xref: /freebsd/sys/net/if_epair.c (revision 0fca6ea1d4eea4c934cfff25ac9ee8ad6fe95583)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
3  *
4  * Copyright (c) 2008 The FreeBSD Foundation
5  * Copyright (c) 2009-2021 Bjoern A. Zeeb <bz@FreeBSD.org>
6  *
7  * This software was developed by CK Software GmbH under sponsorship
8  * from the FreeBSD Foundation.
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  * 2. Redistributions in binary form must reproduce the above copyright
16  * notice, this list of conditions and the following disclaimer in the
17  * documentation and/or other materials provided with the distribution.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  */
31 
32 /*
33  * A pair of virtual back-to-back connected ethernet like interfaces
34  * (``two interfaces with a virtual cross-over cable'').
35  *
36  * This is mostly intended to be used to provide connectivity between
37  * different virtual network stack instances.
38  */
39 
40 #include <sys/cdefs.h>
41 #include "opt_rss.h"
42 #include "opt_inet.h"
43 #include "opt_inet6.h"
44 
45 #include <sys/param.h>
46 #include <sys/bus.h>
47 #include <sys/hash.h>
48 #include <sys/interrupt.h>
49 #include <sys/jail.h>
50 #include <sys/kernel.h>
51 #include <sys/libkern.h>
52 #include <sys/malloc.h>
53 #include <sys/mbuf.h>
54 #include <sys/module.h>
55 #include <sys/proc.h>
56 #include <sys/queue.h>
57 #include <sys/sched.h>
58 #include <sys/smp.h>
59 #include <sys/socket.h>
60 #include <sys/sockio.h>
61 #include <sys/taskqueue.h>
62 
63 #include <net/bpf.h>
64 #include <net/ethernet.h>
65 #include <net/if.h>
66 #include <net/if_var.h>
67 #include <net/if_clone.h>
68 #include <net/if_media.h>
69 #include <net/if_var.h>
70 #include <net/if_private.h>
71 #include <net/if_types.h>
72 #include <net/netisr.h>
73 #ifdef RSS
74 #include <net/rss_config.h>
75 #ifdef INET
76 #include <netinet/in_rss.h>
77 #endif
78 #ifdef INET6
79 #include <netinet6/in6_rss.h>
80 #endif
81 #endif
82 #include <net/vnet.h>
83 
84 static const char epairname[] = "epair";
85 #define	RXRSIZE	4096	/* Probably overkill by 4-8x. */
86 
87 static MALLOC_DEFINE(M_EPAIR, epairname,
88     "Pair of virtual cross-over connected Ethernet-like interfaces");
89 
90 VNET_DEFINE_STATIC(struct if_clone *, epair_cloner);
91 #define	V_epair_cloner	VNET(epair_cloner)
92 
93 static unsigned int next_index = 0;
94 #define	EPAIR_LOCK_INIT()		mtx_init(&epair_n_index_mtx, "epairidx", \
95 					    NULL, MTX_DEF)
96 #define	EPAIR_LOCK_DESTROY()		mtx_destroy(&epair_n_index_mtx)
97 #define	EPAIR_LOCK()			mtx_lock(&epair_n_index_mtx)
98 #define	EPAIR_UNLOCK()			mtx_unlock(&epair_n_index_mtx)
99 
100 struct epair_softc;
101 struct epair_queue {
102 	struct mtx		 mtx;
103 	struct mbufq		 q;
104 	int			 id;
105 	enum {
106 		EPAIR_QUEUE_IDLE,
107 		EPAIR_QUEUE_WAKING,
108 		EPAIR_QUEUE_RUNNING,
109 	}			 state;
110 	struct task		 tx_task;
111 	struct epair_softc	*sc;
112 };
113 
114 static struct mtx epair_n_index_mtx;
115 struct epair_softc {
116 	struct ifnet		*ifp;		/* This ifp. */
117 	struct ifnet		*oifp;		/* other ifp of pair. */
118 	int			 num_queues;
119 	struct epair_queue	*queues;
