xref: /freebsd/sys/net/pfil.c (revision c7046f76)
1 /*	$FreeBSD$ */
2 /*	$NetBSD: pfil.c,v 1.20 2001/11/12 23:49:46 lukem Exp $	*/
3 
4 /*-
5  * SPDX-License-Identifier: BSD-3-Clause
6  *
7  * Copyright (c) 2019 Gleb Smirnoff <glebius@FreeBSD.org>
8  * Copyright (c) 1996 Matthew R. Green
9  * All rights reserved.
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions
13  * are met:
14  * 1. Redistributions of source code must retain the above copyright
15  *    notice, this list of conditions and the following disclaimer.
16  * 2. Redistributions in binary form must reproduce the above copyright
17  *    notice, this list of conditions and the following disclaimer in the
18  *    documentation and/or other materials provided with the distribution.
19  * 3. The name of the author may not be used to endorse or promote products
20  *    derived from this software without specific prior written permission.
21  *
22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
26  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32  * SUCH DAMAGE.
33  */
34 
35 #include <sys/param.h>
36 #include <sys/conf.h>
37 #include <sys/kernel.h>
38 #include <sys/epoch.h>
39 #include <sys/errno.h>
40 #include <sys/lock.h>
41 #include <sys/malloc.h>
42 #include <sys/socket.h>
43 #include <sys/socketvar.h>
44 #include <sys/systm.h>
45 #include <sys/lock.h>
46 #include <sys/mutex.h>
47 #include <sys/proc.h>
48 #include <sys/queue.h>
49 #include <sys/ucred.h>
50 #include <sys/jail.h>
51 
52 #include <net/if.h>
53 #include <net/if_var.h>
54 #include <net/pfil.h>
55 
56 static MALLOC_DEFINE(M_PFIL, "pfil", "pfil(9) packet filter hooks");
57 
58 static int pfil_ioctl(struct cdev *, u_long, caddr_t, int, struct thread *);
59 static struct cdevsw pfil_cdevsw = {
60 	.d_ioctl =	pfil_ioctl,
61 	.d_name =	PFILDEV,
62 	.d_version =	D_VERSION,
63 };
64 static struct cdev *pfil_dev;
65 
66 static struct mtx pfil_lock;
67 MTX_SYSINIT(pfil_mtxinit, &pfil_lock, "pfil(9) lock", MTX_DEF);
68 #define	PFIL_LOCK()	mtx_lock(&pfil_lock)
69 #define	PFIL_UNLOCK()	mtx_unlock(&pfil_lock)
70 #define	PFIL_LOCK_ASSERT()	mtx_assert(&pfil_lock, MA_OWNED)
71 
72 struct pfil_hook {
73 	pfil_func_t	 hook_func;
74 	void		*hook_ruleset;
75 	int		 hook_flags;
76 	int		 hook_links;
77 	enum pfil_types	 hook_type;
78 	const char	*hook_modname;
79 	const char	*hook_rulname;
80 	LIST_ENTRY(pfil_hook) hook_list;
81 };
82 
83 struct pfil_link {
84 	CK_STAILQ_ENTRY(pfil_link) link_chain;
85 	pfil_func_t		 link_func;
86 	void			*link_ruleset;
87 	int			 link_flags;
88 	struct pfil_hook	*link_hook;
89 	struct epoch_context	 link_epoch_ctx;
90 };
91 
