1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * linux/fs/nfs/dns_resolve.c
4  *
5  * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
6  *
7  * Resolves DNS hostnames into valid ip addresses
8  */
9 
10 #ifdef CONFIG_NFS_USE_KERNEL_DNS
11 
12 #include <linux/module.h>
13 #include <linux/sunrpc/clnt.h>
14 #include <linux/sunrpc/addr.h>
15 #include <linux/dns_resolver.h>
16 #include "dns_resolve.h"
17 
nfs_dns_resolve_name(struct net * net,char * name,size_t namelen,struct sockaddr * sa,size_t salen)18 ssize_t nfs_dns_resolve_name(struct net *net, char *name, size_t namelen,
19 		struct sockaddr *sa, size_t salen)
20 {
21 	ssize_t ret;
22 	char *ip_addr = NULL;
23 	int ip_len;
24 
25 	ip_len = dns_query(net, NULL, name, namelen, NULL, &ip_addr, NULL,
26 			   false);
27 	if (ip_len > 0)
28 		ret = rpc_pton(net, ip_addr, ip_len, sa, salen);
29 	else
30 		ret = -ESRCH;
31 	kfree(ip_addr);
32 	return ret;
33 }
34 
35 #else
36 
37 #include <linux/module.h>
38 #include <linux/hash.h>
39 #include <linux/string.h>
40 #include <linux/kmod.h>
41 #include <linux/slab.h>
42 #include <linux/socket.h>
43 #include <linux/seq_file.h>
44 #include <linux/inet.h>
45 #include <linux/sunrpc/clnt.h>
46 #include <linux/sunrpc/addr.h>
47 #include <linux/sunrpc/cache.h>
48 #include <linux/sunrpc/svcauth.h>
49 #include <linux/sunrpc/rpc_pipe_fs.h>
50 #include <linux/nfs_fs.h>
51 
52 #include "nfs4_fs.h"
53 #include "dns_resolve.h"
54 #include "cache_lib.h"
55 #include "netns.h"
56 
57 #define NFS_DNS_HASHBITS 4
58 #define NFS_DNS_HASHTBL_SIZE (1 << NFS_DNS_HASHBITS)
59 
60 struct nfs_dns_ent {
61 	struct cache_head h;
62 
63 	char *hostname;
64 	size_t namelen;
65 
66 	struct sockaddr_storage addr;
67 	size_t addrlen;
68 	struct rcu_head rcu_head;
69 };
70 
71 
nfs_dns_ent_update(struct cache_head * cnew,struct cache_head * ckey)72 static void nfs_dns_ent_update(struct cache_head *cnew,
73 		struct cache_head *ckey)
74 {
75 	struct nfs_dns_ent *new;
76 	struct nfs_dns_ent *key;
77 
78 	new = container_of(cnew, struct nfs_dns_ent, h);
79 	key = container_of(ckey, struct nfs_dns_ent, h);
80 
81 	memcpy(&new->addr, &key->addr, key->addrlen);
82 	new->addrlen = key->addrlen;
83 }
84 
nfs_dns_ent_init(struct cache_head * cnew,struct cache_head * ckey)85 static void nfs_dns_ent_init(struct cache_head *cnew,
86 		struct cache_head *ckey)
87 {
88 	struct nfs_dns_ent *new;
89 	struct nfs_dns_ent *key;
90 
91 	new = container_of(cnew, struct nfs_dns_ent, h);
92 	key = container_of(ckey, struct nfs_dns_ent, h);
93 
94 	kfree(new->hostname);
95 	new->hostname = kmemdup_nul(key->hostname, key->namelen, GFP_KERNEL);
96 	if (new->hostname) {
97 		new->namelen = key->namelen;
98 		nfs_dns_ent_update(cnew, ckey);
99 	} else {
100 		new->namelen = 0;
101 		new->addrlen = 0;
102 	}
103 }
104 
nfs_dns_ent_free_rcu(struct rcu_head * head)105 static void nfs_dns_ent_free_rcu(struct rcu_head *head)
106 {
107 	struct nfs_dns_ent *item;
108 
109 	item = container_of(head, struct nfs_dns_ent, rcu_head);
110 	kfree(item->hostname);
111 	kfree(item);
112 }
113 
nfs_dns_ent_put(struct kref * ref)114 static void nfs_dns_ent_put(struct kref *ref)
115 {
116 	struct nfs_dns_ent *item;
117 
118 	item = container_of(ref, struct nfs_dns_ent, h.ref);
119 	call_rcu(&item->rcu_head, nfs_dns_ent_free_rcu);
120 }
121 
nfs_dns_ent_alloc(void)122 static struct cache_head *nfs_dns_ent_alloc(void)
123 {
124 	struct nfs_dns_ent *item = kmalloc(sizeof(*item), GFP_KERNEL);
125 
