xref: /linux/net/ipv6/sit.c (revision 26b0d14106954ae46d2f4f7eec3481828a210f7d)
1 /*
2  *	IPv6 over IPv4 tunnel device - Simple Internet Transition (SIT)
3  *	Linux INET6 implementation
4  *
5  *	Authors:
6  *	Pedro Roque		<roque@di.fc.ul.pt>
7  *	Alexey Kuznetsov	<kuznet@ms2.inr.ac.ru>
8  *
9  *	This program is free software; you can redistribute it and/or
10  *      modify it under the terms of the GNU General Public License
11  *      as published by the Free Software Foundation; either version
12  *      2 of the License, or (at your option) any later version.
13  *
14  *	Changes:
15  * Roger Venning <r.venning@telstra.com>:	6to4 support
16  * Nate Thompson <nate@thebog.net>:		6to4 support
17  * Fred Templin <fred.l.templin@boeing.com>:	isatap support
18  */
19 
20 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
21 
22 #include <linux/module.h>
23 #include <linux/capability.h>
24 #include <linux/errno.h>
25 #include <linux/types.h>
26 #include <linux/socket.h>
27 #include <linux/sockios.h>
28 #include <linux/net.h>
29 #include <linux/in6.h>
30 #include <linux/netdevice.h>
31 #include <linux/if_arp.h>
32 #include <linux/icmp.h>
33 #include <linux/slab.h>
34 #include <asm/uaccess.h>
35 #include <linux/init.h>
36 #include <linux/netfilter_ipv4.h>
37 #include <linux/if_ether.h>
38 
39 #include <net/sock.h>
40 #include <net/snmp.h>
41 
42 #include <net/ipv6.h>
43 #include <net/protocol.h>
44 #include <net/transp_v6.h>
45 #include <net/ip6_fib.h>
46 #include <net/ip6_route.h>
47 #include <net/ndisc.h>
48 #include <net/addrconf.h>
49 #include <net/ip.h>
50 #include <net/udp.h>
51 #include <net/icmp.h>
52 #include <net/ipip.h>
53 #include <net/inet_ecn.h>
54 #include <net/xfrm.h>
55 #include <net/dsfield.h>
56 #include <net/net_namespace.h>
57 #include <net/netns/generic.h>
58 
59 /*
60    This version of net/ipv6/sit.c is cloned of net/ipv4/ip_gre.c
61 
62    For comments look at net/ipv4/ip_gre.c --ANK
63  */
64 
65 #define HASH_SIZE  16
66 #define HASH(addr) (((__force u32)addr^((__force u32)addr>>4))&0xF)
67 
68 static int ipip6_tunnel_init(struct net_device *dev);
69 static void ipip6_tunnel_setup(struct net_device *dev);
70 static void ipip6_dev_free(struct net_device *dev);
71 
72 static int sit_net_id __read_mostly;
73 struct sit_net {
74 	struct ip_tunnel __rcu *tunnels_r_l[HASH_SIZE];
75 	struct ip_tunnel __rcu *tunnels_r[HASH_SIZE];
76 	struct ip_tunnel __rcu *tunnels_l[HASH_SIZE];
77 	struct ip_tunnel __rcu *tunnels_wc[1];
78 	struct ip_tunnel __rcu **tunnels[4];
79 
80 	struct net_device *fb_tunnel_dev;
81 };
82 
83 /*
84  * Locking : hash tables are protected by RCU and RTNL
85  */
86 
87 #define for_each_ip_tunnel_rcu(start) \
88 	for (t = rcu_dereference(start); t; t = rcu_dereference(t->next))
89 
90 /* often modified stats are per cpu, other are shared (netdev->stats) */
91 struct pcpu_tstats {
92 	u64	rx_packets;
93 	u64	rx_bytes;
94 	u64	tx_packets;
95 	u64	tx_bytes;
96 	struct u64_stats_sync	syncp;
97 };
98 
99 static struct rtnl_link_stats64 *ipip6_get_stats64(struct net_device *dev,
100 						   struct rtnl_link_stats64 *tot)
101 {
102 	int i;
103 
104 	for_each_possible_cpu(i) {
105 		const struct pcpu_tstats *tstats = per_cpu_ptr(dev->tstats, i);
106 		u64 rx_packets, rx_bytes, tx_packets, tx_bytes;
107 		unsigned int start;
108 
109 		do {
110 			start = u64_stats_fetch_begin_bh(&tstats->syncp);
111 			rx_packets = tstats->rx_packets;
112 			tx_packets = tstats->tx_packets;
113 			rx_bytes = tstats->rx_bytes;
114 			tx_bytes = tstats->tx_bytes;
115 		} while (u64_stats_fetch_retry_bh(&tstats->syncp, start));
116 
117 		tot->rx_packets += rx_packets;
118 		tot->tx_packets += tx_packets;
119 		tot->rx_bytes   += rx_bytes;
120 		tot->tx_bytes   += tx_bytes;
121 	}
122 
123 	tot->rx_errors = dev->stats.rx_errors;
124 	tot->tx_fifo_errors = dev->stats.tx_fifo_errors;
125 	tot->tx_carrier_errors = dev->stats.tx_carrier_errors;
126 	tot->tx_dropped = dev->stats.tx_dropped;
127 	tot->tx_aborted_errors = dev->stats.tx_aborted_errors;
128 	tot->tx_errors = dev->stats.tx_errors;
129 
130 	return tot;
131 }
132 
133 /*
134  * Must be invoked with rcu_read_lock
135  */
136 static struct ip_tunnel *ipip6_tunnel_lookup(struct net *net,
137 		struct net_device *dev, __be32 remote, __be32 local)
138 {
139 	unsigned int h0 = HASH(remote);
140 	unsigned int h1 = HASH(local);
141 	struct ip_tunnel *t;
142 	struct sit_net *sitn = net_generic(net, sit_net_id);
143 
144 	for_each_ip_tunnel_rcu(sitn->tunnels_r_l[h0 ^ h1]) {
145 		if (local == t->parms.iph.saddr &&
146 		    remote == t->parms.iph.daddr &&
147 		    (!dev || !t->parms.link || dev->iflink == t->parms.link) &&
148 		    (t->dev->flags & IFF_UP))
149 			return t;
150 	}
151 	for_each_ip_tunnel_rcu(sitn->tunnels_r[h0]) {