92 typedef CK_STAILQ_HEAD(pfil_chain, pfil_link)	pfil_chain_t;
93 struct pfil_head {
94 	int		 head_nhooksin;
95 	int		 head_nhooksout;
96 	pfil_chain_t	 head_in;
97 	pfil_chain_t	 head_out;
98 	int		 head_flags;
99 	enum pfil_types	 head_type;
100 	LIST_ENTRY(pfil_head) head_list;
101 	const char	*head_name;
102 };
103 
104 LIST_HEAD(pfilheadhead, pfil_head);
105 VNET_DEFINE_STATIC(struct pfilheadhead, pfil_head_list) =
106     LIST_HEAD_INITIALIZER(pfil_head_list);
107 #define	V_pfil_head_list	VNET(pfil_head_list)
108 
109 LIST_HEAD(pfilhookhead, pfil_hook);
110 VNET_DEFINE_STATIC(struct pfilhookhead, pfil_hook_list) =
111     LIST_HEAD_INITIALIZER(pfil_hook_list);
112 #define	V_pfil_hook_list	VNET(pfil_hook_list)
113 
114 static struct pfil_link *pfil_link_remove(pfil_chain_t *, pfil_hook_t );
115 static void pfil_link_free(epoch_context_t);
116 
117 int
118 pfil_realloc(pfil_packet_t *p, int flags, struct ifnet *ifp)
119 {
120 	struct mbuf *m;
121 
122 	MPASS(flags & PFIL_MEMPTR);
123 
124 	if ((m = m_devget(p->mem, PFIL_LENGTH(flags), 0, ifp, NULL)) == NULL)
125 		return (ENOMEM);
126 	*p = pfil_packet_align(*p);
127 	*p->m = m;
128 
129 	return (0);
130 }
131 
132 static __noinline int
133 pfil_fake_mbuf(pfil_func_t func, pfil_packet_t *p, struct ifnet *ifp, int flags,
134     void *ruleset, struct inpcb *inp)
135 {
136 	struct mbuf m, *mp;
137 	pfil_return_t rv;
138 
139 	(void)m_init(&m, M_NOWAIT, MT_DATA, M_NOFREE | M_PKTHDR);
140 	m_extadd(&m, p->mem, PFIL_LENGTH(flags), NULL, NULL, NULL, 0,
141 	    EXT_RXRING);
142 	m.m_len = m.m_pkthdr.len = PFIL_LENGTH(flags);
143 	mp = &m;
144 	flags &= ~(PFIL_MEMPTR | PFIL_LENMASK);
145 
146 	rv = func(&mp, ifp, flags, ruleset, inp);
147 	if (rv == PFIL_PASS && mp != &m) {
148 		/*
149 		 * Firewalls that need pfil_fake_mbuf() most likely don't
150 		 * know they need return PFIL_REALLOCED.
151 		 */
152 		rv = PFIL_REALLOCED;
153 		*p = pfil_packet_align(*p);
154 		*p->m = mp;
155 	}
156 
157 	return (rv);
158 }
159 
160 /*
161  * pfil_run_hooks() runs the specified packet filter hook chain.
162  */
163 int
164 pfil_run_hooks(struct pfil_head *head, pfil_packet_t p, struct ifnet *ifp,
165     int flags, struct inpcb *inp)
166 {
167 	pfil_chain_t *pch;
168 	struct pfil_link *link;
169 	pfil_return_t rv;
170 	bool realloc = false;
171 
172 	NET_EPOCH_ASSERT();
173 
174 	if (PFIL_DIR(flags) == PFIL_IN)
175 		pch = &head->head_in;
176 	else if (__predict_true(PFIL_DIR(flags) == PFIL_OUT))
177 		pch = &head->head_out;
178 	else
179 		panic("%s: bogus flags %d", __func__, flags);
180 
181 	rv = PFIL_PASS;
182 	CK_STAILQ_FOREACH(link, pch, link_chain) {
183 		if ((flags & PFIL_MEMPTR) && !(link->link_flags & PFIL_MEMPTR))
