1 /* $OpenBSD: altq_red.c,v 1.13 2007/05/28 17:16:38 henning Exp $ */
2 /* $KAME: altq_red.c,v 1.10 2002/04/03 05:38:51 kjc Exp $ */
3
4 /*
5 * Copyright (C) 1997-2002
6 * Sony Computer Science Laboratories Inc. All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY SONY CSL AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL SONY CSL OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 */
30 /*
31 * Copyright (c) 1990-1994 Regents of the University of California.
32 * All rights reserved.
33 *
34 * Redistribution and use in source and binary forms, with or without
35 * modification, are permitted provided that the following conditions
36 * are met:
37 * 1. Redistributions of source code must retain the above copyright
38 * notice, this list of conditions and the following disclaimer.
39 * 2. Redistributions in binary form must reproduce the above copyright
40 * notice, this list of conditions and the following disclaimer in the
41 * documentation and/or other materials provided with the distribution.
42 * 3. All advertising materials mentioning features or use of this software
43 * must display the following acknowledgement:
44 * This product includes software developed by the Computer Systems
45 * Engineering Group at Lawrence Berkeley Laboratory.
46 * 4. Neither the name of the University nor of the Laboratory may be used
47 * to endorse or promote products derived from this software without
48 * specific prior written permission.
49 *
50 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
51 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
53 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
54 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
55 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
56 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
57 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
58 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
59 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
60 * SUCH DAMAGE.
61 */
62
63 #include <sys/param.h>
64 #include <sys/malloc.h>
65 #include <sys/mbuf.h>
66 #include <sys/socket.h>
67 #include <sys/systm.h>
68 #include <sys/errno.h>
69
70 #include <net/if.h>
71 #include <net/if_types.h>
72
73 #include <netinet/in.h>
74 #include <netinet/in_systm.h>
75 #include <netinet/ip.h>
76 #ifdef INET6
77 #include <netinet/ip6.h>
78 #endif
79
80 #include <net/pfvar.h>
81 #include <altq/altq.h>
82 #include <altq/altq_red.h>
83
84 /*
85 * ALTQ/RED (Random Early Detection) implementation using 32-bit
86 * fixed-point calculation.
87 *
88 * written by kjc using the ns code as a reference.
89 * you can learn more about red and ns from Sally's home page at
90 * http://www-nrg.ee.lbl.gov/floyd/
91 *
92 * most of the red parameter values are fixed in this implementation
93 * to prevent fixed-point overflow/underflow.
94 * if you change the parameters, watch out for overflow/underflow!
95 *
96 * the parameters used are recommended values by Sally.
97 * the corresponding ns config looks:
98 * q_weight=0.00195
99 * minthresh=5 maxthresh=15 queue-size=60
100 * linterm=30
101 * dropmech=drop-tail
102 * bytes=false (can't be handled by 32-bit fixed-point)
103 * doubleq=false dqthresh=false
104 * wait=true
105 */
106 /*
107 * alternative red parameters for a slow link.
108 *
109 * assume the queue length becomes from zero to L and keeps L, it takes
110 * N packets for q_avg to reach 63% of L.
111 * when q_weight is 0.002, N is about 500 packets.
112 * for a slow link like dial-up, 500 packets takes more than 1 minute!
113 * when q_weight is 0.008, N is about 127 packets.
114 * when q_weight is 0.016, N is about 63 packets.
115 * bursts of 50 packets are allowed for 0.002, bursts of 25 packets
116 * are allowed for 0.016.
117 * see Sally's paper for more details.
118 */
119 /* normal red parameters */
120 #define W_WEIGHT 512 /* inverse of weight of EWMA (511/512) */
121 /* q_weight = 0.00195 */
122
123 /* red parameters for a slow link */
124 #define W_WEIGHT_1 128 /* inverse of weight of EWMA (127/128) */
125 /* q_weight = 0.0078125 */
126
127 /* red parameters for a very slow link (e.g., dialup) */
128 #define W_WEIGHT_2 64 /* inverse of weight of EWMA (63/64) */
129 /* q_weight = 0.015625 */
130
131 /* fixed-point uses 12-bit decimal places */
132 #define FP_SHIFT 12 /* fixed-point shift */
133
134 /* red parameters for drop probability */
135 #define INV_P_MAX 10 /* inverse of max drop probability */
136 #define TH_MIN 5 /* min threshold */
137 #define TH_MAX 15 /* max threshold */
138
139 #define RED_LIMIT 60 /* default max queue length */
140 #define RED_STATS /* collect statistics */
141
142 /*
143 * our default policy for forced-drop is drop-tail.
