xref: /freebsd/sys/net/if_epair.c (revision 00698711dee1d990d3db9c41bf58394e589eecfe)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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 __FBSDID("$FreeBSD$");
42 
43 #include <sys/param.h>
44 #include <sys/hash.h>
45 #include <sys/jail.h>
46 #include <sys/kernel.h>
47 #include <sys/libkern.h>
48 #include <sys/malloc.h>
49 #include <sys/mbuf.h>
50 #include <sys/module.h>
51 #include <sys/proc.h>
52 #include <sys/queue.h>
53 #include <sys/smp.h>
54 #include <sys/socket.h>
55 #include <sys/sockio.h>
56 #include <sys/sysctl.h>
57 #include <sys/types.h>
58 #include <sys/buf_ring.h>
59 #include <sys/bus.h>
60 #include <sys/interrupt.h>
61 
62 #include <net/bpf.h>
63 #include <net/ethernet.h>
64 #include <net/if.h>
65 #include <net/if_var.h>
66 #include <net/if_clone.h>
67 #include <net/if_media.h>
68 #include <net/if_var.h>
69 #include <net/if_types.h>
70 #include <net/netisr.h>
71 #include <net/vnet.h>
72 
73 static int epair_clone_match(struct if_clone *, const char *);
74 static int epair_clone_create(struct if_clone *, char *, size_t, caddr_t);
75 static int epair_clone_destroy(struct if_clone *, struct ifnet *);
76 
77 static const char epairname[] = "epair";
78 #define	RXRSIZE	4096	/* Probably overkill by 4-8x. */
79 
80 static MALLOC_DEFINE(M_EPAIR, epairname,
81     "Pair of virtual cross-over connected Ethernet-like interfaces");
82 
83 VNET_DEFINE_STATIC(struct if_clone *, epair_cloner);
84 #define	V_epair_cloner	VNET(epair_cloner)
85 
86 static unsigned int next_index = 0;
87 #define	EPAIR_LOCK_INIT()		mtx_init(&epair_n_index_mtx, "epairidx", \
88 					    NULL, MTX_DEF)
89 #define	EPAIR_LOCK_DESTROY()		mtx_destroy(&epair_n_index_mtx)
90 #define	EPAIR_LOCK()			mtx_lock(&epair_n_index_mtx)
91 #define	EPAIR_UNLOCK()			mtx_unlock(&epair_n_index_mtx)
92 
93 static void				*swi_cookie[MAXCPU];	/* swi(9). */
94 static STAILQ_HEAD(, epair_softc)	swi_sc[MAXCPU];
95 
96 static struct mtx epair_n_index_mtx;
97 struct epair_softc {
98 	struct ifnet	*ifp;		/* This ifp. */
99 	struct ifnet	*oifp;		/* other ifp of pair. */
100 	void		*swi_cookie;	/* swi(9). */
101 	struct buf_ring	*rxring[2];
102 	volatile int	ridx;		/* 0 || 1 */
103 	struct ifmedia	media;		/* Media config (fake). */
104 	uint32_t	cpuidx;
105 	STAILQ_ENTRY(epair_softc) entry;
106 };
107 
108 static void
109 epair_clear_mbuf(struct mbuf *m)
110 {
111 	/* Remove any CSUM_SND_TAG as ether_input will barf. */
112 	if (m->m_pkthdr.csum_flags & CSUM_SND_TAG) {
113 		m_snd_tag_rele(m->m_pkthdr.snd_tag);
114 		m->m_pkthdr.snd_tag = NULL;
115 		m->m_pkthdr.csum_flags &= ~CSUM_SND_TAG;
116 	}
117 
118 	m_tag_delete_nonpersistent(m);
119 }
120 
121 static void
122 epair_if_input(struct epair_softc *sc, int ridx)
123 {
124 	struct epoch_tracker et;
125 	struct ifnet *ifp;
126 	struct mbuf *m;
127 
128 	ifp = sc->ifp;
129 	NET_EPOCH_ENTER(et);
130 	do {