152 		if (remote == t->parms.iph.daddr &&
153 		    (!dev || !t->parms.link || dev->iflink == t->parms.link) &&
154 		    (t->dev->flags & IFF_UP))
155 			return t;
156 	}
157 	for_each_ip_tunnel_rcu(sitn->tunnels_l[h1]) {
158 		if (local == t->parms.iph.saddr &&
159 		    (!dev || !t->parms.link || dev->iflink == t->parms.link) &&
160 		    (t->dev->flags & IFF_UP))
161 			return t;
162 	}
163 	t = rcu_dereference(sitn->tunnels_wc[0]);
164 	if ((t != NULL) && (t->dev->flags & IFF_UP))
165 		return t;
166 	return NULL;
167 }
168 
169 static struct ip_tunnel __rcu **__ipip6_bucket(struct sit_net *sitn,
170 		struct ip_tunnel_parm *parms)
171 {
172 	__be32 remote = parms->iph.daddr;
173 	__be32 local = parms->iph.saddr;
174 	unsigned int h = 0;
175 	int prio = 0;
176 
177 	if (remote) {
178 		prio |= 2;
179 		h ^= HASH(remote);
180 	}
181 	if (local) {
182 		prio |= 1;
183 		h ^= HASH(local);
184 	}
185 	return &sitn->tunnels[prio][h];
186 }
187 
188 static inline struct ip_tunnel __rcu **ipip6_bucket(struct sit_net *sitn,
189 		struct ip_tunnel *t)
190 {
191 	return __ipip6_bucket(sitn, &t->parms);
192 }
193 
194 static void ipip6_tunnel_unlink(struct sit_net *sitn, struct ip_tunnel *t)
195 {
196 	struct ip_tunnel __rcu **tp;
197 	struct ip_tunnel *iter;
198 
199 	for (tp = ipip6_bucket(sitn, t);
200 	     (iter = rtnl_dereference(*tp)) != NULL;
201 	     tp = &iter->next) {
202 		if (t == iter) {
203 			rcu_assign_pointer(*tp, t->next);
204 			break;
205 		}
206 	}
207 }
208 
209 static void ipip6_tunnel_link(struct sit_net *sitn, struct ip_tunnel *t)
210 {
211 	struct ip_tunnel __rcu **tp = ipip6_bucket(sitn, t);
212 
213 	rcu_assign_pointer(t->next, rtnl_dereference(*tp));
214 	rcu_assign_pointer(*tp, t);
215 }
216 
217 static void ipip6_tunnel_clone_6rd(struct net_device *dev, struct sit_net *sitn)
218 {
219 #ifdef CONFIG_IPV6_SIT_6RD
220 	struct ip_tunnel *t = netdev_priv(dev);
221 
222 	if (t->dev == sitn->fb_tunnel_dev) {
223 		ipv6_addr_set(&t->ip6rd.prefix, htonl(0x20020000), 0, 0, 0);
224 		t->ip6rd.relay_prefix = 0;
225 		t->ip6rd.prefixlen = 16;
226 		t->ip6rd.relay_prefixlen = 0;
227 	} else {
228 		struct ip_tunnel *t0 = netdev_priv(sitn->fb_tunnel_dev);
229 		memcpy(&t->ip6rd, &t0->ip6rd, sizeof(t->ip6rd));
230 	}
231 #endif
232 }
233 
234 static struct ip_tunnel *ipip6_tunnel_locate(struct net *net,
235 		struct ip_tunnel_parm *parms, int create)
236 {
237 	__be32 remote = parms->iph.daddr;
238 	__be32 local = parms->iph.saddr;
239 	struct ip_tunnel *t, *nt;
240 	struct ip_tunnel __rcu **tp;
241 	struct net_device *dev;
242 	char name[IFNAMSIZ];
243 	struct sit_net *sitn = net_generic(net, sit_net_id);
244 
245 	for (tp = __ipip6_bucket(sitn, parms);
246 	    (t = rtnl_dereference(*tp)) != NULL;
247 	     tp = &t->next) {
248 		if (local == t->parms.iph.saddr &&
249 		    remote == t->parms.iph.daddr &&
250 		    parms->link == t->parms.link) {
251 			if (create)
252 				return NULL;
253 			else
254 				return t;
255 		}
256 	}
257 	if (!create)
258 		goto failed;
259 
260 	if (parms->name[0])
261 		strlcpy(name, parms->name, IFNAMSIZ);
262 	else
263 		strcpy(name, "sit%d");
264 
265 	dev = alloc_netdev(sizeof(*t), name, ipip6_tunnel_setup);
266 	if (dev == NULL)
267 		return NULL;
268 
269 	dev_net_set(dev, net);
270 
271 	nt = netdev_priv(dev);
272 
273 	nt->parms = *parms;
274 	if (ipip6_tunnel_init(dev) < 0)
275 		goto failed_free;
276 	ipip6_tunnel_clone_6rd(dev, sitn);
277 
278 	if (parms->i_flags & SIT_ISATAP)
279 		dev->priv_flags |= IFF_ISATAP;
280 
281 	if (register_netdevice(dev) < 0)
282 		goto failed_free;
283 
284 	strcpy(nt->parms.name, dev->name);
285 
286 	dev_hold(dev);
287 
288 	ipip6_tunnel_link(sitn, nt);
289 	return nt;
290 
291 failed_free:
292 	ipip6_dev_free(dev);
293 failed:
294 	return NULL;
295 }
296 
297 #define for_each_prl_rcu(start)			\
298 	for (prl = rcu_dereference(start);	\
299 	     prl;				\
300 	     prl = rcu_dereference(prl->next))
301 
302 static struct ip_tunnel_prl_entry *
303 __ipip6_tunnel_locate_prl(struct ip_tunnel *t, __be32 addr)
304 {
305 	struct ip_tunnel_prl_entry *prl;
306 
307 	for_each_prl_rcu(t->prl)
308 		if (prl->addr == addr)
309 			break;
310 	return prl;
311 
312 }
313 
314 static int ipip6_tunnel_get_prl(struct ip_tunnel *t,
315 				struct ip_tunnel_prl __user *a)
316 {
317 	struct ip_tunnel_prl kprl, *kp;
318 	struct ip_tunnel_prl_entry *prl;
319 	unsigned int cmax, c = 0, ca, len;
320 	int ret = 0;
321 
322 	if (copy_from_user(&kprl, a, sizeof(kprl)))
323 		return -EFAULT;
324 	cmax = kprl.datalen / sizeof(kprl);
325 	if (cmax > 1 && kprl.addr != htonl(INADDR_ANY))
326 		cmax = 1;
327 
328 	/* For simple GET or for root users,
329 	 * we try harder to allocate.
