xref: /freebsd/sys/netpfil/ipfw/test/main.c (revision 0fca6ea1d4eea4c934cfff25ac9ee8ad6fe95583)
1 /*
2  *
3  * Testing program for schedulers
4  *
5  * The framework include a simple controller which, at each
6  * iteration, decides whether we can enqueue and/or dequeue.
7  * Then the mainloop runs the required number of tests,
8  * keeping track of statistics.
9  */
10 
11 // #define USE_BURST	// what is this for ?
12 
13 #include "dn_test.h"
14 
15 struct cfg_s {
16 	int ac;
17 	char * const *av;
18 
19 	const char *name;
20 	int loops;
21 	struct timeval time;
22 
23 	/* running counters */
24 	uint32_t	_enqueue;
25 	uint32_t	drop;
26 	uint32_t	pending;
27 	uint32_t	dequeue;
28 
29 	/* generator parameters */
30 	int32_t th_min, th_max;	/* thresholds for hysteresis; negative means per flow */
31 #ifdef USE_BURST
32 	int maxburst;
33 #endif /* USE_BURST */
34 	int lmin, lmax;	/* packet len */
35 	int flows;	/* number of flows */
36 	int flowsets;	/* number of flowsets */
37 	int wsum;	/* sum of weights of all flows */
38 #ifdef USE_CUR
39 	int max_y;	/* max random number in the generation */
40 	int cur_y
41 	int cur_fs;	/* used in generation, between 0 and max_y - 1 */
42 #endif /* USE_CUR */
43 	const char *fs_config; /* flowset config */
44 	int can_dequeue;
45 	int burst;	/* count of packets sent in a burst */
46 	struct mbuf *tosend;	/* packet to send -- also flag to enqueue */
47 
48 	struct mbuf *freelist;
49 
50 	struct mbuf *head, *tail;	/* a simple tailq */
51 
52 	/* scheduler hooks */
53 	int (*enq)(struct dn_sch_inst *, struct dn_queue *,
54 		struct mbuf *);
55 	struct mbuf * (*deq)(struct dn_sch_inst *);
56 	/* size of the three fields including sched-specific areas */
57 	uint32_t schk_len;
58 	uint32_t q_len; /* size of a queue including sched-fields */
59 	uint32_t si_len; /* size of a sch_inst including sched-fields */
60 	char *q;	/* array of flow queues */
61 		/* use a char* because size is variable */
62 	/*
63 	 * The scheduler template (one) followd by schk_datalen bytes
64 	 * for scheduler-specific parameters, total size is schk_len
65 	 */
66 	struct dn_schk *sched;
67 	/*
68 	 * one scheduler instance, followed by si_datalen bytes
69 	 * for scheduler specific parameters of this instance,
70 	 * total size is si_len. si->sched points to sched
71 	 */
72 	struct dn_sch_inst *si;
73 	struct dn_fsk *fs;	/* array of flowsets */
74 
75 	/* generator state */
76 	int state;	/* 0 = going up (enqueue), 1: going down (dequeue) */
77 
78 	/*
79 	 * We keep lists for each backlog level, and always serve
80 	 * the one with shortest backlog. llmask contains a bitmap
81 	 * of lists, and ll are the heads of the lists. The last
82 	 * entry (BACKLOG) contains all entries considered 'full'
83 	 * XXX to optimize things, entry i could contain queues with
84 	 * 2^{i-1}+1 .. 2^i entries.
85 	 */
86 #define BACKLOG	30 /* this many backlogged classes, we only need BACKLOG+1 */
87 	uint64_t	llmask;
88 	struct list_head ll[BACKLOG + 10];
89 
90 	double *q_wfi;	/* (byte) Worst-case Fair Index of the flows  */
91 	double wfi;	/* (byte) Worst-case Fair Index of the system */
92 };
93 
94 /* FI2Q and Q2FI converts from flow_id (i.e. queue index)
95  * to dn_queue and back. We cannot simply use pointer arithmetic
96  * because the queu has variable size, q_len
97  */
98 #define FI2Q(c, i)	((struct dn_queue *)((c)->q + (c)->q_len * (i)))
99 #define Q2FI(c, q)	(((char *)(q) - (c)->q)/(c)->q_len)
100 
101 int debug = 0;
102 
103 struct dn_parms dn_cfg;
104 
105 static void controller(struct cfg_s *c);
106 
107 /* release a packet for a given flow_id.