131 		m = buf_ring_dequeue_sc(sc->rxring[ridx]);
132 		if (m == NULL)
133 			break;
134 
135 		MPASS((m->m_pkthdr.csum_flags & CSUM_SND_TAG) == 0);
136 		(*ifp->if_input)(ifp, m);
137 
138 	} while (1);
139 	NET_EPOCH_EXIT(et);
140 }
141 
142 static void
143 epair_sintr(struct epair_softc *sc)
144 {
145 	int ridx, nidx;
146 
147 	if_ref(sc->ifp);
148 	do {
149 		ridx = sc->ridx;
150 		nidx = (ridx == 0) ? 1 : 0;
151 	} while (!atomic_cmpset_int(&sc->ridx, ridx, nidx));
152 	epair_if_input(sc, ridx);
153 
154 	if_rele(sc->ifp);
155 }
156 
157 static void
158 epair_intr(void *arg)
159 {
160 	struct epair_softc *sc;
161 	uint32_t cpuidx;
162 
163 	cpuidx = (uintptr_t)arg;
164 	/* If this is a problem, this is a read-mostly situation. */
165 	EPAIR_LOCK();
166 	STAILQ_FOREACH(sc, &swi_sc[cpuidx], entry) {
167 		/* Do this lockless. */
168 		if (buf_ring_empty(sc->rxring[sc->ridx]))
169 			continue;
170 		epair_sintr(sc);
171 	}
172 	EPAIR_UNLOCK();
173 
174 	return;
175 }
176 
177 static int
178 epair_menq(struct mbuf *m, struct epair_softc *osc)
179 {
180 	struct ifnet *ifp, *oifp;
181 	int len, ret;
182 	int ridx;
183 	short mflags;
184 	bool was_empty;
185 
186 	/*
187 	 * I know this looks weird. We pass the "other sc" as we need that one
188 	 * and can get both ifps from it as well.
189 	 */
190 	oifp = osc->ifp;
191 	ifp = osc->oifp;
192 
193 	M_ASSERTPKTHDR(m);
194 	epair_clear_mbuf(m);
195 	if_setrcvif(m, oifp);
196 	M_SETFIB(m, oifp->if_fib);
197 
198 	/* Save values as once the mbuf is queued, it's not ours anymore. */
199 	len = m->m_pkthdr.len;
200 	mflags = m->m_flags;
201 
202 	MPASS(m->m_nextpkt == NULL);
203 	MPASS((m->m_pkthdr.csum_flags & CSUM_SND_TAG) == 0);
204 
205 	ridx = atomic_load_int(&osc->ridx);
206 	was_empty = buf_ring_empty(osc->rxring[ridx]);
207 	ret = buf_ring_enqueue(osc->rxring[ridx], m);
208 	if (ret != 0) {
209 		/* Ring is full. */
210 		m_freem(m);
211 		return (0);
212 	}
213 
214 	if_inc_counter(ifp, IFCOUNTER_OPACKETS, 1);
215 	/*
216 	 * IFQ_HANDOFF_ADJ/ip_handoff() update statistics,
217 	 * but as we bypass all this we have to duplicate
218 	 * the logic another time.
219 	 */
220 	if_inc_counter(ifp, IFCOUNTER_OBYTES, len);
221 	if (mflags & (M_BCAST|M_MCAST))
222 		if_inc_counter(ifp, IFCOUNTER_OMCASTS, 1);
223 	/* Someone else received the packet. */
224 	if_inc_counter(oifp, IFCOUNTER_IPACKETS, 1);
225 
226 	/* Kick the interrupt handler for the first packet. */
227 	if (was_empty && osc->swi_cookie != NULL)
228 		swi_sched(osc->swi_cookie, 0);
229 
230 	return (0);
231 }
232 
233 static void
234 epair_start(struct ifnet *ifp)
235 {
236 	struct mbuf *m;
237 	struct epair_softc *sc;
238 	struct ifnet *oifp;
239 
240 	/*
241 	 * We get packets here from ether_output via if_handoff()
242 	 * and need to put them into the input queue of the oifp
243 	 * and will put the packet into the receive-queue (rxq) of the
244 	 * other interface (oifp) of our pair.