120 	struct ifmedia		 media;		/* Media config (fake). */
121 	STAILQ_ENTRY(epair_softc) entry;
122 };
123 
124 struct epair_tasks_t {
125 	int			 tasks;
126 	struct taskqueue	 *tq[MAXCPU];
127 };
128 
129 static struct epair_tasks_t epair_tasks;
130 
131 static void
132 epair_clear_mbuf(struct mbuf *m)
133 {
134 	M_ASSERTPKTHDR(m);
135 
136 	/* Remove any CSUM_SND_TAG as ether_input will barf. */
137 	if (m->m_pkthdr.csum_flags & CSUM_SND_TAG) {
138 		m_snd_tag_rele(m->m_pkthdr.snd_tag);
139 		m->m_pkthdr.snd_tag = NULL;
140 		m->m_pkthdr.csum_flags &= ~CSUM_SND_TAG;
141 	}
142 
143 	/* Clear vlan information. */
144 	m->m_flags &= ~M_VLANTAG;
145 	m->m_pkthdr.ether_vtag = 0;
146 
147 	m_tag_delete_nonpersistent(m);
148 }
149 
150 static void
151 epair_tx_start_deferred(void *arg, int pending)
152 {
153 	struct epair_queue *q = (struct epair_queue *)arg;
154 	if_t ifp;
155 	struct mbuf *m, *n;
156 	bool resched;
157 
158 	ifp = q->sc->ifp;
159 
160 	if_ref(ifp);
161 	CURVNET_SET(ifp->if_vnet);
162 
163 	mtx_lock(&q->mtx);
164 	m = mbufq_flush(&q->q);
165 	q->state = EPAIR_QUEUE_RUNNING;
166 	mtx_unlock(&q->mtx);
167 
168 	while (m != NULL) {
169 		n = STAILQ_NEXT(m, m_stailqpkt);
170 		m->m_nextpkt = NULL;
171 		if_input(ifp, m);
172 		m = n;
173 	}
174 
175 	/*
176 	 * Avoid flushing the queue more than once per task.  We can otherwise
177 	 * end up starving ourselves in a multi-epair routing configuration.
178 	 */
179 	mtx_lock(&q->mtx);
180 	if (!mbufq_empty(&q->q)) {
181 		resched = true;
182 		q->state = EPAIR_QUEUE_WAKING;
183 	} else {
184 		resched = false;
185 		q->state = EPAIR_QUEUE_IDLE;
186 	}
187 	mtx_unlock(&q->mtx);
188 
189 	if (resched)
190 		taskqueue_enqueue(epair_tasks.tq[q->id], &q->tx_task);
191 
192 	CURVNET_RESTORE();
193 	if_rele(ifp);
194 }
195 
196 static struct epair_queue *
197 epair_select_queue(struct epair_softc *sc, struct mbuf *m)
198 {
199 	uint32_t bucket;
200 #ifdef RSS
201 	struct ether_header *eh;
202 	int ret;
203 
204 	ret = rss_m2bucket(m, &bucket);
205 	if (ret) {
206 		/* Actually hash the packet. */
207 		eh = mtod(m, struct ether_header *);
208 
209 		switch (ntohs(eh->ether_type)) {
210 #ifdef INET
211 		case ETHERTYPE_IP:
212 			rss_soft_m2cpuid_v4(m, 0, &bucket);
213 			break;
214 #endif
215 #ifdef INET6
216 		case ETHERTYPE_IPV6:
217 			rss_soft_m2cpuid_v6(m, 0, &bucket);
218 			break;
219 #endif
220 		default:
221 			bucket = 0;
222 			break;
223 		}
224 	}
225 	bucket %= sc->num_queues;
226 #else
227 	bucket = 0;
228 #endif
229 	return (&sc->queues[bucket]);
230 }
231 
232 static void
233 epair_prepare_mbuf(struct mbuf *m, struct ifnet *src_ifp)
234 {
235 	M_ASSERTPKTHDR(m);
236 	epair_clear_mbuf(m);
237 	if_setrcvif(m, src_ifp);
238 	M_SETFIB(m, src_ifp->if_fib);
239 
240 	MPASS(m->m_nextpkt == NULL);
241 	MPASS((m->m_pkthdr.csum_flags & CSUM_SND_TAG) == 0);
242 }
243 
244 static void
245 epair_menq(struct mbuf *m, struct epair_softc *osc)
246 {
247 	struct epair_queue *q;
248 	struct ifnet *ifp, *oifp;
249 	int error, len;
250 	bool mcast;
251 
252 	/*
253 	 * I know this looks weird. We pass the "other sc" as we need that one
254 	 * and can get both ifps from it as well.