108  * Put the mbuf in the freelist, and in case move the
109  * flow to the end of the bucket.
110  */
111 static int
112 drop(struct cfg_s *c, struct mbuf *m)
113 {
114 	struct dn_queue *q;
115 	int i;
116 
117 	c->drop++;
118 	q = FI2Q(c, m->flow_id);
119 	i = q->ni.length; // XXX or ffs...
120 
121 	ND("q %p id %d current length %d", q, m->flow_id, i);
122 	if (i < BACKLOG) {
123 		struct list_head *h = &q->ni.h;
124 		c->llmask &= ~(1<<(i+1));
125 		c->llmask |= (1<<(i));
126 		list_del(h);
127 		list_add_tail(h, &c->ll[i]);
128 	}
129 	m->m_nextpkt = c->freelist;
130 	c->freelist = m;
131 	return 0;
132 }
133 
134 /*
135  * dn_sch_inst does not have a queue, for the RR we
136  * allocate a mq right after si
137  */
138 static int
139 default_enqueue(struct dn_sch_inst *si, struct dn_queue *q, struct mbuf *m)
140 {
141 	struct mq *mq = (struct mq *)si;
142 
143 	(void)q;
144 	/* this is the default function if no scheduler is provided */
145 	if (mq->head == NULL)
146 		mq->head = m;
147 	else
148 		mq->tail->m_nextpkt = m;
149 	mq->tail = m;
150 	return 0; /* default - success */
151 }
152 
153 static struct mbuf *
154 default_dequeue(struct dn_sch_inst *si)
155 {
156 	struct mq *mq = (struct mq *)si;
157 	struct mbuf *m;
158 	/* this is the default function if no scheduler is provided */
159 	if ((m = mq->head)) {
160 		m = mq->head;
161 		mq->head = m->m_nextpkt;
162 		m->m_nextpkt = NULL;
163 	}
164 	return m;
165 }
166 
167 static void
168 gnet_stats_enq(struct cfg_s *c, struct mbuf *mb)
169 {
170 	struct dn_sch_inst *si = c->si;
171 	struct dn_queue *_q = FI2Q(c, mb->flow_id);
172 
173 	if (_q->ni.length == 1) {
174 		_q->ni.bytes = 0;
175 		_q->ni.sch_bytes = si->ni.bytes;
176 	}
177 }
178 
179 static void
180 gnet_stats_deq(struct cfg_s *c, struct mbuf *mb)
181 {
182 	struct dn_sch_inst *si = c->si;
183 	struct dn_queue *_q = FI2Q(c, mb->flow_id);
184 	int len = mb->m_pkthdr.len;
185 
186 	_q->ni.bytes += len;
187 	si->ni.bytes += len;
188 
189 	if (_q->ni.length == 0) {
190 		double bytes = (double)_q->ni.bytes;
191 		double sch_bytes = (double)si->ni.bytes - _q->ni.sch_bytes;
192 		double weight = (double)_q->fs->fs.par[0] / c->wsum;
193 		double wfi = sch_bytes * weight - bytes;
194 
195 		if (c->q_wfi[mb->flow_id] < wfi)
196 			c->q_wfi[mb->flow_id] = wfi;
197 	}
198 }
199 
200 static int
201 mainloop(struct cfg_s *c)
202 {
203 	int i;
204 	struct mbuf *m;
205 
206 	for (i=0; i < c->loops; i++) {
207 		/* implement histeresis */
208 		controller(c);
209 		DX(3, "loop %d enq %d send %p rx %d",
210 			i, c->_enqueue, c->tosend, c->can_dequeue);
211 		if ( (m = c->tosend) ) {
212 			int ret;
213 			struct dn_queue *q = FI2Q(c, m->flow_id);
214 			c->_enqueue++;
215 			ret = c->enq(c->si, q, m);
216 			if (ret) {
217 				drop(c, m);
218 				D("loop %d enqueue fail", i );
219 				/*
220 				 * XXX do not insist; rather, try dequeue
221 				 */
222 				goto do_dequeue;
223 			} else {
224 				ND("enqueue ok");
225 				c->pending++;
226 				gnet_stats_enq(c, m);
