xref: /dragonfly/sys/net/stf/if_stf.c (revision 6bd457ed) 
1 /*	$FreeBSD: src/sys/net/if_stf.c,v 1.1.2.11 2003/01/23 21:06:44 sam Exp $	*/
2 /*	$DragonFly: src/sys/net/stf/if_stf.c,v 1.14 2005/01/26 00:37:39 joerg Exp $	*/
3 /*	$KAME: if_stf.c,v 1.73 2001/12/03 11:08:30 keiichi Exp $	*/
4 
5 /*
6  * Copyright (C) 2000 WIDE Project.
7  * All rights reserved.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  * 3. Neither the name of the project nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  */
33 
34 /*
35  * 6to4 interface, based on RFC3056.
36  *
37  * 6to4 interface is NOT capable of link-layer (I mean, IPv4) multicasting.
38  * There is no address mapping defined from IPv6 multicast address to IPv4
39  * address.  Therefore, we do not have IFF_MULTICAST on the interface.
40  *
41  * Due to the lack of address mapping for link-local addresses, we cannot
42  * throw packets toward link-local addresses (fe80::x).  Also, we cannot throw
43  * packets to link-local multicast addresses (ff02::x).
44  *
45  * Here are interesting symptoms due to the lack of link-local address:
46  *
47  * Unicast routing exchange:
48  * - RIPng: Impossible.  Uses link-local multicast packet toward ff02::9,
49  *   and link-local addresses as nexthop.
50  * - OSPFv6: Impossible.  OSPFv6 assumes that there's link-local address
51  *   assigned to the link, and makes use of them.  Also, HELLO packets use
52  *   link-local multicast addresses (ff02::5 and ff02::6).
53  * - BGP4+: Maybe.  You can only use global address as nexthop, and global
54  *   address as TCP endpoint address.
55  *
56  * Multicast routing protocols:
57  * - PIM: Hello packet cannot be used to discover adjacent PIM routers.
58  *   Adjacent PIM routers must be configured manually (is it really spec-wise
59  *   correct thing to do?).
60  *
61  * ICMPv6:
62  * - Redirects cannot be used due to the lack of link-local address.
63  *
64  * stf interface does not have, and will not need, a link-local address.
65  * It seems to have no real benefit and does not help the above symptoms much.
66  * Even if we assign link-locals to interface, we cannot really
67  * use link-local unicast/multicast on top of 6to4 cloud (since there's no
68  * encapsulation defined for link-local address), and the above analysis does
69  * not change.  RFC3056 does not mandate the assignment of link-local address
70  * either.
71  *
72  * 6to4 interface has security issues.  Refer to
73  * http://playground.iijlab.net/i-d/draft-itojun-ipv6-transition-abuse-00.txt
74  * for details.  The code tries to filter out some of malicious packets.
75  * Note that there is no way to be 100% secure.
76  */
77 
78 #include "opt_inet.h"
79 #include "opt_inet6.h"
80 
81 #include <sys/param.h>
82 #include <sys/systm.h>
83 #include <sys/socket.h>
84 #include <sys/sockio.h>
85 #include <sys/mbuf.h>
86 #include <sys/errno.h>
87 #include <sys/protosw.h>
88 #include <sys/kernel.h>
89 #include <machine/cpu.h>
90 
91 #include <sys/malloc.h>
92 
93 #include <net/if.h>
94 #include <net/route.h>
95 #include <net/netisr.h>
96 #include <net/if_types.h>
97 #include "if_stf.h"
98 
99 #include <netinet/in.h>
100 #include <netinet/in_systm.h>
101 #include <netinet/ip.h>
102 #include <netinet/ip_var.h>
103 #include <netinet/in_var.h>