255 	 */
256 	oifp = osc->ifp;
257 	ifp = osc->oifp;
258 
259 	epair_prepare_mbuf(m, oifp);
260 
261 	/* Save values as once the mbuf is queued, it's not ours anymore. */
262 	len = m->m_pkthdr.len;
263 	mcast = (m->m_flags & (M_BCAST | M_MCAST)) != 0;
264 
265 	q = epair_select_queue(osc, m);
266 
267 	mtx_lock(&q->mtx);
268 	if (q->state == EPAIR_QUEUE_IDLE) {
269 		q->state = EPAIR_QUEUE_WAKING;
270 		taskqueue_enqueue(epair_tasks.tq[q->id], &q->tx_task);
271 	}
272 	error = mbufq_enqueue(&q->q, m);
273 	mtx_unlock(&q->mtx);
274 
275 	if (error != 0) {
276 		m_freem(m);
277 		if_inc_counter(ifp, IFCOUNTER_OQDROPS, 1);
278 	} else {
279 		if_inc_counter(ifp, IFCOUNTER_OPACKETS, 1);
280 		if_inc_counter(ifp, IFCOUNTER_OBYTES, len);
281 		if (mcast)
282 			if_inc_counter(ifp, IFCOUNTER_OMCASTS, 1);
283 		if_inc_counter(oifp, IFCOUNTER_IPACKETS, 1);
284 	}
285 }
286 
287 static void
288 epair_start(struct ifnet *ifp)
289 {
290 	struct mbuf *m;
291 	struct epair_softc *sc;
292 	struct ifnet *oifp;
293 
294 	/*
295 	 * We get packets here from ether_output via if_handoff()
296 	 * and need to put them into the input queue of the oifp
297 	 * and will put the packet into the receive-queue (rxq) of the
298 	 * other interface (oifp) of our pair.
299 	 */
300 	sc = ifp->if_softc;
301 	oifp = sc->oifp;
302 	sc = oifp->if_softc;
303 	for (;;) {
304 		IFQ_DEQUEUE(&ifp->if_snd, m);
305 		if (m == NULL)
306 			break;
307 		M_ASSERTPKTHDR(m);
308 		BPF_MTAP(ifp, m);
309 
310 		/* In case either interface is not usable drop the packet. */
311 		if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
312 		    (ifp->if_flags & IFF_UP) == 0 ||
313 		    (oifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
314 		    (oifp->if_flags & IFF_UP) == 0) {
315 			m_freem(m);
316 			continue;
317 		}
318 
319 		epair_menq(m, sc);
320 	}
321 }
322 
323 static int
324 epair_transmit(struct ifnet *ifp, struct mbuf *m)
325 {
326 	struct epair_softc *sc;
327 	struct ifnet *oifp;
328 #ifdef ALTQ
329 	int len;
330 	bool mcast;
331 #endif
332 
333 	if (m == NULL)
334 		return (0);
335 	M_ASSERTPKTHDR(m);
336 
337 	/*
338 	 * We could just transmit this, but it makes testing easier if we're a
339 	 * little bit more like real hardware.
340 	 * Allow just that little bit extra for ethernet (and vlan) headers.
341 	 */
342 	if (m->m_pkthdr.len > (ifp->if_mtu + sizeof(struct ether_vlan_header))) {
343 		m_freem(m);
344 		if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
345 		return (E2BIG);
346 	}
347 
348 	/*
349 	 * We are not going to use the interface en/dequeue mechanism
350 	 * on the TX side. We are called from ether_output_frame()
351 	 * and will put the packet into the receive-queue (rxq) of the
352 	 * other interface (oifp) of our pair.
