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[dragonfly.git] / sys / net / altq / altq_red.c

/*      $KAME: altq_red.c,v 1.19 2004/04/17 10:54:49 kjc Exp $  */
/*      $DragonFly: src/sys/net/altq/altq_red.c,v 1.4 2006/12/22 23:44:55 swildner Exp $ */

/*
 * Copyright (C) 1997-2003
 *      Sony Computer Science Laboratories Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY SONY CSL AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL SONY CSL OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */
/*
 * Copyright (c) 1990-1994 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the Computer Systems
 *      Engineering Group at Lawrence Berkeley Laboratory.
 * 4. Neither the name of the University nor of the Laboratory may be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "opt_altq.h"
#include "opt_inet.h"
#include "opt_inet6.h"

#ifdef ALTQ_RED /* red is enabled by ALTQ_RED option in opt_altq.h */

#include <sys/param.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/systm.h>
#include <sys/errno.h>

#include <net/if.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#ifdef INET6
#include <netinet/ip6.h>
#endif

#include <net/pf/pfvar.h>
#include <net/altq/altq.h>
#include <net/altq/altq_red.h>

/*
 * ALTQ/RED (Random Early Detection) implementation using 32-bit
 * fixed-point calculation.
 *
 * written by kjc using the ns code as a reference.
 * you can learn more about red and ns from Sally's home page at
 * http://www-nrg.ee.lbl.gov/floyd/
 *
 * most of the red parameter values are fixed in this implementation
 * to prevent fixed-point overflow/underflow.
 * if you change the parameters, watch out for overflow/underflow!
 *
 * the parameters used are recommended values by Sally.
 * the corresponding ns config looks:
 *      q_weight=0.00195
 *      minthresh=5 maxthresh=15 queue-size=60
 *      linterm=30
 *      dropmech=drop-tail
 *      bytes=false (can't be handled by 32-bit fixed-point)
 *      doubleq=false dqthresh=false
 *      wait=true
 */
/*
 * alternative red parameters for a slow link.
 *
 * assume the queue length becomes from zero to L and keeps L, it takes
 * N packets for q_avg to reach 63% of L.
 * when q_weight is 0.002, N is about 500 packets.
 * for a slow link like dial-up, 500 packets takes more than 1 minute!
 * when q_weight is 0.008, N is about 127 packets.
 * when q_weight is 0.016, N is about 63 packets.
 * bursts of 50 packets are allowed for 0.002, bursts of 25 packets
 * are allowed for 0.016.
 * see Sally's paper for more details.
 */
/* normal red parameters */
#define W_WEIGHT        512     /* inverse of weight of EWMA (511/512) */
                                /* q_weight = 0.00195 */

/* red parameters for a slow link */
#define W_WEIGHT_1      128     /* inverse of weight of EWMA (127/128) */
                                /* q_weight = 0.0078125 */

/* red parameters for a very slow link (e.g., dialup) */
#define W_WEIGHT_2      64      /* inverse of weight of EWMA (63/64) */
                                /* q_weight = 0.015625 */

/* fixed-point uses 12-bit decimal places */
#define FP_SHIFT        12      /* fixed-point shift */

/* red parameters for drop probability */
#define INV_P_MAX       10      /* inverse of max drop probability */
#define TH_MIN          5       /* min threshold */
#define TH_MAX          15      /* max threshold */

#define RED_LIMIT       60      /* default max queue lenght */
#define RED_STATS               /* collect statistics */

/*
 * our default policy for forced-drop is drop-tail.
 * (in altq-1.1.2 or earlier, the default was random-drop.
 * but it makes more sense to punish the cause of the surge.)
 * to switch to the random-drop policy, define "RED_RANDOM_DROP".
 */

/* default red parameter values */
static int default_th_min = TH_MIN;
static int default_th_max = TH_MAX;
static int default_inv_pmax = INV_P_MAX;