104 
105 #include <netinet/ip6.h>
106 #include <netinet6/ip6_var.h>
107 #include <netinet6/in6_var.h>
108 #include <netinet/ip_ecn.h>
109 
110 #include <netinet/ip_encap.h>
111 
112 #include <machine/stdarg.h>
113 
114 #include <net/net_osdep.h>
115 
116 #include <net/bpf.h>
117 
118 #define IN6_IS_ADDR_6TO4(x)	(ntohs((x)->s6_addr16[0]) == 0x2002)
119 #define GET_V4(x)	((struct in_addr *)(&(x)->s6_addr16[1]))
120 
121 struct stf_softc {
122 	struct ifnet	sc_if;	   /* common area */
123 	union {
124 		struct route  __sc_ro4;
125 		struct route_in6 __sc_ro6; /* just for safety */
126 	} __sc_ro46;
127 #define sc_ro	__sc_ro46.__sc_ro4
128 	const struct encaptab *encap_cookie;
129 };
130 
131 static struct stf_softc *stf;
132 
133 static MALLOC_DEFINE(M_STF, "stf", "6to4 Tunnel Interface");
134 static int ip_stf_ttl = 40;
135 
136 extern  struct domain inetdomain;
137 struct protosw in_stf_protosw =
138 { SOCK_RAW,	&inetdomain,	IPPROTO_IPV6,	PR_ATOMIC|PR_ADDR,
139   in_stf_input, rip_output,	0,		rip_ctloutput,
140   0,
141   0,            0,              0,              0,
142   &rip_usrreqs
143 };
144 
145 static int stfmodevent (module_t, int, void *);
146 static int stf_encapcheck (const struct mbuf *, int, int, void *);
147 static struct in6_ifaddr *stf_getsrcifa6 (struct ifnet *);
148 static int stf_output (struct ifnet *, struct mbuf *, struct sockaddr *,
149 	struct rtentry *);
150 static int stf_checkaddr4 (struct stf_softc *, struct in_addr *,
151 	struct ifnet *);
152 static int stf_checkaddr6 (struct stf_softc *, struct in6_addr *,
153 	struct ifnet *);
154 static void stf_rtrequest (int, struct rtentry *, struct rt_addrinfo *);
155 static int stf_ioctl (struct ifnet *, u_long, caddr_t, struct ucred *);
156 
157 static int
158 stfmodevent(mod, type, data)
159 	module_t mod;
160 	int type;
161 	void *data;
162 {
163 	struct stf_softc *sc;
164 	int err;
165 	const struct encaptab *p;
166 
167 	switch (type) {
168 	case MOD_LOAD:
169 		stf = malloc(sizeof(struct stf_softc), M_STF, M_WAITOK);
170 		bzero(stf, sizeof(struct stf_softc));
171 		sc = stf;
172 
173 		bzero(sc, sizeof(*sc));
174 		if_initname(&(sc->sc_if), "stf", 0);
175 
176 		p = encap_attach_func(AF_INET, IPPROTO_IPV6, stf_encapcheck,
177 		    (void *)&in_stf_protosw, sc);
178 		if (p == NULL) {
179 			printf("%s: attach failed\n", if_name(&sc->sc_if));
180 			return (ENOMEM);
181 		}
182 		sc->encap_cookie = p;
183 
184 		sc->sc_if.if_mtu    = IPV6_MMTU;
185 		sc->sc_if.if_flags  = 0;
186 		sc->sc_if.if_ioctl  = stf_ioctl;
187 		sc->sc_if.if_output = stf_output;
188 		sc->sc_if.if_type   = IFT_STF;
189 #if 0
190 		/* turn off ingress filter */
191 		sc->sc_if.if_flags  |= IFF_LINK2;
192 #endif
193 		sc->sc_if.if_snd.ifq_maxlen = IFQ_MAXLEN;
194 		if_attach(&sc->sc_if);
195 		bpfattach(&sc->sc_if, DLT_NULL, sizeof(u_int));
196 		break;
197 	case MOD_UNLOAD:
198 		sc = stf;
199 		bpfdetach(&sc->sc_if);
200 		if_detach(&sc->sc_if);
201 		err = encap_detach(sc->encap_cookie);
202 		KASSERT(err == 0, ("Unexpected error detaching encap_cookie"));
203 		free(sc, M_STF);
204 		break;
205 	}
206 
207 	return (0);
208 }
209 
210 static moduledata_t stf_mod = {
211 	"if_stf",
212 	stfmodevent,
213 	0
214 };
215 
216 DECLARE_MODULE(if_stf, stf_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