227 			}
228 		} else if (c->can_dequeue) {
229 do_dequeue:
230 			c->dequeue++;
231 			m = c->deq(c->si);
232 			if (m) {
233 				c->pending--;
234 				drop(c, m);
235 				c->drop--;	/* compensate */
236 				gnet_stats_deq(c, m);
237 			} else {
238 				D("--- ouch, cannot operate on iteration %d, pending %d", i, c->pending);
239 				break;
240 			}
241 		}
242 	}
243 	DX(1, "mainloop ends %d", i);
244 	return 0;
245 }
246 
247 int
248 dump(struct cfg_s *c)
249 {
250 	int i;
251 
252 	for (i=0; i < c->flows; i++) {
253 		//struct dn_queue *q = FI2Q(c, i);
254 		ND(1, "queue %4d tot %10llu", i,
255 		    (unsigned long long)q->ni.tot_bytes);
256 	}
257 	DX(1, "done %d loops\n", c->loops);
258 	return 0;
259 }
260 
261 /* interpret a number in human form */
262 static long
263 getnum(const char *s, char **next, const char *key)
264 {
265 	char *end = NULL;
266 	long l;
267 
268 	if (next)	/* default */
269 		*next = NULL;
270 	if (s && *s) {
271 		DX(3, "token is <%s> %s", s, key ? key : "-");
272 		l = strtol(s, &end, 0);
273 	} else {
274 		DX(3, "empty string");
275 		l = -1;
276 	}
277 	if (l < 0) {
278 		DX(2, "invalid %s for %s", s ? s : "NULL", (key ? key : "") );
279 		return 0;	// invalid
280 	}
281 	if (!end || !*end)
282 		return l;
283 	if (*end == 'n')
284 		l = -l;	/* multiply by n */
285 	else if (*end == 'K')
286 		l = l*1000;
287 	else if (*end == 'M')
288 		l = l*1000000;
289 	else if (*end == 'k')
290 		l = l*1024;
291 	else if (*end == 'm')
292 		l = l*1024*1024;
293 	else if (*end == 'w')
294 		;
295 	else {/* not recognized */
296 		D("suffix %s for %s, next %p", end, key, next);
297 		end--;
298 	}
299 	end++;
300 	DX(3, "suffix now %s for %s, next %p", end, key, next);
301 	if (next && *end) {
302 		DX(3, "setting next to %s for %s", end, key);
303 		*next = end;
304 	}
305 	return l;
306 }
307 
308 /*
309  * flowsets are a comma-separated list of
310  *     weight:maxlen:flows
311  * indicating how many flows are hooked to that fs.
312  * Both weight and range can be min-max-steps.
313  * The first pass (fs != NULL) justs count the number of flowsets and flows,
314  * the second pass (fs == NULL) we complete the setup.
315  */
316 static void
317 parse_flowsets(struct cfg_s *c, const char *fs)
318 {
319 	char *s, *cur, *next;
320 	int n_flows = 0, n_fs = 0, wsum = 0;
321 	int i, j;
322 	struct dn_fs *prev = NULL;
323 	int pass = (fs == NULL);
324 
325 	DX(3, "--- pass %d flows %d flowsets %d", pass, c->flows, c->flowsets);
326 	if (fs != NULL) { /* first pass */
327 		if (c->fs_config)
328 			D("warning, overwriting fs %s with %s",
329 				c->fs_config, fs);
330 		c->fs_config = fs;
331 	}
332 	s = c->fs_config ? strdup(c->fs_config) : NULL;
333 	if (s == NULL) {
334 		if (pass == 0)
335 			D("no fsconfig");
336 		return;
337 	}
338 	for (next = s; (cur = strsep(&next, ","));) {
339 		char *p = NULL;
340 		int w, w_h, w_steps, wi;
341 		int len, len_h, l_steps, li;
342 		int flows;
343 
344 		w = getnum(strsep(&cur, ":"), &p, "weight");
345 		if (w <= 0)