/*
 * red support routines
 */
red_t *
red_alloc(int weight, int inv_pmax, int th_min, int th_max, int flags, int pkttime)
{
        red_t *rp;
        int w, i;
        int npkts_per_sec;

        rp = kmalloc(sizeof(*rp), M_ALTQ, M_WAITOK | M_ZERO);
        rp->red_avg = 0;
        rp->red_idle = 1;

        if (weight == 0)
                rp->red_weight = W_WEIGHT;
        else
                rp->red_weight = weight;
        if (inv_pmax == 0)
                rp->red_inv_pmax = default_inv_pmax;
        else
                rp->red_inv_pmax = inv_pmax;
        if (th_min == 0)
                rp->red_thmin = default_th_min;
        else
                rp->red_thmin = th_min;
        if (th_max == 0)
                rp->red_thmax = default_th_max;
        else
                rp->red_thmax = th_max;

        rp->red_flags = flags;

        if (pkttime == 0)
                /* default packet time: 1000 bytes / 10Mbps * 8 * 1000000 */
                rp->red_pkttime = 800;
        else
                rp->red_pkttime = pkttime;

        if (weight == 0) {
                /* when the link is very slow, adjust red parameters */
                npkts_per_sec = 1000000 / rp->red_pkttime;
                if (npkts_per_sec < 50) {
                        /* up to about 400Kbps */
                        rp->red_weight = W_WEIGHT_2;
                } else if (npkts_per_sec < 300) {
                        /* up to about 2.4Mbps */
                        rp->red_weight = W_WEIGHT_1;
                }
        }

        /* calculate wshift.  weight must be power of 2 */
        w = rp->red_weight;
        for (i = 0; w > 1; i++)
                w = w >> 1;
        rp->red_wshift = i;
        w = 1 << rp->red_wshift;
        if (w != rp->red_weight) {
                kprintf("invalid weight value %d for red! use %d\n",
                       rp->red_weight, w);
                rp->red_weight = w;
        }

        /*
         * thmin_s and thmax_s are scaled versions of th_min and th_max
         * to be compared with avg.
         */
        rp->red_thmin_s = rp->red_thmin << (rp->red_wshift + FP_SHIFT);
        rp->red_thmax_s = rp->red_thmax << (rp->red_wshift + FP_SHIFT);

        /*
         * precompute probability denominator
         *  probd = (2 * (TH_MAX-TH_MIN) / pmax) in fixed-point
         */
        rp->red_probd = (2 * (rp->red_thmax - rp->red_thmin)
                         * rp->red_inv_pmax) << FP_SHIFT;

        /* allocate weight table */
        rp->red_wtab = wtab_alloc(rp->red_weight);

        microtime(&rp->red_last);
        return (rp);
}

void
red_destroy(red_t *rp)
{
        wtab_destroy(rp->red_wtab);
        kfree(rp, M_ALTQ);
}

void
red_getstats(red_t *rp, struct redstats *sp)
{
        sp->q_avg = rp->red_avg >> rp->red_wshift;
        sp->xmit_cnt = rp->red_stats.xmit_cnt;
        sp->drop_cnt = rp->red_stats.drop_cnt;
        sp->drop_forced = rp->red_stats.drop_forced;
        sp->drop_unforced = rp->red_stats.drop_unforced;
        sp->marked_packets = rp->red_stats.marked_packets;
}

int
red_addq(red_t *rp, class_queue_t *q, struct mbuf *m, struct altq_pktattr *pktattr)
{
        int avg, droptype;
        int n;

        avg = rp->red_avg;

        /*
         * if we were idle, we pretend that n packets arrived during
         * the idle period.
         */
        if (rp->red_idle) {
                struct timeval now;
                int t;

                rp->red_idle = 0;
                microtime(&now);
                t = (now.tv_sec - rp->red_last.tv_sec);
                if (t > 60) {
                        /*
                         * being idle for more than 1 minute, set avg to zero.
                         * this prevents t from overflow.
                         */
                        avg = 0;
                } else {
                        t = t * 1000000 + (now.tv_usec - rp->red_last.tv_usec);
                        n = t / rp->red_pkttime - 1;

                        /* the following line does (avg = (1 - Wq)^n * avg) */
                        if (n > 0)
                                avg = (avg >> FP_SHIFT) *
                                    pow_w(rp->red_wtab, n);
                }
        }

        /* run estimator. (note: avg is scaled by WEIGHT in fixed-point) */
        avg += (qlen(q) << FP_SHIFT) - (avg >> rp->red_wshift);
        rp->red_avg = avg;              /* save the new value */

        /*
         * red_count keeps a tally of arriving traffic that has not
         * been dropped.
         */
        rp->red_count++;

