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

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