346 			w = 1;
347 		w_h = p ? getnum(p+1, &p, "weight_max") : w;
348 		w_steps = p ? getnum(p+1, &p, "w_steps") : (w_h == w ?1:2);
349 		len = getnum(strsep(&cur, ":"), &p, "len");
350 		if (len <= 0)
351 			len = 1000;
352 		len_h = p ? getnum(p+1, &p, "len_max") : len;
353 		l_steps = p ? getnum(p+1, &p, "l_steps") : (len_h == len ? 1 : 2);
354 		flows = getnum(strsep(&cur, ":"), NULL, "flows");
355 		if (flows == 0)
356 			flows = 1;
357 		DX(4, "weight %d..%d (%d) len %d..%d (%d) flows %d",
358 			w, w_h, w_steps, len, len_h, l_steps, flows);
359 		if (w == 0 || w_h < w || len == 0 || len_h < len ||
360 				flows == 0) {
361 			DX(4,"wrong parameters %s", s);
362 			return;
363 		}
364 		n_flows += flows * w_steps * l_steps;
365 		for (i = 0; i < w_steps; i++) {
366 			wi = w + ((w_h - w)* i)/(w_steps == 1 ? 1 : (w_steps-1));
367 			for (j = 0; j < l_steps; j++, n_fs++) {
368 				struct dn_fs *fs = &c->fs[n_fs].fs; // tentative
369 				int x;
370 
371 				li = len + ((len_h - len)* j)/(l_steps == 1 ? 1 : (l_steps-1));
372 				x = (wi*2048)/li;
373 				DX(3, "----- fs %4d weight %4d lmax %4d X %4d flows %d",
374 					n_fs, wi, li, x, flows);
375 				if (pass == 0)
376 					continue;
377 				if (c->fs == NULL || c->flowsets <= n_fs) {
378 					D("error in number of flowsets");
379 					return;
380 				}
381 				wsum += wi * flows;
382 				fs->par[0] = wi;
383 				fs->par[1] = li;
384 				fs->index = n_fs;
385 				fs->n_flows = flows;
386 				fs->cur = fs->first_flow = prev==NULL ? 0 : prev->next_flow;
387 				fs->next_flow = fs->first_flow + fs->n_flows;
388 				fs->y = x * flows;
389 				fs->base_y = (prev == NULL) ? 0 : prev->next_y;
390 				fs->next_y = fs->base_y + fs->y;
391 				prev = fs;
392 			}
393 		}
394 	}
395 	c->flows = n_flows;
396 	c->flowsets = n_fs;
397 	c->wsum = wsum;
398 	if (pass == 0)
399 		return;
400 
401 	/* now link all flows to their parent flowsets */
402 	DX(1,"%d flows on %d flowsets", c->flows, c->flowsets);
403 #ifdef USE_CUR
404 	c->max_y = prev ? prev->base_y + prev->y : 0;
405 	DX(1,"%d flows on %d flowsets max_y %d", c->flows, c->flowsets, c->max_y);
406 #endif /* USE_CUR */
407 	for (i=0; i < c->flowsets; i++) {
408 		struct dn_fs *fs = &c->fs[i].fs;
409 		DX(1, "fs %3d w %5d l %4d flow %5d .. %5d y %6d .. %6d",
410 			i, fs->par[0], fs->par[1],
411 			fs->first_flow, fs->next_flow,
412 			fs->base_y, fs->next_y);
413 		for (j = fs->first_flow; j < fs->next_flow; j++) {
414 			struct dn_queue *q = FI2Q(c, j);
415 			q->fs = &c->fs[i];
416 		}
417 	}
418 }
419 
420 /* available schedulers */
421 extern moduledata_t *_g_dn_fifo;
422 extern moduledata_t *_g_dn_wf2qp;
423 extern moduledata_t *_g_dn_rr;
424 extern moduledata_t *_g_dn_qfq;
425 #ifdef WITH_QFQP
426 extern moduledata_t *_g_dn_qfqp;
427 #endif
428 #ifdef WITH_KPS
429 extern moduledata_t *_g_dn_kps;
430 #endif
431 
432 static int
433 init(struct cfg_s *c)
434 {
435 	int i;
436 	int ac = c->ac;
437 	char * const *av = c->av;
438 
439 	c->si_len = sizeof(struct dn_sch_inst);
