xref: /freebsd/sys/net/altq/altq_codel.c (revision a0ee8cc6) 
1 /*
2  * CoDel - The Controlled-Delay Active Queue Management algorithm
3  *
4  *  Copyright (C) 2013 Ermal Luçi <eri@FreeBSD.org>
5  *  Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
6  *  Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
7  *  Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net>
8  *  Copyright (C) 2012 Eric Dumazet <edumazet@google.com>
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions, and the following disclaimer,
15  *    without modification.
16  * 2. Redistributions in binary form must reproduce the above copyright
17  *    notice, this list of conditions and the following disclaimer in the
18  *    documentation and/or other materials provided with the distribution.
19  * 3. The names of the authors may not be used to endorse or promote products
20  *    derived from this software without specific prior written permission.
21  *
22  * Alternatively, provided that this notice is retained in full, this
23  * software may be distributed under the terms of the GNU General
24  * Public License ("GPL") version 2, in which case the provisions of the
25  * GPL apply INSTEAD OF those given above.
26  *
27  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
30  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
31  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
32  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
33  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
34  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
35  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
36  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
37  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
38  * DAMAGE.
39  *
40  * $FreeBSD$
41  */
42 #include "opt_altq.h"
43 #include "opt_inet.h"
44 #include "opt_inet6.h"
45 
46 #ifdef ALTQ_CODEL  /* CoDel is enabled by ALTQ_CODEL option in opt_altq.h */
47 
48 #include <sys/param.h>
49 #include <sys/malloc.h>
50 #include <sys/mbuf.h>
51 #include <sys/socket.h>
52 #include <sys/systm.h>
53 
54 #include <net/if.h>
55 #include <net/if_var.h>
56 #include <netinet/in.h>
57 
58 #include <netpfil/pf/pf.h>
59 #include <netpfil/pf/pf_altq.h>
60 #include <net/altq/if_altq.h>
61 #include <net/altq/altq.h>
62 #include <net/altq/altq_codel.h>
63 
64 static int		 codel_should_drop(struct codel *, class_queue_t *,
65 			    struct mbuf *, u_int64_t);
66 static void		 codel_Newton_step(struct codel_vars *);
67 static u_int64_t	 codel_control_law(u_int64_t t, u_int64_t, u_int32_t);
68 
69 #define	codel_time_after(a, b)		((int64_t)(a) - (int64_t)(b) > 0)
70 #define	codel_time_after_eq(a, b)	((int64_t)(a) - (int64_t)(b) >= 0)
71 #define	codel_time_before(a, b)		((int64_t)(a) - (int64_t)(b) < 0)
72 #define	codel_time_before_eq(a, b)	((int64_t)(a) - (int64_t)(b) <= 0)
73 
74 static int codel_request(struct ifaltq *, int, void *);
75 
76 static int codel_enqueue(struct ifaltq *, struct mbuf *, struct altq_pktattr *);
77 static struct mbuf *codel_dequeue(struct ifaltq *, int);
78 
79 int
80 codel_pfattach(struct pf_altq *a)
81 {
82 	struct ifnet *ifp;
83 
84 	if ((ifp = ifunit(a->ifname)) == NULL || a->altq_disc == NULL)
85 		return (EINVAL);
86 
87 	return (altq_attach(&ifp->if_snd, ALTQT_CODEL, a->altq_disc,
88 	    codel_enqueue, codel_dequeue, codel_request, NULL, NULL));
89 }
90 
91 int
92 codel_add_altq(struct pf_altq *a)
93 {
94 	struct codel_if	*cif;