184 			rv = pfil_fake_mbuf(link->link_func, &p, ifp, flags,
185 			    link->link_ruleset, inp);
186 		else
187 			rv = (*link->link_func)(p, ifp, flags,
188 			    link->link_ruleset, inp);
189 		if (rv == PFIL_DROPPED || rv == PFIL_CONSUMED)
190 			break;
191 		else if (rv == PFIL_REALLOCED) {
192 			flags &= ~(PFIL_MEMPTR | PFIL_LENMASK);
193 			realloc = true;
194 		}
195 	}
196 	if (realloc && rv == PFIL_PASS)
197 		rv = PFIL_REALLOCED;
198 	return (rv);
199 }
200 
201 static __always_inline int
202 pfil_mbuf_common(pfil_chain_t *pch, pfil_packet_t p, struct ifnet *ifp,
203     int flags, struct inpcb *inp)
204 {
205 	struct pfil_link *link;
206 	pfil_return_t rv;
207 
208 	NET_EPOCH_ASSERT();
209 	KASSERT(flags == PFIL_IN || flags == PFIL_OUT,
210 	    ("%s: unsupported flags %d", __func__, flags));
211 
212 	rv = PFIL_PASS;
213 	CK_STAILQ_FOREACH(link, pch, link_chain) {
214 		rv = (*link->link_func)(p, ifp, flags, link->link_ruleset, inp);
215 		if (rv == PFIL_DROPPED || rv == PFIL_CONSUMED)
216 			break;
217 	}
218 	return (rv);
219 }
220 
221 int
222 pfil_mbuf_in(struct pfil_head *head, pfil_packet_t p, struct ifnet *ifp,
223    struct inpcb *inp)
224 {
225 
226 	return (pfil_mbuf_common(&head->head_in, p, ifp, PFIL_IN, inp));
227 }
228 
229 int
230 pfil_mbuf_out(struct pfil_head *head, pfil_packet_t p, struct ifnet *ifp,
231     struct inpcb *inp)
232 {
233 
234 	return (pfil_mbuf_common(&head->head_out, p, ifp, PFIL_OUT, inp));
235 }
236 
237 /*
238  * pfil_head_register() registers a pfil_head with the packet filter hook
239  * mechanism.
240  */
241 pfil_head_t
242 pfil_head_register(struct pfil_head_args *pa)
243 {
244 	struct pfil_head *head, *list;
245 
246 	MPASS(pa->pa_version == PFIL_VERSION);
247 
248 	head = malloc(sizeof(struct pfil_head), M_PFIL, M_WAITOK);
249 
250 	head->head_nhooksin = head->head_nhooksout = 0;
251 	head->head_flags = pa->pa_flags;
252 	head->head_type = pa->pa_type;
253 	head->head_name = pa->pa_headname;
254 	CK_STAILQ_INIT(&head->head_in);
255 	CK_STAILQ_INIT(&head->head_out);
256 
257 	PFIL_LOCK();
258 	LIST_FOREACH(list, &V_pfil_head_list, head_list)
259 		if (strcmp(pa->pa_headname, list->head_name) == 0) {
260 			printf("pfil: duplicate head \"%s\"\n",
261 			    pa->pa_headname);
262 		}
263 	LIST_INSERT_HEAD(&V_pfil_head_list, head, head_list);
264 	PFIL_UNLOCK();
265 
266 	return (head);
267 }
268 
269 /*
270  * pfil_head_unregister() removes a pfil_head from the packet filter hook
271  * mechanism.  The producer of the hook promises that all outstanding
272  * invocations of the hook have completed before it unregisters the hook.
