xref: /freebsd/sys/net/pfil.c (revision 39beb93c3f8bdbf72a61fda42300b5ebed7390c8)
1 /*	$FreeBSD$ */
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/rmlock.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 
50 static struct mtx pfil_global_lock;
51 
52 MTX_SYSINIT(pfil_heads_lock, &pfil_global_lock, "pfil_head_list lock", MTX_DEF);
53 
54 static int pfil_list_add(pfil_list_t *, struct packet_filter_hook *, int);
55 
56 static int pfil_list_remove(pfil_list_t *,
57     int (*)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *), void *);
58 
59 LIST_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  */
65 int
66 pfil_run_hooks(struct pfil_head *ph, struct mbuf **mp, struct ifnet *ifp,
67     int dir, struct inpcb *inp)
68 {
69 	struct rm_priotracker rmpt;
70 	struct packet_filter_hook *pfh;
71 	struct mbuf *m = *mp;
72 	int rv = 0;
73 
74 	PFIL_RLOCK(ph, &rmpt);
75 	KASSERT(ph->ph_nhooks >= 0, ("Pfil hook count dropped < 0"));
76 	for (pfh = pfil_hook_get(dir, ph); pfh != NULL;
77 	     pfh = TAILQ_NEXT(pfh, pfil_link)) {
78 		if (pfh->pfil_func != NULL) {
79 			rv = (*pfh->pfil_func)(pfh->pfil_arg, &m, ifp, dir, inp);
80 			if (rv != 0 || m == NULL)
81 				break;
82 		}
83 	}
84 	PFIL_RUNLOCK(ph, &rmpt);
85 
86 	*mp = m;
87 	return (rv);
88 }
89 
90 /*
91  * pfil_head_register() registers a pfil_head with the packet filter
92  * hook mechanism.
93  */
94 int
95 pfil_head_register(struct pfil_head *ph)
96 {
97 	struct pfil_head *lph;
98 
99 	PFIL_LIST_LOCK();
100 	LIST_FOREACH(lph, &pfil_head_list, ph_list) {
101 		if (ph->ph_type == lph->ph_type &&
102 		    ph->ph_un.phu_val == lph->ph_un.phu_val) {
103 			PFIL_LIST_UNLOCK();
104 			return EEXIST;
105 		}
106 	}
107 	PFIL_LOCK_INIT(ph);
108 	ph->ph_nhooks = 0;
109 	TAILQ_INIT(&ph->ph_in);
110 	TAILQ_INIT(&ph->ph_out);
111 	LIST_INSERT_HEAD(&pfil_head_list, ph, ph_list);
112 	PFIL_LIST_UNLOCK();
113 	return (0);
114 }
115 
116 /*
117  * pfil_head_unregister() removes a pfil_head from the packet filter hook
118  * mechanism.  The producer of the hook promises that all outstanding
119  * invocations of the hook have completed before it unregisters the hook.
120  */
121 int
122 pfil_head_unregister(struct pfil_head *ph)
123 {
124 	struct packet_filter_hook *pfh, *pfnext;
125 
126 	PFIL_LIST_LOCK();
127 	LIST_REMOVE(ph, ph_list);
128 	PFIL_LIST_UNLOCK();
129 	TAILQ_FOREACH_SAFE(pfh, &ph->ph_in, pfil_link, pfnext)
130 		free(pfh, M_IFADDR);
131 	TAILQ_FOREACH_SAFE(pfh, &ph->ph_out, pfil_link, pfnext)
132 		free(pfh, M_IFADDR);
133 	PFIL_LOCK_DESTROY(ph);
134 	return (0);
135 }
136 
137 /*
138  * pfil_head_get() returns the pfil_head for a given key/dlt.
139  */
140 struct pfil_head *
141 pfil_head_get(int type, u_long val)
142 {
143 	struct pfil_head *ph;
144 
145 	PFIL_LIST_LOCK();
146 	LIST_FOREACH(ph, &pfil_head_list, ph_list)
147 		if (ph->ph_type == type && ph->ph_un.phu_val == val)
148 			break;
149 	PFIL_LIST_UNLOCK();
150 
151 	return (ph);
152 }
153 
154 /*
155  * pfil_add_hook() adds a function to the packet filter hook.  the
156  * flags are:
157  *	PFIL_IN		call me on incoming packets
158  *	PFIL_OUT	call me on outgoing packets
159  *	PFIL_ALL	call me on all of the above
160  *	PFIL_WAITOK	OK to call malloc with M_WAITOK.