353 	 */
354 	if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0) {
355 		m_freem(m);
356 		if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
357 		return (ENXIO);
358 	}
359 	if ((ifp->if_flags & IFF_UP) == 0) {
360 		m_freem(m);
361 		if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
362 		return (ENETDOWN);
363 	}
364 
365 	BPF_MTAP(ifp, m);
366 
367 	/*
368 	 * In case the outgoing interface is not usable,
369 	 * drop the packet.
370 	 */
371 	sc = ifp->if_softc;
372 	oifp = sc->oifp;
373 	if ((oifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
374 	    (oifp->if_flags & IFF_UP) == 0) {
375 		if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
376 		m_freem(m);
377 		return (0);
378 	}
379 
380 #ifdef ALTQ
381 	len = m->m_pkthdr.len;
382 	mcast = (m->m_flags & (M_BCAST | M_MCAST)) != 0;
383 	int error = 0;
384 
385 	/* Support ALTQ via the classic if_start() path. */
386 	IF_LOCK(&ifp->if_snd);
387 	if (ALTQ_IS_ENABLED(&ifp->if_snd)) {
388 		ALTQ_ENQUEUE(&ifp->if_snd, m, NULL, error);
389 		if (error)
390 			if_inc_counter(ifp, IFCOUNTER_OQDROPS, 1);
391 		IF_UNLOCK(&ifp->if_snd);
392 		if (!error) {
393 			if_inc_counter(ifp, IFCOUNTER_OBYTES, len);
394 			if (mcast)
395 				if_inc_counter(ifp, IFCOUNTER_OMCASTS, 1);
396 			epair_start(ifp);
397 		}
398 		return (error);
399 	}
400 	IF_UNLOCK(&ifp->if_snd);
401 #endif
402 
403 	epair_menq(m, oifp->if_softc);
404 	return (0);
405 }
406 
407 static void
408 epair_qflush(struct ifnet *ifp __unused)
409 {
410 }
411 
412 static int
413 epair_media_change(struct ifnet *ifp __unused)
414 {
415 
416 	/* Do nothing. */
417 	return (0);
418 }
419 
420 static void
421 epair_media_status(struct ifnet *ifp __unused, struct ifmediareq *imr)
422 {
423 
424 	imr->ifm_status = IFM_AVALID | IFM_ACTIVE;
425 	imr->ifm_active = IFM_ETHER | IFM_10G_T | IFM_FDX;
426 }
427 
428 static int
429 epair_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
430 {
431 	struct epair_softc *sc;
432 	struct ifreq *ifr;
433 	int error;
434 
435 	ifr = (struct ifreq *)data;
436 	switch (cmd) {
437 	case SIOCSIFFLAGS:
438 	case SIOCADDMULTI:
439 	case SIOCDELMULTI:
440 		error = 0;
441 		break;
442 
443 	case SIOCSIFMEDIA:
444 	case SIOCGIFMEDIA:
445 		sc = ifp->if_softc;
446 		error = ifmedia_ioctl(ifp, ifr, &sc->media, cmd);
447 		break;
448 
449 	case SIOCSIFMTU:
450 		/* We basically allow all kinds of MTUs. */
451 		ifp->if_mtu = ifr->ifr_mtu;
452 		error = 0;
453 		break;
454 
455 	default:
456 		/* Let the common ethernet handler process this. */
457 		error = ether_ioctl(ifp, cmd, data);
458 		break;
459 	}
460 
461 	return (error);
462 }
463 
464 static void
465 epair_init(void *dummy __unused)
466 {
467 }
468 
469 /*
470  * Interface cloning functions.
471  * We use our private ones so that we can create/destroy our secondary
472  * device along with the primary one.
473  */
474 static int
475 epair_clone_match(struct if_clone *ifc, const char *name)
476 {
477 	const char *cp;
478 
479 	/*
480 	 * Our base name is epair.
481 	 * Our interfaces will be named epair<n>[ab].
482 	 * So accept anything of the following list:
483 	 * - epair
484 	 * - epair<n>
485 	 * but not the epair<n>[ab] versions.