245 	 */
246 	sc = ifp->if_softc;
247 	oifp = sc->oifp;
248 	sc = oifp->if_softc;
249 	for (;;) {
250 		IFQ_DEQUEUE(&ifp->if_snd, m);
251 		if (m == NULL)
252 			break;
253 		M_ASSERTPKTHDR(m);
254 		BPF_MTAP(ifp, m);
255 
256 		/* In case either interface is not usable drop the packet. */
257 		if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
258 		    (ifp->if_flags & IFF_UP) == 0 ||
259 		    (oifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
260 		    (oifp->if_flags & IFF_UP) == 0) {
261 			m_freem(m);
262 			continue;
263 		}
264 
265 		(void) epair_menq(m, sc);
266 	}
267 }
268 
269 static int
270 epair_transmit(struct ifnet *ifp, struct mbuf *m)
271 {
272 	struct epair_softc *sc;
273 	struct ifnet *oifp;
274 	int error;
275 #ifdef ALTQ
276 	int len;
277 	short mflags;
278 #endif
279 
280 	if (m == NULL)
281 		return (0);
282 	M_ASSERTPKTHDR(m);
283 
284 	/*
285 	 * We are not going to use the interface en/dequeue mechanism
286 	 * on the TX side. We are called from ether_output_frame()
287 	 * and will put the packet into the receive-queue (rxq) of the
288 	 * other interface (oifp) of our pair.
289 	 */
290 	if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0) {
291 		m_freem(m);
292 		if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
293 		return (ENXIO);
294 	}
295 	if ((ifp->if_flags & IFF_UP) == 0) {
296 		m_freem(m);
297 		if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
298 		return (ENETDOWN);
299 	}
300 
301 	BPF_MTAP(ifp, m);
302 
303 	/*
304 	 * In case the outgoing interface is not usable,
305 	 * drop the packet.
306 	 */
307 	sc = ifp->if_softc;
308 	oifp = sc->oifp;
309 	if ((oifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
310 	    (oifp->if_flags & IFF_UP) == 0) {
311 		if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
312 		m_freem(m);
313 		return (0);
314 	}
315 
316 #ifdef ALTQ
317 	len = m->m_pkthdr.len;
318 	mflags = m->m_flags;
319 
320 	/* Support ALTQ via the classic if_start() path. */
321 	IF_LOCK(&ifp->if_snd);
322 	if (ALTQ_IS_ENABLED(&ifp->if_snd)) {
323 		ALTQ_ENQUEUE(&ifp->if_snd, m, NULL, error);
324 		if (error)
325 			if_inc_counter(ifp, IFCOUNTER_OQDROPS, 1);
326 		IF_UNLOCK(&ifp->if_snd);
327 		if (!error) {
328 			if_inc_counter(ifp, IFCOUNTER_OBYTES, len);
329 			if (mflags & (M_BCAST|M_MCAST))
330 				if_inc_counter(ifp, IFCOUNTER_OMCASTS, 1);
331 			epair_start(ifp);
332 		}
333 		return (error);
334 	}
335 	IF_UNLOCK(&ifp->if_snd);
336 #endif
337 
338 	error = epair_menq(m, oifp->if_softc);
339 	return (error);
340 }
341 
342 static int
343 epair_media_change(struct ifnet *ifp __unused)
344 {
345 
346 	/* Do nothing. */
347 	return (0);
348 }
349 
350 static void
351 epair_media_status(struct ifnet *ifp __unused, struct ifmediareq *imr)
352 {
353 
354 	imr->ifm_status = IFM_AVALID | IFM_ACTIVE;
355 	imr->ifm_active = IFM_ETHER | IFM_10G_T | IFM_FDX;
356 }
357 
358 static int
359 epair_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
360 {
361 	struct epair_softc *sc;
362 	struct ifreq *ifr;
363 	int error;
364 
365 	ifr = (struct ifreq *)data;
366 	switch (cmd) {
367 	case SIOCSIFFLAGS:
368 	case SIOCADDMULTI:
369 	case SIOCDELMULTI:
370 		error = 0;
371 		break;
372 
373 	case SIOCSIFMEDIA:
374 	case SIOCGIFMEDIA:
375 		sc = ifp->if_softc;
376 		error = ifmedia_ioctl(ifp, ifr, &sc->media, cmd);
377 		break;
378 
379 	case SIOCSIFMTU:
380 		/* We basically allow all kinds of MTUs. */
381 		ifp->if_mtu = ifr->ifr_mtu;
382 		error = 0;
383 		break;
384 
385 	default:
386 		/* Let the common ethernet handler process this. */
387 		error = ether_ioctl(ifp, cmd, data);
388 		break;
389 	}
390 
391 	return (error);
392 }
393 
394 static void
395 epair_init(void *dummy __unused)
396 {
397 }
398 
399 /*
400  * Interface cloning functions.