440 	c->q_len = sizeof(struct dn_queue);
441 	moduledata_t *mod = NULL;
442 	struct dn_alg *p = NULL;
443 
444 	c->th_min = -1; /* 1 packet per flow */
445 	c->th_max = -20;/* 20 packets per flow */
446 	c->lmin = c->lmax = 1280;	/* packet len */
447 	c->flows = 1;
448 	c->flowsets = 1;
449 	c->name = "null";
450 	ac--; av++;
451 	while (ac > 1) {
452 		if (!strcmp(*av, "-n")) {
453 			c->loops = getnum(av[1], NULL, av[0]);
454 		} else if (!strcmp(*av, "-d")) {
455 			debug = atoi(av[1]);
456 		} else if (!strcmp(*av, "-alg")) {
457 			if (!strcmp(av[1], "rr"))
458 				mod = _g_dn_rr;
459 			else if (!strcmp(av[1], "wf2qp"))
460 				mod = _g_dn_wf2qp;
461 			else if (!strcmp(av[1], "fifo"))
462 				mod = _g_dn_fifo;
463 			else if (!strcmp(av[1], "qfq"))
464 				mod = _g_dn_qfq;
465 #ifdef WITH_QFQP
466 			else if (!strcmp(av[1], "qfq+") ||
467 			    !strcmp(av[1], "qfqp") )
468 				mod = _g_dn_qfqp;
469 #endif
470 #ifdef WITH_KPS
471 			else if (!strcmp(av[1], "kps"))
472 				mod = _g_dn_kps;
473 #endif
474 			else
475 				mod = NULL;
476 			c->name = mod ? mod->name : "NULL";
477 			DX(3, "using scheduler %s", c->name);
478 		} else if (!strcmp(*av, "-len")) {
479 			c->lmin = getnum(av[1], NULL, av[0]);
480 			c->lmax = c->lmin;
481 			DX(3, "setting max to %d", c->th_max);
482 #ifdef USE_BURST
483 		} else if (!strcmp(*av, "-burst")) {
484 			c->maxburst = getnum(av[1], NULL, av[0]);
485 			DX(3, "setting max to %d", c->th_max);
486 #endif /* USE_BURST */
487 		} else if (!strcmp(*av, "-qmax")) {
488 			c->th_max = getnum(av[1], NULL, av[0]);
489 			DX(3, "setting max to %d", c->th_max);
490 		} else if (!strcmp(*av, "-qmin")) {
491 			c->th_min = getnum(av[1], NULL, av[0]);
492 			DX(3, "setting min to %d", c->th_min);
493 		} else if (!strcmp(*av, "-flows")) {
494 			c->flows = getnum(av[1], NULL, av[0]);
495 			DX(3, "setting flows to %d", c->flows);
496 		} else if (!strcmp(*av, "-flowsets")) {
497 			parse_flowsets(c, av[1]); /* first pass */
498 			DX(3, "setting flowsets to %d", c->flowsets);
499 		} else {
500 			D("option %s not recognised, ignore", *av);
501 		}
502 		ac -= 2; av += 2;
503 	}
504 #ifdef USE_BURST
505 	if (c->maxburst <= 0)
506 		c->maxburst = 1;
507 #endif /* USE_BURST */
508 	if (c->loops <= 0)
509 		c->loops = 1;
510 	if (c->flows <= 0)
511 		c->flows = 1;
512 	if (c->flowsets <= 0)
513 		c->flowsets = 1;
514 	if (c->lmin <= 0)
515 		c->lmin = 1;
516 	if (c->lmax <= 0)
517 		c->lmax = 1;
518 	/* multiply by N */
519 	if (c->th_min < 0)
520 		c->th_min = c->flows * -c->th_min;
521 	if (c->th_max < 0)
522 		c->th_max = c->flows * -c->th_max;
523 	if (c->th_max <= c->th_min)
524 		c->th_max = c->th_min + 1;
525 
526 	/* now load parameters from the module */
527 	if (mod) {
528 		p = mod->p;
529 		DX(3, "using module %s f %p p %p", mod->name, mod->f, mod->p);
530 		DX(3, "modname %s ty %d", p->name, p->type);
531 		// XXX check enq and deq not null
532 		c->enq = p->enqueue;
533 		c->deq = p->dequeue;
534 		c->si_len += p->si_datalen;
