xref: /freebsd/sys/netpfil/ipfw/test/main.c (revision 1603881667360c015f6685131f2f25474fa67a72)
1 /*
2  * $FreeBSD$
3  *
4  * Testing program for schedulers
5  *
6  * The framework include a simple controller which, at each
7  * iteration, decides whether we can enqueue and/or dequeue.
8  * Then the mainloop runs the required number of tests,
9  * keeping track of statistics.
10  */
11 
12 // #define USE_BURST	// what is this for ?
13 
14 #include "dn_test.h"
15 
16 struct cfg_s {
17 	int ac;
18 	char * const *av;
19 
20 	const char *name;
21 	int loops;
22 	struct timeval time;
23 
24 	/* running counters */
25 	uint32_t	_enqueue;
26 	uint32_t	drop;
27 	uint32_t	pending;
28 	uint32_t	dequeue;
29 
30 	/* generator parameters */
31 	int32_t th_min, th_max;	/* thresholds for hysteresis; negative means per flow */
32 #ifdef USE_BURST
33 	int maxburst;
34 #endif /* USE_BURST */
35 	int lmin, lmax;	/* packet len */
36 	int flows;	/* number of flows */
37 	int flowsets;	/* number of flowsets */
38 	int wsum;	/* sum of weights of all flows */
39 #ifdef USE_CUR
40 	int max_y;	/* max random number in the generation */
41 	int cur_y
42 	int cur_fs;	/* used in generation, between 0 and max_y - 1 */
43 #endif /* USE_CUR */
44 	const char *fs_config; /* flowset config */
45 	int can_dequeue;
46 	int burst;	/* count of packets sent in a burst */
47 	struct mbuf *tosend;	/* packet to send -- also flag to enqueue */
48 
49 	struct mbuf *freelist;
50 
51 	struct mbuf *head, *tail;	/* a simple tailq */
52 
53 	/* scheduler hooks */
54 	int (*enq)(struct dn_sch_inst *, struct dn_queue *,
55 		struct mbuf *);
56 	struct mbuf * (*deq)(struct dn_sch_inst *);
57 	/* size of the three fields including sched-specific areas */
58 	uint32_t schk_len;
59 	uint32_t q_len; /* size of a queue including sched-fields */
60 	uint32_t si_len; /* size of a sch_inst including sched-fields */
61 	char *q;	/* array of flow queues */
62 		/* use a char* because size is variable */
63 	/*
64 	 * The scheduler template (one) followd by schk_datalen bytes
65 	 * for scheduler-specific parameters, total size is schk_len
66 	 */
67 	struct dn_schk *sched;
68 	/*
69 	 * one scheduler instance, followed by si_datalen bytes
70 	 * for scheduler specific parameters of this instance,
71 	 * total size is si_len. si->sched points to sched
72 	 */
73 	struct dn_sch_inst *si;
74 	struct dn_fsk *fs;	/* array of flowsets */
75 
76 	/* generator state */
77 	int state;	/* 0 = going up (enqueue), 1: going down (dequeue) */
78 
79 	/*
80 	 * We keep lists for each backlog level, and always serve
81 	 * the one with shortest backlog. llmask contains a bitmap
82 	 * of lists, and ll are the heads of the lists. The last
83 	 * entry (BACKLOG) contains all entries considered 'full'
84 	 * XXX to optimize things, entry i could contain queues with
85 	 * 2^{i-1}+1 .. 2^i entries.
86 	 */
87 #define BACKLOG	30 /* this many backlogged classes, we only need BACKLOG+1 */
88 	uint64_t	llmask;
89 	struct list_head ll[BACKLOG + 10];
90 
91 	double *q_wfi;	/* (byte) Worst-case Fair Index of the flows  */
92 	double wfi;	/* (byte) Worst-case Fair Index of the system */
93 };
94 
95 /* FI2Q and Q2FI converts from flow_id (i.e. queue index)
96  * to dn_queue and back. We cannot simply use pointer arithmetic
97  * because the queu has variable size, q_len
98  */
99 #define FI2Q(c, i)	((struct dn_queue *)((c)->q + (c)->q_len * (i)))
100 #define Q2FI(c, q)	(((char *)(q) - (c)->q)/(c)->q_len)
101 
102 int debug = 0;
103 
104 struct dn_parms dn_cfg;
105 
106 static void controller(struct cfg_s *c);
107 
108 /* release a packet for a given flow_id.
