xref: /freebsd/sys/net/altq/altq_codel.c (revision 4d846d26) 
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 <net/if_private.h>
57 #include <netinet/in.h>
58 
59 #include <netpfil/pf/pf.h>
60 #include <netpfil/pf/pf_altq.h>
61 #include <net/altq/if_altq.h>
62 #include <net/altq/altq.h>
63 #include <net/altq/altq_codel.h>
64 
65 static int		 codel_should_drop(struct codel *, class_queue_t *,
66 			    struct mbuf *, u_int64_t);
67 static void		 codel_Newton_step(struct codel_vars *);
68 static u_int64_t	 codel_control_law(u_int64_t t, u_int64_t, u_int32_t);
69 
70 #define	codel_time_after(a, b)		((int64_t)(a) - (int64_t)(b) > 0)
71 #define	codel_time_after_eq(a, b)	((int64_t)(a) - (int64_t)(b) >= 0)
72 #define	codel_time_before(a, b)		((int64_t)(a) - (int64_t)(b) < 0)
73 #define	codel_time_before_eq(a, b)	((int64_t)(a) - (int64_t)(b) <= 0)
74 
75 static int codel_request(struct ifaltq *, int, void *);
76 
77 static int codel_enqueue(struct ifaltq *, struct mbuf *, struct altq_pktattr *);
78 static struct mbuf *codel_dequeue(struct ifaltq *, int);
79 
80 int
81 codel_pfattach(struct pf_altq *a)
82 {
83 	struct ifnet *ifp;
84 
85 	if ((ifp = ifunit(a->ifname)) == NULL || a->altq_disc == NULL)
86 		return (EINVAL);
87 
88 	return (altq_attach(&ifp->if_snd, ALTQT_CODEL, a->altq_disc,
89 	    codel_enqueue, codel_dequeue, codel_request));
90 }
91 
92 int
93 codel_add_altq(struct ifnet *ifp, struct pf_altq *a)
94 {
95 	struct codel_if	*cif;
96 	struct codel_opts	*opts;
97 
98 	if (ifp == 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, int version)
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 	m = codel_getq(&cif->codel, cif->cl_q);
251 	if (m != NULL) {
252 		IFQ_DEC_LEN(ifq);
253 		PKTCNTR_ADD(&cif->cl_stats.cl_xmitcnt, m_pktlen(m));
254 		return (m);
255 	}
256 
257 	return (NULL);
258 }
259 
260 struct codel *
261 codel_alloc(int target, int interval, int ecn)
262 {
263 	struct codel *c;
264 
265 	c = malloc(sizeof(*c), M_DEVBUF, M_NOWAIT | M_ZERO);
266 	if (c != NULL) {
267 		c->params.target = machclk_freq * target / 1000;
268 		c->params.interval = machclk_freq * interval / 1000;
269 		c->params.ecn = ecn;
270 		c->stats.maxpacket = 256;
271 	}
272 
273 	return (c);
274 }
275 
276 void
277 codel_destroy(struct codel *c)
278 {
279 
280 	free(c, M_DEVBUF);
281 }
282 
283 #define	MTAG_CODEL	1438031249
284 int
285 codel_addq(struct codel *c, class_queue_t *q, struct mbuf *m)
286 {
287 	struct m_tag *mtag;
288 	uint64_t *enqueue_time;
289 
290 	if (qlen(q) < qlimit(q)) {
291 		mtag = m_tag_locate(m, MTAG_CODEL, 0, NULL);
292 		if (mtag == NULL)
293 			mtag = m_tag_alloc(MTAG_CODEL, 0, sizeof(uint64_t),
294 			    M_NOWAIT);
295 		if (mtag == NULL) {
296 			m_freem(m);
297 			return (-1);
298 		}
299 		enqueue_time = (uint64_t *)(mtag + 1);
300 		*enqueue_time = read_machclk();
301 		m_tag_prepend(m, mtag);
302 		_addq(q, m);
303 		return (0);
304 	}
305 	c->drop_overlimit++;
306 	m_freem(m);
307 
308 	return (-1);
309 }
310 
311 static int
312 codel_should_drop(struct codel *c, class_queue_t *q, struct mbuf *m,
313     u_int64_t now)
314 {
315 	struct m_tag *mtag;
316 	uint64_t *enqueue_time;
317 
318 	if (m == NULL) {
319 		c->vars.first_above_time = 0;
320 		return (0);
321 	}
322 
323 	mtag = m_tag_locate(m, MTAG_CODEL, 0, NULL);
324 	if (mtag == NULL) {
325 		/* Only one warning per second. */
326 		if (ppsratecheck(&c->last_log, &c->last_pps, 1))
327 			printf("%s: could not found the packet mtag!\n",
328 			    __func__);
329 		c->vars.first_above_time = 0;
330 		return (0);
331 	}
332 	enqueue_time = (uint64_t *)(mtag + 1);
333 	c->vars.ldelay = now - *enqueue_time;
334 	c->stats.maxpacket = MAX(c->stats.maxpacket, m_pktlen(m));
335 
336 	if (codel_time_before(c->vars.ldelay, c->params.target) ||
337 	    qsize(q) <= c->stats.maxpacket) {
338 		/* went below - stay below for at least interval */
339 		c->vars.first_above_time = 0;
340 		return (0);
341 	}
342 	if (c->vars.first_above_time == 0) {
343 		/* just went above from below. If we stay above
344 		 * for at least interval we'll say it's ok to drop
