anycast.c

  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 */
 47static struct hlist_head inet6_acaddr_lst[IN6_ADDR_HSIZE];
 48static DEFINE_SPINLOCK(acaddr_hash_lock);
 49
 50#define ac_dereference(a, idev)						\
 51	rcu_dereference_protected(a, lockdep_is_held(&(idev)->lock))
 52
 53static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr);
 54
 55static u32 inet6_acaddr_hash(const struct net *net,
 56			     const struct in6_addr *addr)
 57{
 58	u32 val = __ipv6_addr_jhash(addr, net_hash_mix(net));
 59
 60	return hash_32(val, IN6_ADDR_HSIZE_SHIFT);
 61}
 62
 63/*
 64 *	socket join an anycast group
 65 */
 66
 67int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 68{
 69	struct ipv6_pinfo *np = inet6_sk(sk);
 70	struct ipv6_ac_socklist *pac = NULL;
 71	struct net *net = sock_net(sk);
 72	netdevice_tracker dev_tracker;
 73	struct net_device *dev = NULL;
 74	struct inet6_dev *idev;
 75	int err = 0, ishost;
 76
 77	if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
 78		return -EPERM;
 79	if (ipv6_addr_is_multicast(addr))
 80		return -EINVAL;
 81
 82	if (ifindex)
 83		dev = netdev_get_by_index(net, ifindex, &dev_tracker, GFP_KERNEL);
 84
 85	if (ipv6_chk_addr_and_flags(net, addr, dev, true, 0, IFA_F_TENTATIVE)) {
 86		err = -EINVAL;
 87		goto error;
 88	}
 89
 90	pac = sock_kmalloc(sk, sizeof(struct ipv6_ac_socklist), GFP_KERNEL);
 91	if (!pac) {
 92		err = -ENOMEM;
 93		goto error;
 94	}
 95
 96	pac->acl_next = NULL;
 97	pac->acl_addr = *addr;
 98
 99	ishost = !READ_ONCE(net->ipv6.devconf_all->forwarding);
100
101	if (ifindex == 0) {
102		struct rt6_info *rt;
103
104		rcu_read_lock();
105		rt = rt6_lookup(net, addr, NULL, 0, NULL, 0);
106		if (rt) {
107			dev = dst_dev_rcu(&rt->dst);
108			netdev_hold(dev, &dev_tracker, GFP_ATOMIC);
109			ip6_rt_put(rt);
110		} else if (ishost) {
111			rcu_read_unlock();
112			err = -EADDRNOTAVAIL;
113			goto error;
114		} else {
115			/* router, no matching interface: just pick one */
116			dev = netdev_get_by_flags_rcu(net, &dev_tracker, IFF_UP,
117						      IFF_UP | IFF_LOOPBACK);
118		}
119		rcu_read_unlock();
120	}
121
122	if (!dev) {
123		err = -ENODEV;
124		goto error;
125	}
126
127	idev = in6_dev_get(dev);
128	if (!idev) {
129		if (ifindex)
130			err = -ENODEV;
131		else
132			err = -EADDRNOTAVAIL;
133		goto error;
134	}
135
136	/* reset ishost, now that we have a specific device */
137	ishost = !READ_ONCE(idev->cnf.forwarding);
138
139	pac->acl_ifindex = dev->ifindex;
140
141	/* XXX
142	 * For hosts, allow link-local or matching prefix anycasts.
143	 * This obviates the need for propagating anycast routes while
144	 * still allowing some non-router anycast participation.