401  * We use our private ones so that we can create/destroy our secondary
402  * device along with the primary one.
403  */
404 static int
405 epair_clone_match(struct if_clone *ifc, const char *name)
406 {
407 	const char *cp;
408 
409 	/*
410 	 * Our base name is epair.
411 	 * Our interfaces will be named epair<n>[ab].
412 	 * So accept anything of the following list:
413 	 * - epair
414 	 * - epair<n>
415 	 * but not the epair<n>[ab] versions.
416 	 */
417 	if (strncmp(epairname, name, sizeof(epairname)-1) != 0)
418 		return (0);
419 
420 	for (cp = name + sizeof(epairname) - 1; *cp != '\0'; cp++) {
421 		if (*cp < '0' || *cp > '9')
422 			return (0);
423 	}
424 
425 	return (1);
426 }
427 
428 static void
429 epair_clone_add(struct if_clone *ifc, struct epair_softc *scb)
430 {
431 	struct ifnet *ifp;
432 	uint8_t eaddr[ETHER_ADDR_LEN];	/* 00:00:00:00:00:00 */
433 
434 	ifp = scb->ifp;
435 	/* Copy epairNa etheraddr and change the last byte. */
436 	memcpy(eaddr, scb->oifp->if_hw_addr, ETHER_ADDR_LEN);
437 	eaddr[5] = 0x0b;
438 	ether_ifattach(ifp, eaddr);
439 
440 	if_clone_addif(ifc, ifp);
441 }
442 
443 static int
444 epair_clone_create(struct if_clone *ifc, char *name, size_t len, caddr_t params)
445 {
446 	struct epair_softc *sca, *scb;
447 	struct ifnet *ifp;
448 	char *dp;
449 	int error, unit, wildcard;
450 	uint64_t hostid;
451 	uint32_t key[3];
452 	uint32_t hash;
453 	uint8_t eaddr[ETHER_ADDR_LEN];	/* 00:00:00:00:00:00 */
454 
455 	/* Try to see if a special unit was requested. */
456 	error = ifc_name2unit(name, &unit);
457 	if (error != 0)
458 		return (error);
459 	wildcard = (unit < 0);
460 
461 	error = ifc_alloc_unit(ifc, &unit);
462 	if (error != 0)
463 		return (error);
464 
465 	/*
466 	 * If no unit had been given, we need to adjust the ifName.
467 	 * Also make sure there is space for our extra [ab] suffix.
468 	 */
469 	for (dp = name; *dp != '\0'; dp++);
470 	if (wildcard) {
471 		error = snprintf(dp, len - (dp - name), "%d", unit);
472 		if (error > len - (dp - name) - 1) {
473 			/* ifName too long. */
474 			ifc_free_unit(ifc, unit);
475 			return (ENOSPC);
476 		}
477 		dp += error;
478 	}
479 	if (len - (dp - name) - 1 < 1) {
480 		/* No space left for our [ab] suffix. */
481 		ifc_free_unit(ifc, unit);
482 		return (ENOSPC);
483 	}
484 	*dp = 'b';
485 	/* Must not change dp so we can replace 'a' by 'b' later. */
486 	*(dp+1) = '\0';
487 
488 	/* Check if 'a' and 'b' interfaces already exist. */
489 	if (ifunit(name) != NULL)
490 		return (EEXIST);
491 	*dp = 'a';
492 	if (ifunit(name) != NULL)
493 		return (EEXIST);
494 
495 	/* Allocate memory for both [ab] interfaces */
496 	sca = malloc(sizeof(struct epair_softc), M_EPAIR, M_WAITOK | M_ZERO);
497 	sca->ifp = if_alloc(IFT_ETHER);
498 	if (sca->ifp == NULL) {
499 		free(sca, M_EPAIR);
500 		ifc_free_unit(ifc, unit);
501 		return (ENOSPC);
502 	}
503 	sca->rxring[0] = buf_ring_alloc(RXRSIZE, M_EPAIR, M_WAITOK,NULL);
504 	sca->rxring[1] = buf_ring_alloc(RXRSIZE, M_EPAIR, M_WAITOK, NULL);
505 
506 	scb = malloc(sizeof(struct epair_softc), M_EPAIR, M_WAITOK | M_ZERO);
507 	scb->ifp = if_alloc(IFT_ETHER);
508 	if (scb->ifp == NULL) {
509 		free(scb, M_EPAIR);
510 		if_free(sca->ifp);
511 		free(sca, M_EPAIR);
512 		ifc_free_unit(ifc, unit);
513 		return (ENOSPC);
514 	}
515 	scb->rxring[0] = buf_ring_alloc(RXRSIZE, M_EPAIR, M_WAITOK, NULL);
516 	scb->rxring[1] = buf_ring_alloc(RXRSIZE, M_EPAIR, M_WAITOK, NULL);
517 
518 	/*
519 	 * Cross-reference the interfaces so we will be able to free both.