217 
218 static int
219 stf_encapcheck(m, off, proto, arg)
220 	const struct mbuf *m;
221 	int off;
222 	int proto;
223 	void *arg;
224 {
225 	struct ip ip;
226 	struct in6_ifaddr *ia6;
227 	struct stf_softc *sc;
228 	struct in_addr a, b;
229 
230 	sc = (struct stf_softc *)arg;
231 	if (sc == NULL)
232 		return 0;
233 
234 	if ((sc->sc_if.if_flags & IFF_UP) == 0)
235 		return 0;
236 
237 	/* IFF_LINK0 means "no decapsulation" */
238 	if ((sc->sc_if.if_flags & IFF_LINK0) != 0)
239 		return 0;
240 
241 	if (proto != IPPROTO_IPV6)
242 		return 0;
243 
244 	m_copydata(m, 0, sizeof(ip), (caddr_t)&ip);
245 
246 	if (ip.ip_v != 4)
247 		return 0;
248 
249 	ia6 = stf_getsrcifa6(&sc->sc_if);
250 	if (ia6 == NULL)
251 		return 0;
252 
253 	/*
254 	 * check if IPv4 dst matches the IPv4 address derived from the
255 	 * local 6to4 address.
256 	 * success on: dst = 10.1.1.1, ia6->ia_addr = 2002:0a01:0101:...
257 	 */
258 	if (bcmp(GET_V4(&ia6->ia_addr.sin6_addr), &ip.ip_dst,
259 	    sizeof(ip.ip_dst)) != 0)
260 		return 0;
261 
262 	/*
263 	 * check if IPv4 src matches the IPv4 address derived from the
264 	 * local 6to4 address masked by prefixmask.
265 	 * success on: src = 10.1.1.1, ia6->ia_addr = 2002:0a00:.../24
266 	 * fail on: src = 10.1.1.1, ia6->ia_addr = 2002:0b00:.../24
267 	 */
268 	bzero(&a, sizeof(a));
269 	a.s_addr = GET_V4(&ia6->ia_addr.sin6_addr)->s_addr;
270 	a.s_addr &= GET_V4(&ia6->ia_prefixmask.sin6_addr)->s_addr;
271 	b = ip.ip_src;
272 	b.s_addr &= GET_V4(&ia6->ia_prefixmask.sin6_addr)->s_addr;
273 	if (a.s_addr != b.s_addr)
274 		return 0;
275 
276 	/* stf interface makes single side match only */
277 	return 32;
278 }
279 
280 static struct in6_ifaddr *
281 stf_getsrcifa6(ifp)
282 	struct ifnet *ifp;
283 {
284 	struct ifaddr *ia;
285 	struct in_ifaddr *ia4;
286 	struct sockaddr_in6 *sin6;
287 	struct in_addr in;
288 
289 	TAILQ_FOREACH(ia, &ifp->if_addrlist, ifa_list) {
290 		if (ia->ifa_addr == NULL)
291 			continue;
292 		if (ia->ifa_addr->sa_family != AF_INET6)
293 			continue;
294 		sin6 = (struct sockaddr_in6 *)ia->ifa_addr;
295 		if (!IN6_IS_ADDR_6TO4(&sin6->sin6_addr))
296 			continue;
297 
298 		bcopy(GET_V4(&sin6->sin6_addr), &in, sizeof(in));
299 		LIST_FOREACH(ia4, INADDR_HASH(in.s_addr), ia_hash)
300 			if (ia4->ia_addr.sin_addr.s_addr == in.s_addr)
301 				break;
302 		if (ia4 == NULL)
303 			continue;
304 
305 		return (struct in6_ifaddr *)ia;
306 	}
307 
308 	return NULL;
309 }
310 
311 static int
312 stf_output(ifp, m, dst, rt)
313 	struct ifnet *ifp;
314 	struct mbuf *m;
315 	struct sockaddr *dst;
316 	struct rtentry *rt;
317 {
318 	struct stf_softc *sc;
319 	struct sockaddr_in6 *dst6;
320 	struct in_addr *in4;
321 	struct sockaddr_in *dst4;
322 	u_int8_t tos;
323 	struct ip *ip;
324 	struct ip6_hdr *ip6;
325 	struct in6_ifaddr *ia6;
326 	static const uint32_t af = AF_INET6;
327 
328 	sc = (struct stf_softc*)ifp;
329 	dst6 = (struct sockaddr_in6 *)dst;
330 
331 	/* just in case */
332 	if ((ifp->if_flags & IFF_UP) == 0) {
333 		m_freem(m);
334 		return ENETDOWN;
335 	}
336 
337 	/*
338 	 * If we don't have an ip4 address that match my inner ip6 address,
339 	 * we shouldn't generate output.  Without this check, we'll end up
340 	 * using wrong IPv4 source.