109  * Put the mbuf in the freelist, and in case move the
110  * flow to the end of the bucket.
111  */
112 static int
113 drop(struct cfg_s *c, struct mbuf *m)
114 {
115 	struct dn_queue *q;
116 	int i;
117 
118 	c->drop++;
119 	q = FI2Q(c, m->flow_id);
120 	i = q->ni.length; // XXX or ffs...
121 
122 	ND("q %p id %d current length %d", q, m->flow_id, i);
123 	if (i < BACKLOG) {
124 		struct list_head *h = &q->ni.h;
125 		c->llmask &= ~(1<<(i+1));
126 		c->llmask |= (1<<(i));
127 		list_del(h);
128 		list_add_tail(h, &c->ll[i]);
129 	}
130 	m->m_nextpkt = c->freelist;
131 	c->freelist = m;
132 	return 0;
133 }
134 
135 /*
136  * dn_sch_inst does not have a queue, for the RR we
137  * allocate a mq right after si
138  */
139 static int
140 default_enqueue(struct dn_sch_inst *si, struct dn_queue *q, struct mbuf *m)
141 {
142 	struct mq *mq = (struct mq *)si;
143 
144 	(void)q;
145 	/* this is the default function if no scheduler is provided */
146 	if (mq->head == NULL)
147 		mq->head = m;
148 	else
149 		mq->tail->m_nextpkt = m;
150 	mq->tail = m;
151 	return 0; /* default - success */
152 }
153 
154 static struct mbuf *
155 default_dequeue(struct dn_sch_inst *si)
156 {
157 	struct mq *mq = (struct mq *)si;
158 	struct mbuf *m;
159 	/* this is the default function if no scheduler is provided */
160 	if ((m = mq->head)) {
161 		m = mq->head;
162 		mq->head = m->m_nextpkt;
163 		m->m_nextpkt = NULL;
164 	}
165 	return m;
166 }
167 
168 static void
169 gnet_stats_enq(struct cfg_s *c, struct mbuf *mb)
170 {
171 	struct dn_sch_inst *si = c->si;
172 	struct dn_queue *_q = FI2Q(c, mb->flow_id);
173 
174 	if (_q->ni.length == 1) {
175 		_q->ni.bytes = 0;
176 		_q->ni.sch_bytes = si->ni.bytes;
177 	}
178 }
179 
180 static void
181 gnet_stats_deq(struct cfg_s *c, struct mbuf *mb)
182 {
183 	struct dn_sch_inst *si = c->si;
184 	struct dn_queue *_q = FI2Q(c, mb->flow_id);
185 	int len = mb->m_pkthdr.len;
186 
187 	_q->ni.bytes += len;
188 	si->ni.bytes += len;
189 
190 	if (_q->ni.length == 0) {
191 		double bytes = (double)_q->ni.bytes;
192 		double sch_bytes = (double)si->ni.bytes - _q->ni.sch_bytes;
193 		double weight = (double)_q->fs->fs.par[0] / c->wsum;
194 		double wfi = sch_bytes * weight - bytes;
195 
196 		if (c->q_wfi[mb->flow_id] < wfi)
197 			c->q_wfi[mb->flow_id] = wfi;
198 	}
199 }
200 
201 static int
202 mainloop(struct cfg_s *c)
203 {
204 	int i;
205 	struct mbuf *m;
206 
207 	for (i=0; i < c->loops; i++) {
208 		/* implement histeresis */
209 		controller(c);
210 		DX(3, "loop %d enq %d send %p rx %d",
211 			i, c->_enqueue, c->tosend, c->can_dequeue);
212 		if ( (m = c->tosend) ) {
213 			int ret;
214 			struct dn_queue *q = FI2Q(c, m->flow_id);
215 			c->_enqueue++;
216 			ret = c->enq(c->si, q, m);
217 			if (ret) {
218 				drop(c, m);
219 				D("loop %d enqueue fail", i );
220 				/*
221 				 * XXX do not insist; rather, try dequeue
222 				 */
223 				goto do_dequeue;
224 			} else {
225 				ND("enqueue ok");
226 				c->pending++;
227 				gnet_stats_enq(c, m);