520 	 */
521 	sca->oifp = scb->ifp;
522 	scb->oifp = sca->ifp;
523 
524 	EPAIR_LOCK();
525 #ifdef SMP
526 	/* Get an approximate distribution. */
527 	hash = next_index % mp_ncpus;
528 #else
529 	hash = 0;
530 #endif
531 	if (swi_cookie[hash] == NULL) {
532 		void *cookie;
533 
534 		EPAIR_UNLOCK();
535 		error = swi_add(NULL, epairname,
536 		    epair_intr, (void *)(uintptr_t)hash,
537 		    SWI_NET, INTR_MPSAFE, &cookie);
538 		if (error) {
539 			buf_ring_free(scb->rxring[0], M_EPAIR);
540 			buf_ring_free(scb->rxring[1], M_EPAIR);
541 			if_free(scb->ifp);
542 			free(scb, M_EPAIR);
543 			buf_ring_free(sca->rxring[0], M_EPAIR);
544 			buf_ring_free(sca->rxring[1], M_EPAIR);
545 			if_free(sca->ifp);
546 			free(sca, M_EPAIR);
547 			ifc_free_unit(ifc, unit);
548 			return (ENOSPC);
549 		}
550 		EPAIR_LOCK();
551 		/* Recheck under lock even though a race is very unlikely. */
552 		if (swi_cookie[hash] == NULL) {
553 			swi_cookie[hash] = cookie;
554 		} else {
555 			EPAIR_UNLOCK();
556 			(void) swi_remove(cookie);
557 			EPAIR_LOCK();
558 		}
559 	}
560 	sca->cpuidx = hash;
561 	STAILQ_INSERT_TAIL(&swi_sc[hash], sca, entry);
562 	sca->swi_cookie = swi_cookie[hash];
563 	scb->cpuidx = hash;
564 	STAILQ_INSERT_TAIL(&swi_sc[hash], scb, entry);
565 	scb->swi_cookie = swi_cookie[hash];
566 	EPAIR_UNLOCK();
567 
568 	/* Initialise pseudo media types. */
569 	ifmedia_init(&sca->media, 0, epair_media_change, epair_media_status);
570 	ifmedia_add(&sca->media, IFM_ETHER | IFM_10G_T, 0, NULL);
571 	ifmedia_set(&sca->media, IFM_ETHER | IFM_10G_T);
572 	ifmedia_init(&scb->media, 0, epair_media_change, epair_media_status);
573 	ifmedia_add(&scb->media, IFM_ETHER | IFM_10G_T, 0, NULL);
574 	ifmedia_set(&scb->media, IFM_ETHER | IFM_10G_T);
575 
576 	/* Finish initialization of interface <n>a. */
577 	ifp = sca->ifp;
578 	ifp->if_softc = sca;
579 	strlcpy(ifp->if_xname, name, IFNAMSIZ);
580 	ifp->if_dname = epairname;
581 	ifp->if_dunit = unit;
582 	ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
583 	ifp->if_flags |= IFF_KNOWSEPOCH;
584 	ifp->if_capabilities = IFCAP_VLAN_MTU;
585 	ifp->if_capenable = IFCAP_VLAN_MTU;
586 	ifp->if_start = epair_start;
587 	ifp->if_ioctl = epair_ioctl;
588 	ifp->if_init  = epair_init;
589 	if_setsendqlen(ifp, ifqmaxlen);
590 	if_setsendqready(ifp);
591 
592 	/*
593 	 * Calculate the etheraddr hashing the hostid and the
594 	 * interface index. The result would be hopefully unique.
595 	 * Note that the "a" component of an epair instance may get moved
596 	 * to a different VNET after creation. In that case its index
597 	 * will be freed and the index can get reused by new epair instance.