144 * (in altq-1.1.2 or earlier, the default was random-drop.
145 * but it makes more sense to punish the cause of the surge.)
146 * to switch to the random-drop policy, define "RED_RANDOM_DROP".
147 */
148
149 /* default red parameter values */
150 static int default_th_min = TH_MIN;
151 static int default_th_max = TH_MAX;
152 static int default_inv_pmax = INV_P_MAX;
153
154 /*
155 * red support routines
156 */
157 red_t *
158 red_alloc(int weight, int inv_pmax, int th_min, int th_max, int flags,
159 int pkttime)
160 {
161 red_t *rp;
162 int w, i;
163 int npkts_per_sec;
164
165 MALLOC(rp, red_t *, sizeof(red_t), M_DEVBUF, M_WAITOK);
166 if (rp == NULL)
167 return (NULL);
168 bzero(rp, sizeof(red_t));
169
170 rp->red_avg = 0;
171 rp->red_idle = 1;
172
173 if (weight == 0)
174 rp->red_weight = W_WEIGHT;
175 else
176 rp->red_weight = weight;
177 if (inv_pmax == 0)
178 rp->red_inv_pmax = default_inv_pmax;
179 else
180 rp->red_inv_pmax = inv_pmax;
181 if (th_min == 0)
182 rp->red_thmin = default_th_min;
183 else
184 rp->red_thmin = th_min;
185 if (th_max == 0)
186 rp->red_thmax = default_th_max;
187 else
188 rp->red_thmax = th_max;
189
190 rp->red_flags = flags;
191
192 if (pkttime == 0)
193 /* default packet time: 1000 bytes / 10Mbps * 8 * 1000000 */
194 rp->red_pkttime = 800;
195 else
196 rp->red_pkttime = pkttime;
197
198 if (weight == 0) {
199 /* when the link is very slow, adjust red parameters */
200 npkts_per_sec = 1000000 / rp->red_pkttime;
201 if (npkts_per_sec < 50) {
202 /* up to about 400Kbps */
203 rp->red_weight = W_WEIGHT_2;
204 } else if (npkts_per_sec < 300) {
205 /* up to about 2.4Mbps */
206 rp->red_weight = W_WEIGHT_1;
207 }
208 }
209
210 /* calculate wshift. weight must be power of 2 */
211 w = rp->red_weight;
212 for (i = 0; w > 1; i++)
213 w = w >> 1;
214 rp->red_wshift = i;
215 w = 1 << rp->red_wshift;
216 if (w != rp->red_weight) {
217 printf("invalid weight value %d for red! use %d\n",
218 rp->red_weight, w);
219 rp->red_weight = w;
220 }
221
222 /*
223 * thmin_s and thmax_s are scaled versions of th_min and th_max
224 * to be compared with avg.
225 */
226 rp->red_thmin_s = rp->red_thmin << (rp->red_wshift + FP_SHIFT);
227 rp->red_thmax_s = rp->red_thmax << (rp->red_wshift + FP_SHIFT);
228
229 /*
230 * precompute probability denominator
231 * probd = (2 * (TH_MAX-TH_MIN) / pmax) in fixed-point
232 */
233 rp->red_probd = (2 * (rp->red_thmax - rp->red_thmin)
234 * rp->red_inv_pmax) << FP_SHIFT;
235
236 /* allocate weight table */
237 rp->red_wtab = wtab_alloc(rp->red_weight);
238
239 microtime(&rp->red_last);
240 return (rp);
241 }
242
243 void
244 red_destroy(red_t *rp)
245 {
246 wtab_destroy(rp->red_wtab);
247 FREE(rp, M_DEVBUF);
248 }
249
250 void
251 red_getstats(red_t *rp, struct redstats *sp)
252 {
253 sp->q_avg = rp->red_avg >> rp->red_wshift;
254 sp->xmit_cnt = rp->red_stats.xmit_cnt;
255 sp->drop_cnt = rp->red_stats.drop_cnt;
256 sp->drop_forced = rp->red_stats.drop_forced;
257 sp->drop_unforced = rp->red_stats.drop_unforced;
258 sp->marked_packets = rp->red_stats.marked_packets;
259 }
260
261 int
262 red_addq(red_t *rp, class_queue_t *q, struct mbuf *m,
263 struct altq_pktattr *pktattr)
264 {
265 int avg, droptype;
266 int n;
267
268 avg = rp->red_avg;
269
270 /*
271 * if we were idle, we pretend that n packets arrived during
272 * the idle period.
273 */
274 if (rp->red_idle) {
275 struct timeval now;
276 int t;
277
278 rp->red_idle = 0;
279 microtime(&now);
280 t = (now.tv_sec - rp->red_last.tv_sec);
281 if (t > 60) {
282 /*
283 * being idle for more than 1 minute, set avg to zero.
