pfil.c revision 155201 
1/*	$FreeBSD: head/sys/net/pfil.c 155201 2006-02-02 03:13:16Z csjp $ */
2/*	$NetBSD: pfil.c,v 1.20 2001/11/12 23:49:46 lukem Exp $	*/
3
4/*-
5 * Copyright (c) 1996 Matthew R. Green
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. The name of the author may not be used to endorse or promote products
17 *    derived from this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
24 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
25 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
26 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
27 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32#include <sys/param.h>
33#include <sys/kernel.h>
34#include <sys/errno.h>
35#include <sys/lock.h>
36#include <sys/malloc.h>
37#include <sys/rwlock.h>
38#include <sys/socket.h>
39#include <sys/socketvar.h>
40#include <sys/systm.h>
41#include <sys/condvar.h>
42#include <sys/lock.h>
43#include <sys/mutex.h>
44#include <sys/proc.h>
45#include <sys/queue.h>
46
47#include <net/if.h>
48#include <net/pfil.h>
49
50static struct mtx pfil_global_lock;
51
52MTX_SYSINIT(pfil_heads_lock, &pfil_global_lock, "pfil_head_list lock", MTX_DEF);
53
54static int pfil_list_add(pfil_list_t *, struct packet_filter_hook *, int);
55
56static int pfil_list_remove(pfil_list_t *,
57    int (*)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *), void *);
58
59LIST_HEAD(, pfil_head) pfil_head_list =
60    LIST_HEAD_INITIALIZER(&pfil_head_list);
61
62/*
63 * pfil_run_hooks() runs the specified packet filter hooks.
64 */
65int
66pfil_run_hooks(struct pfil_head *ph, struct mbuf **mp, struct ifnet *ifp,
67    int dir, struct inpcb *inp)
68{
69	struct packet_filter_hook *pfh;
70	struct mbuf *m = *mp;
71	int rv = 0;
72
73	PFIL_RLOCK(ph);
74	KASSERT(ph->ph_nhooks >= 0, ("Pfil hook count dropped < 0"));
75	for (pfh = pfil_hook_get(dir, ph); pfh != NULL;
76	     pfh = TAILQ_NEXT(pfh, pfil_link)) {
77		if (pfh->pfil_func != NULL) {
78			rv = (*pfh->pfil_func)(pfh->pfil_arg, &m, ifp, dir, inp);
79			if (rv != 0 || m == NULL)
80				break;
81		}
82	}
83	PFIL_RUNLOCK(ph);
84
85	*mp = m;
86	return (rv);
87}
88
89/*
90 * pfil_head_register() registers a pfil_head with the packet filter
91 * hook mechanism.
92 */
93int
94pfil_head_register(struct pfil_head *ph)
95{
96	struct pfil_head *lph;
97
98	PFIL_LIST_LOCK();
99	LIST_FOREACH(lph, &pfil_head_list, ph_list)
100		if (ph->ph_type == lph->ph_type &&
101		    ph->ph_un.phu_val == lph->ph_un.phu_val) {
102			PFIL_LIST_UNLOCK();
103			return EEXIST;
104		}
105	PFIL_LIST_UNLOCK();
106
107	rw_init(&ph->ph_mtx, "PFil hook read/write mutex");
108	PFIL_WLOCK(ph);
109	ph->ph_nhooks = 0;
110
111	TAILQ_INIT(&ph->ph_in);
112	TAILQ_INIT(&ph->ph_out);
113
114	PFIL_LIST_LOCK();
115	LIST_INSERT_HEAD(&pfil_head_list, ph, ph_list);
116	PFIL_LIST_UNLOCK();
117
118	PFIL_WUNLOCK(ph);
119
120	return (0);
121}
122
123/*
124 * pfil_head_unregister() removes a pfil_head from the packet filter
125 * hook mechanism.
126 */
127int
128pfil_head_unregister(struct pfil_head *ph)
129{
130	struct packet_filter_hook *pfh, *pfnext;
131
132	PFIL_LIST_LOCK();
133	/*
134	 * LIST_REMOVE is safe for unlocked pfil_heads in ph_list.
135	 * No need to WLOCK all of them.
136	 */
137	LIST_REMOVE(ph, ph_list);
138	PFIL_LIST_UNLOCK();
139
140	PFIL_WLOCK(ph);
141
142	TAILQ_FOREACH_SAFE(pfh, &ph->ph_in, pfil_link, pfnext)
143		free(pfh, M_IFADDR);
144	TAILQ_FOREACH_SAFE(pfh, &ph->ph_out, pfil_link, pfnext)
145		free(pfh, M_IFADDR);
146	rw_destroy(&ph->ph_mtx);
147
148	return (0);
149}
150
151/*
152 * pfil_head_get() returns the pfil_head for a given key/dlt.