228 			}
229 		} else if (c->can_dequeue) {
230 do_dequeue:
231 			c->dequeue++;
232 			m = c->deq(c->si);
233 			if (m) {
234 				c->pending--;
235 				drop(c, m);
236 				c->drop--;	/* compensate */
237 				gnet_stats_deq(c, m);
238 			} else {
239 				D("--- ouch, cannot operate on iteration %d, pending %d", i, c->pending);
240 				break;
241 			}
242 		}
243 	}
244 	DX(1, "mainloop ends %d", i);
245 	return 0;
246 }
247 
248 int
249 dump(struct cfg_s *c)
250 {
251 	int i;
252 
253 	for (i=0; i < c->flows; i++) {
254 		//struct dn_queue *q = FI2Q(c, i);
255 		ND(1, "queue %4d tot %10llu", i,
256 		    (unsigned long long)q->ni.tot_bytes);
257 	}
258 	DX(1, "done %d loops\n", c->loops);
259 	return 0;
260 }
261 
262 /* interpret a number in human form */
263 static long
264 getnum(const char *s, char **next, const char *key)
265 {
266 	char *end = NULL;
267 	long l;
268 
269 	if (next)	/* default */
270 		*next = NULL;
271 	if (s && *s) {
272 		DX(3, "token is <%s> %s", s, key ? key : "-");
273 		l = strtol(s, &end, 0);
274 	} else {
275 		DX(3, "empty string");
276 		l = -1;
277 	}
278 	if (l < 0) {
279 		DX(2, "invalid %s for %s", s ? s : "NULL", (key ? key : "") );
280 		return 0;	// invalid
281 	}
282 	if (!end || !*end)
283 		return l;
284 	if (*end == 'n')
285 		l = -l;	/* multiply by n */
286 	else if (*end == 'K')
287 		l = l*1000;
288 	else if (*end == 'M')
289 		l = l*1000000;
290 	else if (*end == 'k')
291 		l = l*1024;
292 	else if (*end == 'm')
293 		l = l*1024*1024;
294 	else if (*end == 'w')
295 		;
296 	else {/* not recognized */
297 		D("suffix %s for %s, next %p", end, key, next);
298 		end--;
299 	}
300 	end++;
301 	DX(3, "suffix now %s for %s, next %p", end, key, next);
302 	if (next && *end) {
303 		DX(3, "setting next to %s for %s", end, key);
304 		*next = end;
305 	}
306 	return l;
307 }
308 
309 /*
310  * flowsets are a comma-separated list of
311  *     weight:maxlen:flows
312  * indicating how many flows are hooked to that fs.
313  * Both weight and range can be min-max-steps.
314  * The first pass (fs != NULL) justs count the number of flowsets and flows,
315  * the second pass (fs == NULL) we complete the setup.
316  */
317 static void
318 parse_flowsets(struct cfg_s *c, const char *fs)
319 {
320 	char *s, *cur, *next;
321 	int n_flows = 0, n_fs = 0, wsum = 0;
322 	int i, j;
323 	struct dn_fs *prev = NULL;
324 	int pass = (fs == NULL);
325 
326 	DX(3, "--- pass %d flows %d flowsets %d", pass, c->flows, c->flowsets);
327 	if (fs != NULL) { /* first pass */
328 		if (c->fs_config)
329 			D("warning, overwriting fs %s with %s",
330 				c->fs_config, fs);
331 		c->fs_config = fs;
332 	}
333 	s = c->fs_config ? strdup(c->fs_config) : NULL;
334 	if (s == NULL) {
335 		if (pass == 0)
336 			D("no fsconfig");
337 		return;
338 	}
339 	for (next = s; (cur = strsep(&next, ","));) {
340 		char *p = NULL;
341 		int w, w_h, w_steps, wi;
342 		int len, len_h, l_steps, li;
343 		int flows;
344 
345 		w = getnum(strsep(&cur, ":"), &p, "weight");
346 		if (w <= 0)