126 	if (item != NULL) {
127 		item->hostname = NULL;
128 		item->namelen = 0;
129 		item->addrlen = 0;
130 		return &item->h;
131 	}
132 	return NULL;
133 };
134 
nfs_dns_hash(const struct nfs_dns_ent * key)135 static unsigned int nfs_dns_hash(const struct nfs_dns_ent *key)
136 {
137 	return hash_str(key->hostname, NFS_DNS_HASHBITS);
138 }
139 
nfs_dns_request(struct cache_detail * cd,struct cache_head * ch,char ** bpp,int * blen)140 static void nfs_dns_request(struct cache_detail *cd,
141 		struct cache_head *ch,
142 		char **bpp, int *blen)
143 {
144 	struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
145 
146 	qword_add(bpp, blen, key->hostname);
147 	(*bpp)[-1] = '\n';
148 }
149 
nfs_dns_upcall(struct cache_detail * cd,struct cache_head * ch)150 static int nfs_dns_upcall(struct cache_detail *cd,
151 		struct cache_head *ch)
152 {
153 	struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
154 
155 	if (test_and_set_bit(CACHE_PENDING, &ch->flags))
156 		return 0;
157 	if (!nfs_cache_upcall(cd, key->hostname))
158 		return 0;
159 	clear_bit(CACHE_PENDING, &ch->flags);
160 	return sunrpc_cache_pipe_upcall_timeout(cd, ch);
161 }
162 
nfs_dns_match(struct cache_head * ca,struct cache_head * cb)163 static int nfs_dns_match(struct cache_head *ca,
164 		struct cache_head *cb)
165 {
166 	struct nfs_dns_ent *a;
167 	struct nfs_dns_ent *b;
168 
169 	a = container_of(ca, struct nfs_dns_ent, h);
170 	b = container_of(cb, struct nfs_dns_ent, h);
171 
172 	if (a->namelen == 0 || a->namelen != b->namelen)
173 		return 0;
174 	return memcmp(a->hostname, b->hostname, a->namelen) == 0;
175 }
176 
nfs_dns_show(struct seq_file * m,struct cache_detail * cd,struct cache_head * h)177 static int nfs_dns_show(struct seq_file *m, struct cache_detail *cd,
178 		struct cache_head *h)
179 {
180 	struct nfs_dns_ent *item;
181 	long ttl;
182 
183 	if (h == NULL) {
184 		seq_puts(m, "# ip address      hostname        ttl\n");
185 		return 0;
186 	}
187 	item = container_of(h, struct nfs_dns_ent, h);
188 	ttl = item->h.expiry_time - seconds_since_boot();
189 	if (ttl < 0)
190 		ttl = 0;
191 
192 	if (!test_bit(CACHE_NEGATIVE, &h->flags)) {
193 		char buf[INET6_ADDRSTRLEN+IPV6_SCOPE_ID_LEN+1];
194 
195 		rpc_ntop((struct sockaddr *)&item->addr, buf, sizeof(buf));
196 		seq_printf(m, "%15s ", buf);
197 	} else
198 		seq_puts(m, "<none>          ");
199 	seq_printf(m, "%15s %ld\n", item->hostname, ttl);
200 	return 0;
201 }
202 
nfs_dns_lookup(struct cache_detail * cd,struct nfs_dns_ent * key)203 static struct nfs_dns_ent *nfs_dns_lookup(struct cache_detail *cd,
204 		struct nfs_dns_ent *key)
205 {
206 	struct cache_head *ch;
207 
208 	ch = sunrpc_cache_lookup_rcu(cd,
209 			&key->h,
210 			nfs_dns_hash(key));
211 	if (!ch)
212 		return NULL;
213 	return container_of(ch, struct nfs_dns_ent, h);
214 }
215 
nfs_dns_update(struct cache_detail * cd,struct nfs_dns_ent * new,struct nfs_dns_ent * key)216 static struct nfs_dns_ent *nfs_dns_update(struct cache_detail *cd,
217 		struct nfs_dns_ent *new,
218 		struct nfs_dns_ent *key)
219 {
220 	struct cache_head *ch;
221 
222 	ch = sunrpc_cache_update(cd,
223 			&new->h, &key->h,
224 			nfs_dns_hash(key));
225 	if (!ch)
226 		return NULL;
227 	return container_of(ch, struct nfs_dns_ent, h);
228 }
229 
nfs_dns_parse(struct cache_detail * cd,char * buf,int buflen)230 static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
231 {
232 	char buf1[NFS_DNS_HOSTNAME_MAXLEN+1];
233 	struct nfs_dns_ent key, *item;