598 	 * Make sure we do not create same etheraddr again.
599 	 */
600 	getcredhostid(curthread->td_ucred, (unsigned long *)&hostid);
601 	if (hostid == 0)
602 		arc4rand(&hostid, sizeof(hostid), 0);
603 
604 	EPAIR_LOCK();
605 	if (ifp->if_index > next_index)
606 		next_index = ifp->if_index;
607 	else
608 		next_index++;
609 
610 	key[0] = (uint32_t)next_index;
611 	EPAIR_UNLOCK();
612 	key[1] = (uint32_t)(hostid & 0xffffffff);
613 	key[2] = (uint32_t)((hostid >> 32) & 0xfffffffff);
614 	hash = jenkins_hash32(key, 3, 0);
615 
616 	eaddr[0] = 0x02;
617 	memcpy(&eaddr[1], &hash, 4);
618 	eaddr[5] = 0x0a;
619 	ether_ifattach(ifp, eaddr);
620 	ifp->if_baudrate = IF_Gbps(10);	/* arbitrary maximum */
621 	ifp->if_transmit = epair_transmit;
622 
623 	/* Swap the name and finish initialization of interface <n>b. */
624 	*dp = 'b';
625 
626 	ifp = scb->ifp;
627 	ifp->if_softc = scb;
628 	strlcpy(ifp->if_xname, name, IFNAMSIZ);
629 	ifp->if_dname = epairname;
630 	ifp->if_dunit = unit;
631 	ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
632 	ifp->if_flags |= IFF_KNOWSEPOCH;
633 	ifp->if_capabilities = IFCAP_VLAN_MTU;
634 	ifp->if_capenable = IFCAP_VLAN_MTU;
635 	ifp->if_start = epair_start;
636 	ifp->if_ioctl = epair_ioctl;
637 	ifp->if_init  = epair_init;
638 	if_setsendqlen(ifp, ifqmaxlen);
639 	if_setsendqready(ifp);
640 	/* We need to play some tricks here for the second interface. */
641 	strlcpy(name, epairname, len);
642 
643 	/* Correctly set the name for the cloner list. */
644 	strlcpy(name, scb->ifp->if_xname, len);
645 	epair_clone_add(ifc, scb);
646 
647 	ifp->if_baudrate = IF_Gbps(10);	/* arbitrary maximum */
648 	ifp->if_transmit = epair_transmit;
649 
650 	/*
651 	 * Restore name to <n>a as the ifp for this will go into the
652 	 * cloner list for the initial call.
653 	 */
654 	strlcpy(name, sca->ifp->if_xname, len);
655 
656 	/* Tell the world, that we are ready to rock. */
657 	sca->ifp->if_drv_flags |= IFF_DRV_RUNNING;
658 	if_link_state_change(sca->ifp, LINK_STATE_UP);
659 	scb->ifp->if_drv_flags |= IFF_DRV_RUNNING;
660 	if_link_state_change(scb->ifp, LINK_STATE_UP);
661 
662 	return (0);
663 }
664 
665 static void
666 epair_drain_rings(struct epair_softc *sc)
667 {
668 	int ridx;
669 	struct mbuf *m;
670 
671 	for (ridx = 0; ridx < 2; ridx++) {
672 		do {
673 			m = buf_ring_dequeue_sc(sc->rxring[ridx]);
674 			if (m == NULL)
675 				break;
676 			m_freem(m);
677 		} while (1);
678 	}
679 }
680 
681 static int
682 epair_clone_destroy(struct if_clone *ifc, struct ifnet *ifp)
683 {
684 	struct ifnet *oifp;
685 	struct epair_softc *sca, *scb;
686 	int unit, error;
687 
688 	/*
689 	 * In case we called into if_clone_destroyif() ourselves
690 	 * again to remove the second interface, the softc will be
691 	 * NULL. In that case so not do anything but return success.