347 			w = 1;
348 		w_h = p ? getnum(p+1, &p, "weight_max") : w;
349 		w_steps = p ? getnum(p+1, &p, "w_steps") : (w_h == w ?1:2);
350 		len = getnum(strsep(&cur, ":"), &p, "len");
351 		if (len <= 0)
352 			len = 1000;
353 		len_h = p ? getnum(p+1, &p, "len_max") : len;
354 		l_steps = p ? getnum(p+1, &p, "l_steps") : (len_h == len ? 1 : 2);
355 		flows = getnum(strsep(&cur, ":"), NULL, "flows");
356 		if (flows == 0)
357 			flows = 1;
358 		DX(4, "weight %d..%d (%d) len %d..%d (%d) flows %d",
359 			w, w_h, w_steps, len, len_h, l_steps, flows);
360 		if (w == 0 || w_h < w || len == 0 || len_h < len ||
361 				flows == 0) {
362 			DX(4,"wrong parameters %s", s);
363 			return;
364 		}
365 		n_flows += flows * w_steps * l_steps;
366 		for (i = 0; i < w_steps; i++) {
367 			wi = w + ((w_h - w)* i)/(w_steps == 1 ? 1 : (w_steps-1));
368 			for (j = 0; j < l_steps; j++, n_fs++) {
369 				struct dn_fs *fs = &c->fs[n_fs].fs; // tentative
370 				int x;
371 
372 				li = len + ((len_h - len)* j)/(l_steps == 1 ? 1 : (l_steps-1));
373 				x = (wi*2048)/li;
374 				DX(3, "----- fs %4d weight %4d lmax %4d X %4d flows %d",
375 					n_fs, wi, li, x, flows);
376 				if (pass == 0)
377 					continue;
378 				if (c->fs == NULL || c->flowsets <= n_fs) {
379 					D("error in number of flowsets");
380 					return;
381 				}
382 				wsum += wi * flows;
383 				fs->par[0] = wi;
384 				fs->par[1] = li;
385 				fs->index = n_fs;
386 				fs->n_flows = flows;
387 				fs->cur = fs->first_flow = prev==NULL ? 0 : prev->next_flow;
388 				fs->next_flow = fs->first_flow + fs->n_flows;
389 				fs->y = x * flows;
390 				fs->base_y = (prev == NULL) ? 0 : prev->next_y;
391 				fs->next_y = fs->base_y + fs->y;
392 				prev = fs;
393 			}
394 		}
395 	}
396 	c->flows = n_flows;
397 	c->flowsets = n_fs;
398 	c->wsum = wsum;
399 	if (pass == 0)
400 		return;
401 
402 	/* now link all flows to their parent flowsets */
403 	DX(1,"%d flows on %d flowsets", c->flows, c->flowsets);
404 #ifdef USE_CUR
405 	c->max_y = prev ? prev->base_y + prev->y : 0;
406 	DX(1,"%d flows on %d flowsets max_y %d", c->flows, c->flowsets, c->max_y);
407 #endif /* USE_CUR */
408 	for (i=0; i < c->flowsets; i++) {
409 		struct dn_fs *fs = &c->fs[i].fs;
410 		DX(1, "fs %3d w %5d l %4d flow %5d .. %5d y %6d .. %6d",
411 			i, fs->par[0], fs->par[1],
412 			fs->first_flow, fs->next_flow,
413 			fs->base_y, fs->next_y);
414 		for (j = fs->first_flow; j < fs->next_flow; j++) {
415 			struct dn_queue *q = FI2Q(c, j);
416 			q->fs = &c->fs[i];
417 		}
418 	}
419 }
420 
421 /* available schedulers */
422 extern moduledata_t *_g_dn_fifo;
423 extern moduledata_t *_g_dn_wf2qp;
424 extern moduledata_t *_g_dn_rr;
425 extern moduledata_t *_g_dn_qfq;
426 #ifdef WITH_QFQP
427 extern moduledata_t *_g_dn_qfqp;
428 #endif
429 #ifdef WITH_KPS
430 extern moduledata_t *_g_dn_kps;
431 #endif
432 
433 static int
434 init(struct cfg_s *c)
435 {
436 	int i;
437 	int ac = c->ac;
438 	char * const *av = c->av;
439 
440 	c->si_len = sizeof(struct dn_sch_inst);