145	 */
146	if (!ipv6_chk_prefix(addr, dev)) {
147		if (ishost)
148			err = -EADDRNOTAVAIL;
149		if (err)
150			goto error_idev;
151	}
152
153	err = __ipv6_dev_ac_inc(idev, addr);
154	if (!err) {
155		pac->acl_next = np->ipv6_ac_list;
156		np->ipv6_ac_list = pac;
157		pac = NULL;
158	}
159
160error_idev:
161	in6_dev_put(idev);
162error:
163	netdev_put(dev, &dev_tracker);
164
165	if (pac)
166		sock_kfree_s(sk, pac, sizeof(*pac));
167	return err;
168}
169
170/*
171 *	socket leave an anycast group
172 */
173int ipv6_sock_ac_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
174{
175	struct ipv6_ac_socklist *pac, *prev_pac;
176	struct ipv6_pinfo *np = inet6_sk(sk);
177	struct net *net = sock_net(sk);
178	struct net_device *dev;
179
180	prev_pac = NULL;
181	for (pac = np->ipv6_ac_list; pac; pac = pac->acl_next) {
182		if ((ifindex == 0 || pac->acl_ifindex == ifindex) &&
183		     ipv6_addr_equal(&pac->acl_addr, addr))
184			break;
185		prev_pac = pac;
186	}
187	if (!pac)
188		return -ENOENT;
189	if (prev_pac)
190		prev_pac->acl_next = pac->acl_next;
191	else
192		np->ipv6_ac_list = pac->acl_next;
193
194	dev = dev_get_by_index(net, pac->acl_ifindex);
195	if (dev) {
196		ipv6_dev_ac_dec(dev, &pac->acl_addr);
197		dev_put(dev);
198	}
199
200	sock_kfree_s(sk, pac, sizeof(*pac));
201	return 0;
202}
203
204void __ipv6_sock_ac_close(struct sock *sk)
205{
206	struct ipv6_pinfo *np = inet6_sk(sk);
207	struct net *net = sock_net(sk);
208	struct net_device *dev = NULL;
209	struct ipv6_ac_socklist *pac;
210	int prev_index = 0;
211
212	pac = np->ipv6_ac_list;
213	np->ipv6_ac_list = NULL;
214
215	while (pac) {
216		struct ipv6_ac_socklist *next = pac->acl_next;
217
218		if (pac->acl_ifindex != prev_index) {
219			dev_put(dev);
220			dev = dev_get_by_index(net, pac->acl_ifindex);
221			prev_index = pac->acl_ifindex;
222		}
223		if (dev)
224			ipv6_dev_ac_dec(dev, &pac->acl_addr);
225		sock_kfree_s(sk, pac, sizeof(*pac));
226		pac = next;
227	}
228
229	dev_put(dev);
230}
231
232void ipv6_sock_ac_close(struct sock *sk)
233{
234	struct ipv6_pinfo *np = inet6_sk(sk);
235
236	if (!np->ipv6_ac_list)
237		return;
238
239	__ipv6_sock_ac_close(sk);
240}
241
242static void ipv6_add_acaddr_hash(struct net *net, struct ifacaddr6 *aca)
243{
244	unsigned int hash = inet6_acaddr_hash(net, &aca->aca_addr);
245
246	spin_lock(&acaddr_hash_lock);
247	hlist_add_head_rcu(&aca->aca_addr_lst, &inet6_acaddr_lst[hash]);
248	spin_unlock(&acaddr_hash_lock);
249}
250
251static void ipv6_del_acaddr_hash(struct ifacaddr6 *aca)
252{
253	spin_lock(&acaddr_hash_lock);
254	hlist_del_init_rcu(&aca->aca_addr_lst);
255	spin_unlock(&acaddr_hash_lock);
256}
257
258static void aca_get(struct ifacaddr6 *aca)
259{
