xref: /linux/net/ipv6/anycast.c (revision 24bce201d79807b668bf9d9e0aca801c5c0d5f78) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *	Anycast support for IPv6
4  *	Linux INET6 implementation
5  *
6  *	Authors:
7  *	David L Stevens (dlstevens@us.ibm.com)
8  *
9  *	based heavily on net/ipv6/mcast.c
10  */
11 
12 #include <linux/capability.h>
13 #include <linux/module.h>
14 #include <linux/errno.h>
15 #include <linux/types.h>
16 #include <linux/random.h>
17 #include <linux/string.h>
18 #include <linux/socket.h>
19 #include <linux/sockios.h>
20 #include <linux/net.h>
21 #include <linux/in6.h>
22 #include <linux/netdevice.h>
23 #include <linux/if_arp.h>
24 #include <linux/route.h>
25 #include <linux/init.h>
26 #include <linux/proc_fs.h>
27 #include <linux/seq_file.h>
28 #include <linux/slab.h>
29 
30 #include <net/net_namespace.h>
31 #include <net/sock.h>
32 #include <net/snmp.h>
33 
34 #include <net/ipv6.h>
35 #include <net/protocol.h>
36 #include <net/if_inet6.h>
37 #include <net/ndisc.h>
38 #include <net/addrconf.h>
39 #include <net/ip6_route.h>
40 
41 #include <net/checksum.h>
42 
43 #define IN6_ADDR_HSIZE_SHIFT	8
44 #define IN6_ADDR_HSIZE		BIT(IN6_ADDR_HSIZE_SHIFT)
45 /*	anycast address hash table
46  */
47 static struct hlist_head inet6_acaddr_lst[IN6_ADDR_HSIZE];
48 static DEFINE_SPINLOCK(acaddr_hash_lock);
49 
50 static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr);
51 
52 static u32 inet6_acaddr_hash(struct net *net, const struct in6_addr *addr)
53 {
54 	u32 val = ipv6_addr_hash(addr) ^ net_hash_mix(net);
55 
56 	return hash_32(val, IN6_ADDR_HSIZE_SHIFT);
57 }
58 
59 /*
60  *	socket join an anycast group
61  */
62 
63 int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
64 {
65 	struct ipv6_pinfo *np = inet6_sk(sk);
66 	struct net_device *dev = NULL;
67 	struct inet6_dev *idev;
68 	struct ipv6_ac_socklist *pac;
69 	struct net *net = sock_net(sk);
70 	int	ishost = !net->ipv6.devconf_all->forwarding;
71 	int	err = 0;
72 
73 	ASSERT_RTNL();
74 
75 	if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
76 		return -EPERM;
77 	if (ipv6_addr_is_multicast(addr))
78 		return -EINVAL;
79 
80 	if (ifindex)
81 		dev = __dev_get_by_index(net, ifindex);
82 
83 	if (ipv6_chk_addr_and_flags(net, addr, dev, true, 0, IFA_F_TENTATIVE))
84 		return -EINVAL;
85 
86 	pac = sock_kmalloc(sk, sizeof(struct ipv6_ac_socklist), GFP_KERNEL);
87 	if (!pac)
88 		return -ENOMEM;
89 	pac->acl_next = NULL;
90 	pac->acl_addr = *addr;
91 
92 	if (ifindex == 0) {
93 		struct rt6_info *rt;
94 
95 		rt = rt6_lookup(net, addr, NULL, 0, NULL, 0);
96 		if (rt) {
97 			dev = rt->dst.dev;
98 			ip6_rt_put(rt);
99 		} else if (ishost) {
100 			err = -EADDRNOTAVAIL;
101 			goto error;
102 		} else {
103 			/* router, no matching interface: just pick one */
104 			dev = __dev_get_by_flags(net, IFF_UP,
105 						 IFF_UP | IFF_LOOPBACK);
106 		}
107 	}
108 
109 	if (!dev) {
110 		err = -ENODEV;
111 		goto error;
112 	}
113 
114 	idev = __in6_dev_get(dev);
115 	if (!idev) {
116 		if (ifindex)
117 			err = -ENODEV;
118 		else
119 			err = -EADDRNOTAVAIL;
120 		goto error;
121 	}
122 	/* reset ishost, now that we have a specific device */
123 	ishost = !idev->cnf.forwarding;
124 
125 	pac->acl_ifindex = dev->ifindex;
126 
127 	/* XXX
128 	 * For hosts, allow link-local or matching prefix anycasts.