284 * this prevents t from overflow.
285 */
286 avg = 0;
287 } else {
288 t = t * 1000000 + (now.tv_usec - rp->red_last.tv_usec);
289 n = t / rp->red_pkttime - 1;
290
291 /* the following line does (avg = (1 - Wq)^n * avg) */
292 if (n > 0)
293 avg = (avg >> FP_SHIFT) *
294 pow_w(rp->red_wtab, n);
295 }
296 }
297
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 */
301
302 /*
303 * red_count keeps a tally of arriving traffic that has not
304 * been dropped.
305 */
306 rp->red_count++;
307
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 */
316 rp->red_count = 1;
317 rp->red_old = 1;
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. */
324 rp->red_count = 0;
325 #ifdef RED_STATS
326 rp->red_stats.marked_packets++;
327 #endif
328 } else {
329 /* unforced drop by red */
330 droptype = DTYPE_EARLY;
331 }
332 }
333 } else {
334 /* avg < th_min */
335 rp->red_old = 0;
336 }
337
338 /*
339 * if the queue length hits the hard limit, it's a forced drop.
340 */
341 if (droptype == DTYPE_NODROP && qlen(q) >= qlimit(q))
342 droptype = DTYPE_FORCED;
343
344 #ifdef RED_RANDOM_DROP
345 /* if successful or forced drop, enqueue this packet. */
346 if (droptype != DTYPE_EARLY)
347 _addq(q, m);
348 #else
349 /* if successful, enqueue this packet. */
350 if (droptype == DTYPE_NODROP)
351 _addq(q, m);
352 #endif
353 if (droptype != DTYPE_NODROP) {
354 if (droptype == DTYPE_EARLY) {
355 /* drop the incoming packet */
356 #ifdef RED_STATS
357 rp->red_stats.drop_unforced++;
358 #endif
359 } else {
360 /* forced drop, select a victim packet in the queue. */
361 #ifdef RED_RANDOM_DROP
362 m = _getq_random(q);
363 #endif
364 #ifdef RED_STATS
365 rp->red_stats.drop_forced++;
366 #endif
367 }
368 #ifdef RED_STATS
369 PKTCNTR_ADD(&rp->red_stats.drop_cnt, m_pktlen(m));
370 #endif
371 rp->red_count = 0;
372 m_freem(m);
373 return (-1);
374 }
375 /* successfully queued */
376 #ifdef RED_STATS
377 PKTCNTR_ADD(&rp->red_stats.xmit_cnt, m_pktlen(m));
378 #endif
379 return (0);
380 }
381
382 /*
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))).
390 */
391 int
392 drop_early(int fp_len, int fp_probd, int count)
393 {
394 int d; /* denominator of drop-probability */
395
396 d = fp_probd - count * fp_len;
397 if (d <= 0)
398 /* count exceeds the hard limit: drop or mark */
399 return (1);
400
401 /*
402 * now the range of d is [1..600] in fixed-point. (when
403 * th_max-th_min=10 and p_max=1/30)
404 * drop probability = (avg - TH_MIN) / d
405 */
406
407 if ((random() % d) < fp_len) {
408 /* drop or mark */
409 return (1);
410 }
411 /* no drop/mark */
412 return (0);
413 }
414
415 /*
416 * try to mark CE bit to the packet.
417 * returns 1 if successfully marked, 0 otherwise.