273  */
274 void
275 pfil_head_unregister(pfil_head_t ph)
276 {
277 	struct pfil_link *link, *next;
278 
279 	PFIL_LOCK();
280 	LIST_REMOVE(ph, head_list);
281 
282 	CK_STAILQ_FOREACH_SAFE(link, &ph->head_in, link_chain, next) {
283 		link->link_hook->hook_links--;
284 		free(link, M_PFIL);
285 	}
286 	CK_STAILQ_FOREACH_SAFE(link, &ph->head_out, link_chain, next) {
287 		link->link_hook->hook_links--;
288 		free(link, M_PFIL);
289 	}
290 	PFIL_UNLOCK();
291 }
292 
293 pfil_hook_t
294 pfil_add_hook(struct pfil_hook_args *pa)
295 {
296 	struct pfil_hook *hook, *list;
297 
298 	MPASS(pa->pa_version == PFIL_VERSION);
299 
300 	hook = malloc(sizeof(struct pfil_hook), M_PFIL, M_WAITOK | M_ZERO);
301 	hook->hook_func = pa->pa_func;
302 	hook->hook_ruleset = pa->pa_ruleset;
303 	hook->hook_flags = pa->pa_flags;
304 	hook->hook_type = pa->pa_type;
305 	hook->hook_modname = pa->pa_modname;
306 	hook->hook_rulname = pa->pa_rulname;
307 
308 	PFIL_LOCK();
309 	LIST_FOREACH(list, &V_pfil_hook_list, hook_list)
310 		if (strcmp(pa->pa_modname, list->hook_modname) == 0 &&
311 		    strcmp(pa->pa_rulname, list->hook_rulname) == 0) {
312 			printf("pfil: duplicate hook \"%s:%s\"\n",
313 			    pa->pa_modname, pa->pa_rulname);
314 		}
315 	LIST_INSERT_HEAD(&V_pfil_hook_list, hook, hook_list);
316 	PFIL_UNLOCK();
317 
318 	return (hook);
319 }
320 
321 static int
322 pfil_unlink(struct pfil_link_args *pa, pfil_head_t head, pfil_hook_t hook)
323 {
324 	struct pfil_link *in, *out;
325 
326 	PFIL_LOCK_ASSERT();
327 
328 	if (pa->pa_flags & PFIL_IN) {
329 		in = pfil_link_remove(&head->head_in, hook);
330 		if (in != NULL) {
331 			head->head_nhooksin--;
332 			hook->hook_links--;
333 		}
334 	} else
335 		in = NULL;
336 	if (pa->pa_flags & PFIL_OUT) {
337 		out = pfil_link_remove(&head->head_out, hook);
338 		if (out != NULL) {
339 			head->head_nhooksout--;
340 			hook->hook_links--;
341 		}
342 	} else
343 		out = NULL;
344 	PFIL_UNLOCK();
345 
346 	if (in != NULL)
347 		NET_EPOCH_CALL(pfil_link_free, &in->link_epoch_ctx);
348 	if (out != NULL)
349 		NET_EPOCH_CALL(pfil_link_free, &out->link_epoch_ctx);
350 
351 	if (in == NULL && out == NULL)
352 		return (ENOENT);
353 	else
354 		return (0);
355 }
356 
357 int
358 pfil_link(struct pfil_link_args *pa)
359 {
360 	struct pfil_link *in, *out, *link;
361 	struct pfil_head *head;
362 	struct pfil_hook *hook;
363 	int error;
364 
365 	MPASS(pa->pa_version == PFIL_VERSION);
366 
367 	if ((pa->pa_flags & (PFIL_IN | PFIL_UNLINK)) == PFIL_IN)
368 		in = malloc(sizeof(*in), M_PFIL, M_WAITOK | M_ZERO);
369 	else
370 		in = NULL;
371 	if ((pa->pa_flags & (PFIL_OUT | PFIL_UNLINK)) == PFIL_OUT)
372 		out = malloc(sizeof(*out), M_PFIL, M_WAITOK | M_ZERO);
373 	else
374 		out = NULL;
375 
376 	PFIL_LOCK();
377 	if (pa->pa_flags & PFIL_HEADPTR)
378 		head = pa->pa_head;
379 	else
380 		LIST_FOREACH(head, &V_pfil_head_list, head_list)
381 			if (strcmp(pa->pa_headname, head->head_name) == 0)
382 				break;
383 	if (pa->pa_flags & PFIL_HOOKPTR)
384 		hook = pa->pa_hook;
385 	else
386 		LIST_FOREACH(hook, &V_pfil_hook_list, hook_list)
