1 /* $NetBSD: pfil.c,v 1.20 2001/11/12 23:49:46 lukem Exp $ */
2
3 /*
4 * Copyright (c) 1996 Matthew R. Green
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. The name of the author may not be used to endorse or promote products
16 * derived from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
23 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
25 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31 #include <sys/param.h>
32 #include <sys/errno.h>
33 #include <sys/malloc.h>
34 #include <sys/socket.h>
35 #include <sys/socketvar.h>
36 #include <sys/systm.h>
37 #include <sys/proc.h>
38 #include <sys/queue.h>
39 #include <sys/sysctl.h>
40
41 #include <net/if.h>
42 #include <net/if_var.h>
43 #include <net/pfil.h>
44 #include <net/netmsg2.h>
45 #include <net/netisr2.h>
46
47 #define PFIL_CFGPORT netisr_cpuport(0)
48
49 /*
50 * The packet filter hooks are designed for anything to call them to
51 * possibly intercept the packet.
52 */
53 struct packet_filter_hook {
54 TAILQ_ENTRY(packet_filter_hook) pfil_link;
55 pfil_func_t pfil_func;
56 void *pfil_arg;
57 int pfil_flags;
58 };
59
60 struct netmsg_pfil {
61 struct netmsg_base base;
62 pfil_func_t pfil_func;
63 void *pfil_arg;
64 int pfil_flags;
65 struct pfil_head *pfil_ph;
66 };
67
68 static LIST_HEAD(, pfil_head) pfil_head_list =
69 LIST_HEAD_INITIALIZER(&pfil_head_list);
70
71 static pfil_list_t *pfil_list_alloc(void);
72 static void pfil_list_free(pfil_list_t *);
73 static void pfil_list_dup(const pfil_list_t *, pfil_list_t *,
74 const struct packet_filter_hook *);
75 static void pfil_list_add(pfil_list_t *, pfil_func_t, void *, int);
76 static struct packet_filter_hook *
77 pfil_list_find(const pfil_list_t *, pfil_func_t,
78 const void *);
79
80 static void pfil_remove_hook_dispatch(netmsg_t);
81 static void pfil_add_hook_dispatch(netmsg_t);
82
83 int filters_default_to_accept = 0;
84 SYSCTL_INT(_net, OID_AUTO, filters_default_to_accept, CTLFLAG_RW,
85 &filters_default_to_accept, 0,
86 "cause ipfw* modules to not block by default");
87 TUNABLE_INT("net.filters_default_to_accept", &filters_default_to_accept);
88
89 /*
90 * pfil_run_hooks() runs the specified packet filter hooks.
91 */
92 int
pfil_run_hooks(struct pfil_head * ph,struct mbuf ** mp,struct ifnet * ifp,int dir)93 pfil_run_hooks(struct pfil_head *ph, struct mbuf **mp, struct ifnet *ifp,
94 int dir)
95 {
96 struct packet_filter_hook *pfh;
97 struct mbuf *m = *mp;
98 pfil_list_t *list;
99 int rv = 0;
100
101 if (dir == PFIL_IN)
102 list = ph->ph_in;
103 else if (dir == PFIL_OUT)
104 list = ph->ph_out;
105 else
106 return 0; /* XXX panic? */
107
108 /* Make sure 'list' is really used. */
109 cpu_ccfence();
110 TAILQ_FOREACH(pfh, list, pfil_link) {
111 if (pfh->pfil_func != NULL) {
112 rv = pfh->pfil_func(pfh->pfil_arg, &m, ifp, dir);
113 if (rv != 0 || m == NULL)
114 break;
115 }
116 }
117
118 *mp = m;
119 return (rv);
120 }
121
122 /*
123 * pfil_head_register() registers a pfil_head with the packet filter
124 * hook mechanism.
125 */
126 int
pfil_head_register(struct pfil_head * ph)127 pfil_head_register(struct pfil_head *ph)
128 {
129 struct pfil_head *lph;
130
131 LIST_FOREACH(lph, &pfil_head_list, ph_list) {
132 if (ph->ph_type == lph->ph_type &&
133 ph->ph_un.phu_val == lph->ph_un.phu_val)
134 return EEXIST;
135 }
136
137 ph->ph_in = pfil_list_alloc();
138 ph->ph_out = pfil_list_alloc();
139 ph->ph_hashooks = 0;
140
141 LIST_INSERT_HEAD(&pfil_head_list, ph, ph_list);
142
143 return (0);
144 }
145
146 /*
147 * pfil_head_unregister() removes a pfil_head from the packet filter
148 * hook mechanism.
149 */
150 int
pfil_head_unregister(struct pfil_head * pfh)151 pfil_head_unregister(struct pfil_head *pfh)
152 {
153 LIST_REMOVE(pfh, ph_list);
154 return (0);
155 }
156
157 /*
158 * pfil_head_get() returns the pfil_head for a given key/dlt.
159 */
160 struct pfil_head *
pfil_head_get(int type,u_long val)161 pfil_head_get(int type, u_long val)
162 {
163 struct pfil_head *ph;
164
165 LIST_FOREACH(ph, &pfil_head_list, ph_list) {
166 if (ph->ph_type == type && ph->ph_un.phu_val == val)
167 break;
168 }
169 return (ph);
170 }
171
172 static void
pfil_add_hook_dispatch(netmsg_t nmsg)173 pfil_add_hook_dispatch(netmsg_t nmsg)
174 {
175 struct netmsg_pfil *pfilmsg = (struct netmsg_pfil *)nmsg;
176 pfil_func_t func = pfilmsg->pfil_func;
177 void *arg = pfilmsg->pfil_arg;
178 int flags = pfilmsg->pfil_flags;
179 struct pfil_head *ph = pfilmsg->pfil_ph;
180 const struct packet_filter_hook *pfh;
181 pfil_list_t *list_in = NULL, *list_out = NULL;
182 pfil_list_t *old_list_in = NULL, *old_list_out = NULL;
183 int err = 0;
184
185 /* This probably should not happen ... */
186 if ((flags & (PFIL_IN | PFIL_OUT)) == 0)
187 goto reply; /* XXX panic? */
188
189 /*
190 * If pfil hooks exist on any of the requested lists,
191 * then bail out.