330 	 */
331 	kp = (cmax <= 1 || capable(CAP_NET_ADMIN)) ?
332 		kcalloc(cmax, sizeof(*kp), GFP_KERNEL) :
333 		NULL;
334 
335 	rcu_read_lock();
336 
337 	ca = t->prl_count < cmax ? t->prl_count : cmax;
338 
339 	if (!kp) {
340 		/* We don't try hard to allocate much memory for
341 		 * non-root users.
342 		 * For root users, retry allocating enough memory for
343 		 * the answer.
344 		 */
345 		kp = kcalloc(ca, sizeof(*kp), GFP_ATOMIC);
346 		if (!kp) {
347 			ret = -ENOMEM;
348 			goto out;
349 		}
350 	}
351 
352 	c = 0;
353 	for_each_prl_rcu(t->prl) {
354 		if (c >= cmax)
355 			break;
356 		if (kprl.addr != htonl(INADDR_ANY) && prl->addr != kprl.addr)
357 			continue;
358 		kp[c].addr = prl->addr;
359 		kp[c].flags = prl->flags;
360 		c++;
361 		if (kprl.addr != htonl(INADDR_ANY))
362 			break;
363 	}
364 out:
365 	rcu_read_unlock();
366 
367 	len = sizeof(*kp) * c;
368 	ret = 0;
369 	if ((len && copy_to_user(a + 1, kp, len)) || put_user(len, &a->datalen))
370 		ret = -EFAULT;
371 
372 	kfree(kp);
373 
374 	return ret;
375 }
376 
377 static int
378 ipip6_tunnel_add_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a, int chg)
379 {
380 	struct ip_tunnel_prl_entry *p;
381 	int err = 0;
382 
383 	if (a->addr == htonl(INADDR_ANY))
384 		return -EINVAL;
385 
386 	ASSERT_RTNL();
387 
388 	for (p = rtnl_dereference(t->prl); p; p = rtnl_dereference(p->next)) {
389 		if (p->addr == a->addr) {
390 			if (chg) {
391 				p->flags = a->flags;
392 				goto out;
393 			}
394 			err = -EEXIST;
395 			goto out;
396 		}
397 	}
398 
399 	if (chg) {
400 		err = -ENXIO;
401 		goto out;
402 	}
403 
404 	p = kzalloc(sizeof(struct ip_tunnel_prl_entry), GFP_KERNEL);
405 	if (!p) {
406 		err = -ENOBUFS;
407 		goto out;
408 	}
409 
410 	p->next = t->prl;
411 	p->addr = a->addr;
412 	p->flags = a->flags;
413 	t->prl_count++;
414 	rcu_assign_pointer(t->prl, p);
415 out:
416 	return err;
417 }
418 
419 static void prl_list_destroy_rcu(struct rcu_head *head)
420 {
421 	struct ip_tunnel_prl_entry *p, *n;
422 
423 	p = container_of(head, struct ip_tunnel_prl_entry, rcu_head);
424 	do {
425 		n = rcu_dereference_protected(p->next, 1);
426 		kfree(p);
427 		p = n;
428 	} while (p);
429 }
430 
431 static int
432 ipip6_tunnel_del_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a)
433 {
434 	struct ip_tunnel_prl_entry *x;
435 	struct ip_tunnel_prl_entry __rcu **p;
436 	int err = 0;
437 
438 	ASSERT_RTNL();
439 
440 	if (a && a->addr != htonl(INADDR_ANY)) {
441 		for (p = &t->prl;
442 		     (x = rtnl_dereference(*p)) != NULL;
443 		     p = &x->next) {
444 			if (x->addr == a->addr) {
445 				*p = x->next;
446 				kfree_rcu(x, rcu_head);
447 				t->prl_count--;
448 				goto out;
449 			}
450 		}
451 		err = -ENXIO;
452 	} else {
453 		x = rtnl_dereference(t->prl);
454 		if (x) {
455 			t->prl_count = 0;
456 			call_rcu(&x->rcu_head, prl_list_destroy_rcu);
457 			t->prl = NULL;
458 		}
459 	}
460 out:
461 	return err;
462 }
463 
464 static int
465 isatap_chksrc(struct sk_buff *skb, const struct iphdr *iph, struct ip_tunnel *t)
466 {
467 	struct ip_tunnel_prl_entry *p;
468 	int ok = 1;
469 
470 	rcu_read_lock();
471 	p = __ipip6_tunnel_locate_prl(t, iph->saddr);
472 	if (p) {
473 		if (p->flags & PRL_DEFAULT)
474 			skb->ndisc_nodetype = NDISC_NODETYPE_DEFAULT;
475 		else
476 			skb->ndisc_nodetype = NDISC_NODETYPE_NODEFAULT;
477 	} else {
478 		const struct in6_addr *addr6 = &ipv6_hdr(skb)->saddr;
479 
480 		if (ipv6_addr_is_isatap(addr6) &&
481 		    (addr6->s6_addr32[3] == iph->saddr) &&
482 		    ipv6_chk_prefix(addr6, t->dev))
483 			skb->ndisc_nodetype = NDISC_NODETYPE_HOST;
484 		else
485 			ok = 0;
486 	}
487 	rcu_read_unlock();
488 	return ok;
489 }
490 
491 static void ipip6_tunnel_uninit(struct net_device *dev)
492 {
493 	struct net *net = dev_net(dev);
494 	struct sit_net *sitn = net_generic(net, sit_net_id);
495 
496 	if (dev == sitn->fb_tunnel_dev) {
497 		RCU_INIT_POINTER(sitn->tunnels_wc[0], NULL);
498 	} else {
499 		ipip6_tunnel_unlink(sitn, netdev_priv(dev));
500 		ipip6_tunnel_del_prl(netdev_priv(dev), NULL);
501 	}
502 	dev_put(dev);
503 }
504 
505 
506 static int ipip6_err(struct sk_buff *skb, u32 info)