387 			if (strcmp(pa->pa_modname, hook->hook_modname) == 0 &&
388 			    strcmp(pa->pa_rulname, hook->hook_rulname) == 0)
389 				break;
390 	if (head == NULL || hook == NULL) {
391 		error = ENOENT;
392 		goto fail;
393 	}
394 
395 	if (pa->pa_flags & PFIL_UNLINK)
396 		return (pfil_unlink(pa, head, hook));
397 
398 	if (head->head_type != hook->hook_type ||
399 	    ((hook->hook_flags & pa->pa_flags) & ~head->head_flags)) {
400 		error = EINVAL;
401 		goto fail;
402 	}
403 
404 	if (pa->pa_flags & PFIL_IN)
405 		CK_STAILQ_FOREACH(link, &head->head_in, link_chain)
406 			if (link->link_hook == hook) {
407 				error = EEXIST;
408 				goto fail;
409 			}
410 	if (pa->pa_flags & PFIL_OUT)
411 		CK_STAILQ_FOREACH(link, &head->head_out, link_chain)
412 			if (link->link_hook == hook) {
413 				error = EEXIST;
414 				goto fail;
415 			}
416 
417 	if (pa->pa_flags & PFIL_IN) {
418 		in->link_hook = hook;
419 		in->link_func = hook->hook_func;
420 		in->link_flags = hook->hook_flags;
421 		in->link_ruleset = hook->hook_ruleset;
422 		if (pa->pa_flags & PFIL_APPEND)
423 			CK_STAILQ_INSERT_TAIL(&head->head_in, in, link_chain);
424 		else
425 			CK_STAILQ_INSERT_HEAD(&head->head_in, in, link_chain);
426 		hook->hook_links++;
427 		head->head_nhooksin++;
428 	}
429 	if (pa->pa_flags & PFIL_OUT) {
430 		out->link_hook = hook;
431 		out->link_func = hook->hook_func;
432 		out->link_flags = hook->hook_flags;
433 		out->link_ruleset = hook->hook_ruleset;
434 		if (pa->pa_flags & PFIL_APPEND)
435 			CK_STAILQ_INSERT_HEAD(&head->head_out, out, link_chain);
436 		else
437 			CK_STAILQ_INSERT_TAIL(&head->head_out, out, link_chain);
438 		hook->hook_links++;
439 		head->head_nhooksout++;
440 	}
441 	PFIL_UNLOCK();
442 
443 	return (0);
444 
445 fail:
446 	PFIL_UNLOCK();
447 	free(in, M_PFIL);
448 	free(out, M_PFIL);
449 	return (error);
450 }
451 
452 static void
453 pfil_link_free(epoch_context_t ctx)
454 {
455 	struct pfil_link *link;
456 
457 	link = __containerof(ctx, struct pfil_link, link_epoch_ctx);
458 	free(link, M_PFIL);
459 }
460 
461 /*
462  * pfil_remove_hook removes a filter from all filtering points.
463  */
464 void
465 pfil_remove_hook(pfil_hook_t hook)
466 {
467 	struct pfil_head *head;
468 	struct pfil_link *in, *out;
469 
470 	PFIL_LOCK();
471 	LIST_FOREACH(head, &V_pfil_head_list, head_list) {
472 retry:
473 		in = pfil_link_remove(&head->head_in, hook);
474 		if (in != NULL) {
475 			head->head_nhooksin--;
476 			hook->hook_links--;
477 			NET_EPOCH_CALL(pfil_link_free, &in->link_epoch_ctx);
478 		}
479 		out = pfil_link_remove(&head->head_out, hook);
480 		if (out != NULL) {
481 			head->head_nhooksout--;
482 			hook->hook_links--;
483 			NET_EPOCH_CALL(pfil_link_free, &out->link_epoch_ctx);
484 		}
485 		if (in != NULL || out != NULL)
486 			/* What if some stupid admin put same filter twice? */
487 			goto retry;
488 	}
489 	LIST_REMOVE(hook, hook_list);
490 	PFIL_UNLOCK();
491 	MPASS(hook->hook_links == 0);
492 	free(hook, M_PFIL);
493 }
494 
495 /*
496  * Internal: Remove a pfil hook from a hook chain.