129 	 * This obviates the need for propagating anycast routes while
130 	 * still allowing some non-router anycast participation.
131 	 */
132 	if (!ipv6_chk_prefix(addr, dev)) {
133 		if (ishost)
134 			err = -EADDRNOTAVAIL;
135 		if (err)
136 			goto error;
137 	}
138 
139 	err = __ipv6_dev_ac_inc(idev, addr);
140 	if (!err) {
141 		pac->acl_next = np->ipv6_ac_list;
142 		np->ipv6_ac_list = pac;
143 		pac = NULL;
144 	}
145 
146 error:
147 	if (pac)
148 		sock_kfree_s(sk, pac, sizeof(*pac));
149 	return err;
150 }
151 
152 /*
153  *	socket leave an anycast group
154  */
155 int ipv6_sock_ac_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
156 {
157 	struct ipv6_pinfo *np = inet6_sk(sk);
158 	struct net_device *dev;
159 	struct ipv6_ac_socklist *pac, *prev_pac;
160 	struct net *net = sock_net(sk);
161 
162 	ASSERT_RTNL();
163 
164 	prev_pac = NULL;
165 	for (pac = np->ipv6_ac_list; pac; pac = pac->acl_next) {
166 		if ((ifindex == 0 || pac->acl_ifindex == ifindex) &&
167 		     ipv6_addr_equal(&pac->acl_addr, addr))
168 			break;
169 		prev_pac = pac;
170 	}
171 	if (!pac)
172 		return -ENOENT;
173 	if (prev_pac)
174 		prev_pac->acl_next = pac->acl_next;
175 	else
176 		np->ipv6_ac_list = pac->acl_next;
177 
178 	dev = __dev_get_by_index(net, pac->acl_ifindex);
179 	if (dev)
180 		ipv6_dev_ac_dec(dev, &pac->acl_addr);
181 
182 	sock_kfree_s(sk, pac, sizeof(*pac));
183 	return 0;
184 }
185 
186 void __ipv6_sock_ac_close(struct sock *sk)
187 {
188 	struct ipv6_pinfo *np = inet6_sk(sk);
189 	struct net_device *dev = NULL;
190 	struct ipv6_ac_socklist *pac;
191 	struct net *net = sock_net(sk);
192 	int	prev_index;
193 
194 	ASSERT_RTNL();
195 	pac = np->ipv6_ac_list;
196 	np->ipv6_ac_list = NULL;
197 
198 	prev_index = 0;
199 	while (pac) {
200 		struct ipv6_ac_socklist *next = pac->acl_next;
201 
202 		if (pac->acl_ifindex != prev_index) {
203 			dev = __dev_get_by_index(net, pac->acl_ifindex);
204 			prev_index = pac->acl_ifindex;
205 		}
206 		if (dev)
207 			ipv6_dev_ac_dec(dev, &pac->acl_addr);
208 		sock_kfree_s(sk, pac, sizeof(*pac));
209 		pac = next;
210 	}
211 }
212 
213 void ipv6_sock_ac_close(struct sock *sk)
214 {
215 	struct ipv6_pinfo *np = inet6_sk(sk);
216 
217 	if (!np->ipv6_ac_list)
218 		return;
219 	rtnl_lock();
220 	__ipv6_sock_ac_close(sk);
221 	rtnl_unlock();
222 }
223 
224 static void ipv6_add_acaddr_hash(struct net *net, struct ifacaddr6 *aca)
225 {
226 	unsigned int hash = inet6_acaddr_hash(net, &aca->aca_addr);
227 
228 	spin_lock(&acaddr_hash_lock);
229 	hlist_add_head_rcu(&aca->aca_addr_lst, &inet6_acaddr_lst[hash]);
230 	spin_unlock(&acaddr_hash_lock);
231 }
232 
233 static void ipv6_del_acaddr_hash(struct ifacaddr6 *aca)
234 {
235 	spin_lock(&acaddr_hash_lock);
236 	hlist_del_init_rcu(&aca->aca_addr_lst);
237 	spin_unlock(&acaddr_hash_lock);
238 }
239 
240 static void aca_get(struct ifacaddr6 *aca)