        /* see if we drop early */
        droptype = DTYPE_NODROP;
        if (avg >= rp->red_thmin_s && qlen(q) > 1) {
                if (avg >= rp->red_thmax_s) {
                        /* avg >= th_max: forced drop */
                        droptype = DTYPE_FORCED;
                } else if (rp->red_old == 0) {
                        /* first exceeds th_min */
                        rp->red_count = 1;
                        rp->red_old = 1;
                } else if (drop_early((avg - rp->red_thmin_s) >> rp->red_wshift,
                                      rp->red_probd, rp->red_count)) {
                        /* mark or drop by red */
                        if ((rp->red_flags & REDF_ECN) &&
                            mark_ecn(m, pktattr, rp->red_flags)) {
                                /* successfully marked.  do not drop. */
                                rp->red_count = 0;
#ifdef RED_STATS
                                rp->red_stats.marked_packets++;
#endif
                        } else {
                                /* unforced drop by red */
                                droptype = DTYPE_EARLY;
                        }
                }
        } else {
                /* avg < th_min */
                rp->red_old = 0;
        }

        /*
         * if the queue length hits the hard limit, it's a forced drop.
         */
        if (droptype == DTYPE_NODROP && qlen(q) >= qlimit(q))
                droptype = DTYPE_FORCED;

#ifdef RED_RANDOM_DROP
        /* if successful or forced drop, enqueue this packet. */
        if (droptype != DTYPE_EARLY)
                _addq(q, m);
#else
        /* if successful, enqueue this packet. */
        if (droptype == DTYPE_NODROP)
                _addq(q, m);
#endif
        if (droptype != DTYPE_NODROP) {
                if (droptype == DTYPE_EARLY) {
                        /* drop the incoming packet */
#ifdef RED_STATS
                        rp->red_stats.drop_unforced++;
#endif
                } else {
                        /* forced drop, select a victim packet in the queue. */
#ifdef RED_RANDOM_DROP
                        m = _getq_random(q);
#endif
#ifdef RED_STATS
                        rp->red_stats.drop_forced++;
#endif
                }
#ifdef RED_STATS
                PKTCNTR_ADD(&rp->red_stats.drop_cnt, m_pktlen(m));
#endif
                rp->red_count = 0;
                m_freem(m);
                return (-1);
        }
        /* successfully queued */
#ifdef RED_STATS
        PKTCNTR_ADD(&rp->red_stats.xmit_cnt, m_pktlen(m));
#endif
        return (0);
}

/*
 * early-drop probability is calculated as follows:
 *   prob = p_max * (avg - th_min) / (th_max - th_min)
 *   prob_a = prob / (2 - count*prob)
 *          = (avg-th_min) / (2*(th_max-th_min)*inv_p_max - count*(avg-th_min))
 * here prob_a increases as successive undrop count increases.
 * (prob_a starts from prob/2, becomes prob when (count == (1 / prob)),
 * becomes 1 when (count >= (2 / prob))).
 */
int
drop_early(int fp_len, int fp_probd, int count)
{
        int d;          /* denominator of drop-probability */

        d = fp_probd - count * fp_len;
        if (d <= 0) {
                /* count exceeds the hard limit: drop or mark */
                return (1);
        }

        /*
         * now the range of d is [1..600] in fixed-point. (when
         * th_max-th_min=10 and p_max=1/30)
         * drop probability = (avg - TH_MIN) / d
         */

        if ((karc4random() % d) < fp_len) {
                /* drop or mark */
                return (1);
        }
        /* no drop/mark */
        return (0);
}

/*
 * try to mark CE bit to the packet.
 *    returns 1 if successfully marked, 0 otherwise.
 */
int
mark_ecn(struct mbuf *m, struct altq_pktattr *pktattr, int flags)
{
        struct mbuf *m0;
        void *hdr;
        int  af;

        if ((m->m_pkthdr.fw_flags & ALTQ_MBUF_TAGGED) == 0)
                return (0);
        af = m->m_pkthdr.ecn_af;
        hdr = m->m_pkthdr.header;

        if (af != AF_INET && af != AF_INET6)
                return (0);

        /* verify that pattr_hdr is within the mbuf data */
        for (m0 = m; m0 != NULL; m0 = m0->m_next) {
                if (((caddr_t)hdr >= m0->m_data) &&
                    ((caddr_t)hdr < m0->m_data + m0->m_len))
                        break;
        }
        if (m0 == NULL) {
                /* ick, tag info is stale */
                return (0);
        }

        switch (af) {
        case AF_INET:
                if (flags & REDF_ECN4) {
                        struct ip *ip = hdr;
                        uint8_t otos;
                        int sum;

