[PATCH] genetlink: don't touch module ref count
[linux-3.10.git] / net / netlink / genetlink.c
1 /*
2  * NETLINK      Generic Netlink Family
3  *
4  *              Authors:        Jamal Hadi Salim
5  *                              Thomas Graf <tgraf@suug.ch>
6  */
7
8 #include <linux/config.h>
9 #include <linux/module.h>
10 #include <linux/kernel.h>
11 #include <linux/errno.h>
12 #include <linux/types.h>
13 #include <linux/socket.h>
14 #include <linux/string.h>
15 #include <linux/skbuff.h>
16 #include <net/sock.h>
17 #include <net/genetlink.h>
18
19 struct sock *genl_sock = NULL;
20
21 static DECLARE_MUTEX(genl_sem); /* serialization of message processing */
22
23 static void genl_lock(void)
24 {
25         down(&genl_sem);
26 }
27
28 static int genl_trylock(void)
29 {
30         return down_trylock(&genl_sem);
31 }
32
33 static void genl_unlock(void)
34 {
35         up(&genl_sem);
36
37         if (genl_sock && genl_sock->sk_receive_queue.qlen)
38                 genl_sock->sk_data_ready(genl_sock, 0);
39 }
40
41 #define GENL_FAM_TAB_SIZE       16
42 #define GENL_FAM_TAB_MASK       (GENL_FAM_TAB_SIZE - 1)
43
44 static struct list_head family_ht[GENL_FAM_TAB_SIZE];
45
46 static int genl_ctrl_event(int event, void *data);
47
48 static inline unsigned int genl_family_hash(unsigned int id)
49 {
50         return id & GENL_FAM_TAB_MASK;
51 }
52
53 static inline struct list_head *genl_family_chain(unsigned int id)
54 {
55         return &family_ht[genl_family_hash(id)];
56 }
57
58 static struct genl_family *genl_family_find_byid(unsigned int id)
59 {
60         struct genl_family *f;
61
62         list_for_each_entry(f, genl_family_chain(id), family_list)
63                 if (f->id == id)
64                         return f;
65
66         return NULL;
67 }
68
69 static struct genl_family *genl_family_find_byname(char *name)
70 {
71         struct genl_family *f;
72         int i;
73
74         for (i = 0; i < GENL_FAM_TAB_SIZE; i++)
75                 list_for_each_entry(f, genl_family_chain(i), family_list)
76                         if (strcmp(f->name, name) == 0)
77                                 return f;
78
79         return NULL;
80 }
81
82 static struct genl_ops *genl_get_cmd(u8 cmd, struct genl_family *family)
83 {
84         struct genl_ops *ops;
85
86         list_for_each_entry(ops, &family->ops_list, ops_list)
87                 if (ops->cmd == cmd)
88                         return ops;
89
90         return NULL;
91 }
92
93 /* Of course we are going to have problems once we hit
94  * 2^16 alive types, but that can only happen by year 2K
95 */
96 static inline u16 genl_generate_id(void)
97 {
98         static u16 id_gen_idx;
99         int overflowed = 0;
100
101         do {
102                 if (id_gen_idx == 0)
103                         id_gen_idx = GENL_MIN_ID;
104
105                 if (++id_gen_idx > GENL_MAX_ID) {
106                         if (!overflowed) {
107                                 overflowed = 1;
108                                 id_gen_idx = 0;
109                                 continue;
110                         } else
111                                 return 0;
112                 }
113
114         } while (genl_family_find_byid(id_gen_idx));
115
116         return id_gen_idx;
117 }
118
119 /**
120  * genl_register_ops - register generic netlink operations
121  * @family: generic netlink family
122  * @ops: operations to be registered
123  *
124  * Registers the specified operations and assigns them to the specified
125  * family. Either a doit or dumpit callback must be specified or the
126  * operation will fail. Only one operation structure per command
127  * identifier may be registered.
128  *
129  * See include/net/genetlink.h for more documenation on the operations
130  * structure.
131  *
132  * Returns 0 on success or a negative error code.