241 {
242 	refcount_inc(&aca->aca_refcnt);
243 }
244 
245 static void aca_free_rcu(struct rcu_head *h)
246 {
247 	struct ifacaddr6 *aca = container_of(h, struct ifacaddr6, rcu);
248 
249 	fib6_info_release(aca->aca_rt);
250 	kfree(aca);
251 }
252 
253 static void aca_put(struct ifacaddr6 *ac)
254 {
255 	if (refcount_dec_and_test(&ac->aca_refcnt)) {
256 		call_rcu(&ac->rcu, aca_free_rcu);
257 	}
258 }
259 
260 static struct ifacaddr6 *aca_alloc(struct fib6_info *f6i,
261 				   const struct in6_addr *addr)
262 {
263 	struct ifacaddr6 *aca;
264 
265 	aca = kzalloc(sizeof(*aca), GFP_ATOMIC);
266 	if (!aca)
267 		return NULL;
268 
269 	aca->aca_addr = *addr;
270 	fib6_info_hold(f6i);
271 	aca->aca_rt = f6i;
272 	INIT_HLIST_NODE(&aca->aca_addr_lst);
273 	aca->aca_users = 1;
274 	/* aca_tstamp should be updated upon changes */
275 	aca->aca_cstamp = aca->aca_tstamp = jiffies;
276 	refcount_set(&aca->aca_refcnt, 1);
277 
278 	return aca;
279 }
280 
281 /*
282  *	device anycast group inc (add if not found)
283  */
284 int __ipv6_dev_ac_inc(struct inet6_dev *idev, const struct in6_addr *addr)
285 {
286 	struct ifacaddr6 *aca;
287 	struct fib6_info *f6i;
288 	struct net *net;
289 	int err;
290 
291 	ASSERT_RTNL();
292 
293 	write_lock_bh(&idev->lock);
294 	if (idev->dead) {
295 		err = -ENODEV;
296 		goto out;
297 	}
298 
299 	for (aca = idev->ac_list; aca; aca = aca->aca_next) {
300 		if (ipv6_addr_equal(&aca->aca_addr, addr)) {
301 			aca->aca_users++;
302 			err = 0;
303 			goto out;
304 		}
305 	}
306 
307 	net = dev_net(idev->dev);
308 	f6i = addrconf_f6i_alloc(net, idev, addr, true, GFP_ATOMIC);
309 	if (IS_ERR(f6i)) {
310 		err = PTR_ERR(f6i);
311 		goto out;
312 	}
313 	aca = aca_alloc(f6i, addr);
314 	if (!aca) {
315 		fib6_info_release(f6i);
316 		err = -ENOMEM;
317 		goto out;
318 	}
319 
320 	aca->aca_next = idev->ac_list;
321 	idev->ac_list = aca;
322 
323 	/* Hold this for addrconf_join_solict() below before we unlock,
324 	 * it is already exposed via idev->ac_list.
325 	 */
326 	aca_get(aca);
327 	write_unlock_bh(&idev->lock);
328 
329 	ipv6_add_acaddr_hash(net, aca);
330 
331 	ip6_ins_rt(net, f6i);
332 
333 	addrconf_join_solict(idev->dev, &aca->aca_addr);
334 
335 	aca_put(aca);
336 	return 0;
337 out:
338 	write_unlock_bh(&idev->lock);
339 	return err;
340 }
341 
342 /*
343  *	device anycast group decrement
344  */
345 int __ipv6_dev_ac_dec(struct inet6_dev *idev, const struct in6_addr *addr)
346 {
347 	struct ifacaddr6 *aca, *prev_aca;
348 
349 	ASSERT_RTNL();
350 
351 	write_lock_bh(&idev->lock);
352 	prev_aca = NULL;
353 	for (aca = idev->ac_list; aca; aca = aca->aca_next) {
354 		if (ipv6_addr_equal(&aca->aca_addr, addr))
355 			break;
356 		prev_aca = aca;
357 	}
358 	if (!aca) {
359 		write_unlock_bh(&idev->lock);
360 		return -ENOENT;
361 	}
362 	if (--aca->aca_users > 0) {