260	refcount_inc(&aca->aca_refcnt);
261}
262
263static void aca_free_rcu(struct rcu_head *h)
264{
265	struct ifacaddr6 *aca = container_of(h, struct ifacaddr6, rcu);
266
267	fib6_info_release(aca->aca_rt);
268	kfree(aca);
269}
270
271static void aca_put(struct ifacaddr6 *ac)
272{
273	if (refcount_dec_and_test(&ac->aca_refcnt))
274		call_rcu_hurry(&ac->rcu, aca_free_rcu);
275}
276
277static struct ifacaddr6 *aca_alloc(struct fib6_info *f6i,
278				   const struct in6_addr *addr)
279{
280	struct ifacaddr6 *aca;
281
282	aca = kzalloc(sizeof(*aca), GFP_ATOMIC);
283	if (!aca)
284		return NULL;
285
286	aca->aca_addr = *addr;
287	fib6_info_hold(f6i);
288	aca->aca_rt = f6i;
289	INIT_HLIST_NODE(&aca->aca_addr_lst);
290	aca->aca_users = 1;
291	/* aca_tstamp should be updated upon changes */
292	aca->aca_cstamp = aca->aca_tstamp = jiffies;
293	refcount_set(&aca->aca_refcnt, 1);
294
295	return aca;
296}
297
298static void inet6_ifacaddr_notify(struct net_device *dev,
299				  const struct ifacaddr6 *ifaca, int event)
300{
301	struct inet6_fill_args fillargs = {
302		.event = event,
303		.netnsid = -1,
304	};
305	struct net *net = dev_net(dev);
306	struct sk_buff *skb;
307	int err = -ENOMEM;
308
309	skb = nlmsg_new(NLMSG_ALIGN(sizeof(struct ifaddrmsg)) +
310			nla_total_size(sizeof(struct in6_addr)) +
311			nla_total_size(sizeof(struct ifa_cacheinfo)),
312			GFP_KERNEL);
313	if (!skb)
314		goto error;
315
316	err = inet6_fill_ifacaddr(skb, ifaca, &fillargs);
317	if (err < 0) {
318		pr_err("Failed to fill in anycast addresses (err %d)\n", err);
319		nlmsg_free(skb);
320		goto error;
321	}
322
323	rtnl_notify(skb, net, 0, RTNLGRP_IPV6_ACADDR, NULL, GFP_KERNEL);
324	return;
325error:
326	rtnl_set_sk_err(net, RTNLGRP_IPV6_ACADDR, err);
327}
328
329/*
330 *	device anycast group inc (add if not found)
331 */
332int __ipv6_dev_ac_inc(struct inet6_dev *idev, const struct in6_addr *addr)
333{
334	struct ifacaddr6 *aca;
335	struct fib6_info *f6i;
336	struct net *net;
337	int err;
338
339	write_lock_bh(&idev->lock);
340	if (idev->dead) {
341		err = -ENODEV;
342		goto out;
343	}
344
345	for (aca = ac_dereference(idev->ac_list, idev); aca;
346	     aca = ac_dereference(aca->aca_next, idev)) {
347		if (ipv6_addr_equal(&aca->aca_addr, addr)) {
348			aca->aca_users++;
349			err = 0;
350			goto out;
351		}
352	}
353
354	net = dev_net(idev->dev);
355	f6i = addrconf_f6i_alloc(net, idev, addr, true, GFP_ATOMIC, NULL);
356	if (IS_ERR(f6i)) {
357		err = PTR_ERR(f6i);
358		goto out;
359	}
360	aca = aca_alloc(f6i, addr);
361	if (!aca) {
362		fib6_info_release(f6i);
363		err = -ENOMEM;
364		goto out;
365	}
366
367	/* Hold this for addrconf_join_solict() below before we unlock,
368	 * it is already exposed via idev->ac_list.