95 	struct ifnet	*ifp;
96 	struct codel_opts	*opts;
97 
98 	if ((ifp = ifunit(a->ifname)) == NULL)
99 		return (EINVAL);
100 	if (!ALTQ_IS_READY(&ifp->if_snd))
101 		return (ENODEV);
102 
103 	opts = &a->pq_u.codel_opts;
104 
105 	cif = malloc(sizeof(struct codel_if), M_DEVBUF, M_NOWAIT | M_ZERO);
106 	if (cif == NULL)
107 		return (ENOMEM);
108 	cif->cif_bandwidth = a->ifbandwidth;
109 	cif->cif_ifq = &ifp->if_snd;
110 
111 	cif->cl_q = malloc(sizeof(class_queue_t), M_DEVBUF, M_NOWAIT | M_ZERO);
112 	if (cif->cl_q == NULL) {
113 		free(cif, M_DEVBUF);
114 		return (ENOMEM);
115 	}
116 
117 	if (a->qlimit == 0)
118 		a->qlimit = 50;	/* use default. */
119 	qlimit(cif->cl_q) = a->qlimit;
120 	qtype(cif->cl_q) = Q_CODEL;
121 	qlen(cif->cl_q) = 0;
122 	qsize(cif->cl_q) = 0;
123 
124 	if (opts->target == 0)
125 		opts->target = 5;
126 	if (opts->interval == 0)
127 		opts->interval = 100;
128 	cif->codel.params.target = machclk_freq * opts->target / 1000;
129 	cif->codel.params.interval = machclk_freq * opts->interval / 1000;
130 	cif->codel.params.ecn = opts->ecn;
131 	cif->codel.stats.maxpacket = 256;
132 
133 	cif->cl_stats.qlength = qlen(cif->cl_q);
134 	cif->cl_stats.qlimit = qlimit(cif->cl_q);
135 
136 	/* keep the state in pf_altq */
137 	a->altq_disc = cif;
138 
139 	return (0);
140 }
141 
142 int
143 codel_remove_altq(struct pf_altq *a)
144 {
145 	struct codel_if *cif;
146 
147 	if ((cif = a->altq_disc) == NULL)
148 		return (EINVAL);
149 	a->altq_disc = NULL;
150 
151 	if (cif->cl_q)
152 		free(cif->cl_q, M_DEVBUF);
153 	free(cif, M_DEVBUF);
154 
155 	return (0);
156 }
157 
158 int
159 codel_getqstats(struct pf_altq *a, void *ubuf, int *nbytes)
160 {
161 	struct codel_if *cif;
162 	struct codel_ifstats stats;
163 	int error = 0;
164 
165 	if ((cif = altq_lookup(a->ifname, ALTQT_CODEL)) == NULL)
166 		return (EBADF);
167 
168 	if (*nbytes < sizeof(stats))
169 		return (EINVAL);
170 
171 	stats = cif->cl_stats;
172 	stats.stats = cif->codel.stats;
173 
174 	if ((error = copyout((caddr_t)&stats, ubuf, sizeof(stats))) != 0)
175 		return (error);
176 	*nbytes = sizeof(stats);
177 
178 	return (0);
179 }
180 
181 static int
182 codel_request(struct ifaltq *ifq, int req, void *arg)
183 {
184 	struct codel_if	*cif = (struct codel_if *)ifq->altq_disc;
185 	struct mbuf *m;
186 
187 	IFQ_LOCK_ASSERT(ifq);
188 
189 	switch (req) {
190 	case ALTRQ_PURGE:
191 		if (!ALTQ_IS_ENABLED(cif->cif_ifq))
192 			break;
193 
194 		if (qempty(cif->cl_q))
195 			break;
196 
197 		while ((m = _getq(cif->cl_q)) != NULL) {
198 			PKTCNTR_ADD(&cif->cl_stats.cl_dropcnt, m_pktlen(m));
199 			m_freem(m);
200 			IFQ_DEC_LEN(cif->cif_ifq);
201 		}
202 		cif->cif_ifq->ifq_len = 0;
203 		break;
204 	}
205 
206 	return (0);
207 }
208 
209 static int
210 codel_enqueue(struct ifaltq *ifq, struct mbuf *m, struct altq_pktattr *pktattr)
211 {
212 
213 	struct codel_if *cif = (struct codel_if *) ifq->altq_disc;
214 
215 	IFQ_LOCK_ASSERT(ifq);
216 
217 	/* grab class set by classifier */
218 	if ((m->m_flags & M_PKTHDR) == 0) {
219 		/* should not happen */
220 		printf("altq: packet for %s does not have pkthdr\n",
221 		   ifq->altq_ifp->if_xname);
222 		m_freem(m);
223 		PKTCNTR_ADD(&cif->cl_stats.cl_dropcnt, m_pktlen(m));
224 		return (ENOBUFS);
225 	}
226 
227 	if (codel_addq(&cif->codel, cif->cl_q, m)) {
228 		PKTCNTR_ADD(&cif->cl_stats.cl_dropcnt, m_pktlen(m));
229 		return (ENOBUFS);
230 	}
231 	IFQ_INC_LEN(ifq);