507 {
508 
509 /* All the routers (except for Linux) return only
510    8 bytes of packet payload. It means, that precise relaying of
511    ICMP in the real Internet is absolutely infeasible.
512  */
513 	const struct iphdr *iph = (const struct iphdr *)skb->data;
514 	const int type = icmp_hdr(skb)->type;
515 	const int code = icmp_hdr(skb)->code;
516 	struct ip_tunnel *t;
517 	int err;
518 
519 	switch (type) {
520 	default:
521 	case ICMP_PARAMETERPROB:
522 		return 0;
523 
524 	case ICMP_DEST_UNREACH:
525 		switch (code) {
526 		case ICMP_SR_FAILED:
527 		case ICMP_PORT_UNREACH:
528 			/* Impossible event. */
529 			return 0;
530 		case ICMP_FRAG_NEEDED:
531 			/* Soft state for pmtu is maintained by IP core. */
532 			return 0;
533 		default:
534 			/* All others are translated to HOST_UNREACH.
535 			   rfc2003 contains "deep thoughts" about NET_UNREACH,
536 			   I believe they are just ether pollution. --ANK
537 			 */
538 			break;
539 		}
540 		break;
541 	case ICMP_TIME_EXCEEDED:
542 		if (code != ICMP_EXC_TTL)
543 			return 0;
544 		break;
545 	}
546 
547 	err = -ENOENT;
548 
549 	rcu_read_lock();
550 	t = ipip6_tunnel_lookup(dev_net(skb->dev),
551 				skb->dev,
552 				iph->daddr,
553 				iph->saddr);
554 	if (t == NULL || t->parms.iph.daddr == 0)
555 		goto out;
556 
557 	err = 0;
558 	if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)
559 		goto out;
560 
561 	if (time_before(jiffies, t->err_time + IPTUNNEL_ERR_TIMEO))
562 		t->err_count++;
563 	else
564 		t->err_count = 1;
565 	t->err_time = jiffies;
566 out:
567 	rcu_read_unlock();
568 	return err;
569 }
570 
571 static inline void ipip6_ecn_decapsulate(const struct iphdr *iph, struct sk_buff *skb)
572 {
573 	if (INET_ECN_is_ce(iph->tos))
574 		IP6_ECN_set_ce(ipv6_hdr(skb));
575 }
576 
577 static int ipip6_rcv(struct sk_buff *skb)
578 {
579 	const struct iphdr *iph;
580 	struct ip_tunnel *tunnel;
581 
582 	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
583 		goto out;
584 
585 	iph = ip_hdr(skb);
586 
587 	rcu_read_lock();
588 	tunnel = ipip6_tunnel_lookup(dev_net(skb->dev), skb->dev,
589 				     iph->saddr, iph->daddr);
590 	if (tunnel != NULL) {
591 		struct pcpu_tstats *tstats;
592 
593 		secpath_reset(skb);
594 		skb->mac_header = skb->network_header;
595 		skb_reset_network_header(skb);
596 		IPCB(skb)->flags = 0;
597 		skb->protocol = htons(ETH_P_IPV6);
598 		skb->pkt_type = PACKET_HOST;
599 
600 		if ((tunnel->dev->priv_flags & IFF_ISATAP) &&
601 		    !isatap_chksrc(skb, iph, tunnel)) {
602 			tunnel->dev->stats.rx_errors++;
603 			rcu_read_unlock();
604 			kfree_skb(skb);
605 			return 0;
606 		}
607 
608 		tstats = this_cpu_ptr(tunnel->dev->tstats);
609 		tstats->rx_packets++;
610 		tstats->rx_bytes += skb->len;
611 
612 		__skb_tunnel_rx(skb, tunnel->dev);
613 
614 		ipip6_ecn_decapsulate(iph, skb);
615 
616 		netif_rx(skb);
617 
618 		rcu_read_unlock();
619 		return 0;
620 	}
621 
622 	/* no tunnel matched,  let upstream know, ipsec may handle it */
623 	rcu_read_unlock();
624 	return 1;
625 out:
626 	kfree_skb(skb);
627 	return 0;
628 }
629 
630 /*
631  * Returns the embedded IPv4 address if the IPv6 address
632  * comes from 6rd / 6to4 (RFC 3056) addr space.
633  */
634 static inline
635 __be32 try_6rd(const struct in6_addr *v6dst, struct ip_tunnel *tunnel)
636 {
637 	__be32 dst = 0;
638 
639 #ifdef CONFIG_IPV6_SIT_6RD
640 	if (ipv6_prefix_equal(v6dst, &tunnel->ip6rd.prefix,
641 			      tunnel->ip6rd.prefixlen)) {
642 		unsigned int pbw0, pbi0;
643 		int pbi1;
644 		u32 d;
645 
646 		pbw0 = tunnel->ip6rd.prefixlen >> 5;
647 		pbi0 = tunnel->ip6rd.prefixlen & 0x1f;
648 
649 		d = (ntohl(v6dst->s6_addr32[pbw0]) << pbi0) >>
650 		    tunnel->ip6rd.relay_prefixlen;
651 
652 		pbi1 = pbi0 - tunnel->ip6rd.relay_prefixlen;
653 		if (pbi1 > 0)
654 			d |= ntohl(v6dst->s6_addr32[pbw0 + 1]) >>
655 			     (32 - pbi1);
656 
657 		dst = tunnel->ip6rd.relay_prefix | htonl(d);
658 	}
659 #else
660 	if (v6dst->s6_addr16[0] == htons(0x2002)) {
661 		/* 6to4 v6 addr has 16 bits prefix, 32 v4addr, 16 SLA, ... */
662 		memcpy(&dst, &v6dst->s6_addr16[1], 4);
663 	}
664 #endif
665 	return dst;
666 }
667 
668 /*
669  *	This function assumes it is being called from dev_queue_xmit()
670  *	and that skb is filled properly by that function.