341 	 */
342 	ia6 = stf_getsrcifa6(ifp);
343 	if (ia6 == NULL) {
344 		m_freem(m);
345 		return ENETDOWN;
346 	}
347 
348 	if (m->m_len < sizeof(*ip6)) {
349 		m = m_pullup(m, sizeof(*ip6));
350 		if (!m)
351 			return ENOBUFS;
352 	}
353 	ip6 = mtod(m, struct ip6_hdr *);
354 	tos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
355 
356 	/*
357 	 * Pickup the right outer dst addr from the list of candidates.
358 	 * ip6_dst has priority as it may be able to give us shorter IPv4 hops.
359 	 */
360 	if (IN6_IS_ADDR_6TO4(&ip6->ip6_dst))
361 		in4 = GET_V4(&ip6->ip6_dst);
362 	else if (IN6_IS_ADDR_6TO4(&dst6->sin6_addr))
363 		in4 = GET_V4(&dst6->sin6_addr);
364 	else {
365 		m_freem(m);
366 		return ENETUNREACH;
367 	}
368 
369 	if (ifp->if_bpf)
370 		bpf_ptap(ifp->if_bpf, m, &af, sizeof(af));
371 
372 	M_PREPEND(m, sizeof(struct ip), MB_DONTWAIT);
373 	if (m && m->m_len < sizeof(struct ip))
374 		m = m_pullup(m, sizeof(struct ip));
375 	if (m == NULL)
376 		return ENOBUFS;
377 	ip = mtod(m, struct ip *);
378 
379 	bzero(ip, sizeof(*ip));
380 
381 	bcopy(GET_V4(&((struct sockaddr_in6 *)&ia6->ia_addr)->sin6_addr),
382 	    &ip->ip_src, sizeof(ip->ip_src));
383 	bcopy(in4, &ip->ip_dst, sizeof(ip->ip_dst));
384 	ip->ip_p = IPPROTO_IPV6;
385 	ip->ip_ttl = ip_stf_ttl;
386 	ip->ip_len = m->m_pkthdr.len;	/*host order*/
387 	if (ifp->if_flags & IFF_LINK1)
388 		ip_ecn_ingress(ECN_ALLOWED, &ip->ip_tos, &tos);
389 	else
390 		ip_ecn_ingress(ECN_NOCARE, &ip->ip_tos, &tos);
391 
392 	dst4 = (struct sockaddr_in *)&sc->sc_ro.ro_dst;
393 	if (dst4->sin_family != AF_INET ||
394 	    bcmp(&dst4->sin_addr, &ip->ip_dst, sizeof(ip->ip_dst)) != 0) {
395 		/* cache route doesn't match */
396 		dst4->sin_family = AF_INET;
397 		dst4->sin_len = sizeof(struct sockaddr_in);
398 		bcopy(&ip->ip_dst, &dst4->sin_addr, sizeof(dst4->sin_addr));
399 		if (sc->sc_ro.ro_rt) {
400 			RTFREE(sc->sc_ro.ro_rt);
401 			sc->sc_ro.ro_rt = NULL;
402 		}
403 	}
404 
405 	if (sc->sc_ro.ro_rt == NULL) {
406 		rtalloc(&sc->sc_ro);
407 		if (sc->sc_ro.ro_rt == NULL) {
408 			m_freem(m);
409 			return ENETUNREACH;
410 		}
411 	}
412 
413 	return ip_output(m, NULL, &sc->sc_ro, 0, NULL, NULL);
414 }
415 
416 static int
417 stf_checkaddr4(sc, in, inifp)
418 	struct stf_softc *sc;
419 	struct in_addr *in;
420 	struct ifnet *inifp;	/* incoming interface */
421 {
422 	struct in_ifaddr *ia4;
423 
424 	/*
425 	 * reject packets with the following address:
426 	 * 224.0.0.0/4 0.0.0.0/8 127.0.0.0/8 255.0.0.0/8
427 	 */
428 	if (IN_MULTICAST(ntohl(in->s_addr)))