369	 */
370	aca_get(aca);
371	aca->aca_next = idev->ac_list;
372	rcu_assign_pointer(idev->ac_list, aca);
373
374	write_unlock_bh(&idev->lock);
375
376	ipv6_add_acaddr_hash(net, aca);
377
378	ip6_ins_rt(net, f6i);
379
380	addrconf_join_solict(idev->dev, &aca->aca_addr);
381
382	inet6_ifacaddr_notify(idev->dev, aca, RTM_NEWANYCAST);
383
384	aca_put(aca);
385	return 0;
386out:
387	write_unlock_bh(&idev->lock);
388	return err;
389}
390
391/*
392 *	device anycast group decrement
393 */
394int __ipv6_dev_ac_dec(struct inet6_dev *idev, const struct in6_addr *addr)
395{
396	struct ifacaddr6 *aca, *prev_aca;
397
398	write_lock_bh(&idev->lock);
399	prev_aca = NULL;
400	for (aca = ac_dereference(idev->ac_list, idev); aca;
401	     aca = ac_dereference(aca->aca_next, idev)) {
402		if (ipv6_addr_equal(&aca->aca_addr, addr))
403			break;
404		prev_aca = aca;
405	}
406	if (!aca) {
407		write_unlock_bh(&idev->lock);
408		return -ENOENT;
409	}
410	if (--aca->aca_users > 0) {
411		write_unlock_bh(&idev->lock);
412		return 0;
413	}
414	if (prev_aca)
415		rcu_assign_pointer(prev_aca->aca_next, aca->aca_next);
416	else
417		rcu_assign_pointer(idev->ac_list, aca->aca_next);
418	write_unlock_bh(&idev->lock);
419	ipv6_del_acaddr_hash(aca);
420	addrconf_leave_solict(idev, &aca->aca_addr);
421
422	ip6_del_rt(dev_net(idev->dev), aca->aca_rt, false);
423
424	inet6_ifacaddr_notify(idev->dev, aca, RTM_DELANYCAST);
425
426	aca_put(aca);
427	return 0;
428}
429
430static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr)
431{
432	struct inet6_dev *idev = in6_dev_get(dev);
433	int err;
434
435	if (!idev)
436		return -ENODEV;
437
438	err = __ipv6_dev_ac_dec(idev, addr);
439	in6_dev_put(idev);
440
441	return err;
442}
443
444void ipv6_ac_destroy_dev(struct inet6_dev *idev)
445{
446	struct ifacaddr6 *aca;
447
448	write_lock_bh(&idev->lock);
449	while ((aca = ac_dereference(idev->ac_list, idev)) != NULL) {
450		rcu_assign_pointer(idev->ac_list, aca->aca_next);
451		write_unlock_bh(&idev->lock);
452
453		ipv6_del_acaddr_hash(aca);
454
455		addrconf_leave_solict(idev, &aca->aca_addr);
456
457		ip6_del_rt(dev_net(idev->dev), aca->aca_rt, false);
458
459		aca_put(aca);
460
461		write_lock_bh(&idev->lock);
462	}
463	write_unlock_bh(&idev->lock);
464}
465
466/*
467 *	check if the interface has this anycast address
468 *	called with rcu_read_lock()
469 */
470static bool ipv6_chk_acast_dev(struct net_device *dev, const struct in6_addr *addr)
471{
472	struct inet6_dev *idev;
473	struct ifacaddr6 *aca;
474
475	idev = __in6_dev_get(dev);
476	if (idev) {
477		for (aca = rcu_dereference(idev->ac_list); aca;
478		     aca = rcu_dereference(aca->aca_next))
479			if (ipv6_addr_equal(&aca->aca_addr, addr))
480				break;
481		return aca != NULL;
482	}
483	return false;
484}
485
486/*
487 *	check if given interface (or any, if dev==0) has this anycast address
488 */
489bool ipv6_chk_acast_addr(struct net *net, struct net_device *dev,
490			 const struct in6_addr *addr)
491{
492	struct net_device *nh_dev;
493	struct ifacaddr6 *aca;
494	bool found = false;
495
496	rcu_read_lock();
497	if (dev)
498		found = ipv6_chk_acast_dev(dev, addr);
499	else {
500		unsigned int hash = inet6_acaddr_hash(net, addr);
501
502		hlist_for_each_entry_rcu(aca, &inet6_acaddr_lst[hash],
503					 aca_addr_lst) {
504			nh_dev = fib6_info_nh_dev(aca->aca_rt);
505			if (!nh_dev || !net_eq(dev_net(nh_dev), net))
506				continue;
507			if (ipv6_addr_equal(&aca->aca_addr, addr)) {
508				found = true;
509				break;
510			}
511		}
512	}
513	rcu_read_unlock();
514	return found;
515}
516
517/*	check if this anycast address is link-local on given interface or
518 *	is global
519 */
520bool ipv6_chk_acast_addr_src(struct net *net, struct net_device *dev,
521			     const struct in6_addr *addr)
522{
523	return ipv6_chk_acast_addr(net,
524				   (ipv6_addr_type(addr) & IPV6_ADDR_LINKLOCAL ?