671  */
672 
673 static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
674 				     struct net_device *dev)
675 {
676 	struct ip_tunnel *tunnel = netdev_priv(dev);
677 	struct pcpu_tstats *tstats;
678 	const struct iphdr  *tiph = &tunnel->parms.iph;
679 	const struct ipv6hdr *iph6 = ipv6_hdr(skb);
680 	u8     tos = tunnel->parms.iph.tos;
681 	__be16 df = tiph->frag_off;
682 	struct rtable *rt;     			/* Route to the other host */
683 	struct net_device *tdev;		/* Device to other host */
684 	struct iphdr  *iph;			/* Our new IP header */
685 	unsigned int max_headroom;		/* The extra header space needed */
686 	__be32 dst = tiph->daddr;
687 	struct flowi4 fl4;
688 	int    mtu;
689 	const struct in6_addr *addr6;
690 	int addr_type;
691 
692 	if (skb->protocol != htons(ETH_P_IPV6))
693 		goto tx_error;
694 
695 	if (tos == 1)
696 		tos = ipv6_get_dsfield(iph6);
697 
698 	/* ISATAP (RFC4214) - must come before 6to4 */
699 	if (dev->priv_flags & IFF_ISATAP) {
700 		struct neighbour *neigh = NULL;
701 		bool do_tx_error = false;
702 
703 		if (skb_dst(skb))
704 			neigh = dst_neigh_lookup(skb_dst(skb), &iph6->daddr);
705 
706 		if (neigh == NULL) {
707 			net_dbg_ratelimited("sit: nexthop == NULL\n");
708 			goto tx_error;
709 		}
710 
711 		addr6 = (const struct in6_addr *)&neigh->primary_key;
712 		addr_type = ipv6_addr_type(addr6);
713 
714 		if ((addr_type & IPV6_ADDR_UNICAST) &&
715 		     ipv6_addr_is_isatap(addr6))
716 			dst = addr6->s6_addr32[3];
717 		else
718 			do_tx_error = true;
719 
720 		neigh_release(neigh);
721 		if (do_tx_error)
722 			goto tx_error;
723 	}
724 
725 	if (!dst)
726 		dst = try_6rd(&iph6->daddr, tunnel);
727 
728 	if (!dst) {
729 		struct neighbour *neigh = NULL;
730 		bool do_tx_error = false;
731 
732 		if (skb_dst(skb))
733 			neigh = dst_neigh_lookup(skb_dst(skb), &iph6->daddr);
734 
735 		if (neigh == NULL) {
736 			net_dbg_ratelimited("sit: nexthop == NULL\n");
737 			goto tx_error;
738 		}
739 
740 		addr6 = (const struct in6_addr *)&neigh->primary_key;
741 		addr_type = ipv6_addr_type(addr6);
742 
743 		if (addr_type == IPV6_ADDR_ANY) {
744 			addr6 = &ipv6_hdr(skb)->daddr;
745 			addr_type = ipv6_addr_type(addr6);
746 		}
747 
748 		if ((addr_type & IPV6_ADDR_COMPATv4) != 0)
749 			dst = addr6->s6_addr32[3];
750 		else
751 			do_tx_error = true;
752 
753 		neigh_release(neigh);
754 		if (do_tx_error)
755 			goto tx_error;
756 	}
757 
758 	rt = ip_route_output_ports(dev_net(dev), &fl4, NULL,
759 				   dst, tiph->saddr,
760 				   0, 0,
761 				   IPPROTO_IPV6, RT_TOS(tos),
762 				   tunnel->parms.link);
763 	if (IS_ERR(rt)) {
764 		dev->stats.tx_carrier_errors++;
765 		goto tx_error_icmp;
766 	}
767 	if (rt->rt_type != RTN_UNICAST) {
768 		ip_rt_put(rt);
769 		dev->stats.tx_carrier_errors++;
770 		goto tx_error_icmp;
771 	}
772 	tdev = rt->dst.dev;
773 
774 	if (tdev == dev) {
775 		ip_rt_put(rt);
776 		dev->stats.collisions++;
777 		goto tx_error;
778 	}
779 
780 	if (df) {
781 		mtu = dst_mtu(&rt->dst) - sizeof(struct iphdr);
782 
783 		if (mtu < 68) {
784 			dev->stats.collisions++;
785 			ip_rt_put(rt);
786 			goto tx_error;
787 		}
788 
789 		if (mtu < IPV6_MIN_MTU) {
790 			mtu = IPV6_MIN_MTU;
791 			df = 0;
792 		}
793 
794 		if (tunnel->parms.iph.daddr && skb_dst(skb))
795 			skb_dst(skb)->ops->update_pmtu(skb_dst(skb), mtu);
796 
797 		if (skb->len > mtu) {
798 			icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
799 			ip_rt_put(rt);
800 			goto tx_error;
801 		}
802 	}
803 
804 	if (tunnel->err_count > 0) {
805 		if (time_before(jiffies,
806 				tunnel->err_time + IPTUNNEL_ERR_TIMEO)) {
807 			tunnel->err_count--;
808 			dst_link_failure(skb);
809 		} else
810 			tunnel->err_count = 0;
811 	}
812 
813 	/*
814 	 * Okay, now see if we can stuff it in the buffer as-is.
815 	 */
816 	max_headroom = LL_RESERVED_SPACE(tdev)+sizeof(struct iphdr);
817 
818 	if (skb_headroom(skb) < max_headroom || skb_shared(skb) ||
819 	    (skb_cloned(skb) && !skb_clone_writable(skb, 0))) {
820 		struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
821 		if (!new_skb) {
822 			ip_rt_put(rt);
823 			dev->stats.tx_dropped++;
824 			dev_kfree_skb(skb);
825 			return NETDEV_TX_OK;
826 		}
827 		if (skb->sk)
828 			skb_set_owner_w(new_skb, skb->sk);
829 		dev_kfree_skb(skb);
830 		skb = new_skb;
831 		iph6 = ipv6_hdr(skb);
832 	}
833 
834 	skb->transport_header = skb->network_header;
835 	skb_push(skb, sizeof(struct iphdr));
836 	skb_reset_network_header(skb);
837 	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
838 	IPCB(skb)->flags = 0;
839 	skb_dst_drop(skb);
840 	skb_dst_set(skb, &rt->dst);
841 
842 	/*
843 	 *	Push down and install the IPIP header.