486 	 */
487 	if (strncmp(epairname, name, sizeof(epairname)-1) != 0)
488 		return (0);
489 
490 	for (cp = name + sizeof(epairname) - 1; *cp != '\0'; cp++) {
491 		if (*cp < '0' || *cp > '9')
492 			return (0);
493 	}
494 
495 	return (1);
496 }
497 
498 static void
499 epair_clone_add(struct if_clone *ifc, struct epair_softc *scb)
500 {
501 	struct ifnet *ifp;
502 	uint8_t eaddr[ETHER_ADDR_LEN];	/* 00:00:00:00:00:00 */
503 
504 	ifp = scb->ifp;
505 	/* Copy epairNa etheraddr and change the last byte. */
506 	memcpy(eaddr, scb->oifp->if_hw_addr, ETHER_ADDR_LEN);
507 	eaddr[5] = 0x0b;
508 	ether_ifattach(ifp, eaddr);
509 
510 	if_clone_addif(ifc, ifp);
511 }
512 
513 static struct epair_softc *
514 epair_alloc_sc(struct if_clone *ifc)
515 {
516 	struct epair_softc *sc;
517 
518 	struct ifnet *ifp = if_alloc(IFT_ETHER);
519 	sc = malloc(sizeof(struct epair_softc), M_EPAIR, M_WAITOK | M_ZERO);
520 	sc->ifp = ifp;
521 	sc->num_queues = epair_tasks.tasks;
522 	sc->queues = mallocarray(sc->num_queues, sizeof(struct epair_queue),
523 	    M_EPAIR, M_WAITOK);
524 	for (int i = 0; i < sc->num_queues; i++) {
525 		struct epair_queue *q = &sc->queues[i];
526 		q->id = i;
527 		q->state = EPAIR_QUEUE_IDLE;
528 		mtx_init(&q->mtx, "epairq", NULL, MTX_DEF | MTX_NEW);
529 		mbufq_init(&q->q, RXRSIZE);
530 		q->sc = sc;
531 		NET_TASK_INIT(&q->tx_task, 0, epair_tx_start_deferred, q);
532 	}
533 
534 	/* Initialise pseudo media types. */
535 	ifmedia_init(&sc->media, 0, epair_media_change, epair_media_status);
536 	ifmedia_add(&sc->media, IFM_ETHER | IFM_10G_T, 0, NULL);
537 	ifmedia_set(&sc->media, IFM_ETHER | IFM_10G_T);
538 
539 	return (sc);
540 }
541 
542 static void
543 epair_setup_ifp(struct epair_softc *sc, char *name, int unit)
544 {
545 	struct ifnet *ifp = sc->ifp;
546 
547 	ifp->if_softc = sc;
548 	strlcpy(ifp->if_xname, name, IFNAMSIZ);
549 	ifp->if_dname = epairname;
550 	ifp->if_dunit = unit;
551 	ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
552 	ifp->if_capabilities = IFCAP_VLAN_MTU;
553 	ifp->if_capenable = IFCAP_VLAN_MTU;
554 	ifp->if_transmit = epair_transmit;
555 	ifp->if_qflush = epair_qflush;
556 	ifp->if_start = epair_start;
557 	ifp->if_ioctl = epair_ioctl;
558 	ifp->if_init  = epair_init;
559 	if_setsendqlen(ifp, ifqmaxlen);
560 	if_setsendqready(ifp);
561 
562 	ifp->if_baudrate = IF_Gbps(10);	/* arbitrary maximum */
563 }
564 
565 static void
566 epair_generate_mac(struct epair_softc *sc, uint8_t *eaddr)
567 {
568 	uint32_t key[3];
569 	uint32_t hash;
570 	uint64_t hostid;
571 
572 	EPAIR_LOCK();
573 #ifdef SMP
574 	/* Get an approximate distribution. */
575 	hash = next_index % mp_ncpus;
576 #else
577 	hash = 0;
578 #endif
579 	EPAIR_UNLOCK();
580 
581 	/*
582 	 * Calculate the etheraddr hashing the hostid and the
583 	 * interface index. The result would be hopefully unique.