133  */
134 int genl_register_ops(struct genl_family *family, struct genl_ops *ops)
135 {
136         int err = -EINVAL;
137
138         if (ops->dumpit == NULL && ops->doit == NULL)
139                 goto errout;
140
141         if (genl_get_cmd(ops->cmd, family)) {
142                 err = -EEXIST;
143                 goto errout;
144         }
145
146         genl_lock();
147         list_add_tail(&ops->ops_list, &family->ops_list);
148         genl_unlock();
149
150         genl_ctrl_event(CTRL_CMD_NEWOPS, ops);
151         err = 0;
152 errout:
153         return err;
154 }
155
156 /**
157  * genl_unregister_ops - unregister generic netlink operations
158  * @family: generic netlink family
159  * @ops: operations to be unregistered
160  *
161  * Unregisters the specified operations and unassigns them from the
162  * specified family. The operation blocks until the current message
163  * processing has finished and doesn't start again until the
164  * unregister process has finished.
165  *
166  * Note: It is not necessary to unregister all operations before
167  *       unregistering the family, unregistering the family will cause
168  *       all assigned operations to be unregistered automatically.
169  *
170  * Returns 0 on success or a negative error code.
171  */
172 int genl_unregister_ops(struct genl_family *family, struct genl_ops *ops)
173 {
174         struct genl_ops *rc;
175
176         genl_lock();
177         list_for_each_entry(rc, &family->ops_list, ops_list) {
178                 if (rc == ops) {
179                         list_del(&ops->ops_list);
180                         genl_unlock();
181                         genl_ctrl_event(CTRL_CMD_DELOPS, ops);
182                         return 0;
183                 }
184         }
185         genl_unlock();
186
187         return -ENOENT;
188 }
189
190 /**
191  * genl_register_family - register a generic netlink family
192  * @family: generic netlink family
193  *
194  * Registers the specified family after validating it first. Only one
195  * family may be registered with the same family name or identifier.
196  * The family id may equal GENL_ID_GENERATE causing an unique id to
197  * be automatically generated and assigned.
198  *
199  * Return 0 on success or a negative error code.
200  */
201 int genl_register_family(struct genl_family *family)
202 {
203         int err = -EINVAL;
204
205         if (family->id && family->id < GENL_MIN_ID)
206                 goto errout;
207
208         if (family->id > GENL_MAX_ID)
209                 goto errout;
210
211         INIT_LIST_HEAD(&family->ops_list);
212
213         genl_lock();
214
215         if (genl_family_find_byname(family->name)) {
216                 err = -EEXIST;
217                 goto errout_locked;
218         }
219
220         if (genl_family_find_byid(family->id)) {
221                 err = -EEXIST;
222                 goto errout_locked;
223         }
224
225         if (family->id == GENL_ID_GENERATE) {
226                 u16 newid = genl_generate_id();
227
228                 if (!newid) {
229                         err = -ENOMEM;
230                         goto errout_locked;
231                 }
232
233                 family->id = newid;
234         }
235
236         if (family->maxattr) {
237                 family->attrbuf = kmalloc((family->maxattr+1) *
238                                         sizeof(struct nlattr *), GFP_KERNEL);
239                 if (family->attrbuf == NULL) {
240                         err = -ENOMEM;
241                         goto errout;
242                 }
243         } else
244                 family->attrbuf = NULL;
245
246         list_add_tail(&family->family_list, genl_family_chain(family->id));
247         genl_unlock();
248
249         genl_ctrl_event(CTRL_CMD_NEWFAMILY, family);
250
251         return 0;
252
253 errout_locked:
254         genl_unlock();
255 errout:
256         return err;
257 }
258
259 /**
260  * genl_unregister_family - unregister generic netlink family
261  * @family: generic netlink family
262  *
263  * Unregisters the specified family.
264  *
265  * Returns 0 on success or a negative error code.