535 		c->q_len += p->q_datalen;
536 		c->schk_len += p->schk_datalen;
537 	} else {
538 		/* make sure c->si has room for a queue */
539 		c->enq = default_enqueue;
540 		c->deq = default_dequeue;
541 	}
542 
543 	/* allocate queues, flowsets and one scheduler */
544 	D("using %d flows, %d flowsets", c->flows, c->flowsets);
545 	D("q_len %d dn_fsk %d si %d sched %d",
546 		c->q_len, (int)sizeof(struct dn_fsk),
547 		c->si_len, c->schk_len);
548 	c->sched = calloc(1, c->schk_len); /* one parent scheduler */
549 	c->si = calloc(1, c->si_len); /* one scheduler instance */
550 	c->fs = calloc(c->flowsets, sizeof(struct dn_fsk));
551 	c->q = calloc(c->flows, c->q_len);	/* one queue per flow */
552 	c->q_wfi = calloc(c->flows, sizeof(double)); /* stats, one per flow */
553 	if (!c->sched || !c->si || !c->fs || !c->q || !c->q_wfi) {
554 		D("error allocating memory");
555 		exit(1);
556 	}
557 	c->si->sched = c->sched; /* link scheduler instance to template */
558 	if (p) {
559 		/* run initialization code if needed */
560 		if (p->config)
561 			p->config(c->si->sched);
562 		if (p->new_sched)
563 			p->new_sched(c->si);
564 	}
565 	/* parse_flowsets links queues to their flowsets */
566 	parse_flowsets(c, NULL); /* second pass */
567 	/* complete the work calling new_fsk */
568 	for (i = 0; i < c->flowsets; i++) {
569 		struct dn_fsk *fsk = &c->fs[i];
570 		if (fsk->fs.par[1] == 0)
571 			fsk->fs.par[1] = 1000;	/* default pkt len */
572 		fsk->sched = c->si->sched;
573 		if (p && p->new_fsk)
574 			p->new_fsk(fsk);
575 	}
576 	/* --- now the scheduler is initialized --- */
577 
578 	/*
579 	 * initialize the lists for the generator, and put
580 	 * all flows in the list for backlog = 0
581 	 */
582 	for (i=0; i <= BACKLOG+5; i++)
583 		INIT_LIST_HEAD(&c->ll[i]);
584 
585 	for (i = 0; i < c->flows; i++) {
586 		struct dn_queue *q = FI2Q(c, i);
587 		if (q->fs == NULL)
588 			q->fs = &c->fs[0]; /* XXX */
589 		q->_si = c->si;
590 		if (p && p->new_queue)
591 			p->new_queue(q);
592 		INIT_LIST_HEAD(&q->ni.h);
593 		list_add_tail(&q->ni.h, &c->ll[0]);
594 	}
595 	c->llmask = 1; /* all flows are in the first list */
596 	return 0;
597 }
598 
599 int
600 main(int ac, char *av[])
601 {
602 	struct cfg_s c;
603 	double ll;
604 	int i;
605 	char msg[40];
606 
607 	bzero(&c, sizeof(c));
608 	c.ac = ac;
609 	c.av = av;
610 	init(&c);
611 	gettimeofday(&c.time, NULL);
612 	D("th_min %d th_max %d", c.th_min, c.th_max);
613 
614 	mainloop(&c);
615 	{
616 		struct timeval end;
617 		gettimeofday(&end, NULL);
618 		timersub(&end, &c.time, &c.time);
619 	}
620 	ll = c.time.tv_sec*1000000 + c.time.tv_usec;
621 	ll *= 1000;	/* convert to nanoseconds */
622 	ll /= c._enqueue;
623 	sprintf(msg, "1::%d", c.flows);
624 	for (i = 0; i < c.flows; i++) {
625 		if (c.wfi < c.q_wfi[i])
626 			c.wfi = c.q_wfi[i];
627 	}
628 	D("sched=%-12s\ttime=%d.%03d sec (%.0f nsec) enq %lu %lu deq\n"
629 	   "\twfi=%.02f\tflow=%-16s",
630 	   c.name, (int)c.time.tv_sec, (int)c.time.tv_usec / 1000, ll,