584 	 * Note that the "a" component of an epair instance may get moved
585 	 * to a different VNET after creation. In that case its index
586 	 * will be freed and the index can get reused by new epair instance.
587 	 * Make sure we do not create same etheraddr again.
588 	 */
589 	getcredhostid(curthread->td_ucred, (unsigned long *)&hostid);
590 	if (hostid == 0)
591 		arc4rand(&hostid, sizeof(hostid), 0);
592 
593 	struct ifnet *ifp = sc->ifp;
594 	EPAIR_LOCK();
595 	if (ifp->if_index > next_index)
596 		next_index = ifp->if_index;
597 	else
598 		next_index++;
599 
600 	key[0] = (uint32_t)next_index;
601 	EPAIR_UNLOCK();
602 	key[1] = (uint32_t)(hostid & 0xffffffff);
603 	key[2] = (uint32_t)((hostid >> 32) & 0xfffffffff);
604 	hash = jenkins_hash32(key, 3, 0);
605 
606 	eaddr[0] = 0x02;
607 	memcpy(&eaddr[1], &hash, 4);
608 	eaddr[5] = 0x0a;
609 }
610 
611 static void
612 epair_free_sc(struct epair_softc *sc)
613 {
614 
615 	if_free(sc->ifp);
616 	ifmedia_removeall(&sc->media);
617 	for (int i = 0; i < sc->num_queues; i++) {
618 		struct epair_queue *q = &sc->queues[i];
619 		mtx_destroy(&q->mtx);
620 	}
621 	free(sc->queues, M_EPAIR);
622 	free(sc, M_EPAIR);
623 }
624 
625 static void
626 epair_set_state(struct ifnet *ifp, bool running)
627 {
628 	if (running) {
629 		ifp->if_drv_flags |= IFF_DRV_RUNNING;
630 		if_link_state_change(ifp, LINK_STATE_UP);
631 	} else {
632 		if_link_state_change(ifp, LINK_STATE_DOWN);
633 		ifp->if_drv_flags &= ~IFF_DRV_RUNNING;
634 	}
635 }
636 
637 static int
638 epair_handle_unit(struct if_clone *ifc, char *name, size_t len, int *punit)
639 {
640 	int error = 0, unit, wildcard;
641 	char *dp;
642 
643 	/* Try to see if a special unit was requested. */
644 	error = ifc_name2unit(name, &unit);
645 	if (error != 0)
646 		return (error);
647 	wildcard = (unit < 0);
648 
649 	error = ifc_alloc_unit(ifc, &unit);
650 	if (error != 0)
651 		return (error);
652 
653 	/*
654 	 * If no unit had been given, we need to adjust the ifName.
655 	 * Also make sure there is space for our extra [ab] suffix.
656 	 */
657 	for (dp = name; *dp != '\0'; dp++);
658 	if (wildcard) {
659 		int slen = snprintf(dp, len - (dp - name), "%d", unit);
660 		if (slen > len - (dp - name) - 1) {
661 			/* ifName too long. */
662 			error = ENOSPC;
663 			goto done;
664 		}
665 		dp += slen;
666 	}
667 	if (len - (dp - name) - 1 < 1) {
668 		/* No space left for our [ab] suffix. */
669 		error = ENOSPC;
670 		goto done;
671 	}
672 	*dp = 'b';
673 	/* Must not change dp so we can replace 'a' by 'b' later. */
674 	*(dp+1) = '\0';
675 
676 	/* Check if 'a' and 'b' interfaces already exist. */
677 	if (ifunit(name) != NULL) {
678 		error = EEXIST;
679 		goto done;
680 	}
681 
682 	*dp = 'a';
683 	if (ifunit(name) != NULL) {
684 		error = EEXIST;
685 		goto done;
686 	}
687 	*punit = unit;
688 done:
689 	if (error != 0)
690 		ifc_free_unit(ifc, unit);
691 
692 	return (error);
693 }
694 
695 static int
696 epair_clone_create(struct if_clone *ifc, char *name, size_t len,
697     struct ifc_data *ifd, struct ifnet **ifpp)
698 {
699 	struct epair_softc *sca, *scb;
700 	struct ifnet *ifp;
701 	char *dp;
702 	int error, unit;
703 	uint8_t eaddr[ETHER_ADDR_LEN];	/* 00:00:00:00:00:00 */
704 
705 	error = epair_handle_unit(ifc, name, len, &unit);
706 	if (error != 0)
707 		return (error);
708 
709 	/* Allocate memory for both [ab] interfaces */
710 	sca = epair_alloc_sc(ifc);
711 	scb = epair_alloc_sc(ifc);
712 
713 	/*
714 	 * Cross-reference the interfaces so we will be able to free both.