441 	c->q_len = sizeof(struct dn_queue);
442 	moduledata_t *mod = NULL;
443 	struct dn_alg *p = NULL;
444 
445 	c->th_min = -1; /* 1 packet per flow */
446 	c->th_max = -20;/* 20 packets per flow */
447 	c->lmin = c->lmax = 1280;	/* packet len */
448 	c->flows = 1;
449 	c->flowsets = 1;
450 	c->name = "null";
451 	ac--; av++;
452 	while (ac > 1) {
453 		if (!strcmp(*av, "-n")) {
454 			c->loops = getnum(av[1], NULL, av[0]);
455 		} else if (!strcmp(*av, "-d")) {
456 			debug = atoi(av[1]);
457 		} else if (!strcmp(*av, "-alg")) {
458 			if (!strcmp(av[1], "rr"))
459 				mod = _g_dn_rr;
460 			else if (!strcmp(av[1], "wf2qp"))
461 				mod = _g_dn_wf2qp;
462 			else if (!strcmp(av[1], "fifo"))
463 				mod = _g_dn_fifo;
464 			else if (!strcmp(av[1], "qfq"))
465 				mod = _g_dn_qfq;
466 #ifdef WITH_QFQP
467 			else if (!strcmp(av[1], "qfq+") ||
468 			    !strcmp(av[1], "qfqp") )
469 				mod = _g_dn_qfqp;
470 #endif
471 #ifdef WITH_KPS
472 			else if (!strcmp(av[1], "kps"))
473 				mod = _g_dn_kps;
474 #endif
475 			else
476 				mod = NULL;
477 			c->name = mod ? mod->name : "NULL";
478 			DX(3, "using scheduler %s", c->name);
479 		} else if (!strcmp(*av, "-len")) {
480 			c->lmin = getnum(av[1], NULL, av[0]);
481 			c->lmax = c->lmin;
482 			DX(3, "setting max to %d", c->th_max);
483 #ifdef USE_BURST
484 		} else if (!strcmp(*av, "-burst")) {
485 			c->maxburst = getnum(av[1], NULL, av[0]);
486 			DX(3, "setting max to %d", c->th_max);
487 #endif /* USE_BURST */
488 		} else if (!strcmp(*av, "-qmax")) {
489 			c->th_max = getnum(av[1], NULL, av[0]);
490 			DX(3, "setting max to %d", c->th_max);
491 		} else if (!strcmp(*av, "-qmin")) {
492 			c->th_min = getnum(av[1], NULL, av[0]);
493 			DX(3, "setting min to %d", c->th_min);
494 		} else if (!strcmp(*av, "-flows")) {
495 			c->flows = getnum(av[1], NULL, av[0]);
496 			DX(3, "setting flows to %d", c->flows);
497 		} else if (!strcmp(*av, "-flowsets")) {
498 			parse_flowsets(c, av[1]); /* first pass */
499 			DX(3, "setting flowsets to %d", c->flowsets);
500 		} else {
501 			D("option %s not recognised, ignore", *av);
502 		}
503 		ac -= 2; av += 2;
504 	}
505 #ifdef USE_BURST
506 	if (c->maxburst <= 0)
507 		c->maxburst = 1;
508 #endif /* USE_BURST */
509 	if (c->loops <= 0)
510 		c->loops = 1;
511 	if (c->flows <= 0)
512 		c->flows = 1;
513 	if (c->flowsets <= 0)
514 		c->flowsets = 1;
515 	if (c->lmin <= 0)
516 		c->lmin = 1;
517 	if (c->lmax <= 0)
518 		c->lmax = 1;
519 	/* multiply by N */
520 	if (c->th_min < 0)
521 		c->th_min = c->flows * -c->th_min;
522 	if (c->th_max < 0)
523 		c->th_max = c->flows * -c->th_max;
524 	if (c->th_max <= c->th_min)
525 		c->th_max = c->th_min + 1;
526 
527 	/* now load parameters from the module */
528 	if (mod) {
529 		p = mod->p;
530 		DX(3, "using module %s f %p p %p", mod->name, mod->f, mod->p);
531 		DX(3, "modname %s ty %d", p->name, p->type);
532 		// XXX check enq and deq not null
533 		c->enq = p->enqueue;
534 		c->deq = p->dequeue;
535 		c->si_len += p->si_datalen;