844 	 */
845 
846 	iph 			=	ip_hdr(skb);
847 	iph->version		=	4;
848 	iph->ihl		=	sizeof(struct iphdr)>>2;
849 	iph->frag_off		=	df;
850 	iph->protocol		=	IPPROTO_IPV6;
851 	iph->tos		=	INET_ECN_encapsulate(tos, ipv6_get_dsfield(iph6));
852 	iph->daddr		=	fl4.daddr;
853 	iph->saddr		=	fl4.saddr;
854 
855 	if ((iph->ttl = tiph->ttl) == 0)
856 		iph->ttl	=	iph6->hop_limit;
857 
858 	nf_reset(skb);
859 	tstats = this_cpu_ptr(dev->tstats);
860 	__IPTUNNEL_XMIT(tstats, &dev->stats);
861 	return NETDEV_TX_OK;
862 
863 tx_error_icmp:
864 	dst_link_failure(skb);
865 tx_error:
866 	dev->stats.tx_errors++;
867 	dev_kfree_skb(skb);
868 	return NETDEV_TX_OK;
869 }
870 
871 static void ipip6_tunnel_bind_dev(struct net_device *dev)
872 {
873 	struct net_device *tdev = NULL;
874 	struct ip_tunnel *tunnel;
875 	const struct iphdr *iph;
876 	struct flowi4 fl4;
877 
878 	tunnel = netdev_priv(dev);
879 	iph = &tunnel->parms.iph;
880 
881 	if (iph->daddr) {
882 		struct rtable *rt = ip_route_output_ports(dev_net(dev), &fl4, NULL,
883 							  iph->daddr, iph->saddr,
884 							  0, 0,
885 							  IPPROTO_IPV6,
886 							  RT_TOS(iph->tos),
887 							  tunnel->parms.link);
888 
889 		if (!IS_ERR(rt)) {
890 			tdev = rt->dst.dev;
891 			ip_rt_put(rt);
892 		}
893 		dev->flags |= IFF_POINTOPOINT;
894 	}
895 
896 	if (!tdev && tunnel->parms.link)
897 		tdev = __dev_get_by_index(dev_net(dev), tunnel->parms.link);
898 
899 	if (tdev) {
900 		dev->hard_header_len = tdev->hard_header_len + sizeof(struct iphdr);
901 		dev->mtu = tdev->mtu - sizeof(struct iphdr);
902 		if (dev->mtu < IPV6_MIN_MTU)
903 			dev->mtu = IPV6_MIN_MTU;
904 	}
905 	dev->iflink = tunnel->parms.link;
906 }
907 
908 static int
909 ipip6_tunnel_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd)
910 {
911 	int err = 0;
912 	struct ip_tunnel_parm p;
913 	struct ip_tunnel_prl prl;
914 	struct ip_tunnel *t;
915 	struct net *net = dev_net(dev);
916 	struct sit_net *sitn = net_generic(net, sit_net_id);
917 #ifdef CONFIG_IPV6_SIT_6RD
918 	struct ip_tunnel_6rd ip6rd;
919 #endif
920 
921 	switch (cmd) {
922 	case SIOCGETTUNNEL:
923 #ifdef CONFIG_IPV6_SIT_6RD
924 	case SIOCGET6RD:
925 #endif
926 		t = NULL;
927 		if (dev == sitn->fb_tunnel_dev) {
928 			if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) {
929 				err = -EFAULT;
930 				break;
931 			}
932 			t = ipip6_tunnel_locate(net, &p, 0);
933 		}
934 		if (t == NULL)
935 			t = netdev_priv(dev);
936 
937 		err = -EFAULT;
938 		if (cmd == SIOCGETTUNNEL) {
939 			memcpy(&p, &t->parms, sizeof(p));
940 			if (copy_to_user(ifr->ifr_ifru.ifru_data, &p,
941 					 sizeof(p)))
942 				goto done;
943 #ifdef CONFIG_IPV6_SIT_6RD
944 		} else {
945 			ip6rd.prefix = t->ip6rd.prefix;
946 			ip6rd.relay_prefix = t->ip6rd.relay_prefix;
947 			ip6rd.prefixlen = t->ip6rd.prefixlen;
948 			ip6rd.relay_prefixlen = t->ip6rd.relay_prefixlen;
949 			if (copy_to_user(ifr->ifr_ifru.ifru_data, &ip6rd,
950 					 sizeof(ip6rd)))
951 				goto done;
952 #endif
953 		}
954 		err = 0;
955 		break;
956 
957 	case SIOCADDTUNNEL:
958 	case SIOCCHGTUNNEL:
959 		err = -EPERM;
960 		if (!capable(CAP_NET_ADMIN))
961 			goto done;
962 
963 		err = -EFAULT;
964 		if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
965 			goto done;
966 
967 		err = -EINVAL;
968 		if (p.iph.version != 4 || p.iph.protocol != IPPROTO_IPV6 ||
969 		    p.iph.ihl != 5 || (p.iph.frag_off&htons(~IP_DF)))
970 			goto done;
971 		if (p.iph.ttl)
972 			p.iph.frag_off |= htons(IP_DF);
973 
974 		t = ipip6_tunnel_locate(net, &p, cmd == SIOCADDTUNNEL);
975 
976 		if (dev != sitn->fb_tunnel_dev && cmd == SIOCCHGTUNNEL) {
977 			if (t != NULL) {
978 				if (t->dev != dev) {
979 					err = -EEXIST;
980 					break;
981 				}
982 			} else {
983 				if (((dev->flags&IFF_POINTOPOINT) && !p.iph.daddr) ||
984 				    (!(dev->flags&IFF_POINTOPOINT) && p.iph.daddr)) {
985 					err = -EINVAL;
986 					break;
987 				}
988 				t = netdev_priv(dev);
989 				ipip6_tunnel_unlink(sitn, t);
990 				synchronize_net();
991 				t->parms.iph.saddr = p.iph.saddr;
992 				t->parms.iph.daddr = p.iph.daddr;
993 				memcpy(dev->dev_addr, &p.iph.saddr, 4);
994 				memcpy(dev->broadcast, &p.iph.daddr, 4);
995 				ipip6_tunnel_link(sitn, t);
996 				netdev_state_change(dev);
997 			}
998 		}
999 
1000 		if (t) {
1001 			err = 0;
1002 			if (cmd == SIOCCHGTUNNEL) {
1003 				t->parms.iph.ttl = p.iph.ttl;