161  */
162 int
163 pfil_add_hook(int (*func)(void *, struct mbuf **, struct ifnet *, int,
164   struct inpcb *), void *arg, int flags, struct pfil_head *ph)
165 {
166 	struct packet_filter_hook *pfh1 = NULL;
167 	struct packet_filter_hook *pfh2 = NULL;
168 	int err;
169 
170 	if (flags & PFIL_IN) {
171 		pfh1 = (struct packet_filter_hook *)malloc(sizeof(*pfh1),
172 		    M_IFADDR, (flags & PFIL_WAITOK) ? M_WAITOK : M_NOWAIT);
173 		if (pfh1 == NULL) {
174 			err = ENOMEM;
175 			goto error;
176 		}
177 	}
178 	if (flags & PFIL_OUT) {
179 		pfh2 = (struct packet_filter_hook *)malloc(sizeof(*pfh1),
180 		    M_IFADDR, (flags & PFIL_WAITOK) ? M_WAITOK : M_NOWAIT);
181 		if (pfh2 == NULL) {
182 			err = ENOMEM;
183 			goto error;
184 		}
185 	}
186 	PFIL_WLOCK(ph);
187 	if (flags & PFIL_IN) {
188 		pfh1->pfil_func = func;
189 		pfh1->pfil_arg = arg;
190 		err = pfil_list_add(&ph->ph_in, pfh1, flags & ~PFIL_OUT);
191 		if (err)
192 			goto locked_error;
193 		ph->ph_nhooks++;
194 	}
195 	if (flags & PFIL_OUT) {
196 		pfh2->pfil_func = func;
197 		pfh2->pfil_arg = arg;
198 		err = pfil_list_add(&ph->ph_out, pfh2, flags & ~PFIL_IN);
199 		if (err) {
200 			if (flags & PFIL_IN)
201 				pfil_list_remove(&ph->ph_in, func, arg);
202 			goto locked_error;
203 		}
204 		ph->ph_nhooks++;
205 	}
206 	PFIL_WUNLOCK(ph);
207 	return 0;
208 locked_error:
209 	PFIL_WUNLOCK(ph);
210 error:
211 	if (pfh1 != NULL)
212 		free(pfh1, M_IFADDR);
213 	if (pfh2 != NULL)
214 		free(pfh2, M_IFADDR);
215 	return err;
216 }
217 
218 /*
219  * pfil_remove_hook removes a specific function from the packet filter
220  * hook list.
221  */
222 int
223 pfil_remove_hook(int (*func)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *),
224     void *arg, int flags, struct pfil_head *ph)
225 {
226 	int err = 0;
227 
228 	PFIL_WLOCK(ph);
229 
230 	if (flags & PFIL_IN) {
231 		err = pfil_list_remove(&ph->ph_in, func, arg);
232 		if (err == 0)
233 			ph->ph_nhooks--;
234 	}
235 	if ((err == 0) && (flags & PFIL_OUT)) {
236 		err = pfil_list_remove(&ph->ph_out, func, arg);
237 		if (err == 0)
238 			ph->ph_nhooks--;
239 	}
240 	PFIL_WUNLOCK(ph);
241 
242 	return err;
243 }
244 
245 static int
246 pfil_list_add(pfil_list_t *list, struct packet_filter_hook *pfh1, int flags)
247 {
248 	struct packet_filter_hook *pfh;
249 
250 	/*
251 	 * First make sure the hook is not already there.
252 	 */
253 	TAILQ_FOREACH(pfh, list, pfil_link)
254 		if (pfh->pfil_func == pfh1->pfil_func &&
255 		    pfh->pfil_arg == pfh1->pfil_arg)
256 			return EEXIST;
257 	/*
258 	 * insert the input list in reverse order of the output list
259 	 * so that the same path is followed in or out of the kernel.
260 	 */
261 	if (flags & PFIL_IN)
262 		TAILQ_INSERT_HEAD(list, pfh1, pfil_link);
263 	else
264 		TAILQ_INSERT_TAIL(list, pfh1, pfil_link);
265 
266 	return 0;
267 }
268 
269 /*
270  * pfil_list_remove is an internal function that takes a function off the
271  * specified list.
272  */
273 static int
274 pfil_list_remove(pfil_list_t *list,
275     int (*func)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *), void *arg)
276 {
277 	struct packet_filter_hook *pfh;
278 
279 	TAILQ_FOREACH(pfh, list, pfil_link)
280 		if (pfh->pfil_func == func && pfh->pfil_arg == arg) {
281 			TAILQ_REMOVE(list, pfh, pfil_link);
282 			free(pfh, M_IFADDR);
283 			return 0;
284 		}
285 	return ENOENT;
286 }
287