418 */
419 int
420 mark_ecn(struct mbuf *m, struct altq_pktattr *pktattr, int flags)
421 {
422 struct mbuf *m0;
423 void *hdr;
424
425 hdr = m->m_pkthdr.pf.hdr;
426
427 /* verify that pattr_hdr is within the mbuf data */
428 for (m0 = m; m0 != NULL; m0 = m0->m_next)
429 if (((caddr_t)(hdr) >= m0->m_data) &&
430 ((caddr_t)(hdr) < m0->m_data + m0->m_len))
431 break;
432 if (m0 == NULL) {
433 /* ick, tag info is stale */
434 return (0);
435 }
436
437 switch (((struct ip *)hdr)->ip_v) {
438 case 4:
439 if (flags & REDF_ECN4) {
440 struct ip *ip = hdr;
441 u_int8_t otos;
442 int sum;
443
444 if ((ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_NOTECT)
445 return (0); /* not-ECT */
446 if ((ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_CE)
447 return (1); /* already marked */
448
449 /*
450 * ecn-capable but not marked,
451 * mark CE and update checksum
452 */
453 otos = ip->ip_tos;
454 ip->ip_tos |= IPTOS_ECN_CE;
455 /*
456 * update checksum (from RFC1624)
457 * HC' = ~(~HC + ~m + m')
458 */
459 sum = ~ntohs(ip->ip_sum) & 0xffff;
460 sum += (~otos & 0xffff) + ip->ip_tos;
461 sum = (sum >> 16) + (sum & 0xffff);
462 sum += (sum >> 16); /* add carry */
463 ip->ip_sum = htons(~sum & 0xffff);
464 return (1);
465 }
466 break;
467 #ifdef INET6
468 case 6:
469 if (flags & REDF_ECN6) {
470 struct ip6_hdr *ip6 = hdr;
471 u_int32_t flowlabel;
472
473 flowlabel = ntohl(ip6->ip6_flow);
474 if ((flowlabel >> 28) != 6)
475 return (0); /* version mismatch! */
476 if ((flowlabel & (IPTOS_ECN_MASK << 20)) ==
477 (IPTOS_ECN_NOTECT << 20))
478 return (0); /* not-ECT */
479 if ((flowlabel & (IPTOS_ECN_MASK << 20)) ==
480 (IPTOS_ECN_CE << 20))
481 return (1); /* already marked */
482 /*
483 * ecn-capable but not marked, mark CE
484 */
485 flowlabel |= (IPTOS_ECN_CE << 20);
486 ip6->ip6_flow = htonl(flowlabel);
487 return (1);
488 }
489 break;
490 #endif /* INET6 */
491 }
492
493 /* not marked */
494 return (0);
495 }
496
497 struct mbuf *
498 red_getq(rp, q)
499 red_t *rp;
500 class_queue_t *q;
501 {
502 struct mbuf *m;
503
504 if ((m = _getq(q)) == NULL) {
505 if (rp->red_idle == 0) {
506 rp->red_idle = 1;
507 microtime(&rp->red_last);
508 }
509 return NULL;
510 }
511
512 rp->red_idle = 0;
513 return (m);
514 }
515
516 /*
517 * helper routine to calibrate avg during idle.
518 * pow_w(wtab, n) returns (1 - Wq)^n in fixed-point
519 * here Wq = 1/weight and the code assumes Wq is close to zero.
520 *
521 * w_tab[n] holds ((1 - Wq)^(2^n)) in fixed-point.
522 */
523 static struct wtab *wtab_list = NULL; /* pointer to wtab list */
524
525 struct wtab *
526 wtab_alloc(int weight)
527 {
528 struct wtab *w;
529 int i;
530
531 for (w = wtab_list; w != NULL; w = w->w_next)
532 if (w->w_weight == weight) {
533 w->w_refcount++;
534 return (w);
535 }
536
537 MALLOC(w, struct wtab *, sizeof(struct wtab), M_DEVBUF, M_WAITOK);
538 if (w == NULL)
539 panic("wtab_alloc: malloc failed!");
540 bzero(w, sizeof(struct wtab));
541 w->w_weight = weight;
542 w->w_refcount = 1;
543 w->w_next = wtab_list;
544 wtab_list = w;
545
546 /* initialize the weight table */
547 w->w_tab[0] = ((weight - 1) << FP_SHIFT) / weight;
548 for (i = 1; i < 32; i++) {
549 w->w_tab[i] = (w->w_tab[i-1] * w->w_tab[i-1]) >> FP_SHIFT;
550 if (w->w_tab[i] == 0 && w->w_param_max == 0)
551 w->w_param_max = 1 << i;
552 }
553
554 return (w);
555 }
556
557 int
558 wtab_destroy(struct wtab *w)
559 {
560 struct wtab *prev;
561
562 if (--w->w_refcount > 0)
563 return (0);
564
565 if (wtab_list == w)
566 wtab_list = w->w_next;
567 else for (prev = wtab_list; prev->w_next != NULL; prev = prev->w_next)
568 if (prev->w_next == w) {
569 prev->w_next = w->w_next;
570 break;
571 }
572
573 FREE(w, M_DEVBUF);
574 return (0);
575 }
576
577 int32_t
578 pow_w(struct wtab *w, int n)
579 {
580 int i, bit;
581 int32_t val;
582
583 if (n >= w->w_param_max)
584 return (0);
585
586 val = 1 << FP_SHIFT;
587 if (n <= 0)
588 return (val);
589
590 bit = 1;
591 i = 0;
592 while (n) {
593 if (n & bit) {
594 val = (val * w->w_tab[i]) >> FP_SHIFT;
595 n &= ~bit;
596 }
597 i++;
598 bit <<= 1;
599 }
600 return (val);
601 }