1 files changed, 459 insertions, 0 deletions

diff --git a/net/sched/sch_red.c b/net/sched/sch_red.c
new file mode 100644
index 0000000..664d0e4
--- /dev/null
+++ b/net/sched/sch_red.c
@@ -0,0 +1,459 @@
+/*
+ * net/sched/sch_red.c	Random Early Detection queue.
+ *
+ *		This program is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ *
+ * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
+ *
+ * Changes:
+ * J Hadi Salim <hadi@nortel.com> 980914:	computation fixes
+ * Alexey Makarenko <makar@phoenix.kharkov.ua> 990814: qave on idle link was calculated incorrectly.
+ * J Hadi Salim <hadi@nortelnetworks.com> 980816:  ECN support	
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <asm/uaccess.h>
+#include <asm/system.h>
+#include <linux/bitops.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/in.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/if_ether.h>
+#include <linux/inet.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/notifier.h>
+#include <net/ip.h>
+#include <net/route.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/pkt_sched.h>
+#include <net/inet_ecn.h>
+#include <net/dsfield.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:
+	-----------------------------
+
+	limit		- bytes (must be > qth_max + burst)
+
+	Hard limit on queue length, should be chosen >qth_max
+	to allow packet bursts. This parameter does not
+	affect the algorithms behaviour and can be chosen
+	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;
+};
+
+static int red_ecn_mark(struct sk_buff *skb)
+{
+	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;
+	}
+}
+
+static int
+red_enqueue(struct sk_buff *skb, struct Qdisc* sch)
+{
+	struct red_sched_data *q = qdisc_priv(sch);
+
+	psched_time_t now;
+
+	if (!PSCHED_IS_PASTPERFECT(q->qidlestart)) {
+		long us_idle;
+		int  shift;
+
+		PSCHED_GET_TIME(now);
+		us_idle = PSCHED_TDIFF_SAFE(now, q->qidlestart, q->Scell_max);
+		PSCHED_SET_PASTPERFECT(q->qidlestart);
+
+/*
+   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)
+		 */
+	}
+
+	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;
+	}
+
+	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;
+	}
+	q->qR = net_random()&q->Rmask;
+	goto enqueue;
+
+drop:
+	kfree_skb(skb);
+	sch->qstats.drops++;
+	return NET_XMIT_CN;
+}
+
+static int
+red_requeue(struct sk_buff *skb, struct Qdisc* sch)
+{
+	struct red_sched_data *q = qdisc_priv(sch);
+
+	PSCHED_SET_PASTPERFECT(q->qidlestart);
+
+	__skb_queue_head(&sch->q, skb);
+	sch->qstats.backlog += skb->len;
+	sch->qstats.requeues++;
+	return 0;
+}
+
+static struct sk_buff *
+red_dequeue(struct Qdisc* sch)
+{
+	struct sk_buff *skb;
+	struct red_sched_data *q = qdisc_priv(sch);
+
+	skb = __skb_dequeue(&sch->q);
+	if (skb) {
+		sch->qstats.backlog -= skb->len;
+		return skb;
+	}
+	PSCHED_GET_TIME(q->qidlestart);
+	return NULL;
+}
+
+static unsigned int red_drop(struct Qdisc* sch)
+{
+	struct sk_buff *skb;
+	struct red_sched_data *q = qdisc_priv(sch);
+
+	skb = __skb_dequeue_tail(&sch->q);
+	if (skb) {
+		unsigned int len = skb->len;
+		sch->qstats.backlog -= len;
+		sch->qstats.drops++;
+		q->st.other++;
+		kfree_skb(skb);
+		return len;
+	}
+	PSCHED_GET_TIME(q->qidlestart);
+	return 0;
+}
+
+static void red_reset(struct Qdisc* sch)
+{
+	struct red_sched_data *q = qdisc_priv(sch);
+
+	__skb_queue_purge(&sch->q);
+	sch->qstats.backlog = 0;
+	PSCHED_SET_PASTPERFECT(q->qidlestart);
+	q->qave = 0;
+	q->qcount = -1;
+}
+
+static int red_change(struct Qdisc *sch, struct rtattr *opt)
+{
+	struct red_sched_data *q = qdisc_priv(sch);
+	struct rtattr *tb[TCA_RED_STAB];
+	struct tc_red_qopt *ctl;
+
+	if (opt == NULL ||
+	    rtattr_parse_nested(tb, TCA_RED_STAB, opt) ||
+	    tb[TCA_RED_PARMS-1] == 0 || tb[TCA_RED_STAB-1] == 0 ||
+	    RTA_PAYLOAD(tb[TCA_RED_PARMS-1]) < sizeof(*ctl) ||
+	    RTA_PAYLOAD(tb[TCA_RED_STAB-1]) < 256)
+		return -EINVAL;
+
+	ctl = RTA_DATA(tb[TCA_RED_PARMS-1]);
+
+	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;
+	if (skb_queue_len(&sch->q) == 0)
+		PSCHED_SET_PASTPERFECT(q->qidlestart);
+	sch_tree_unlock(sch);
+	return 0;
+}
+
+static int red_init(struct Qdisc* sch, struct rtattr *opt)
+{
+	return red_change(sch, opt);
+}
+
+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;
+
+	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;
+
+	return skb->len;
+
+rtattr_failure:
+	skb_trim(skb, b - skb->data);
+	return -1;
+}
+
+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));
+}
+
+static struct Qdisc_ops red_qdisc_ops = {
+	.next		=	NULL,
+	.cl_ops		=	NULL,
+	.id		=	"red",
+	.priv_size	=	sizeof(struct red_sched_data),
+	.enqueue	=	red_enqueue,
+	.dequeue	=	red_dequeue,
+	.requeue	=	red_requeue,
+	.drop		=	red_drop,
+	.init		=	red_init,
+	.reset		=	red_reset,
+	.change		=	red_change,
+	.dump		=	red_dump,
+	.dump_stats	=	red_dump_stats,
+	.owner		=	THIS_MODULE,
+};
+
+static int __init red_module_init(void)
+{
+	return register_qdisc(&red_qdisc_ops);
+}
+static void __exit red_module_exit(void) 
+{
+	unregister_qdisc(&red_qdisc_ops);
+}
+module_init(red_module_init)
+module_exit(red_module_exit)
+MODULE_LICENSE("GPL");