1004 				t->parms.iph.tos = p.iph.tos;
1005 				if (t->parms.link != p.link) {
1006 					t->parms.link = p.link;
1007 					ipip6_tunnel_bind_dev(dev);
1008 					netdev_state_change(dev);
1009 				}
1010 			}
1011 			if (copy_to_user(ifr->ifr_ifru.ifru_data, &t->parms, sizeof(p)))
1012 				err = -EFAULT;
1013 		} else
1014 			err = (cmd == SIOCADDTUNNEL ? -ENOBUFS : -ENOENT);
1015 		break;
1016 
1017 	case SIOCDELTUNNEL:
1018 		err = -EPERM;
1019 		if (!capable(CAP_NET_ADMIN))
1020 			goto done;
1021 
1022 		if (dev == sitn->fb_tunnel_dev) {
1023 			err = -EFAULT;
1024 			if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
1025 				goto done;
1026 			err = -ENOENT;
1027 			if ((t = ipip6_tunnel_locate(net, &p, 0)) == NULL)
1028 				goto done;
1029 			err = -EPERM;
1030 			if (t == netdev_priv(sitn->fb_tunnel_dev))
1031 				goto done;
1032 			dev = t->dev;
1033 		}
1034 		unregister_netdevice(dev);
1035 		err = 0;
1036 		break;
1037 
1038 	case SIOCGETPRL:
1039 		err = -EINVAL;
1040 		if (dev == sitn->fb_tunnel_dev)
1041 			goto done;
1042 		err = -ENOENT;
1043 		if (!(t = netdev_priv(dev)))
1044 			goto done;
1045 		err = ipip6_tunnel_get_prl(t, ifr->ifr_ifru.ifru_data);
1046 		break;
1047 
1048 	case SIOCADDPRL:
1049 	case SIOCDELPRL:
1050 	case SIOCCHGPRL:
1051 		err = -EPERM;
1052 		if (!capable(CAP_NET_ADMIN))
1053 			goto done;
1054 		err = -EINVAL;
1055 		if (dev == sitn->fb_tunnel_dev)
1056 			goto done;
1057 		err = -EFAULT;
1058 		if (copy_from_user(&prl, ifr->ifr_ifru.ifru_data, sizeof(prl)))
1059 			goto done;
1060 		err = -ENOENT;
1061 		if (!(t = netdev_priv(dev)))
1062 			goto done;
1063 
1064 		switch (cmd) {
1065 		case SIOCDELPRL:
1066 			err = ipip6_tunnel_del_prl(t, &prl);
1067 			break;
1068 		case SIOCADDPRL:
1069 		case SIOCCHGPRL:
1070 			err = ipip6_tunnel_add_prl(t, &prl, cmd == SIOCCHGPRL);
1071 			break;
1072 		}
1073 		netdev_state_change(dev);
1074 		break;
1075 
1076 #ifdef CONFIG_IPV6_SIT_6RD
1077 	case SIOCADD6RD:
1078 	case SIOCCHG6RD:
1079 	case SIOCDEL6RD:
1080 		err = -EPERM;
1081 		if (!capable(CAP_NET_ADMIN))
1082 			goto done;
1083 
1084 		err = -EFAULT;
1085 		if (copy_from_user(&ip6rd, ifr->ifr_ifru.ifru_data,
1086 				   sizeof(ip6rd)))
1087 			goto done;
1088 
1089 		t = netdev_priv(dev);
1090 
1091 		if (cmd != SIOCDEL6RD) {
1092 			struct in6_addr prefix;
1093 			__be32 relay_prefix;
1094 
1095 			err = -EINVAL;
1096 			if (ip6rd.relay_prefixlen > 32 ||
1097 			    ip6rd.prefixlen + (32 - ip6rd.relay_prefixlen) > 64)
1098 				goto done;
1099 
1100 			ipv6_addr_prefix(&prefix, &ip6rd.prefix,
1101 					 ip6rd.prefixlen);
1102 			if (!ipv6_addr_equal(&prefix, &ip6rd.prefix))
1103 				goto done;
1104 			if (ip6rd.relay_prefixlen)
1105 				relay_prefix = ip6rd.relay_prefix &
1106 					       htonl(0xffffffffUL <<
1107 						     (32 - ip6rd.relay_prefixlen));
1108 			else
1109 				relay_prefix = 0;
1110 			if (relay_prefix != ip6rd.relay_prefix)
1111 				goto done;
1112 
1113 			t->ip6rd.prefix = prefix;
1114 			t->ip6rd.relay_prefix = relay_prefix;
1115 			t->ip6rd.prefixlen = ip6rd.prefixlen;
1116 			t->ip6rd.relay_prefixlen = ip6rd.relay_prefixlen;
1117 		} else
1118 			ipip6_tunnel_clone_6rd(dev, sitn);
1119 
1120 		err = 0;
1121 		break;
1122 #endif
1123 
1124 	default:
1125 		err = -EINVAL;
1126 	}
1127 
1128 done:
1129 	return err;
1130 }
1131 
1132 static int ipip6_tunnel_change_mtu(struct net_device *dev, int new_mtu)
1133 {
1134 	if (new_mtu < IPV6_MIN_MTU || new_mtu > 0xFFF8 - sizeof(struct iphdr))
1135 		return -EINVAL;
1136 	dev->mtu = new_mtu;
1137 	return 0;
1138 }
1139 
1140 static const struct net_device_ops ipip6_netdev_ops = {
1141 	.ndo_uninit	= ipip6_tunnel_uninit,
1142 	.ndo_start_xmit	= ipip6_tunnel_xmit,
1143 	.ndo_do_ioctl	= ipip6_tunnel_ioctl,
1144 	.ndo_change_mtu	= ipip6_tunnel_change_mtu,
1145 	.ndo_get_stats64= ipip6_get_stats64,
1146 };
1147 
1148 static void ipip6_dev_free(struct net_device *dev)
1149 {
1150 	free_percpu(dev->tstats);
1151 	free_netdev(dev);
1152 }
1153 
1154 static void ipip6_tunnel_setup(struct net_device *dev)
1155 {
1156 	dev->netdev_ops		= &ipip6_netdev_ops;
1157 	dev->destructor 	= ipip6_dev_free;
1158 
1159 	dev->type		= ARPHRD_SIT;
1160 	dev->hard_header_len 	= LL_MAX_HEADER + sizeof(struct iphdr);
1161 	dev->mtu		= ETH_DATA_LEN - sizeof(struct iphdr);
1162 	dev->flags		= IFF_NOARP;