692 	 */
693 	if (ifp->if_softc == NULL)
694 		return (0);
695 
696 	unit = ifp->if_dunit;
697 	sca = ifp->if_softc;
698 	oifp = sca->oifp;
699 	scb = oifp->if_softc;
700 
701 	/* Frist get the interfaces down and detached. */
702 	if_link_state_change(ifp, LINK_STATE_DOWN);
703 	ifp->if_drv_flags &= ~IFF_DRV_RUNNING;
704 	if_link_state_change(oifp, LINK_STATE_DOWN);
705 	oifp->if_drv_flags &= ~IFF_DRV_RUNNING;
706 
707 	ether_ifdetach(ifp);
708 	ether_ifdetach(oifp);
709 
710 	/* Second stop interrupt handler. */
711 	EPAIR_LOCK();
712 	STAILQ_REMOVE(&swi_sc[sca->cpuidx], sca, epair_softc, entry);
713 	STAILQ_REMOVE(&swi_sc[scb->cpuidx], scb, epair_softc, entry);
714 	EPAIR_UNLOCK();
715 	sca->swi_cookie = NULL;
716 	scb->swi_cookie = NULL;
717 
718 	/* Third free any queued packets and all the resources. */
719 	CURVNET_SET_QUIET(oifp->if_vnet);
720 	epair_drain_rings(scb);
721 	oifp->if_softc = NULL;
722 	error = if_clone_destroyif(ifc, oifp);
723 	if (error)
724 		panic("%s: if_clone_destroyif() for our 2nd iface failed: %d",
725 		    __func__, error);
726 	if_free(oifp);
727 	ifmedia_removeall(&scb->media);
728 	buf_ring_free(scb->rxring[0], M_EPAIR);
729 	buf_ring_free(scb->rxring[1], M_EPAIR);
730 	free(scb, M_EPAIR);
731 	CURVNET_RESTORE();
732 
733 	epair_drain_rings(sca);
734 	if_free(ifp);
735 	ifmedia_removeall(&sca->media);
736 	buf_ring_free(sca->rxring[0], M_EPAIR);
737 	buf_ring_free(sca->rxring[1], M_EPAIR);
738 	free(sca, M_EPAIR);
739 
740 	/* Last free the cloner unit. */
741 	ifc_free_unit(ifc, unit);
742 
743 	return (0);
744 }
745 
746 static void
747 vnet_epair_init(const void *unused __unused)
748 {
749 
750 	V_epair_cloner = if_clone_advanced(epairname, 0,
751 	    epair_clone_match, epair_clone_create, epair_clone_destroy);
752 }
753 VNET_SYSINIT(vnet_epair_init, SI_SUB_PSEUDO, SI_ORDER_ANY,
754     vnet_epair_init, NULL);
755 
756 static void
757 vnet_epair_uninit(const void *unused __unused)
758 {
759 
760 	if_clone_detach(V_epair_cloner);
761 }
762 VNET_SYSUNINIT(vnet_epair_uninit, SI_SUB_INIT_IF, SI_ORDER_ANY,
763     vnet_epair_uninit, NULL);
764 
765 static int
766 epair_modevent(module_t mod, int type, void *data)
767 {
768 	int i;
769 
770 	switch (type) {
771 	case MOD_LOAD:
772 		for (i = 0; i < MAXCPU; i++) {
773 			swi_cookie[i] = NULL;
774 			STAILQ_INIT(&swi_sc[i]);
775 		}
776 		EPAIR_LOCK_INIT();
777 		if (bootverbose)
778 			printf("%s: %s initialized.\n", __func__, epairname);
779 		break;
780 	case MOD_UNLOAD:
781 		EPAIR_LOCK();
782 		for (i = 0; i < MAXCPU; i++) {
783 			if (!STAILQ_EMPTY(&swi_sc[i])) {
784 				printf("%s: swi_sc[%d] active\n", __func__, i);
785 				EPAIR_UNLOCK();
786 				return (EBUSY);
787 			}
788 		}
789 		EPAIR_UNLOCK();
790 		for (i = 0; i < MAXCPU; i++)
791 			if (swi_cookie[i] != NULL)
792 				(void) swi_remove(swi_cookie[i]);
793 		EPAIR_LOCK_DESTROY();
794 		if (bootverbose)
795 			printf("%s: %s unloaded.\n", __func__, epairname);
796 		break;
797 	default:
798 		return (EOPNOTSUPP);
799 	}
800 	return (0);
801 }
802 
803 static moduledata_t epair_mod = {
804 	"if_epair",
805 	epair_modevent,
806 	0
807 };
808 
809 DECLARE_MODULE(if_epair, epair_mod, SI_SUB_PSEUDO, SI_ORDER_MIDDLE);
810 MODULE_VERSION(if_epair, 3);
811