363 		write_unlock_bh(&idev->lock);
364 		return 0;
365 	}
366 	if (prev_aca)
367 		prev_aca->aca_next = aca->aca_next;
368 	else
369 		idev->ac_list = aca->aca_next;
370 	write_unlock_bh(&idev->lock);
371 	ipv6_del_acaddr_hash(aca);
372 	addrconf_leave_solict(idev, &aca->aca_addr);
373 
374 	ip6_del_rt(dev_net(idev->dev), aca->aca_rt, false);
375 
376 	aca_put(aca);
377 	return 0;
378 }
379 
380 /* called with rtnl_lock() */
381 static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr)
382 {
383 	struct inet6_dev *idev = __in6_dev_get(dev);
384 
385 	if (!idev)
386 		return -ENODEV;
387 	return __ipv6_dev_ac_dec(idev, addr);
388 }
389 
390 void ipv6_ac_destroy_dev(struct inet6_dev *idev)
391 {
392 	struct ifacaddr6 *aca;
393 
394 	write_lock_bh(&idev->lock);
395 	while ((aca = idev->ac_list) != NULL) {
396 		idev->ac_list = aca->aca_next;
397 		write_unlock_bh(&idev->lock);
398 
399 		ipv6_del_acaddr_hash(aca);
400 
401 		addrconf_leave_solict(idev, &aca->aca_addr);
402 
403 		ip6_del_rt(dev_net(idev->dev), aca->aca_rt, false);
404 
405 		aca_put(aca);
406 
407 		write_lock_bh(&idev->lock);
408 	}
409 	write_unlock_bh(&idev->lock);
410 }
411 
412 /*
413  *	check if the interface has this anycast address
414  *	called with rcu_read_lock()
415  */
416 static bool ipv6_chk_acast_dev(struct net_device *dev, const struct in6_addr *addr)
417 {
418 	struct inet6_dev *idev;
419 	struct ifacaddr6 *aca;
420 
421 	idev = __in6_dev_get(dev);
422 	if (idev) {
423 		read_lock_bh(&idev->lock);
424 		for (aca = idev->ac_list; aca; aca = aca->aca_next)
425 			if (ipv6_addr_equal(&aca->aca_addr, addr))
426 				break;
427 		read_unlock_bh(&idev->lock);
428 		return aca != NULL;
429 	}
430 	return false;
431 }
432 
433 /*
434  *	check if given interface (or any, if dev==0) has this anycast address
435  */
436 bool ipv6_chk_acast_addr(struct net *net, struct net_device *dev,
437 			 const struct in6_addr *addr)
438 {
439 	struct net_device *nh_dev;
440 	struct ifacaddr6 *aca;
441 	bool found = false;
442 
443 	rcu_read_lock();
444 	if (dev)
445 		found = ipv6_chk_acast_dev(dev, addr);
446 	else {
447 		unsigned int hash = inet6_acaddr_hash(net, addr);
448 
449 		hlist_for_each_entry_rcu(aca, &inet6_acaddr_lst[hash],
450 					 aca_addr_lst) {
451 			nh_dev = fib6_info_nh_dev(aca->aca_rt);
452 			if (!nh_dev || !net_eq(dev_net(nh_dev), net))
453 				continue;
454 			if (ipv6_addr_equal(&aca->aca_addr, addr)) {
455 				found = true;
456 				break;
457 			}
458 		}
459 	}
460 	rcu_read_unlock();
461 	return found;
462 }
463 
464 /*	check if this anycast address is link-local on given interface or
465  *	is global
466  */
467 bool ipv6_chk_acast_addr_src(struct net *net, struct net_device *dev,
468 			     const struct in6_addr *addr)
469 {
470 	return ipv6_chk_acast_addr(net,
471 				   (ipv6_addr_type(addr) & IPV6_ADDR_LINKLOCAL ?