266  */
267 int genl_unregister_family(struct genl_family *family)
268 {
269         struct genl_family *rc;
270
271         genl_lock();
272
273         list_for_each_entry(rc, genl_family_chain(family->id), family_list) {
274                 if (family->id != rc->id || strcmp(rc->name, family->name))
275                         continue;
276
277                 list_del(&rc->family_list);
278                 INIT_LIST_HEAD(&family->ops_list);
279                 genl_unlock();
280
281                 kfree(family->attrbuf);
282                 genl_ctrl_event(CTRL_CMD_DELFAMILY, family);
283                 return 0;
284         }
285
286         genl_unlock();
287
288         return -ENOENT;
289 }
290
291 static inline int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
292                                int *errp)
293 {
294         struct genl_ops *ops;
295         struct genl_family *family;
296         struct genl_info info;
297         struct genlmsghdr *hdr = nlmsg_data(nlh);
298         int hdrlen, err = -EINVAL;
299
300         if (!(nlh->nlmsg_flags & NLM_F_REQUEST))
301                 goto ignore;
302
303         if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
304                 goto ignore;
305
306         family = genl_family_find_byid(nlh->nlmsg_type);
307         if (family == NULL) {
308                 err = -ENOENT;
309                 goto errout;
310         }
311
312         hdrlen = GENL_HDRLEN + family->hdrsize;
313         if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
314                 goto errout;
315
316         ops = genl_get_cmd(hdr->cmd, family);
317         if (ops == NULL) {
318                 err = -EOPNOTSUPP;
319                 goto errout;
320         }
321
322         if ((ops->flags & GENL_ADMIN_PERM) && security_netlink_recv(skb)) {
323                 err = -EPERM;
324                 goto errout;
325         }
326
327         if (nlh->nlmsg_flags & NLM_F_DUMP) {
328                 if (ops->dumpit == NULL) {
329                         err = -EOPNOTSUPP;
330                         goto errout;
331                 }
332
333                 *errp = err = netlink_dump_start(genl_sock, skb, nlh,
334                                                  ops->dumpit, NULL);
335                 if (err == 0)
336                         skb_pull(skb, min(NLMSG_ALIGN(nlh->nlmsg_len),
337                                           skb->len));
338                 return -1;
339         }
340
341         if (ops->doit == NULL) {
342                 err = -EOPNOTSUPP;
343                 goto errout;
344         }
345
346         if (family->attrbuf) {
347                 err = nlmsg_parse(nlh, hdrlen, family->attrbuf, family->maxattr,
348                                   ops->policy);
349                 if (err < 0)
350                         goto errout;
351         }
352
353         info.snd_seq = nlh->nlmsg_seq;
354         info.snd_pid = NETLINK_CB(skb).pid;
355         info.nlhdr = nlh;
356         info.genlhdr = nlmsg_data(nlh);
357         info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
358         info.attrs = family->attrbuf;
359
360         *errp = err = ops->doit(skb, &info);
361         return err;
362
363 ignore:
364         return 0;
365
366 errout:
367         *errp = err;
368         return -1;
369 }
370
371 static void genl_rcv(struct sock *sk, int len)
372 {
373         unsigned int qlen = 0;
374
375         do {
376                 if (genl_trylock())
377                         return;
378                 netlink_run_queue(sk, &qlen, &genl_rcv_msg);
379                 genl_unlock();
380         } while (qlen && genl_sock && genl_sock->sk_receive_queue.qlen);
381 }
382
383 /**************************************************************************
384  * Controller
385  **************************************************************************/
386
387 static int ctrl_fill_info(struct genl_family *family, u32 pid, u32 seq,
388                           u32 flags, struct sk_buff *skb, u8 cmd)
389 {
390         void *hdr;
391
392         hdr = genlmsg_put(skb, pid, seq, GENL_ID_CTRL, 0, flags, cmd,
393                           family->version);
394         if (hdr == NULL)
395                 return -1;
396
397         NLA_PUT_STRING(skb, CTRL_ATTR_FAMILY_NAME, family->name);
398         NLA_PUT_U16(skb, CTRL_ATTR_FAMILY_ID, family->id);
399
400         return genlmsg_end(skb, hdr);
401
402 nla_put_failure:
403         return genlmsg_cancel(skb, hdr);
404 }
405
406 static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
407 {
408
409         int i, n = 0;
410         struct genl_family *rt;
411         int chains_to_skip = cb->args[0];
412         int fams_to_skip = cb->args[1];
413
414         for (i = 0; i < GENL_FAM_TAB_SIZE; i++) {
415                 if (i < chains_to_skip)
416                         continue;
