xref: /freebsd/sys/net/if_epair.c (revision 2e3f49888ec8851bafb22011533217487764fdb0)
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 	if (ifp == NULL)
520 		return (NULL);
521 
522 	sc = malloc(sizeof(struct epair_softc), M_EPAIR, M_WAITOK | M_ZERO);
523 	sc->ifp = ifp;
524 	sc->num_queues = epair_tasks.tasks;
525 	sc->queues = mallocarray(sc->num_queues, sizeof(struct epair_queue),
526 	    M_EPAIR, M_WAITOK);
527 	for (int i = 0; i < sc->num_queues; i++) {
528 		struct epair_queue *q = &sc->queues[i];
529 		q->id = i;
530 		q->state = EPAIR_QUEUE_IDLE;
531 		mtx_init(&q->mtx, "epairq", NULL, MTX_DEF | MTX_NEW);
532 		mbufq_init(&q->q, RXRSIZE);
533 		q->sc = sc;
534 		NET_TASK_INIT(&q->tx_task, 0, epair_tx_start_deferred, q);
535 	}
536 
537 	/* Initialise pseudo media types. */
538 	ifmedia_init(&sc->media, 0, epair_media_change, epair_media_status);
539 	ifmedia_add(&sc->media, IFM_ETHER | IFM_10G_T, 0, NULL);
540 	ifmedia_set(&sc->media, IFM_ETHER | IFM_10G_T);
541 
542 	return (sc);
543 }
544 
545 static void
546 epair_setup_ifp(struct epair_softc *sc, char *name, int unit)
547 {
548 	struct ifnet *ifp = sc->ifp;
549 
550 	ifp->if_softc = sc;
551 	strlcpy(ifp->if_xname, name, IFNAMSIZ);
552 	ifp->if_dname = epairname;
553 	ifp->if_dunit = unit;
554 	ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
555 	ifp->if_capabilities = IFCAP_VLAN_MTU;
556 	ifp->if_capenable = IFCAP_VLAN_MTU;
557 	ifp->if_transmit = epair_transmit;
558 	ifp->if_qflush = epair_qflush;
559 	ifp->if_start = epair_start;
560 	ifp->if_ioctl = epair_ioctl;
561 	ifp->if_init  = epair_init;
562 	if_setsendqlen(ifp, ifqmaxlen);
563 	if_setsendqready(ifp);
564 
565 	ifp->if_baudrate = IF_Gbps(10);	/* arbitrary maximum */
566 }
567 
568 static void
569 epair_generate_mac(struct epair_softc *sc, uint8_t *eaddr)
570 {
571 	uint32_t key[3];
572 	uint32_t hash;
573 	uint64_t hostid;
574 
575 	EPAIR_LOCK();
576 #ifdef SMP
577 	/* Get an approximate distribution. */
578 	hash = next_index % mp_ncpus;
579 #else
580 	hash = 0;
581 #endif
582 	EPAIR_UNLOCK();
583 
584 	/*
585 	 * Calculate the etheraddr hashing the hostid and the
586 	 * interface index. The result would be hopefully unique.
587 	 * Note that the "a" component of an epair instance may get moved
588 	 * to a different VNET after creation. In that case its index
589 	 * will be freed and the index can get reused by new epair instance.
590 	 * Make sure we do not create same etheraddr again.