                        if (ip->ip_v != 4)
                                return (0);     /* version mismatch! */

                        if ((ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_NOTECT)
                                return (0);     /* not-ECT */
                        if ((ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_CE)
                                return (1);     /* already marked */

                        /*
                         * ecn-capable but not marked,
                         * mark CE and update checksum
                         */
                        otos = ip->ip_tos;
                        ip->ip_tos |= IPTOS_ECN_CE;
                        /*
                         * update checksum (from RFC1624)
                         *         HC' = ~(~HC + ~m + m')
                         */
                        sum = ~ntohs(ip->ip_sum) & 0xffff;
                        sum += (~otos & 0xffff) + ip->ip_tos;
                        sum = (sum >> 16) + (sum & 0xffff);
                        sum += (sum >> 16);  /* add carry */
                        ip->ip_sum = htons(~sum & 0xffff);
                        return (1);
                }
                break;
#ifdef INET6
        case AF_INET6:
                if (flags & REDF_ECN6) {
                        struct ip6_hdr *ip6 = hdr;
                        uint32_t flowlabel;

                        flowlabel = ntohl(ip6->ip6_flow);
                        if ((flowlabel >> 28) != 6)
                                return (0);     /* version mismatch! */
                        if ((flowlabel & (IPTOS_ECN_MASK << 20)) ==
                            (IPTOS_ECN_NOTECT << 20))
                                return (0);     /* not-ECT */
                        if ((flowlabel & (IPTOS_ECN_MASK << 20)) ==
                            (IPTOS_ECN_CE << 20))
                                return (1);     /* already marked */
                        /*
                         * ecn-capable but not marked,  mark CE
                         */
                        flowlabel |= (IPTOS_ECN_CE << 20);
                        ip6->ip6_flow = htonl(flowlabel);
                        return (1);
                }
                break;
#endif  /* INET6 */
        }

        /* not marked */
        return (0);
}

struct mbuf *
red_getq(red_t *rp, class_queue_t *q)
{
        struct mbuf *m;

        if ((m = _getq(q)) == NULL) {
                if (rp->red_idle == 0) {
                        rp->red_idle = 1;
                        microtime(&rp->red_last);
                }
                return NULL;
        }

        rp->red_idle = 0;
        return (m);
}

/*
 * helper routine to calibrate avg during idle.
 * pow_w(wtab, n) returns (1 - Wq)^n in fixed-point
 * here Wq = 1/weight and the code assumes Wq is close to zero.
 *
 * w_tab[n] holds ((1 - Wq)^(2^n)) in fixed-point.
 */
static SLIST_HEAD(, wtab) wtab_list = SLIST_HEAD_INITIALIZER(&wtab_list);

struct wtab *
wtab_alloc(int weight)
{
        struct wtab *w;
        int i;

        SLIST_FOREACH(w, &wtab_list, w_link) {
                if (w->w_weight == weight) {
                        w->w_refcount++;
                        return (w);
                }
        }

        w = kmalloc(sizeof(*w), M_ALTQ, M_WAITOK | M_ZERO);
        w->w_weight = weight;
        w->w_refcount = 1;
        SLIST_INSERT_HEAD(&wtab_list, w, w_link);

        /* initialize the weight table */
        w->w_tab[0] = ((weight - 1) << FP_SHIFT) / weight;
        for (i = 1; i < 32; i++) {
                w->w_tab[i] = (w->w_tab[i-1] * w->w_tab[i-1]) >> FP_SHIFT;
                if (w->w_tab[i] == 0 && w->w_param_max == 0)
                        w->w_param_max = 1 << i;
        }

        return (w);
}

int
wtab_destroy(struct wtab *w)
{
        if (--w->w_refcount > 0)
                return (0);

        SLIST_REMOVE(&wtab_list, w, wtab, w_link);
        kfree(w, M_ALTQ);

        return (0);
}

int32_t
pow_w(struct wtab *w, int n)
{
        int i, bit;
        int32_t val;

        if (n >= w->w_param_max)
                return (0);

        val = 1 << FP_SHIFT;
        if (n <= 0)
                return (val);

        bit = 1;
        i = 0;
        while (n) {
                if (n & bit) {
                        val = (val * w->w_tab[i]) >> FP_SHIFT;
                        n &= ~bit;
                }
                i++;
                bit <<=  1;
        }
        return (val);
}

#endif /* ALTQ_RED */