345 		 */
346 		c->vars.first_above_time = now + c->params.interval;
347 		return (0);
348 	}
349 	if (codel_time_after(now, c->vars.first_above_time))
350 		return (1);
351 
352 	return (0);
353 }
354 
355 /*
356  * Run a Newton method step:
357  * new_invsqrt = (invsqrt / 2) * (3 - count * invsqrt^2)
358  *
359  * Here, invsqrt is a fixed point number (< 1.0), 32bit mantissa, aka Q0.32
360  */
361 static void
362 codel_Newton_step(struct codel_vars *vars)
363 {
364 	uint32_t invsqrt, invsqrt2;
365 	uint64_t val;
366 
367 /* sizeof_in_bits(rec_inv_sqrt) */
368 #define	REC_INV_SQRT_BITS (8 * sizeof(u_int16_t))
369 /* needed shift to get a Q0.32 number from rec_inv_sqrt */
370 #define	REC_INV_SQRT_SHIFT (32 - REC_INV_SQRT_BITS)
371 
372 	invsqrt = ((u_int32_t)vars->rec_inv_sqrt) << REC_INV_SQRT_SHIFT;
373 	invsqrt2 = ((u_int64_t)invsqrt * invsqrt) >> 32;
374 	val = (3LL << 32) - ((u_int64_t)vars->count * invsqrt2);
375 	val >>= 2; /* avoid overflow in following multiply */
376 	val = (val * invsqrt) >> (32 - 2 + 1);
377 
378 	vars->rec_inv_sqrt = val >> REC_INV_SQRT_SHIFT;
379 }
380 
381 static u_int64_t
382 codel_control_law(u_int64_t t, u_int64_t interval, u_int32_t rec_inv_sqrt)
383 {
384 
385 	return (t + (u_int32_t)(((u_int64_t)interval *
386 	    (rec_inv_sqrt << REC_INV_SQRT_SHIFT)) >> 32));
387 }
388 
389 struct mbuf *
390 codel_getq(struct codel *c, class_queue_t *q)
391 {
392 	struct mbuf	*m;
393 	u_int64_t	 now;
394 	int		 drop;
395 
396 	if ((m = _getq(q)) == NULL) {
397 		c->vars.dropping = 0;
398 		return (m);
399 	}
400 
401 	now = read_machclk();
402 	drop = codel_should_drop(c, q, m, now);
403 	if (c->vars.dropping) {
404 		if (!drop) {
405 			/* sojourn time below target - leave dropping state */
406 			c->vars.dropping = 0;
407 		} else if (codel_time_after_eq(now, c->vars.drop_next)) {
408 			/* It's time for the next drop. Drop the current
409 			 * packet and dequeue the next. The dequeue might
410 			 * take us out of dropping state.
411 			 * If not, schedule the next drop.
412 			 * A large backlog might result in drop rates so high
413 			 * that the next drop should happen now,
414 			 * hence the while loop.
415 			 */
416 			while (c->vars.dropping &&
417 			    codel_time_after_eq(now, c->vars.drop_next)) {
418 				c->vars.count++; /* don't care of possible wrap
419 						  * since there is no more
420 						  * divide */
421 				codel_Newton_step(&c->vars);
422 				/* TODO ECN */
423 				PKTCNTR_ADD(&c->stats.drop_cnt, m_pktlen(m));
424 				m_freem(m);
425 				m = _getq(q);
426 				if (!codel_should_drop(c, q, m, now))
427 					/* leave dropping state */
428 					c->vars.dropping = 0;
429 				else
430 					/* and schedule the next drop */
431 					c->vars.drop_next =
432 					    codel_control_law(c->vars.drop_next,
433 						c->params.interval,
434 						c->vars.rec_inv_sqrt);
435 			}
436 		}
437 	} else if (drop) {
438 		/* TODO ECN */
439 		PKTCNTR_ADD(&c->stats.drop_cnt, m_pktlen(m));
440 		m_freem(m);
441 
442 		m = _getq(q);
443 		drop = codel_should_drop(c, q, m, now);
444 
445 		c->vars.dropping = 1;
446 		/* if min went above target close to when we last went below it
447 		 * assume that the drop rate that controlled the queue on the
448 		 * last cycle is a good starting point to control it now.
449 		 */
450 		if (codel_time_before(now - c->vars.drop_next,
451 		    16 * c->params.interval)) {
452 			c->vars.count = (c->vars.count - c->vars.lastcount) | 1;
453 			/* we dont care if rec_inv_sqrt approximation
454 			 * is not very precise :
455 			 * Next Newton steps will correct it quadratically.
456 			 */
457 			codel_Newton_step(&c->vars);
458 		} else {
459 			c->vars.count = 1;
460 			c->vars.rec_inv_sqrt = ~0U >> REC_INV_SQRT_SHIFT;
461 		}
462 		c->vars.lastcount = c->vars.count;
463 		c->vars.drop_next = codel_control_law(now, c->params.interval,
464 		    c->vars.rec_inv_sqrt);
465 	}
466 
467 	return (m);
468 }
469 
470 void
471 codel_getstats(struct codel *c, struct codel_stats *s)
472 {
473 	*s = c->stats;
474 }
475 
476 #endif /* ALTQ_CODEL */
477