232 
233 	return (0);
234 }
235 
236 static struct mbuf *
237 codel_dequeue(struct ifaltq *ifq, int op)
238 {
239 	struct codel_if *cif = (struct codel_if *)ifq->altq_disc;
240 	struct mbuf *m;
241 
242 	IFQ_LOCK_ASSERT(ifq);
243 
244 	if (IFQ_IS_EMPTY(ifq))
245 		return (NULL);
246 
247 	if (op == ALTDQ_POLL)
248 		return (qhead(cif->cl_q));
249 
250 
251 	m = codel_getq(&cif->codel, cif->cl_q);
252 	if (m != NULL) {
253 		IFQ_DEC_LEN(ifq);
254 		PKTCNTR_ADD(&cif->cl_stats.cl_xmitcnt, m_pktlen(m));
255 		return (m);
256 	}
257 
258 	return (NULL);
259 }
260 
261 struct codel *
262 codel_alloc(int target, int interval, int ecn)
263 {
264 	struct codel *c;
265 
266 	c = malloc(sizeof(*c), M_DEVBUF, M_NOWAIT | M_ZERO);
267 	if (c != NULL) {
268 		c->params.target = machclk_freq * target / 1000;
269 		c->params.interval = machclk_freq * interval / 1000;
270 		c->params.ecn = ecn;
271 		c->stats.maxpacket = 256;
272 	}
273 
274 	return (c);
275 }
276 
277 void
278 codel_destroy(struct codel *c)
279 {
280 
281 	free(c, M_DEVBUF);
282 }
283 
284 #define	MTAG_CODEL	1438031249
285 int
286 codel_addq(struct codel *c, class_queue_t *q, struct mbuf *m)
287 {
288 	struct m_tag *mtag;
289 	uint64_t *enqueue_time;
290 
291 	if (qlen(q) < qlimit(q)) {
292 		mtag = m_tag_locate(m, MTAG_CODEL, 0, NULL);
293 		if (mtag == NULL)
294 			mtag = m_tag_alloc(MTAG_CODEL, 0, sizeof(uint64_t),
295 			    M_NOWAIT);
296 		if (mtag == NULL) {
297 			m_freem(m);
298 			return (-1);
299 		}
300 		enqueue_time = (uint64_t *)(mtag + 1);
301 		*enqueue_time = read_machclk();
302 		m_tag_prepend(m, mtag);
303 		_addq(q, m);
304 		return (0);
305 	}
306 	c->drop_overlimit++;
307 	m_freem(m);
308 
309 	return (-1);
310 }
311 
312 static int
313 codel_should_drop(struct codel *c, class_queue_t *q, struct mbuf *m,
314     u_int64_t now)
315 {
316 	struct m_tag *mtag;
317 	uint64_t *enqueue_time;
318 
319 	if (m == NULL) {
320 		c->vars.first_above_time = 0;
321 		return (0);
322 	}
323 
324 	mtag = m_tag_locate(m, MTAG_CODEL, 0, NULL);
325 	if (mtag == NULL) {
326 		/* Only one warning per second. */
327 		if (ppsratecheck(&c->last_log, &c->last_pps, 1))
328 			printf("%s: could not found the packet mtag!\n",
329 			    __func__);
330 		c->vars.first_above_time = 0;
331 		return (0);
332 	}
333 	enqueue_time = (uint64_t *)(mtag + 1);
334 	c->vars.ldelay = now - *enqueue_time;
335 	c->stats.maxpacket = MAX(c->stats.maxpacket, m_pktlen(m));
336 
337 	if (codel_time_before(c->vars.ldelay, c->params.target) ||
338 	    qsize(q) <= c->stats.maxpacket) {
339 		/* went below - stay below for at least interval */
340 		c->vars.first_above_time = 0;
341 		return (0);
342 	}
343 	if (c->vars.first_above_time == 0) {
344 		/* just went above from below. If we stay above
345 		 * for at least interval we'll say it's ok to drop
346 		 */
347 		c->vars.first_above_time = now + c->params.interval;
348 		return (0);
349 	}
350 	if (codel_time_after(now, c->vars.first_above_time))
351 		return (1);
352 
353 	return (0);
354 }
355 
356 /*
357  * Run a Newton method step:
358  * new_invsqrt = (invsqrt / 2) * (3 - count * invsqrt^2)
359  *
360  * Here, invsqrt is a fixed point number (< 1.0), 32bit mantissa, aka Q0.32
361  */
362 static void
363 codel_Newton_step(struct codel_vars *vars)
364 {
365 	uint32_t invsqrt, invsqrt2;
366 	uint64_t val;
367 
368 /* sizeof_in_bits(rec_inv_sqrt) */
369 #define	REC_INV_SQRT_BITS (8 * sizeof(u_int16_t))
