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Linux/fs/nfs/dns_resolve.c

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

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