591 	 */
592 	getcredhostid(curthread->td_ucred, (unsigned long *)&hostid);
593 	if (hostid == 0)
594 		arc4rand(&hostid, sizeof(hostid), 0);
595 
596 	struct ifnet *ifp = sc->ifp;
597 	EPAIR_LOCK();
598 	if (ifp->if_index > next_index)
599 		next_index = ifp->if_index;
600 	else
601 		next_index++;
602 
603 	key[0] = (uint32_t)next_index;
604 	EPAIR_UNLOCK();
605 	key[1] = (uint32_t)(hostid & 0xffffffff);
606 	key[2] = (uint32_t)((hostid >> 32) & 0xfffffffff);
607 	hash = jenkins_hash32(key, 3, 0);
608 
609 	eaddr[0] = 0x02;
610 	memcpy(&eaddr[1], &hash, 4);
611 	eaddr[5] = 0x0a;
612 }
613 
614 static void
615 epair_free_sc(struct epair_softc *sc)
616 {
617 	if (sc == NULL)
618 		return;
619 
620 	if_free(sc->ifp);
621 	ifmedia_removeall(&sc->media);
622 	for (int i = 0; i < sc->num_queues; i++) {
623 		struct epair_queue *q = &sc->queues[i];
624 		mtx_destroy(&q->mtx);
625 	}
626 	free(sc->queues, M_EPAIR);
627 	free(sc, M_EPAIR);
628 }
629 
630 static void
631 epair_set_state(struct ifnet *ifp, bool running)
632 {
633 	if (running) {
634 		ifp->if_drv_flags |= IFF_DRV_RUNNING;
635 		if_link_state_change(ifp, LINK_STATE_UP);
636 	} else {
637 		if_link_state_change(ifp, LINK_STATE_DOWN);
638 		ifp->if_drv_flags &= ~IFF_DRV_RUNNING;
639 	}
640 }
641 
642 static int
643 epair_handle_unit(struct if_clone *ifc, char *name, size_t len, int *punit)
644 {
645 	int error = 0, unit, wildcard;
646 	char *dp;
647 
648 	/* Try to see if a special unit was requested. */
649 	error = ifc_name2unit(name, &unit);
650 	if (error != 0)
651 		return (error);
652 	wildcard = (unit < 0);
653 
654 	error = ifc_alloc_unit(ifc, &unit);
655 	if (error != 0)
656 		return (error);
657 
658 	/*
659 	 * If no unit had been given, we need to adjust the ifName.
660 	 * Also make sure there is space for our extra [ab] suffix.
661 	 */
662 	for (dp = name; *dp != '\0'; dp++);
663 	if (wildcard) {
664 		int slen = snprintf(dp, len - (dp - name), "%d", unit);
665 		if (slen > len - (dp - name) - 1) {
666 			/* ifName too long. */
667 			error = ENOSPC;
668 			goto done;
669 		}
670 		dp += slen;
671 	}
672 	if (len - (dp - name) - 1 < 1) {
673 		/* No space left for our [ab] suffix. */
674 		error = ENOSPC;
675 		goto done;
676 	}
677 	*dp = 'b';
678 	/* Must not change dp so we can replace 'a' by 'b' later. */
679 	*(dp+1) = '\0';
680 
681 	/* Check if 'a' and 'b' interfaces already exist. */
682 	if (ifunit(name) != NULL) {
683 		error = EEXIST;
684 		goto done;
685 	}
686 
687 	*dp = 'a';
688 	if (ifunit(name) != NULL) {
689 		error = EEXIST;
690 		goto done;
691 	}
692 	*punit = unit;
693 done:
694 	if (error != 0)
695 		ifc_free_unit(ifc, unit);
696 
697 	return (error);
698 }
699 
700 static int
701 epair_clone_create(struct if_clone *ifc, char *name, size_t len,
702     struct ifc_data *ifd, struct ifnet **ifpp)
703 {
704 	struct epair_softc *sca, *scb;
705 	struct ifnet *ifp;
706 	char *dp;
707 	int error, unit;
708 	uint8_t eaddr[ETHER_ADDR_LEN];	/* 00:00:00:00:00:00 */
709 
710 	error = epair_handle_unit(ifc, name, len, &unit);
711 	if (error != 0)
712 		return (error);
713 
714 	/* Allocate memory for both [ab] interfaces */
715 	sca = epair_alloc_sc(ifc);
716 	scb = epair_alloc_sc(ifc);
717 	if (sca == NULL || scb == NULL) {
718 		epair_free_sc(sca);
719 		epair_free_sc(scb);
720 		ifc_free_unit(ifc, unit);
721 		return (ENOSPC);
722 	}
723 
724 	/*
725 	 * Cross-reference the interfaces so we will be able to free both.