417                 n = 0;
418                 list_for_each_entry(rt, genl_family_chain(i), family_list) {
419                         if (++n < fams_to_skip)
420                                 continue;
421                         if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).pid,
422                                            cb->nlh->nlmsg_seq, NLM_F_MULTI,
423                                            skb, CTRL_CMD_NEWFAMILY) < 0)
424                                 goto errout;
425                 }
426
427                 fams_to_skip = 0;
428         }
429
430 errout:
431         cb->args[0] = i;
432         cb->args[1] = n;
433
434         return skb->len;
435 }
436
437 static struct sk_buff *ctrl_build_msg(struct genl_family *family, u32 pid,
438                                       int seq, u8 cmd)
439 {
440         struct sk_buff *skb;
441         int err;
442
443         skb = nlmsg_new(NLMSG_GOODSIZE);
444         if (skb == NULL)
445                 return ERR_PTR(-ENOBUFS);
446
447         err = ctrl_fill_info(family, pid, seq, 0, skb, cmd);
448         if (err < 0) {
449                 nlmsg_free(skb);
450                 return ERR_PTR(err);
451         }
452
453         return skb;
454 }
455
456 static struct nla_policy ctrl_policy[CTRL_ATTR_MAX+1] __read_mostly = {
457         [CTRL_ATTR_FAMILY_ID]   = { .type = NLA_U16 },
458         [CTRL_ATTR_FAMILY_NAME] = { .type = NLA_STRING },
459 };
460
461 static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
462 {
463         struct sk_buff *msg;
464         struct genl_family *res = NULL;
465         int err = -EINVAL;
466
467         if (info->attrs[CTRL_ATTR_FAMILY_ID]) {
468                 u16 id = nla_get_u16(info->attrs[CTRL_ATTR_FAMILY_ID]);
469                 res = genl_family_find_byid(id);
470         }
471
472         if (info->attrs[CTRL_ATTR_FAMILY_NAME]) {
473                 char name[GENL_NAMSIZ];
474
475                 if (nla_strlcpy(name, info->attrs[CTRL_ATTR_FAMILY_NAME],
476                                 GENL_NAMSIZ) >= GENL_NAMSIZ)
477                         goto errout;
478
479                 res = genl_family_find_byname(name);
480         }
481
482         if (res == NULL) {
483                 err = -ENOENT;
484                 goto errout;
485         }
486
487         msg = ctrl_build_msg(res, info->snd_pid, info->snd_seq,
488                              CTRL_CMD_NEWFAMILY);
489         if (IS_ERR(msg)) {
490                 err = PTR_ERR(msg);
491                 goto errout;
492         }
493
494         err = genlmsg_unicast(msg, info->snd_pid);
495 errout:
496         return err;
497 }
498
499 static int genl_ctrl_event(int event, void *data)
500 {
501         struct sk_buff *msg;
502
503         if (genl_sock == NULL)
504                 return 0;
505
506         switch (event) {
507         case CTRL_CMD_NEWFAMILY:
508         case CTRL_CMD_DELFAMILY:
509                 msg = ctrl_build_msg(data, 0, 0, event);
510                 if (IS_ERR(msg))
511                         return PTR_ERR(msg);
512
513                 genlmsg_multicast(msg, 0, GENL_ID_CTRL);
514                 break;
515         }
516
517         return 0;
518 }
519
520 static struct genl_ops genl_ctrl_ops = {
521         .cmd            = CTRL_CMD_GETFAMILY,
522         .doit           = ctrl_getfamily,
523         .dumpit         = ctrl_dumpfamily,
524         .policy         = ctrl_policy,
525 };
526
527 static struct genl_family genl_ctrl = {
528         .id = GENL_ID_CTRL,
529         .name = "nlctrl",
530         .version = 0x1,
531         .maxattr = CTRL_ATTR_MAX,
532 };
533
534 static int __init genl_init(void)
535 {
536         int i, err;
537
538         for (i = 0; i < GENL_FAM_TAB_SIZE; i++)
539                 INIT_LIST_HEAD(&family_ht[i]);
540
541         err = genl_register_family(&genl_ctrl);
542         if (err < 0)
543                 goto errout;
544
545         err = genl_register_ops(&genl_ctrl, &genl_ctrl_ops);
546         if (err < 0)
547                 goto errout_register;
548
549         netlink_set_nonroot(NETLINK_GENERIC, NL_NONROOT_RECV);
550         genl_sock = netlink_kernel_create(NETLINK_GENERIC, GENL_MAX_ID,
551                                           genl_rcv, THIS_MODULE);
552         if (genl_sock == NULL) {
553                 panic("GENL: Cannot initialize generic netlink\n");
554                 return -ENOMEM;
555         }
556
557         return 0;
558
559 errout_register:
560         genl_unregister_family(&genl_ctrl);
561 errout:
562         panic("GENL: Cannot register controller: %d\n", err);
563         return err;
564 }
565
566 subsys_initcall(genl_init);
567
568 EXPORT_SYMBOL(genl_sock);
569 EXPORT_SYMBOL(genl_register_ops);
570 EXPORT_SYMBOL(genl_unregister_ops);
571 EXPORT_SYMBOL(genl_register_family);
572 EXPORT_SYMBOL(genl_unregister_family);