370 /* needed shift to get a Q0.32 number from rec_inv_sqrt */
371 #define	REC_INV_SQRT_SHIFT (32 - REC_INV_SQRT_BITS)
372 
373 	invsqrt = ((u_int32_t)vars->rec_inv_sqrt) << REC_INV_SQRT_SHIFT;
374 	invsqrt2 = ((u_int64_t)invsqrt * invsqrt) >> 32;
375 	val = (3LL << 32) - ((u_int64_t)vars->count * invsqrt2);
376 	val >>= 2; /* avoid overflow in following multiply */
377 	val = (val * invsqrt) >> (32 - 2 + 1);
378 
379 	vars->rec_inv_sqrt = val >> REC_INV_SQRT_SHIFT;
380 }
381 
382 static u_int64_t
383 codel_control_law(u_int64_t t, u_int64_t interval, u_int32_t rec_inv_sqrt)
384 {
385 
386 	return (t + (u_int32_t)(((u_int64_t)interval *
387 	    (rec_inv_sqrt << REC_INV_SQRT_SHIFT)) >> 32));
388 }
389 
390 struct mbuf *
391 codel_getq(struct codel *c, class_queue_t *q)
392 {
393 	struct mbuf	*m;
394 	u_int64_t	 now;
395 	int		 drop;
396 
397 	if ((m = _getq(q)) == NULL) {
398 		c->vars.dropping = 0;
399 		return (m);
400 	}
401 
402 	now = read_machclk();
403 	drop = codel_should_drop(c, q, m, now);
404 	if (c->vars.dropping) {
405 		if (!drop) {
406 			/* sojourn time below target - leave dropping state */
407 			c->vars.dropping = 0;
408 		} else if (codel_time_after_eq(now, c->vars.drop_next)) {
409 			/* It's time for the next drop. Drop the current
410 			 * packet and dequeue the next. The dequeue might
411 			 * take us out of dropping state.
412 			 * If not, schedule the next drop.
413 			 * A large backlog might result in drop rates so high
414 			 * that the next drop should happen now,
415 			 * hence the while loop.
416 			 */
417 			while (c->vars.dropping &&
418 			    codel_time_after_eq(now, c->vars.drop_next)) {
419 				c->vars.count++; /* don't care of possible wrap
420 						  * since there is no more
421 						  * divide */
422 				codel_Newton_step(&c->vars);
423 				/* TODO ECN */
424 				PKTCNTR_ADD(&c->stats.drop_cnt, m_pktlen(m));
425 				m_freem(m);
426 				m = _getq(q);
427 				if (!codel_should_drop(c, q, m, now))
428 					/* leave dropping state */
429 					c->vars.dropping = 0;
430 				else
431 					/* and schedule the next drop */
432 					c->vars.drop_next =
433 					    codel_control_law(c->vars.drop_next,
434 						c->params.interval,
435 						c->vars.rec_inv_sqrt);
436 			}
437 		}
438 	} else if (drop) {
439 		/* TODO ECN */
440 		PKTCNTR_ADD(&c->stats.drop_cnt, m_pktlen(m));
441 		m_freem(m);
442 
443 		m = _getq(q);
444 		drop = codel_should_drop(c, q, m, now);
445 
446 		c->vars.dropping = 1;
447 		/* if min went above target close to when we last went below it
448 		 * assume that the drop rate that controlled the queue on the
449 		 * last cycle is a good starting point to control it now.
450 		 */
451 		if (codel_time_before(now - c->vars.drop_next,
452 		    16 * c->params.interval)) {
453 			c->vars.count = (c->vars.count - c->vars.lastcount) | 1;
454 			/* we dont care if rec_inv_sqrt approximation
455 			 * is not very precise :
456 			 * Next Newton steps will correct it quadratically.
457 			 */
458 			codel_Newton_step(&c->vars);
459 		} else {
460 			c->vars.count = 1;
461 			c->vars.rec_inv_sqrt = ~0U >> REC_INV_SQRT_SHIFT;
462 		}
463 		c->vars.lastcount = c->vars.count;
464 		c->vars.drop_next = codel_control_law(now, c->params.interval,
465 		    c->vars.rec_inv_sqrt);
466 	}
467 
468 	return (m);
469 }
470 
471 void
472 codel_getstats(struct codel *c, struct codel_stats *s)
473 {
474 	*s = c->stats;
475 }
476 
477 #endif /* ALTQ_CODEL */
478