429 		return -1;
430 	switch ((ntohl(in->s_addr) & 0xff000000) >> 24) {
431 	case 0: case 127: case 255:
432 		return -1;
433 	}
434 
435 	/*
436 	 * reject packets with broadcast
437 	 */
438 	for (ia4 = TAILQ_FIRST(&in_ifaddrhead);
439 	     ia4;
440 	     ia4 = TAILQ_NEXT(ia4, ia_link))
441 	{
442 		if ((ia4->ia_ifa.ifa_ifp->if_flags & IFF_BROADCAST) == 0)
443 			continue;
444 		if (in->s_addr == ia4->ia_broadaddr.sin_addr.s_addr)
445 			return -1;
446 	}
447 
448 	/*
449 	 * perform ingress filter
450 	 */
451 	if (sc && (sc->sc_if.if_flags & IFF_LINK2) == 0 && inifp) {
452 		struct sockaddr_in sin;
453 		struct rtentry *rt;
454 
455 		bzero(&sin, sizeof(sin));
456 		sin.sin_family = AF_INET;
457 		sin.sin_len = sizeof(struct sockaddr_in);
458 		sin.sin_addr = *in;
459 		rt = rtpurelookup((struct sockaddr *)&sin);
460 		if (!rt || rt->rt_ifp != inifp) {
461 #if 0
462 			log(LOG_WARNING, "%s: packet from 0x%x dropped "
463 			    "due to ingress filter\n", if_name(&sc->sc_if),
464 			    (u_int32_t)ntohl(sin.sin_addr.s_addr));
465 #endif
466 			if (rt)
467 				rtfree(rt);
468 			return -1;
469 		}
470 		rtfree(rt);
471 	}
472 
473 	return 0;
474 }
475 
476 static int
477 stf_checkaddr6(sc, in6, inifp)
478 	struct stf_softc *sc;
479 	struct in6_addr *in6;
480 	struct ifnet *inifp;	/* incoming interface */
481 {
482 	/*
483 	 * check 6to4 addresses
484 	 */
485 	if (IN6_IS_ADDR_6TO4(in6))
486 		return stf_checkaddr4(sc, GET_V4(in6), inifp);
487 
488 	/*
489 	 * reject anything that look suspicious.  the test is implemented
490 	 * in ip6_input too, but we check here as well to
491 	 * (1) reject bad packets earlier, and
492 	 * (2) to be safe against future ip6_input change.
493 	 */
494 	if (IN6_IS_ADDR_V4COMPAT(in6) || IN6_IS_ADDR_V4MAPPED(in6))
495 		return -1;
496 
497 	return 0;
498 }
499 
500 void
501 in_stf_input(struct mbuf *m, ...)
502 {
503 	struct stf_softc *sc;
504 	struct ip *ip;
505 	struct ip6_hdr *ip6;
506 	u_int8_t otos, itos;
507 	struct ifnet *ifp;
508 	int off, proto;
509 	static const uint32_t af = AF_INET6;
510 	__va_list ap;
511 
512 	__va_start(ap, m);
513 	off = __va_arg(ap, int);
514 	proto = __va_arg(ap, int);
515 	__va_end(ap);
516 
517 	if (proto != IPPROTO_IPV6) {
518 		m_freem(m);
519 		return;
520 	}
521 
522 	ip = mtod(m, struct ip *);
523 
524 	sc = (struct stf_softc *)encap_getarg(m);
525 
526 	if (sc == NULL || (sc->sc_if.if_flags & IFF_UP) == 0) {
527 		m_freem(m);
528 		return;
529 	}
530 
531 	ifp = &sc->sc_if;
532 
533 	/*
534 	 * perform sanity check against outer src/dst.