497  */
498 static struct pfil_link *
499 pfil_link_remove(pfil_chain_t *chain, pfil_hook_t hook)
500 {
501 	struct pfil_link *link;
502 
503 	PFIL_LOCK_ASSERT();
504 
505 	CK_STAILQ_FOREACH(link, chain, link_chain)
506 		if (link->link_hook == hook) {
507 			CK_STAILQ_REMOVE(chain, link, pfil_link, link_chain);
508 			return (link);
509 		}
510 
511 	return (NULL);
512 }
513 
514 static void
515 pfil_init(const void *unused __unused)
516 {
517 	struct make_dev_args args;
518 	int error __diagused;
519 
520 	make_dev_args_init(&args);
521 	args.mda_flags = MAKEDEV_WAITOK | MAKEDEV_CHECKNAME;
522 	args.mda_devsw = &pfil_cdevsw;
523 	args.mda_uid = UID_ROOT;
524 	args.mda_gid = GID_WHEEL;
525 	args.mda_mode = 0600;
526 	error = make_dev_s(&args, &pfil_dev, PFILDEV);
527 	KASSERT(error == 0, ("%s: failed to create dev: %d", __func__, error));
528 }
529 /*
530  * Make sure the pfil bits are first before any possible subsystem which
531  * might piggyback on the SI_SUB_PROTO_PFIL.
532  */
533 SYSINIT(pfil_init, SI_SUB_PROTO_PFIL, SI_ORDER_FIRST, pfil_init, NULL);
534 
535 /*
536  * User control interface.
537  */
538 static int pfilioc_listheads(struct pfilioc_list *);
539 static int pfilioc_listhooks(struct pfilioc_list *);
540 static int pfilioc_link(struct pfilioc_link *);
541 
542 static int
543 pfil_ioctl(struct cdev *dev, u_long cmd, caddr_t addr, int flags,
544     struct thread *td)
545 {
546 	int error;
547 
548 	CURVNET_SET(TD_TO_VNET(td));
549 	error = 0;
550 	switch (cmd) {
551 	case PFILIOC_LISTHEADS:
552 		error = pfilioc_listheads((struct pfilioc_list *)addr);
553 		break;
554 	case PFILIOC_LISTHOOKS:
555 		error = pfilioc_listhooks((struct pfilioc_list *)addr);
556 		break;
557 	case PFILIOC_LINK:
558 		error = pfilioc_link((struct pfilioc_link *)addr);
559 		break;
560 	default:
561 		error = EINVAL;
562 		break;
563 	}
564 	CURVNET_RESTORE();
565 	return (error);
566 }
567 
568 static int
569 pfilioc_listheads(struct pfilioc_list *req)
570 {
571 	struct pfil_head *head;
572 	struct pfil_link *link;
573 	struct pfilioc_head *iohead;
574 	struct pfilioc_hook *iohook;
575 	u_int nheads, nhooks, hd, hk;
576 	int error;
577 
578 	PFIL_LOCK();
579 restart:
580 	nheads = nhooks = 0;
581 	LIST_FOREACH(head, &V_pfil_head_list, head_list) {
582 		nheads++;
583 		nhooks += head->head_nhooksin + head->head_nhooksout;
584 	}
585 	PFIL_UNLOCK();
586 
587 	if (req->pio_nheads < nheads || req->pio_nhooks < nhooks) {
588 		req->pio_nheads = nheads;
589 		req->pio_nhooks = nhooks;
590 		return (0);
591 	}
592 
593 	iohead = malloc(sizeof(*iohead) * nheads, M_TEMP, M_WAITOK);
594 	iohook = malloc(sizeof(*iohook) * nhooks, M_TEMP, M_WAITOK);
595 
596 	hd = hk = 0;
597 	PFIL_LOCK();
598 	LIST_FOREACH(head, &V_pfil_head_list, head_list) {
599 		if (hd + 1 > nheads ||
600 		    hk + head->head_nhooksin + head->head_nhooksout > nhooks) {
601 			/* Configuration changed during malloc(). */
602 			free(iohead, M_TEMP);
603 			free(iohook, M_TEMP);
604 			goto restart;