715 	 */
716 	sca->oifp = scb->ifp;
717 	scb->oifp = sca->ifp;
718 
719 	/* Finish initialization of interface <n>a. */
720 	ifp = sca->ifp;
721 	epair_setup_ifp(sca, name, unit);
722 	epair_generate_mac(sca, eaddr);
723 
724 	ether_ifattach(ifp, eaddr);
725 
726 	/* Swap the name and finish initialization of interface <n>b. */
727 	dp = name + strlen(name) - 1;
728 	*dp = 'b';
729 
730 	epair_setup_ifp(scb, name, unit);
731 
732 	ifp = scb->ifp;
733 	/* We need to play some tricks here for the second interface. */
734 	strlcpy(name, epairname, len);
735 	/* Correctly set the name for the cloner list. */
736 	strlcpy(name, scb->ifp->if_xname, len);
737 
738 	epair_clone_add(ifc, scb);
739 
740 	/*
741 	 * Restore name to <n>a as the ifp for this will go into the
742 	 * cloner list for the initial call.
743 	 */
744 	strlcpy(name, sca->ifp->if_xname, len);
745 
746 	/* Tell the world, that we are ready to rock. */
747 	epair_set_state(sca->ifp, true);
748 	epair_set_state(scb->ifp, true);
749 
750 	*ifpp = sca->ifp;
751 
752 	return (0);
753 }
754 
755 static void
756 epair_drain_rings(struct epair_softc *sc)
757 {
758 	for (int i = 0; i < sc->num_queues; i++) {
759 		struct epair_queue *q;
760 		struct mbuf *m, *n;
761 
762 		q = &sc->queues[i];
763 		mtx_lock(&q->mtx);
764 		m = mbufq_flush(&q->q);
765 		mtx_unlock(&q->mtx);
766 
767 		for (; m != NULL; m = n) {
768 			n = m->m_nextpkt;
769 			m_freem(m);
770 		}
771 	}
772 }
773 
774 static int
775 epair_clone_destroy(struct if_clone *ifc, struct ifnet *ifp, uint32_t flags)
776 {
777 	struct ifnet *oifp;
778 	struct epair_softc *sca, *scb;
779 	int unit, error;
780 
781 	/*
782 	 * In case we called into if_clone_destroyif() ourselves
783 	 * again to remove the second interface, the softc will be
784 	 * NULL. In that case so not do anything but return success.