535 	 * for source, perform ingress filter as well.
536 	 */
537 	if (stf_checkaddr4(sc, &ip->ip_dst, NULL) < 0 ||
538 	    stf_checkaddr4(sc, &ip->ip_src, m->m_pkthdr.rcvif) < 0) {
539 		m_freem(m);
540 		return;
541 	}
542 
543 	otos = ip->ip_tos;
544 	m_adj(m, off);
545 
546 	if (m->m_len < sizeof(*ip6)) {
547 		m = m_pullup(m, sizeof(*ip6));
548 		if (!m)
549 			return;
550 	}
551 	ip6 = mtod(m, struct ip6_hdr *);
552 
553 	/*
554 	 * perform sanity check against inner src/dst.
555 	 * for source, perform ingress filter as well.
556 	 */
557 	if (stf_checkaddr6(sc, &ip6->ip6_dst, NULL) < 0 ||
558 	    stf_checkaddr6(sc, &ip6->ip6_src, m->m_pkthdr.rcvif) < 0) {
559 		m_freem(m);
560 		return;
561 	}
562 
563 	itos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
564 	if ((ifp->if_flags & IFF_LINK1) != 0)
565 		ip_ecn_egress(ECN_ALLOWED, &otos, &itos);
566 	else
567 		ip_ecn_egress(ECN_NOCARE, &otos, &itos);
568 	ip6->ip6_flow &= ~htonl(0xff << 20);
569 	ip6->ip6_flow |= htonl((u_int32_t)itos << 20);
570 
571 	m->m_pkthdr.rcvif = ifp;
572 
573 	if (ifp->if_bpf)
574 		bpf_ptap(ifp->if_bpf, m, &af, sizeof(af));
575 
576 	/*
577 	 * Put the packet to the network layer input queue according to the
578 	 * specified address family.
579 	 * See net/if_gif.c for possible issues with packet processing
580 	 * reorder due to extra queueing.
581 	 */
582 	ifp->if_ipackets++;
583 	ifp->if_ibytes += m->m_pkthdr.len;
584 	netisr_dispatch(NETISR_IPV6, m);
585 }
586 
587 /* ARGSUSED */
588 static void
589 stf_rtrequest(cmd, rt, info)
590 	int cmd;
591 	struct rtentry *rt;
592 	struct rt_addrinfo *info;
593 {
594 
595 	if (rt)
596 		rt->rt_rmx.rmx_mtu = IPV6_MMTU;
597 }
598 
599 static int
600 stf_ioctl(ifp, cmd, data, cr)
601 	struct ifnet *ifp;
602 	u_long cmd;
603 	caddr_t data;
604 	struct ucred *cr;
605 {
606 	struct ifaddr *ifa;
607 	struct ifreq *ifr;
608 	struct sockaddr_in6 *sin6;
609 	int error;
610 
611 	error = 0;
612 	switch (cmd) {
613 	case SIOCSIFADDR:
614 		ifa = (struct ifaddr *)data;
615 		if (ifa == NULL || ifa->ifa_addr->sa_family != AF_INET6) {
616 			error = EAFNOSUPPORT;
617 			break;
618 		}
619 		sin6 = (struct sockaddr_in6 *)ifa->ifa_addr;
620 		if (IN6_IS_ADDR_6TO4(&sin6->sin6_addr)) {
621 			ifa->ifa_rtrequest = stf_rtrequest;
622 			ifp->if_flags |= IFF_UP;
623 		} else
624 			error = EINVAL;
625 		break;
626 
627 	case SIOCADDMULTI:
628 	case SIOCDELMULTI:
629 		ifr = (struct ifreq *)data;
630 		if (ifr && ifr->ifr_addr.sa_family == AF_INET6)
631 			;
632 		else
633 			error = EAFNOSUPPORT;
634 		break;
635 
636 	default:
637 		error = EINVAL;
638 		break;
639 	}
640 
641 	return error;
642 }
643