1163 	dev->priv_flags	       &= ~IFF_XMIT_DST_RELEASE;
1164 	dev->iflink		= 0;
1165 	dev->addr_len		= 4;
1166 	dev->features		|= NETIF_F_NETNS_LOCAL;
1167 	dev->features		|= NETIF_F_LLTX;
1168 }
1169 
1170 static int ipip6_tunnel_init(struct net_device *dev)
1171 {
1172 	struct ip_tunnel *tunnel = netdev_priv(dev);
1173 
1174 	tunnel->dev = dev;
1175 
1176 	memcpy(dev->dev_addr, &tunnel->parms.iph.saddr, 4);
1177 	memcpy(dev->broadcast, &tunnel->parms.iph.daddr, 4);
1178 
1179 	ipip6_tunnel_bind_dev(dev);
1180 	dev->tstats = alloc_percpu(struct pcpu_tstats);
1181 	if (!dev->tstats)
1182 		return -ENOMEM;
1183 
1184 	return 0;
1185 }
1186 
1187 static int __net_init ipip6_fb_tunnel_init(struct net_device *dev)
1188 {
1189 	struct ip_tunnel *tunnel = netdev_priv(dev);
1190 	struct iphdr *iph = &tunnel->parms.iph;
1191 	struct net *net = dev_net(dev);
1192 	struct sit_net *sitn = net_generic(net, sit_net_id);
1193 
1194 	tunnel->dev = dev;
1195 	strcpy(tunnel->parms.name, dev->name);
1196 
1197 	iph->version		= 4;
1198 	iph->protocol		= IPPROTO_IPV6;
1199 	iph->ihl		= 5;
1200 	iph->ttl		= 64;
1201 
1202 	dev->tstats = alloc_percpu(struct pcpu_tstats);
1203 	if (!dev->tstats)
1204 		return -ENOMEM;
1205 	dev_hold(dev);
1206 	rcu_assign_pointer(sitn->tunnels_wc[0], tunnel);
1207 	return 0;
1208 }
1209 
1210 static struct xfrm_tunnel sit_handler __read_mostly = {
1211 	.handler	=	ipip6_rcv,
1212 	.err_handler	=	ipip6_err,
1213 	.priority	=	1,
1214 };
1215 
1216 static void __net_exit sit_destroy_tunnels(struct sit_net *sitn, struct list_head *head)
1217 {
1218 	int prio;
1219 
1220 	for (prio = 1; prio < 4; prio++) {
1221 		int h;
1222 		for (h = 0; h < HASH_SIZE; h++) {
1223 			struct ip_tunnel *t;
1224 
1225 			t = rtnl_dereference(sitn->tunnels[prio][h]);
1226 			while (t != NULL) {
1227 				unregister_netdevice_queue(t->dev, head);
1228 				t = rtnl_dereference(t->next);
1229 			}
1230 		}
1231 	}
1232 }
1233 
1234 static int __net_init sit_init_net(struct net *net)
1235 {
1236 	struct sit_net *sitn = net_generic(net, sit_net_id);
1237 	struct ip_tunnel *t;
1238 	int err;
1239 
1240 	sitn->tunnels[0] = sitn->tunnels_wc;
1241 	sitn->tunnels[1] = sitn->tunnels_l;
1242 	sitn->tunnels[2] = sitn->tunnels_r;
1243 	sitn->tunnels[3] = sitn->tunnels_r_l;
1244 
1245 	sitn->fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "sit0",
1246 					   ipip6_tunnel_setup);
1247 	if (!sitn->fb_tunnel_dev) {
1248 		err = -ENOMEM;
1249 		goto err_alloc_dev;
1250 	}
1251 	dev_net_set(sitn->fb_tunnel_dev, net);
1252 
1253 	err = ipip6_fb_tunnel_init(sitn->fb_tunnel_dev);
1254 	if (err)
1255 		goto err_dev_free;
1256 
1257 	ipip6_tunnel_clone_6rd(sitn->fb_tunnel_dev, sitn);
1258 
1259 	if ((err = register_netdev(sitn->fb_tunnel_dev)))
1260 		goto err_reg_dev;
1261 
1262 	t = netdev_priv(sitn->fb_tunnel_dev);
1263 
1264 	strcpy(t->parms.name, sitn->fb_tunnel_dev->name);
1265 	return 0;
1266 
1267 err_reg_dev:
1268 	dev_put(sitn->fb_tunnel_dev);
1269 err_dev_free:
1270 	ipip6_dev_free(sitn->fb_tunnel_dev);
1271 err_alloc_dev:
1272 	return err;
1273 }
1274 
1275 static void __net_exit sit_exit_net(struct net *net)
1276 {
1277 	struct sit_net *sitn = net_generic(net, sit_net_id);
1278 	LIST_HEAD(list);
1279 
1280 	rtnl_lock();
1281 	sit_destroy_tunnels(sitn, &list);
1282 	unregister_netdevice_queue(sitn->fb_tunnel_dev, &list);
1283 	unregister_netdevice_many(&list);
1284 	rtnl_unlock();
1285 }
1286 
1287 static struct pernet_operations sit_net_ops = {
1288 	.init = sit_init_net,
1289 	.exit = sit_exit_net,
1290 	.id   = &sit_net_id,
1291 	.size = sizeof(struct sit_net),
1292 };
1293 
1294 static void __exit sit_cleanup(void)
1295 {
1296 	xfrm4_tunnel_deregister(&sit_handler, AF_INET6);
1297 
1298 	unregister_pernet_device(&sit_net_ops);
1299 	rcu_barrier(); /* Wait for completion of call_rcu()'s */
1300 }
1301 
1302 static int __init sit_init(void)
1303 {
1304 	int err;
1305 
1306 	pr_info("IPv6 over IPv4 tunneling driver\n");
1307 
1308 	err = register_pernet_device(&sit_net_ops);
1309 	if (err < 0)
1310 		return err;
1311 	err = xfrm4_tunnel_register(&sit_handler, AF_INET6);
1312 	if (err < 0) {
1313 		unregister_pernet_device(&sit_net_ops);
1314 		pr_info("%s: can't add protocol\n", __func__);
1315 	}
1316 	return err;
1317 }
1318 
1319 module_init(sit_init);
1320 module_exit(sit_cleanup);
1321 MODULE_LICENSE("GPL");
1322 MODULE_ALIAS_NETDEV("sit0");
1323