1 /* $KAME: altq_red.c,v 1.19 2004/04/17 10:54:49 kjc Exp $ */
2 /* $DragonFly: src/sys/net/altq/altq_red.c,v 1.4 2006/12/22 23:44:55 swildner Exp $ */
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65 #include "opt_inet6.h"
67 #ifdef ALTQ_RED /* red is enabled by ALTQ_RED option in opt_altq.h */
69 #include <sys/param.h>
70 #include <sys/malloc.h>
72 #include <sys/socket.h>
73 #include <sys/systm.h>
74 #include <sys/errno.h>
77 #include <net/ifq_var.h>
79 #include <netinet/in.h>
80 #include <netinet/in_systm.h>
81 #include <netinet/ip.h>
83 #include <netinet/ip6.h>
86 #include <net/pf/pfvar.h>
87 #include <net/altq/altq.h>
88 #include <net/altq/altq_red.h>
91 * ALTQ/RED (Random Early Detection) implementation using 32-bit
92 * fixed-point calculation.
94 * written by kjc using the ns code as a reference.
95 * you can learn more about red and ns from Sally's home page at
96 * http://www-nrg.ee.lbl.gov/floyd/
98 * most of the red parameter values are fixed in this implementation
99 * to prevent fixed-point overflow/underflow.
100 * if you change the parameters, watch out for overflow/underflow!
102 * the parameters used are recommended values by Sally.
103 * the corresponding ns config looks:
105 * minthresh=5 maxthresh=15 queue-size=60
108 * bytes=false (can't be handled by 32-bit fixed-point)
109 * doubleq=false dqthresh=false
113 * alternative red parameters for a slow link.
115 * assume the queue length becomes from zero to L and keeps L, it takes
116 * N packets for q_avg to reach 63% of L.
117 * when q_weight is 0.002, N is about 500 packets.
118 * for a slow link like dial-up, 500 packets takes more than 1 minute!
119 * when q_weight is 0.008, N is about 127 packets.
120 * when q_weight is 0.016, N is about 63 packets.
121 * bursts of 50 packets are allowed for 0.002, bursts of 25 packets
122 * are allowed for 0.016.
123 * see Sally's paper for more details.
125 /* normal red parameters */
126 #define W_WEIGHT 512 /* inverse of weight of EWMA (511/512) */
127 /* q_weight = 0.00195 */
129 /* red parameters for a slow link */
130 #define W_WEIGHT_1 128 /* inverse of weight of EWMA (127/128) */
131 /* q_weight = 0.0078125 */
133 /* red parameters for a very slow link (e.g., dialup) */
134 #define W_WEIGHT_2 64 /* inverse of weight of EWMA (63/64) */
135 /* q_weight = 0.015625 */
137 /* fixed-point uses 12-bit decimal places */
138 #define FP_SHIFT 12 /* fixed-point shift */
140 /* red parameters for drop probability */
141 #define INV_P_MAX 10 /* inverse of max drop probability */
142 #define TH_MIN 5 /* min threshold */
143 #define TH_MAX 15 /* max threshold */
145 #define RED_LIMIT 60 /* default max queue lenght */
146 #define RED_STATS /* collect statistics */
149 * our default policy for forced-drop is drop-tail.
150 * (in altq-1.1.2 or earlier, the default was random-drop.
151 * but it makes more sense to punish the cause of the surge.)
152 * to switch to the random-drop policy, define "RED_RANDOM_DROP".
155 /* default red parameter values */
156 static int default_th_min = TH_MIN;
157 static int default_th_max = TH_MAX;
158 static int default_inv_pmax = INV_P_MAX;
161 * red support routines
164 red_alloc(int weight, int inv_pmax, int th_min, int th_max, int flags, int pkttime)
170 rp = kmalloc(sizeof(*rp), M_ALTQ, M_WAITOK | M_ZERO);
175 rp->red_weight = W_WEIGHT;
177 rp->red_weight = weight;
179 rp->red_inv_pmax = default_inv_pmax;
181 rp->red_inv_pmax = inv_pmax;
183 rp->red_thmin = default_th_min;
185 rp->red_thmin = th_min;
187 rp->red_thmax = default_th_max;
189 rp->red_thmax = th_max;
191 rp->red_flags = flags;
194 /* default packet time: 1000 bytes / 10Mbps * 8 * 1000000 */
195 rp->red_pkttime = 800;
197 rp->red_pkttime = pkttime;
200 /* when the link is very slow, adjust red parameters */
201 npkts_per_sec = 1000000 / rp->red_pkttime;
202 if (npkts_per_sec < 50) {
203 /* up to about 400Kbps */
204 rp->red_weight = W_WEIGHT_2;
205 } else if (npkts_per_sec < 300) {
206 /* up to about 2.4Mbps */
207 rp->red_weight = W_WEIGHT_1;
211 /* calculate wshift. weight must be power of 2 */
213 for (i = 0; w > 1; i++)
216 w = 1 << rp->red_wshift;
217 if (w != rp->red_weight) {
218 kprintf("invalid weight value %d for red! use %d\n",
224 * thmin_s and thmax_s are scaled versions of th_min and th_max
225 * to be compared with avg.