234 	unsigned int ttl;
235 	ssize_t len;
236 	int ret = -EINVAL;
237 
238 	if (buf[buflen-1] != '\n')
239 		goto out;
240 	buf[buflen-1] = '\0';
241 
242 	len = qword_get(&buf, buf1, sizeof(buf1));
243 	if (len <= 0)
244 		goto out;
245 	key.addrlen = rpc_pton(cd->net, buf1, len,
246 			(struct sockaddr *)&key.addr,
247 			sizeof(key.addr));
248 
249 	len = qword_get(&buf, buf1, sizeof(buf1));
250 	if (len <= 0)
251 		goto out;
252 
253 	key.hostname = buf1;
254 	key.namelen = len;
255 	memset(&key.h, 0, sizeof(key.h));
256 
257 	if (get_uint(&buf, &ttl) < 0)
258 		goto out;
259 	if (ttl == 0)
260 		goto out;
261 	key.h.expiry_time = ttl + seconds_since_boot();
262 
263 	ret = -ENOMEM;
264 	item = nfs_dns_lookup(cd, &key);
265 	if (item == NULL)
266 		goto out;
267 
268 	if (key.addrlen == 0)
269 		set_bit(CACHE_NEGATIVE, &key.h.flags);
270 
271 	item = nfs_dns_update(cd, &key, item);
272 	if (item == NULL)
273 		goto out;
274 
275 	ret = 0;
276 	cache_put(&item->h, cd);
277 out:
278 	return ret;
279 }
280 
do_cache_lookup(struct cache_detail * cd,struct nfs_dns_ent * key,struct nfs_dns_ent ** item,struct nfs_cache_defer_req * dreq)281 static int do_cache_lookup(struct cache_detail *cd,
282 		struct nfs_dns_ent *key,
283 		struct nfs_dns_ent **item,
284 		struct nfs_cache_defer_req *dreq)
285 {
286 	int ret = -ENOMEM;
287 
288 	*item = nfs_dns_lookup(cd, key);
289 	if (*item) {
290 		ret = cache_check(cd, &(*item)->h, &dreq->req);
291 		if (ret)
292 			*item = NULL;
293 	}
294 	return ret;
295 }
296 
do_cache_lookup_nowait(struct cache_detail * cd,struct nfs_dns_ent * key,struct nfs_dns_ent ** item)297 static int do_cache_lookup_nowait(struct cache_detail *cd,
298 		struct nfs_dns_ent *key,
299 		struct nfs_dns_ent **item)
300 {
301 	int ret = -ENOMEM;
302 
303 	*item = nfs_dns_lookup(cd, key);
304 	if (!*item)
305 		goto out_err;
306 	ret = -ETIMEDOUT;
307 	if (!test_bit(CACHE_VALID, &(*item)->h.flags)
308 			|| (*item)->h.expiry_time < seconds_since_boot()
309 			|| cd->flush_time > (*item)->h.last_refresh)
310 		goto out_put;
311 	ret = -ENOENT;
312 	if (test_bit(CACHE_NEGATIVE, &(*item)->h.flags))
313 		goto out_put;
314 	return 0;
315 out_put:
316 	cache_put(&(*item)->h, cd);
317 out_err:
318 	*item = NULL;
319 	return ret;
320 }
321 
do_cache_lookup_wait(struct cache_detail * cd,struct nfs_dns_ent * key,struct nfs_dns_ent ** item)322 static int do_cache_lookup_wait(struct cache_detail *cd,
323 		struct nfs_dns_ent *key,
324 		struct nfs_dns_ent **item)
325 {
326 	struct nfs_cache_defer_req *dreq;
327 	int ret = -ENOMEM;
328 
329 	dreq = nfs_cache_defer_req_alloc();
330 	if (!dreq)
331 		goto out;
332 	ret = do_cache_lookup(cd, key, item, dreq);
333 	if (ret == -EAGAIN) {
334 		ret = nfs_cache_wait_for_upcall(dreq);
335 		if (!ret)
336 			ret = do_cache_lookup_nowait(cd, key, item);
337 	}
338 	nfs_cache_defer_req_put(dreq);
339 out:
340 	return ret;
341 }
342 
nfs_dns_resolve_name(struct net * net,char * name,size_t namelen,struct sockaddr * sa,size_t salen)343 ssize_t nfs_dns_resolve_name(struct net *net, char *name,
344 		size_t namelen, struct sockaddr *sa, size_t salen)
345 {
346 	struct nfs_dns_ent key = {
347 		.hostname = name,
348 		.namelen = namelen,
349 	};
350 	struct nfs_dns_ent *item = NULL;
351 	ssize_t ret;
352 	struct nfs_net *nn = net_generic(net, nfs_net_id);
353 
354 	ret = do_cache_lookup_wait(nn->nfs_dns_resolve, &key, &item);
355 	if (ret == 0) {
356 		if (salen >= item->addrlen) {