536 		c->q_len += p->q_datalen;
537 		c->schk_len += p->schk_datalen;
538 	} else {
539 		/* make sure c->si has room for a queue */
540 		c->enq = default_enqueue;
541 		c->deq = default_dequeue;
542 	}
543 
544 	/* allocate queues, flowsets and one scheduler */
545 	D("using %d flows, %d flowsets", c->flows, c->flowsets);
546 	D("q_len %d dn_fsk %d si %d sched %d",
547 		c->q_len, (int)sizeof(struct dn_fsk),
548 		c->si_len, c->schk_len);
549 	c->sched = calloc(1, c->schk_len); /* one parent scheduler */
550 	c->si = calloc(1, c->si_len); /* one scheduler instance */
551 	c->fs = calloc(c->flowsets, sizeof(struct dn_fsk));
552 	c->q = calloc(c->flows, c->q_len);	/* one queue per flow */
553 	c->q_wfi = calloc(c->flows, sizeof(double)); /* stats, one per flow */
554 	if (!c->sched || !c->si || !c->fs || !c->q || !c->q_wfi) {
555 		D("error allocating memory");
556 		exit(1);
557 	}
558 	c->si->sched = c->sched; /* link scheduler instance to template */
559 	if (p) {
560 		/* run initialization code if needed */
561 		if (p->config)
562 			p->config(c->si->sched);
563 		if (p->new_sched)
564 			p->new_sched(c->si);
565 	}
566 	/* parse_flowsets links queues to their flowsets */
567 	parse_flowsets(c, NULL); /* second pass */
568 	/* complete the work calling new_fsk */
569 	for (i = 0; i < c->flowsets; i++) {
570 		struct dn_fsk *fsk = &c->fs[i];
571 		if (fsk->fs.par[1] == 0)
572 			fsk->fs.par[1] = 1000;	/* default pkt len */
573 		fsk->sched = c->si->sched;
574 		if (p && p->new_fsk)
575 			p->new_fsk(fsk);
576 	}
577 	/* --- now the scheduler is initialized --- */
578 
579 	/*
580 	 * initialize the lists for the generator, and put
581 	 * all flows in the list for backlog = 0
582 	 */
583 	for (i=0; i <= BACKLOG+5; i++)
584 		INIT_LIST_HEAD(&c->ll[i]);
585 
586 	for (i = 0; i < c->flows; i++) {
587 		struct dn_queue *q = FI2Q(c, i);
588 		if (q->fs == NULL)
589 			q->fs = &c->fs[0]; /* XXX */
590 		q->_si = c->si;
591 		if (p && p->new_queue)
592 			p->new_queue(q);
593 		INIT_LIST_HEAD(&q->ni.h);
594 		list_add_tail(&q->ni.h, &c->ll[0]);
595 	}
596 	c->llmask = 1; /* all flows are in the first list */
597 	return 0;
598 }
599 
600 int
601 main(int ac, char *av[])
602 {
603 	struct cfg_s c;
604 	double ll;
605 	int i;
606 	char msg[40];
607 
608 	bzero(&c, sizeof(c));
609 	c.ac = ac;
610 	c.av = av;
611 	init(&c);
612 	gettimeofday(&c.time, NULL);
613 	D("th_min %d th_max %d", c.th_min, c.th_max);
614 
615 	mainloop(&c);
616 	{
617 		struct timeval end;
618 		gettimeofday(&end, NULL);
619 		timersub(&end, &c.time, &c.time);
620 	}
621 	ll = c.time.tv_sec*1000000 + c.time.tv_usec;
622 	ll *= 1000;	/* convert to nanoseconds */
623 	ll /= c._enqueue;
624 	sprintf(msg, "1::%d", c.flows);
625 	for (i = 0; i < c.flows; i++) {
626 		if (c.wfi < c.q_wfi[i])
627 			c.wfi = c.q_wfi[i];
628 	}
629 	D("sched=%-12s\ttime=%d.%03d sec (%.0f nsec) enq %lu %lu deq\n"
630 	   "\twfi=%.02f\tflow=%-16s",
631 	   c.name, (int)c.time.tv_sec, (int)c.time.tv_usec / 1000, ll,