726 	 */
727 	sca->oifp = scb->ifp;
728 	scb->oifp = sca->ifp;
729 
730 	/* Finish initialization of interface <n>a. */
731 	ifp = sca->ifp;
732 	epair_setup_ifp(sca, name, unit);
733 	epair_generate_mac(sca, eaddr);
734 
735 	ether_ifattach(ifp, eaddr);
736 
737 	/* Swap the name and finish initialization of interface <n>b. */
738 	dp = name + strlen(name) - 1;
739 	*dp = 'b';
740 
741 	epair_setup_ifp(scb, name, unit);
742 
743 	ifp = scb->ifp;
744 	/* We need to play some tricks here for the second interface. */
745 	strlcpy(name, epairname, len);
746 	/* Correctly set the name for the cloner list. */
747 	strlcpy(name, scb->ifp->if_xname, len);
748 
749 	epair_clone_add(ifc, scb);
750 
751 	/*
752 	 * Restore name to <n>a as the ifp for this will go into the
753 	 * cloner list for the initial call.
754 	 */
755 	strlcpy(name, sca->ifp->if_xname, len);
756 
757 	/* Tell the world, that we are ready to rock. */
758 	epair_set_state(sca->ifp, true);
759 	epair_set_state(scb->ifp, true);
760 
761 	*ifpp = sca->ifp;
762 
763 	return (0);
764 }
765 
766 static void
767 epair_drain_rings(struct epair_softc *sc)
768 {
769 	for (int i = 0; i < sc->num_queues; i++) {
770 		struct epair_queue *q;
771 		struct mbuf *m, *n;
772 
773 		q = &sc->queues[i];
774 		mtx_lock(&q->mtx);
775 		m = mbufq_flush(&q->q);
776 		mtx_unlock(&q->mtx);
777 
778 		for (; m != NULL; m = n) {
779 			n = m->m_nextpkt;
780 			m_freem(m);
781 		}
782 	}
783 }
784 
785 static int
786 epair_clone_destroy(struct if_clone *ifc, struct ifnet *ifp, uint32_t flags)
787 {
788 	struct ifnet *oifp;
789 	struct epair_softc *sca, *scb;
790 	int unit, error;
791 
792 	/*
793 	 * In case we called into if_clone_destroyif() ourselves
794 	 * again to remove the second interface, the softc will be
795 	 * NULL. In that case so not do anything but return success.
796 	 */
797 	if (ifp->if_softc == NULL)
798 		return (0);
799 
800 	unit = ifp->if_dunit;
801 	sca = ifp->if_softc;
802 	oifp = sca->oifp;
803 	scb = oifp->if_softc;
804 
805 	/* Frist get the interfaces down and detached. */
806 	epair_set_state(ifp, false);
807 	epair_set_state(oifp, false);
808 
809 	ether_ifdetach(ifp);
810 	ether_ifdetach(oifp);
811 
812 	/* Third free any queued packets and all the resources. */
813 	CURVNET_SET_QUIET(oifp->if_vnet);
814 	epair_drain_rings(scb);
815 	oifp->if_softc = NULL;
816 	error = if_clone_destroyif(ifc, oifp);
817 	if (error)
818 		panic("%s: if_clone_destroyif() for our 2nd iface failed: %d",
819 		    __func__, error);
820 	epair_free_sc(scb);
821 	CURVNET_RESTORE();
822 
823 	epair_drain_rings(sca);
824 	epair_free_sc(sca);
825 
826 	/* Last free the cloner unit. */
827 	ifc_free_unit(ifc, unit);
828 
829 	return (0);
830 }
831 
832 static void
