlog;
-	opt.qth_max = q->qth_max>>q->Wlog;
-	opt.Wlog = q->Wlog;
-	opt.Plog = q->Plog;
-	opt.Scell_log = q->Scell_log;
-	opt.flags = q->flags;
 	RTA_PUT(skb, TCA_RED_PARMS, sizeof(opt), &opt);
 	rta->rta_len = skb->tail - b;
 
@@ -425,8 +246,14 @@ rtattr_failure:
 static int red_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
 {
 	struct red_sched_data *q = qdisc_priv(sch);
-
-	return gnet_stats_copy_app(d, &q->st, sizeof(q->st));
+	struct tc_red_xstats st = {
+		.early	= q->stats.prob_drop + q->stats.forced_drop,
+		.pdrop	= q->stats.pdrop,
+		.other	= q->stats.other,
+		.marked	= q->stats.prob_mark + q->stats.forced_mark,
+	};
+
+	return gnet_stats_copy_app(d, &st, sizeof(st));
 }
 
 static struct Qdisc_ops red_qdisc_ops = {