227 rp->red_thmin_s = rp->red_thmin << (rp->red_wshift + FP_SHIFT);
228 rp->red_thmax_s = rp->red_thmax << (rp->red_wshift + FP_SHIFT);
231 * precompute probability denominator
232 * probd = (2 * (TH_MAX-TH_MIN) / pmax) in fixed-point
234 rp->red_probd = (2 * (rp->red_thmax - rp->red_thmin)
235 * rp->red_inv_pmax) << FP_SHIFT;
237 /* allocate weight table */
238 rp->red_wtab = wtab_alloc(rp->red_weight);
240 microtime(&rp->red_last);
245 red_destroy(red_t *rp)
247 wtab_destroy(rp->red_wtab);
252 red_getstats(red_t *rp, struct redstats *sp)
254 sp->q_avg = rp->red_avg >> rp->red_wshift;
255 sp->xmit_cnt = rp->red_stats.xmit_cnt;
256 sp->drop_cnt = rp->red_stats.drop_cnt;
257 sp->drop_forced = rp->red_stats.drop_forced;
258 sp->drop_unforced = rp->red_stats.drop_unforced;
259 sp->marked_packets = rp->red_stats.marked_packets;
263 red_addq(red_t *rp, class_queue_t *q, struct mbuf *m, struct altq_pktattr *pktattr)
271 * if we were idle, we pretend that n packets arrived during
280 t = (now.tv_sec - rp->red_last.tv_sec);
283 * being idle for more than 1 minute, set avg to zero.
284 * this prevents t from overflow.
288 t = t * 1000000 + (now.tv_usec - rp->red_last.tv_usec);
289 n = t / rp->red_pkttime - 1;
291 /* the following line does (avg = (1 - Wq)^n * avg) */
293 avg = (avg >> FP_SHIFT) *
294 pow_w(rp->red_wtab, n);
298 /* run estimator. (note: avg is scaled by WEIGHT in fixed-point) */
299 avg += (qlen(q) << FP_SHIFT) - (avg >> rp->red_wshift);
300 rp->red_avg = avg; /* save the new value */
303 * red_count keeps a tally of arriving traffic that has not
308 /* see if we drop early */
309 droptype = DTYPE_NODROP;
310 if (avg >= rp->red_thmin_s && qlen(q) > 1) {
311 if (avg >= rp->red_thmax_s) {
312 /* avg >= th_max: forced drop */
313 droptype = DTYPE_FORCED;
314 } else if (rp->red_old == 0) {
315 /* first exceeds th_min */
318 } else if (drop_early((avg - rp->red_thmin_s) >> rp->red_wshift,
319 rp->red_probd, rp->red_count)) {
320 /* mark or drop by red */
321 if ((rp->red_flags & REDF_ECN) &&
322 mark_ecn(m, pktattr, rp->red_flags)) {
323 /* successfully marked. do not drop. */
326 rp->red_stats.marked_packets++;
329 /* unforced drop by red */
330 droptype = DTYPE_EARLY;
339 * if the queue length hits the hard limit, it's a forced drop.
341 if (droptype == DTYPE_NODROP && qlen(q) >= qlimit(q))
342 droptype = DTYPE_FORCED;
344 #ifdef RED_RANDOM_DROP
345 /* if successful or forced drop, enqueue this packet. */
346 if (droptype != DTYPE_EARLY)
349 /* if successful, enqueue this packet. */
350 if (droptype == DTYPE_NODROP)
353 if (droptype != DTYPE_NODROP) {
354 if (droptype == DTYPE_EARLY) {
355 /* drop the incoming packet */
357 rp->red_stats.drop_unforced++;
360 /* forced drop, select a victim packet in the queue. */
361 #ifdef RED_RANDOM_DROP
365 rp->red_stats.drop_forced++;
369 PKTCNTR_ADD(&rp->red_stats.drop_cnt, m_pktlen(m));
375 /* successfully queued */
377 PKTCNTR_ADD(&rp->red_stats.xmit_cnt, m_pktlen(m));
383 * early-drop probability is calculated as follows:
384 * prob = p_max * (avg - th_min) / (th_max - th_min)
385 * prob_a = prob / (2 - count*prob)
386 * = (avg-th_min) / (2*(th_max-th_min)*inv_p_max - count*(avg-th_min))
387 * here prob_a increases as successive undrop count increases.