833 vnet_epair_init(const void *unused __unused)
834 {
835 	struct if_clone_addreq req = {
836 		.match_f = epair_clone_match,
837 		.create_f = epair_clone_create,
838 		.destroy_f = epair_clone_destroy,
839 	};
840 	V_epair_cloner = ifc_attach_cloner(epairname, &req);
841 }
842 VNET_SYSINIT(vnet_epair_init, SI_SUB_PSEUDO, SI_ORDER_ANY,
843     vnet_epair_init, NULL);
844 
845 static void
846 vnet_epair_uninit(const void *unused __unused)
847 {
848 
849 	ifc_detach_cloner(V_epair_cloner);
850 }
851 VNET_SYSUNINIT(vnet_epair_uninit, SI_SUB_INIT_IF, SI_ORDER_ANY,
852     vnet_epair_uninit, NULL);
853 
854 static int
855 epair_mod_init(void)
856 {
857 	char name[32];
858 	epair_tasks.tasks = 0;
859 
860 #ifdef RSS
861 	int cpu;
862 
863 	CPU_FOREACH(cpu) {
864 		cpuset_t cpu_mask;
865 
866 		/* Pin to this CPU so we get appropriate NUMA allocations. */
867 		thread_lock(curthread);
868 		sched_bind(curthread, cpu);
869 		thread_unlock(curthread);
870 
871 		snprintf(name, sizeof(name), "epair_task_%d", cpu);
872 
873 		epair_tasks.tq[cpu] = taskqueue_create(name, M_WAITOK,
874 		    taskqueue_thread_enqueue,
875 		    &epair_tasks.tq[cpu]);
876 		CPU_SETOF(cpu, &cpu_mask);
877 		taskqueue_start_threads_cpuset(&epair_tasks.tq[cpu], 1, PI_NET,
878 		    &cpu_mask, "%s", name);
879 
880 		epair_tasks.tasks++;
881 	}
882 	thread_lock(curthread);
883 	sched_unbind(curthread);
884 	thread_unlock(curthread);
885 #else
886 	snprintf(name, sizeof(name), "epair_task");
887 
888 	epair_tasks.tq[0] = taskqueue_create(name, M_WAITOK,
889 	    taskqueue_thread_enqueue,
890 	    &epair_tasks.tq[0]);
891 	taskqueue_start_threads(&epair_tasks.tq[0], 1, PI_NET, "%s", name);
892 
893 	epair_tasks.tasks = 1;
894 #endif
895 
896 	return (0);
897 }
898 
899 static void
900 epair_mod_cleanup(void)
901 {
902 
903 	for (int i = 0; i < epair_tasks.tasks; i++) {
904 		taskqueue_drain_all(epair_tasks.tq[i]);
905 		taskqueue_free(epair_tasks.tq[i]);
906 	}
907 }
908 
909 static int
910 epair_modevent(module_t mod, int type, void *data)
911 {
912 	int ret;
913 
914 	switch (type) {
915 	case MOD_LOAD:
916 		EPAIR_LOCK_INIT();
917 		ret = epair_mod_init();
918 		if (ret != 0)
919 			return (ret);
920 		if (bootverbose)
921 			printf("%s: %s initialized.\n", __func__, epairname);
922 		break;
923 	case MOD_UNLOAD:
924 		epair_mod_cleanup();
925 		EPAIR_LOCK_DESTROY();
926 		if (bootverbose)
927 			printf("%s: %s unloaded.\n", __func__, epairname);
928 		break;
929 	default:
930 		return (EOPNOTSUPP);
931 	}
932 	return (0);
933 }
934 
935 static moduledata_t epair_mod = {
936 	"if_epair",
937 	epair_modevent,
938 	0
939 };
940 
941 DECLARE_MODULE(if_epair, epair_mod, SI_SUB_PSEUDO, SI_ORDER_MIDDLE);
942 MODULE_VERSION(if_epair, 3);
943