File: [local] / sys / altq / altq_red.c (download)
Revision 1.1, Tue Mar 4 16:04:32 2008 UTC (16 years, 1 month ago) by nbrk
Branch point for: MAIN
Initial revision
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/* $OpenBSD: altq_red.c,v 1.13 2007/05/28 17:16:38 henning Exp $ */
/* $KAME: altq_red.c,v 1.10 2002/04/03 05:38:51 kjc Exp $ */
/*
* Copyright (C) 1997-2002
* 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 <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 <net/if_types.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#ifdef INET6
#include <netinet/ip6.h>
#endif
#include <net/pfvar.h>
#include <altq/altq.h>
#include <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 length */
#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;
MALLOC(rp, red_t *, sizeof(red_t), M_DEVBUF, M_WAITOK);
if (rp == NULL)
return (NULL);
bzero(rp, sizeof(red_t));
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) {
printf("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);
FREE(rp, M_DEVBUF);
}
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 ((random() % 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;
hdr = m->m_pkthdr.pf.hdr;
/* 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 (((struct ip *)hdr)->ip_v) {
case 4:
if (flags & REDF_ECN4) {
struct ip *ip = hdr;
u_int8_t otos;
int sum;
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 6:
if (flags & REDF_ECN6) {
struct ip6_hdr *ip6 = hdr;
u_int32_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(rp, q)
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 struct wtab *wtab_list = NULL; /* pointer to wtab list */
struct wtab *
wtab_alloc(int weight)
{
struct wtab *w;
int i;
for (w = wtab_list; w != NULL; w = w->w_next)
if (w->w_weight == weight) {
w->w_refcount++;
return (w);
}
MALLOC(w, struct wtab *, sizeof(struct wtab), M_DEVBUF, M_WAITOK);
if (w == NULL)
panic("wtab_alloc: malloc failed!");
bzero(w, sizeof(struct wtab));
w->w_weight = weight;
w->w_refcount = 1;
w->w_next = wtab_list;
wtab_list = w;
/* 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)
{
struct wtab *prev;
if (--w->w_refcount > 0)
return (0);
if (wtab_list == w)
wtab_list = w->w_next;
else for (prev = wtab_list; prev->w_next != NULL; prev = prev->w_next)
if (prev->w_next == w) {
prev->w_next = w->w_next;
break;
}
FREE(w, M_DEVBUF);
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);
}
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