388 * (prob_a starts from prob/2, becomes prob when (count == (1 / prob)),
389 * becomes 1 when (count >= (2 / prob))).
392 drop_early(int fp_len, int fp_probd, int count)
394 int d; /* denominator of drop-probability */
396 d = fp_probd - count * fp_len;
398 /* count exceeds the hard limit: drop or mark */
403 * now the range of d is [1..600] in fixed-point. (when
404 * th_max-th_min=10 and p_max=1/30)
405 * drop probability = (avg - TH_MIN) / d
408 if ((karc4random() % d) < fp_len) {
417 * try to mark CE bit to the packet.
418 * returns 1 if successfully marked, 0 otherwise.
421 mark_ecn(struct mbuf *m, struct altq_pktattr *pktattr, int flags)
427 if (m->m_pkthdr.fw_flags & PF_MBUF_STRUCTURE) {
428 af = m->m_pkthdr.pf.ecn_af;
429 hdr = m->m_pkthdr.pf.hdr;
430 } else if (pktattr) {
431 af = pktattr->pattr_af;
432 hdr = pktattr->pattr_hdr;
437 if (af != AF_INET && af != AF_INET6)
440 /* verify that pattr_hdr is within the mbuf data */
441 for (m0 = m; m0 != NULL; m0 = m0->m_next) {
442 if (((caddr_t)hdr >= m0->m_data) &&
443 ((caddr_t)hdr < m0->m_data + m0->m_len))
447 /* ick, tag info is stale */
453 if (flags & REDF_ECN4) {
458 if ((ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_NOTECT)
459 return (0); /* not-ECT */
460 if ((ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_CE)
461 return (1); /* already marked */
464 * ecn-capable but not marked,
465 * mark CE and update checksum
468 ip->ip_tos |= IPTOS_ECN_CE;
470 * update checksum (from RFC1624)
471 * HC' = ~(~HC + ~m + m')
473 sum = ~ntohs(ip->ip_sum) & 0xffff;
474 sum += (~otos & 0xffff) + ip->ip_tos;
475 sum = (sum >> 16) + (sum & 0xffff);
476 sum += (sum >> 16); /* add carry */
477 ip->ip_sum = htons(~sum & 0xffff);
483 if (flags & REDF_ECN6) {
484 struct ip6_hdr *ip6 = hdr;
487 flowlabel = ntohl(ip6->ip6_flow);
488 if ((flowlabel >> 28) != 6)
489 return (0); /* version mismatch! */
490 if ((flowlabel & (IPTOS_ECN_MASK << 20)) ==
491 (IPTOS_ECN_NOTECT << 20))
492 return (0); /* not-ECT */
493 if ((flowlabel & (IPTOS_ECN_MASK << 20)) ==
494 (IPTOS_ECN_CE << 20))
495 return (1); /* already marked */
497 * ecn-capable but not marked, mark CE
499 flowlabel |= (IPTOS_ECN_CE << 20);
500 ip6->ip6_flow = htonl(flowlabel);
512 red_getq(red_t *rp, class_queue_t *q)
516 if ((m = _getq(q)) == NULL) {
517 if (rp->red_idle == 0) {
519 microtime(&rp->red_last);
529 * helper routine to calibrate avg during idle.
530 * pow_w(wtab, n) returns (1 - Wq)^n in fixed-point
531 * here Wq = 1/weight and the code assumes Wq is close to zero.
533 * w_tab[n] holds ((1 - Wq)^(2^n)) in fixed-point.
535 static SLIST_HEAD(, wtab) wtab_list = SLIST_HEAD_INITIALIZER(&wtab_list);
538 wtab_alloc(int weight)
543 SLIST_FOREACH(w, &wtab_list, w_link) {
544 if (w->w_weight == weight) {
550 w = kmalloc(sizeof(*w), M_ALTQ, M_WAITOK | M_ZERO);
551 w->w_weight = weight;
553 SLIST_INSERT_HEAD(&wtab_list, w, w_link);
555 /* initialize the weight table */
556 w->w_tab[0] = ((weight - 1) << FP_SHIFT) / weight;
557 for (i = 1; i < 32; i++) {
558 w->w_tab[i] = (w->w_tab[i-1] * w->w_tab[i-1]) >> FP_SHIFT;
559 if (w->w_tab[i] == 0 && w->w_param_max == 0)
560 w->w_param_max = 1 << i;
567 wtab_destroy(struct wtab *w)
569 if (--w->w_refcount > 0)
572 SLIST_REMOVE(&wtab_list, w, wtab, w_link);
579 pow_w(struct wtab *w, int n)
584 if (n >= w->w_param_max)
595 val = (val * w->w_tab[i]) >> FP_SHIFT;
604 #endif /* ALTQ_RED */