357 			memcpy(sa, &item->addr, item->addrlen);
358 			ret = item->addrlen;
359 		} else
360 			ret = -EOVERFLOW;
361 		cache_put(&item->h, nn->nfs_dns_resolve);
362 	} else if (ret == -ENOENT)
363 		ret = -ESRCH;
364 	return ret;
365 }
366 
367 static struct cache_detail nfs_dns_resolve_template = {
368 	.owner		= THIS_MODULE,
369 	.hash_size	= NFS_DNS_HASHTBL_SIZE,
370 	.name		= "dns_resolve",
371 	.cache_put	= nfs_dns_ent_put,
372 	.cache_upcall	= nfs_dns_upcall,
373 	.cache_request	= nfs_dns_request,
374 	.cache_parse	= nfs_dns_parse,
375 	.cache_show	= nfs_dns_show,
376 	.match		= nfs_dns_match,
377 	.init		= nfs_dns_ent_init,
378 	.update		= nfs_dns_ent_update,
379 	.alloc		= nfs_dns_ent_alloc,
380 };
381 
382 
nfs_dns_resolver_cache_init(struct net * net)383 int nfs_dns_resolver_cache_init(struct net *net)
384 {
385 	int err;
386 	struct nfs_net *nn = net_generic(net, nfs_net_id);
387 
388 	nn->nfs_dns_resolve = cache_create_net(&nfs_dns_resolve_template, net);
389 	if (IS_ERR(nn->nfs_dns_resolve))
390 		return PTR_ERR(nn->nfs_dns_resolve);
391 
392 	err = nfs_cache_register_net(net, nn->nfs_dns_resolve);
393 	if (err)
394 		goto err_reg;
395 	return 0;
396 
397 err_reg:
398 	cache_destroy_net(nn->nfs_dns_resolve, net);
399 	return err;
400 }
401 
nfs_dns_resolver_cache_destroy(struct net * net)402 void nfs_dns_resolver_cache_destroy(struct net *net)
403 {
404 	struct nfs_net *nn = net_generic(net, nfs_net_id);
405 
406 	nfs_cache_unregister_net(net, nn->nfs_dns_resolve);
407 	cache_destroy_net(nn->nfs_dns_resolve, net);
408 }
409 
nfs4_dns_net_init(struct net * net)410 static int nfs4_dns_net_init(struct net *net)
411 {
412 	return nfs_dns_resolver_cache_init(net);
413 }
414 
nfs4_dns_net_exit(struct net * net)415 static void nfs4_dns_net_exit(struct net *net)
416 {
417 	nfs_dns_resolver_cache_destroy(net);
418 }
419 
420 static struct pernet_operations nfs4_dns_resolver_ops = {
421 	.init = nfs4_dns_net_init,
422 	.exit = nfs4_dns_net_exit,
423 };
424 
rpc_pipefs_event(struct notifier_block * nb,unsigned long event,void * ptr)425 static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
426 			   void *ptr)
427 {
428 	struct super_block *sb = ptr;
429 	struct net *net = sb->s_fs_info;
430 	struct nfs_net *nn = net_generic(net, nfs_net_id);
431 	struct cache_detail *cd = nn->nfs_dns_resolve;
432 	int ret = 0;
433 
434 	if (cd == NULL)
435 		return 0;
436 
437 	if (!try_module_get(THIS_MODULE))
438 		return 0;
439 
440 	switch (event) {
441 	case RPC_PIPEFS_MOUNT:
442 		ret = nfs_cache_register_sb(sb, cd);
443 		break;
444 	case RPC_PIPEFS_UMOUNT:
445 		nfs_cache_unregister_sb(sb, cd);
446 		break;
447 	default:
448 		ret = -ENOTSUPP;
449 		break;
450 	}
451 	module_put(THIS_MODULE);
452 	return ret;
453 }
454 
455 static struct notifier_block nfs_dns_resolver_block = {
456 	.notifier_call	= rpc_pipefs_event,
457 };
458 
nfs_dns_resolver_init(void)459 int nfs_dns_resolver_init(void)
460 {
461 	int err;
462 
463 	err = register_pernet_subsys(&nfs4_dns_resolver_ops);
464 	if (err < 0)
465 		goto out;
466 	err = rpc_pipefs_notifier_register(&nfs_dns_resolver_block);
467 	if (err < 0)
468 		goto out1;
469 	return 0;
470 out1:
471 	unregister_pernet_subsys(&nfs4_dns_resolver_ops);
472 out:
473 	return err;
474 }
475 
nfs_dns_resolver_destroy(void)476 void nfs_dns_resolver_destroy(void)
477 {
478 	rpc_pipefs_notifier_unregister(&nfs_dns_resolver_block);
479 	unregister_pernet_subsys(&nfs4_dns_resolver_ops);
480 }
481 #endif
482