605 		}
606 		strlcpy(iohead[hd].pio_name, head->head_name,
607 			sizeof(iohead[0].pio_name));
608 		iohead[hd].pio_nhooksin = head->head_nhooksin;
609 		iohead[hd].pio_nhooksout = head->head_nhooksout;
610 		iohead[hd].pio_type = head->head_type;
611 		CK_STAILQ_FOREACH(link, &head->head_in, link_chain) {
612 			strlcpy(iohook[hk].pio_module,
613 			    link->link_hook->hook_modname,
614 			    sizeof(iohook[0].pio_module));
615 			strlcpy(iohook[hk].pio_ruleset,
616 			    link->link_hook->hook_rulname,
617 			    sizeof(iohook[0].pio_ruleset));
618 			hk++;
619 		}
620 		CK_STAILQ_FOREACH(link, &head->head_out, link_chain) {
621 			strlcpy(iohook[hk].pio_module,
622 			    link->link_hook->hook_modname,
623 			    sizeof(iohook[0].pio_module));
624 			strlcpy(iohook[hk].pio_ruleset,
625 			    link->link_hook->hook_rulname,
626 			    sizeof(iohook[0].pio_ruleset));
627 			hk++;
628 		}
629 		hd++;
630 	}
631 	PFIL_UNLOCK();
632 
633 	error = copyout(iohead, req->pio_heads,
634 	    sizeof(*iohead) * min(hd, req->pio_nheads));
635 	if (error == 0)
636 		error = copyout(iohook, req->pio_hooks,
637 		    sizeof(*iohook) * min(req->pio_nhooks, hk));
638 
639 	req->pio_nheads = hd;
640 	req->pio_nhooks = hk;
641 
642 	free(iohead, M_TEMP);
643 	free(iohook, M_TEMP);
644 
645 	return (error);
646 }
647 
648 static int
649 pfilioc_listhooks(struct pfilioc_list *req)
650 {
651 	struct pfil_hook *hook;
652 	struct pfilioc_hook *iohook;
653 	u_int nhooks, hk;
654 	int error;
655 
656 	PFIL_LOCK();
657 restart:
658 	nhooks = 0;
659 	LIST_FOREACH(hook, &V_pfil_hook_list, hook_list)
660 		nhooks++;
661 	PFIL_UNLOCK();
662 
663 	if (req->pio_nhooks < nhooks) {
664 		req->pio_nhooks = nhooks;
665 		return (0);
666 	}
667 
668 	iohook = malloc(sizeof(*iohook) * nhooks, M_TEMP, M_WAITOK);
669 
670 	hk = 0;
671 	PFIL_LOCK();
672 	LIST_FOREACH(hook, &V_pfil_hook_list, hook_list) {
673 		if (hk + 1 > nhooks) {
674 			/* Configuration changed during malloc(). */
675 			free(iohook, M_TEMP);
676 			goto restart;
677 		}
678 		strlcpy(iohook[hk].pio_module, hook->hook_modname,
679 		    sizeof(iohook[0].pio_module));
680 		strlcpy(iohook[hk].pio_ruleset, hook->hook_rulname,
681 		    sizeof(iohook[0].pio_ruleset));
682 		iohook[hk].pio_type = hook->hook_type;
683 		iohook[hk].pio_flags = hook->hook_flags;
684 		hk++;
685 	}
686 	PFIL_UNLOCK();
687 
688 	error = copyout(iohook, req->pio_hooks,
689 	    sizeof(*iohook) * min(req->pio_nhooks, hk));
690 	req->pio_nhooks = hk;
691 	free(iohook, M_TEMP);
692 
693 	return (error);
694 }
695 
696 static int
697 pfilioc_link(struct pfilioc_link *req)
698 {
699 	struct pfil_link_args args;
700 
701 	if (req->pio_flags & ~(PFIL_IN | PFIL_OUT | PFIL_UNLINK | PFIL_APPEND))
702 		return (EINVAL);
703 
704 	args.pa_version = PFIL_VERSION;
705 	args.pa_flags = req->pio_flags;
706 	args.pa_headname = req->pio_name;
707 	args.pa_modname = req->pio_module;
708 	args.pa_rulname = req->pio_ruleset;
709 
710 	return (pfil_link(&args));
711 }
712