632 	   (unsigned long)c._enqueue, (unsigned long)c.dequeue, c.wfi,
633 	   c.fs_config ? c.fs_config : msg);
634 	dump(&c);
635 	DX(1, "done ac %d av %p", ac, av);
636 	for (i=0; i < ac; i++)
637 		DX(1, "arg %d %s", i, av[i]);
638 	return 0;
639 }
640 
641 /*
642  * The controller decides whether in this iteration we should send
643  * (the packet is in c->tosend) and/or receive (flag c->can_dequeue)
644  */
645 static void
646 controller(struct cfg_s *c)
647 {
648 	struct mbuf *m;
649 	struct dn_fs *fs;
650 	int flow_id;
651 
652 	/* hysteresis between max and min */
653 	if (c->state == 0 && c->pending >= (uint32_t)c->th_max)
654 		c->state = 1;
655 	else if (c->state == 1 && c->pending <= (uint32_t)c->th_min)
656 		c->state = 0;
657 	ND(1, "state %d pending %2d", c->state, c->pending);
658 	c->can_dequeue = c->state;
659 	c->tosend = NULL;
660 	if (c->can_dequeue)
661 		return;
662 
663 	/*
664 	 * locate the flow to use for enqueueing
665 	 * We take the queue with the lowest number of queued packets,
666 	 * generate a packet for it, and put the queue in the next highest.
667 	 */
668     if (1) {
669 	int i;
670 	struct dn_queue *q;
671 	struct list_head *h;
672 
673 	i = ffs(c->llmask) - 1;
674 	if (i < 0) {
675 		D("no candidate");
676 		c->can_dequeue = 1;
677 		return;
678 	}
679 	h = &c->ll[i];
680 	ND(1, "backlog %d p %p prev %p next %p", i, h, h->prev, h->next);
681 	q = list_first_entry(h, struct dn_queue, ni.h);
682 	list_del(&q->ni.h);
683 	flow_id = Q2FI(c, q);
684 	DX(2, "extracted flow %p %d backlog %d", q, flow_id, i);
685 	if (list_empty(h)) {
686 		ND(2, "backlog %d empty", i);
687 		c->llmask &= ~(1<<i);
688 	}
689 	ND(1, "before %d p %p prev %p next %p", i+1, h+1, h[1].prev, h[1].next);
690 	list_add_tail(&q->ni.h, h+1);
691 	ND(1, " after %d p %p prev %p next %p", i+1, h+1, h[1].prev, h[1].next);
692 	if (i < BACKLOG) {
693 		ND(2, "backlog %d full", i+1);
694 		c->llmask |= 1<<(1+i);
695 	}
696 	fs = &q->fs->fs;
697 	fs->cur = flow_id;
698 #ifdef USE_CUR
699 	c->cur_fs = q->fs - c->fs;
700     } else {
701 	/* XXX this does not work ? */
702 	/* now decide whom to send the packet, and the length */
703 	/* lookup in the flow table */
704 	if (c->cur_y >= c->max_y) {	/* handle wraparound */
705 		c->cur_y = 0;
706 		c->cur_fs = 0;
707 	}
708 	fs = &c->fs[c->cur_fs].fs;
709 	flow_id = fs->cur++;
710 	if (fs->cur >= fs->next_flow)
711 		fs->cur = fs->first_flow;
712 	c->cur_y++;
713 	if (c->cur_y >= fs->next_y)
714 		c->cur_fs++;
715 #endif /* USE_CUR */
716     }
717 
718 	/* construct a packet */
719 	if (c->freelist) {
720 		m = c->tosend = c->freelist;
721 		c->freelist = c->freelist->m_nextpkt;
722 	} else {
723 		m = c->tosend = calloc(1, sizeof(struct mbuf));
724 	}
725 	if (m == NULL)
726 		return;
727 
728 	//m->cfg = c;
729 	m->m_nextpkt = NULL;
730 	m->m_pkthdr.len = fs->par[1]; // XXX maxlen
731 	m->flow_id = flow_id;
732 
733 	ND(2,"y %6d flow %5d fs %3d weight %4d len %4d",
734 		c->cur_y, m->flow_id, c->cur_fs,
735 		fs->par[0], m->m_pkthdr.len);
736 
737 }
738