153 */
154struct pfil_head *
155pfil_head_get(int type, u_long val)
156{
157	struct pfil_head *ph;
158
159	PFIL_LIST_LOCK();
160	LIST_FOREACH(ph, &pfil_head_list, ph_list)
161		if (ph->ph_type == type && ph->ph_un.phu_val == val)
162			break;
163	PFIL_LIST_UNLOCK();
164
165	return (ph);
166}
167
168/*
169 * pfil_add_hook() adds a function to the packet filter hook.  the
170 * flags are:
171 *	PFIL_IN		call me on incoming packets
172 *	PFIL_OUT	call me on outgoing packets
173 *	PFIL_ALL	call me on all of the above
174 *	PFIL_WAITOK	OK to call malloc with M_WAITOK.
175 */
176int
177pfil_add_hook(int (*func)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *),
178    void *arg, int flags, struct pfil_head *ph)
179{
180	struct packet_filter_hook *pfh1 = NULL;
181	struct packet_filter_hook *pfh2 = NULL;
182	int err;
183
184	/* Get memory */
185	if (flags & PFIL_IN) {
186		pfh1 = (struct packet_filter_hook *)malloc(sizeof(*pfh1),
187		    M_IFADDR, (flags & PFIL_WAITOK) ? M_WAITOK : M_NOWAIT);
188		if (pfh1 == NULL) {
189			err = ENOMEM;
190			goto error;
191		}
192	}
193	if (flags & PFIL_OUT) {
194		pfh2 = (struct packet_filter_hook *)malloc(sizeof(*pfh1),
195		    M_IFADDR, (flags & PFIL_WAITOK) ? M_WAITOK : M_NOWAIT);
196		if (pfh2 == NULL) {
197			err = ENOMEM;
198			goto error;
199		}
200	}
201
202	/* Lock */
203	PFIL_WLOCK(ph);
204
205	/* Add */
206	if (flags & PFIL_IN) {
207		pfh1->pfil_func = func;
208		pfh1->pfil_arg = arg;
209		err = pfil_list_add(&ph->ph_in, pfh1, flags & ~PFIL_OUT);
210		if (err)
211			goto done;
212		ph->ph_nhooks++;
213	}
214	if (flags & PFIL_OUT) {
215		pfh2->pfil_func = func;
216		pfh2->pfil_arg = arg;
217		err = pfil_list_add(&ph->ph_out, pfh2, flags & ~PFIL_IN);
218		if (err) {
219			if (flags & PFIL_IN)
220				pfil_list_remove(&ph->ph_in, func, arg);
221			goto done;
222		}
223		ph->ph_nhooks++;
224	}
225
226	PFIL_WUNLOCK(ph);
227
228	return 0;
229done:
230	PFIL_WUNLOCK(ph);
231error:
232	if (pfh1 != NULL)
233		free(pfh1, M_IFADDR);
234	if (pfh2 != NULL)
235		free(pfh2, M_IFADDR);
236	return err;
237}
238
239/*
240 * pfil_remove_hook removes a specific function from the packet filter
241 * hook list.
242 */
243int
244pfil_remove_hook(int (*func)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *),
245    void *arg, int flags, struct pfil_head *ph)
246{
247	int err = 0;
248
249	PFIL_WLOCK(ph);
250
251	if (flags & PFIL_IN) {
252		err = pfil_list_remove(&ph->ph_in, func, arg);
253		if (err == 0)
254			ph->ph_nhooks--;
255	}
256	if ((err == 0) && (flags & PFIL_OUT)) {
257		err = pfil_list_remove(&ph->ph_out, func, arg);
258		if (err == 0)
259			ph->ph_nhooks--;
260	}
261	PFIL_WUNLOCK(ph);
262
263	return err;
264}
265
266static int
267pfil_list_add(pfil_list_t *list, struct packet_filter_hook *pfh1, int flags)
268{
269	struct packet_filter_hook *pfh;
270
271	/*
272	 * First make sure the hook is not already there.
273	 */
274	TAILQ_FOREACH(pfh, list, pfil_link)
275		if (pfh->pfil_func == pfh1->pfil_func &&
276		    pfh->pfil_arg == pfh1->pfil_arg)
277			return EEXIST;
278	/*
279	 * insert the input list in reverse order of the output list
280	 * so that the same path is followed in or out of the kernel.
281	 */
282	if (flags & PFIL_IN)
283		TAILQ_INSERT_HEAD(list, pfh1, pfil_link);
284	else
285		TAILQ_INSERT_TAIL(list, pfh1, pfil_link);
286
287	return 0;
288}
289
290/*
291 * pfil_list_remove is an internal function that takes a function off the
292 * specified list.
293 */
294static int
295pfil_list_remove(pfil_list_t *list,
296    int (*func)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *), void *arg)
297{
298	struct packet_filter_hook *pfh;
299
300	TAILQ_FOREACH(pfh, list, pfil_link)
301		if (pfh->pfil_func == func && pfh->pfil_arg == arg) {
302			TAILQ_REMOVE(list, pfh, pfil_link);
303			free(pfh, M_IFADDR);
304			return 0;
305		}
306	return ENOENT;
307}
308