631 	   (unsigned long)c._enqueue, (unsigned long)c.dequeue, c.wfi,
632 	   c.fs_config ? c.fs_config : msg);
633 	dump(&c);
634 	DX(1, "done ac %d av %p", ac, av);
635 	for (i=0; i < ac; i++)
636 		DX(1, "arg %d %s", i, av[i]);
637 	return 0;
638 }
639 
640 /*
641  * The controller decides whether in this iteration we should send
642  * (the packet is in c->tosend) and/or receive (flag c->can_dequeue)
643  */
644 static void
645 controller(struct cfg_s *c)
646 {
647 	struct mbuf *m;
648 	struct dn_fs *fs;
649 	int flow_id;
650 
651 	/* hysteresis between max and min */
652 	if (c->state == 0 && c->pending >= (uint32_t)c->th_max)
653 		c->state = 1;
654 	else if (c->state == 1 && c->pending <= (uint32_t)c->th_min)
655 		c->state = 0;
656 	ND(1, "state %d pending %2d", c->state, c->pending);
657 	c->can_dequeue = c->state;
658 	c->tosend = NULL;
659 	if (c->can_dequeue)
660 		return;
661 
662 	/*
663 	 * locate the flow to use for enqueueing
664 	 * We take the queue with the lowest number of queued packets,
665 	 * generate a packet for it, and put the queue in the next highest.
666 	 */
667     if (1) {
668 	int i;
669 	struct dn_queue *q;
670 	struct list_head *h;
671 
672 	i = ffs(c->llmask) - 1;
673 	if (i < 0) {
674 		D("no candidate");
675 		c->can_dequeue = 1;
676 		return;
677 	}
678 	h = &c->ll[i];
679 	ND(1, "backlog %d p %p prev %p next %p", i, h, h->prev, h->next);
680 	q = list_first_entry(h, struct dn_queue, ni.h);
681 	list_del(&q->ni.h);
682 	flow_id = Q2FI(c, q);
683 	DX(2, "extracted flow %p %d backlog %d", q, flow_id, i);
684 	if (list_empty(h)) {
685 		ND(2, "backlog %d empty", i);
686 		c->llmask &= ~(1<<i);
687 	}
688 	ND(1, "before %d p %p prev %p next %p", i+1, h+1, h[1].prev, h[1].next);
689 	list_add_tail(&q->ni.h, h+1);
690 	ND(1, " after %d p %p prev %p next %p", i+1, h+1, h[1].prev, h[1].next);
691 	if (i < BACKLOG) {
692 		ND(2, "backlog %d full", i+1);
693 		c->llmask |= 1<<(1+i);
694 	}
695 	fs = &q->fs->fs;
696 	fs->cur = flow_id;
697 #ifdef USE_CUR
698 	c->cur_fs = q->fs - c->fs;
699     } else {
700 	/* XXX this does not work ? */
701 	/* now decide whom to send the packet, and the length */
702 	/* lookup in the flow table */
703 	if (c->cur_y >= c->max_y) {	/* handle wraparound */
704 		c->cur_y = 0;
705 		c->cur_fs = 0;
706 	}
707 	fs = &c->fs[c->cur_fs].fs;
708 	flow_id = fs->cur++;
709 	if (fs->cur >= fs->next_flow)
710 		fs->cur = fs->first_flow;
711 	c->cur_y++;
712 	if (c->cur_y >= fs->next_y)
713 		c->cur_fs++;
714 #endif /* USE_CUR */
715     }
716 
717 	/* construct a packet */
718 	if (c->freelist) {
719 		m = c->tosend = c->freelist;
720 		c->freelist = c->freelist->m_nextpkt;
721 	} else {
722 		m = c->tosend = calloc(1, sizeof(struct mbuf));
723 	}
724 	if (m == NULL)
725 		return;
726 
727 	//m->cfg = c;
728 	m->m_nextpkt = NULL;
729 	m->m_pkthdr.len = fs->par[1]; // XXX maxlen
730 	m->flow_id = flow_id;
731 
732 	ND(2,"y %6d flow %5d fs %3d weight %4d len %4d",
733 		c->cur_y, m->flow_id, c->cur_fs,
734 		fs->par[0], m->m_pkthdr.len);
735 
736 }
737