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-rw-r--r--net/sched/sch_red.c459
1 files changed, 459 insertions, 0 deletions
diff --git a/net/sched/sch_red.c b/net/sched/sch_red.c
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+/*
+ * 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");
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2024-11-23 17:15:35 +0000