472 				    dev : NULL),
473 				   addr);
474 }
475 
476 #ifdef CONFIG_PROC_FS
477 struct ac6_iter_state {
478 	struct seq_net_private p;
479 	struct net_device *dev;
480 	struct inet6_dev *idev;
481 };
482 
483 #define ac6_seq_private(seq)	((struct ac6_iter_state *)(seq)->private)
484 
485 static inline struct ifacaddr6 *ac6_get_first(struct seq_file *seq)
486 {
487 	struct ifacaddr6 *im = NULL;
488 	struct ac6_iter_state *state = ac6_seq_private(seq);
489 	struct net *net = seq_file_net(seq);
490 
491 	state->idev = NULL;
492 	for_each_netdev_rcu(net, state->dev) {
493 		struct inet6_dev *idev;
494 		idev = __in6_dev_get(state->dev);
495 		if (!idev)
496 			continue;
497 		read_lock_bh(&idev->lock);
498 		im = idev->ac_list;
499 		if (im) {
500 			state->idev = idev;
501 			break;
502 		}
503 		read_unlock_bh(&idev->lock);
504 	}
505 	return im;
506 }
507 
508 static struct ifacaddr6 *ac6_get_next(struct seq_file *seq, struct ifacaddr6 *im)
509 {
510 	struct ac6_iter_state *state = ac6_seq_private(seq);
511 
512 	im = im->aca_next;
513 	while (!im) {
514 		if (likely(state->idev != NULL))
515 			read_unlock_bh(&state->idev->lock);
516 
517 		state->dev = next_net_device_rcu(state->dev);
518 		if (!state->dev) {
519 			state->idev = NULL;
520 			break;
521 		}
522 		state->idev = __in6_dev_get(state->dev);
523 		if (!state->idev)
524 			continue;
525 		read_lock_bh(&state->idev->lock);
526 		im = state->idev->ac_list;
527 	}
528 	return im;
529 }
530 
531 static struct ifacaddr6 *ac6_get_idx(struct seq_file *seq, loff_t pos)
532 {
533 	struct ifacaddr6 *im = ac6_get_first(seq);
534 	if (im)
535 		while (pos && (im = ac6_get_next(seq, im)) != NULL)
536 			--pos;
537 	return pos ? NULL : im;
538 }
539 
540 static void *ac6_seq_start(struct seq_file *seq, loff_t *pos)
541 	__acquires(RCU)
542 {
543 	rcu_read_lock();
544 	return ac6_get_idx(seq, *pos);
545 }
546 
547 static void *ac6_seq_next(struct seq_file *seq, void *v, loff_t *pos)
548 {
549 	struct ifacaddr6 *im = ac6_get_next(seq, v);
550 
551 	++*pos;
552 	return im;
553 }
554 
555 static void ac6_seq_stop(struct seq_file *seq, void *v)
556 	__releases(RCU)
557 {
558 	struct ac6_iter_state *state = ac6_seq_private(seq);
559 
560 	if (likely(state->idev != NULL)) {
561 		read_unlock_bh(&state->idev->lock);
562 		state->idev = NULL;
563 	}
564 	rcu_read_unlock();
565 }
566 
567 static int ac6_seq_show(struct seq_file *seq, void *v)
568 {
569 	struct ifacaddr6 *im = (struct ifacaddr6 *)v;
570 	struct ac6_iter_state *state = ac6_seq_private(seq);
571 
572 	seq_printf(seq, "%-4d %-15s %pi6 %5d\n",
573 		   state->dev->ifindex, state->dev->name,
574 		   &im->aca_addr, im->aca_users);
575 	return 0;
576 }
577 
578 static const struct seq_operations ac6_seq_ops = {
579 	.start	=	ac6_seq_start,
580 	.next	=	ac6_seq_next,
581 	.stop	=	ac6_seq_stop,
582 	.show	=	ac6_seq_show,
583 };
584 
585 int __net_init ac6_proc_init(struct net *net)
586 {
587 	if (!proc_create_net("anycast6", 0444, net->proc_net, &ac6_seq_ops,
588 			sizeof(struct ac6_iter_state)))
589 		return -ENOMEM;
590 
591 	return 0;
592 }
593 
594 void ac6_proc_exit(struct net *net)
595 {
596 	remove_proc_entry("anycast6", net->proc_net);
597 }
598 #endif
599 
600 /*	Init / cleanup code
601  */
602 int __init ipv6_anycast_init(void)
603 {
604 	int i;
605 
606 	for (i = 0; i < IN6_ADDR_HSIZE; i++)
607 		INIT_HLIST_HEAD(&inet6_acaddr_lst[i]);
608 	return 0;
609 }
610 
611 void ipv6_anycast_cleanup(void)
612 {
613 	int i;
614 
615 	spin_lock(&acaddr_hash_lock);
616 	for (i = 0; i < IN6_ADDR_HSIZE; i++)
617 		WARN_ON(!hlist_empty(&inet6_acaddr_lst[i]));
618 	spin_unlock(&acaddr_hash_lock);
619 }
620