525				    dev : NULL),
526				   addr);
527}
528
529#ifdef CONFIG_PROC_FS
530struct ac6_iter_state {
531	struct seq_net_private p;
532	struct net_device *dev;
533};
534
535#define ac6_seq_private(seq)	((struct ac6_iter_state *)(seq)->private)
536
537static inline struct ifacaddr6 *ac6_get_first(struct seq_file *seq)
538{
539	struct ac6_iter_state *state = ac6_seq_private(seq);
540	struct net *net = seq_file_net(seq);
541	struct ifacaddr6 *im = NULL;
542
543	for_each_netdev_rcu(net, state->dev) {
544		struct inet6_dev *idev;
545
546		idev = __in6_dev_get(state->dev);
547		if (!idev)
548			continue;
549		im = rcu_dereference(idev->ac_list);
550		if (im)
551			break;
552	}
553	return im;
554}
555
556static struct ifacaddr6 *ac6_get_next(struct seq_file *seq, struct ifacaddr6 *im)
557{
558	struct ac6_iter_state *state = ac6_seq_private(seq);
559	struct inet6_dev *idev;
560
561	im = rcu_dereference(im->aca_next);
562	while (!im) {
563		state->dev = next_net_device_rcu(state->dev);
564		if (!state->dev)
565			break;
566		idev = __in6_dev_get(state->dev);
567		if (!idev)
568			continue;
569		im = rcu_dereference(idev->ac_list);
570	}
571	return im;
572}
573
574static struct ifacaddr6 *ac6_get_idx(struct seq_file *seq, loff_t pos)
575{
576	struct ifacaddr6 *im = ac6_get_first(seq);
577	if (im)
578		while (pos && (im = ac6_get_next(seq, im)) != NULL)
579			--pos;
580	return pos ? NULL : im;
581}
582
583static void *ac6_seq_start(struct seq_file *seq, loff_t *pos)
584	__acquires(RCU)
585{
586	rcu_read_lock();
587	return ac6_get_idx(seq, *pos);
588}
589
590static void *ac6_seq_next(struct seq_file *seq, void *v, loff_t *pos)
591{
592	struct ifacaddr6 *im = ac6_get_next(seq, v);
593
594	++*pos;
595	return im;
596}
597
598static void ac6_seq_stop(struct seq_file *seq, void *v)
599	__releases(RCU)
600{
601	rcu_read_unlock();
602}
603
604static int ac6_seq_show(struct seq_file *seq, void *v)
605{
606	struct ifacaddr6 *im = (struct ifacaddr6 *)v;
607	struct ac6_iter_state *state = ac6_seq_private(seq);
608
609	seq_printf(seq, "%-4d %-15s %pi6 %5d\n",
610		   state->dev->ifindex, state->dev->name,
611		   &im->aca_addr, im->aca_users);
612	return 0;
613}
614
615static const struct seq_operations ac6_seq_ops = {
616	.start	=	ac6_seq_start,
617	.next	=	ac6_seq_next,
618	.stop	=	ac6_seq_stop,
619	.show	=	ac6_seq_show,
620};
621
622int __net_init ac6_proc_init(struct net *net)
623{
624	if (!proc_create_net("anycast6", 0444, net->proc_net, &ac6_seq_ops,
625			sizeof(struct ac6_iter_state)))
626		return -ENOMEM;
627
628	return 0;
629}
630
631void ac6_proc_exit(struct net *net)
632{
633	remove_proc_entry("anycast6", net->proc_net);
634}
635#endif
636
637/*	Init / cleanup code
638 */
639int __init ipv6_anycast_init(void)
640{
641	int i;
642
643	for (i = 0; i < IN6_ADDR_HSIZE; i++)
644		INIT_HLIST_HEAD(&inet6_acaddr_lst[i]);
645	return 0;
646}
647
648void ipv6_anycast_cleanup(void)
649{
650	int i;
651
652	spin_lock(&acaddr_hash_lock);
653	for (i = 0; i < IN6_ADDR_HSIZE; i++)
654		WARN_ON(!hlist_empty(&inet6_acaddr_lst[i]));
655	spin_unlock(&acaddr_hash_lock);
656}