785 	 */
786 	if (ifp->if_softc == NULL)
787 		return (0);
788 
789 	unit = ifp->if_dunit;
790 	sca = ifp->if_softc;
791 	oifp = sca->oifp;
792 	scb = oifp->if_softc;
793 
794 	/* Frist get the interfaces down and detached. */
795 	epair_set_state(ifp, false);
796 	epair_set_state(oifp, false);
797 
798 	ether_ifdetach(ifp);
799 	ether_ifdetach(oifp);
800 
801 	/* Third free any queued packets and all the resources. */
802 	CURVNET_SET_QUIET(oifp->if_vnet);
803 	epair_drain_rings(scb);
804 	oifp->if_softc = NULL;
805 	error = if_clone_destroyif(ifc, oifp);
806 	if (error)
807 		panic("%s: if_clone_destroyif() for our 2nd iface failed: %d",
808 		    __func__, error);
809 	epair_free_sc(scb);
810 	CURVNET_RESTORE();
811 
812 	epair_drain_rings(sca);
813 	epair_free_sc(sca);
814 
815 	/* Last free the cloner unit. */
816 	ifc_free_unit(ifc, unit);
817 
818 	return (0);
819 }
820 
821 static void
822 vnet_epair_init(const void *unused __unused)
823 {
824 	struct if_clone_addreq req = {
825 		.match_f = epair_clone_match,
826 		.create_f = epair_clone_create,
827 		.destroy_f = epair_clone_destroy,
828 	};
829 	V_epair_cloner = ifc_attach_cloner(epairname, &req);
830 }
831 VNET_SYSINIT(vnet_epair_init, SI_SUB_PSEUDO, SI_ORDER_ANY,
832     vnet_epair_init, NULL);
833 
834 static void
835 vnet_epair_uninit(const void *unused __unused)
836 {
837 
838 	ifc_detach_cloner(V_epair_cloner);
839 }
840 VNET_SYSUNINIT(vnet_epair_uninit, SI_SUB_INIT_IF, SI_ORDER_ANY,
841     vnet_epair_uninit, NULL);
842 
843 static int
844 epair_mod_init(void)
845 {
846 	char name[32];
847 	epair_tasks.tasks = 0;
848 
849 #ifdef RSS
850 	int cpu;
851 
852 	CPU_FOREACH(cpu) {
853 		cpuset_t cpu_mask;
854 
855 		/* Pin to this CPU so we get appropriate NUMA allocations. */
856 		thread_lock(curthread);
857 		sched_bind(curthread, cpu);
858 		thread_unlock(curthread);
859 
860 		snprintf(name, sizeof(name), "epair_task_%d", cpu);
861 
862 		epair_tasks.tq[cpu] = taskqueue_create(name, M_WAITOK,
863 		    taskqueue_thread_enqueue,
864 		    &epair_tasks.tq[cpu]);
865 		CPU_SETOF(cpu, &cpu_mask);
866 		taskqueue_start_threads_cpuset(&epair_tasks.tq[cpu], 1, PI_NET,
867 		    &cpu_mask, "%s", name);
868 
869 		epair_tasks.tasks++;
870 	}
871 	thread_lock(curthread);
872 	sched_unbind(curthread);
873 	thread_unlock(curthread);
874 #else
875 	snprintf(name, sizeof(name), "epair_task");
876 
877 	epair_tasks.tq[0] = taskqueue_create(name, M_WAITOK,
878 	    taskqueue_thread_enqueue,
879 	    &epair_tasks.tq[0]);
880 	taskqueue_start_threads(&epair_tasks.tq[0], 1, PI_NET, "%s", name);
881 
882 	epair_tasks.tasks = 1;
883 #endif
884 
885 	return (0);
886 }
887 
888 static void
889 epair_mod_cleanup(void)
890 {
891 
892 	for (int i = 0; i < epair_tasks.tasks; i++) {
893 		taskqueue_drain_all(epair_tasks.tq[i]);
894 		taskqueue_free(epair_tasks.tq[i]);
895 	}
896 }
897 
898 static int
899 epair_modevent(module_t mod, int type, void *data)
900 {
901 	int ret;
902 
903 	switch (type) {
904 	case MOD_LOAD:
905 		EPAIR_LOCK_INIT();
906 		ret = epair_mod_init();
907 		if (ret != 0)
908 			return (ret);
909 		if (bootverbose)
910 			printf("%s: %s initialized.\n", __func__, epairname);
911 		break;
912 	case MOD_UNLOAD:
913 		epair_mod_cleanup();
914 		EPAIR_LOCK_DESTROY();
915 		if (bootverbose)
916 			printf("%s: %s unloaded.\n", __func__, epairname);
917 		break;
918 	default:
919 		return (EOPNOTSUPP);
920 	}
921 	return (0);
922 }
923 
924 static moduledata_t epair_mod = {
925 	"if_epair",
926 	epair_modevent,
927 	0
928 };
929 
930 DECLARE_MODULE(if_epair, epair_mod, SI_SUB_PSEUDO, SI_ORDER_MIDDLE);
931 MODULE_VERSION(if_epair, 3);
932