192 */
193 if (flags & PFIL_IN) {
194 pfh = pfil_list_find(ph->ph_in, func, arg);
195 if (pfh != NULL) {
196 err = EEXIST;
197 goto reply;
198 }
199 }
200 if (flags & PFIL_OUT) {
201 pfh = pfil_list_find(ph->ph_out, func, arg);
202 if (pfh != NULL) {
203 err = EEXIST;
204 goto reply;
205 }
206 }
207
208 /*
209 * Duplicate the requested lists, install new hooks
210 * on the duplication
211 */
212 if (flags & PFIL_IN) {
213 list_in = pfil_list_alloc();
214 pfil_list_dup(ph->ph_in, list_in, NULL);
215 pfil_list_add(list_in, func, arg, flags & ~PFIL_OUT);
216 }
217 if (flags & PFIL_OUT) {
218 list_out = pfil_list_alloc();
219 pfil_list_dup(ph->ph_out, list_out, NULL);
220 pfil_list_add(list_out, func, arg, flags & ~PFIL_IN);
221 }
222
223 /*
224 * Switch list pointers, but keep the old ones
225 */
226 if (list_in != NULL) {
227 old_list_in = ph->ph_in;
228 ph->ph_in = list_in;
229 }
230 if (list_out != NULL) {
231 old_list_out = ph->ph_out;
232 ph->ph_out = list_out;
233 }
234
235 /*
236 * Wait until everyone has finished the old lists iteration
237 */
238 netmsg_service_sync();
239 ph->ph_hashooks = 1;
240
241 /*
242 * Now it is safe to free the old lists, since no one sees it
243 */
244 if (old_list_in != NULL)
245 pfil_list_free(old_list_in);
246 if (old_list_out != NULL)
247 pfil_list_free(old_list_out);
248 reply:
249 lwkt_replymsg(&nmsg->base.lmsg, err);
250 }
251
252 /*
253 * pfil_add_hook() adds a function to the packet filter hook. the
254 * flags are:
255 * PFIL_IN call me on incoming packets
256 * PFIL_OUT call me on outgoing packets
257 * PFIL_ALL call me on all of the above
258 */
259 int
pfil_add_hook(pfil_func_t func,void * arg,int flags,struct pfil_head * ph)260 pfil_add_hook(pfil_func_t func, void *arg, int flags, struct pfil_head *ph)
261 {
262 struct netmsg_pfil pfilmsg;
263 netmsg_base_t nmsg;
264 int error;
265
266 nmsg = &pfilmsg.base;
267 netmsg_init(nmsg, NULL, &curthread->td_msgport,
268 0, pfil_add_hook_dispatch);
269 pfilmsg.pfil_func = func;
270 pfilmsg.pfil_arg = arg;
271 pfilmsg.pfil_flags = flags;
272 pfilmsg.pfil_ph = ph;
273
274 error = lwkt_domsg(PFIL_CFGPORT, &nmsg->lmsg, 0);
275 return error;
276 }
277
278 static void
pfil_remove_hook_dispatch(netmsg_t nmsg)279 pfil_remove_hook_dispatch(netmsg_t nmsg)
280 {
281 struct netmsg_pfil *pfilmsg = (struct netmsg_pfil *)nmsg;
282 pfil_func_t func = pfilmsg->pfil_func;
283 void *arg = pfilmsg->pfil_arg;
284 int flags = pfilmsg->pfil_flags;
285 struct pfil_head *ph = pfilmsg->pfil_ph;
286 struct packet_filter_hook *skip_in = NULL, *skip_out = NULL;
287 pfil_list_t *list_in = NULL, *list_out = NULL;
288 pfil_list_t *old_list_in = NULL, *old_list_out = NULL;
289 int err = 0;
290
291 /* This probably should not happen ... */
292 if ((flags & (PFIL_IN | PFIL_OUT)) == 0)
293 goto reply; /* XXX panic? */
294
295 /*
296 * The pfil hook should exist on all requested lists,
297 * if not just bail out
298 */
299 if (flags & PFIL_IN) {
300 skip_in = pfil_list_find(ph->ph_in, func, arg);
301 if (!skip_in) {
302 err = ENOENT;
303 goto reply;
304 }
305 }
306 if (flags & PFIL_OUT) {
307 skip_out = pfil_list_find(ph->ph_out, func, arg);
308 if (!skip_out) {
309 err = ENOENT;
310 goto reply;
311 }
312 }
313
314 /*
315 * Duplicate the requested lists, but the pfil hook to
316 * be deleted is not copied
317 */
318 if (flags & PFIL_IN) {
319 KKASSERT(skip_in != NULL);
320 list_in = pfil_list_alloc();
321 pfil_list_dup(ph->ph_in, list_in, skip_in);
322 }
323 if (flags & PFIL_OUT) {
324 KKASSERT(skip_out != NULL);
325 list_out = pfil_list_alloc();
326 pfil_list_dup(ph->ph_out, list_out, skip_out);
327 }
328
329 /*
330 * Switch list pointers, but keep the old ones
331 */
332 if (list_in != NULL) {
333 old_list_in = ph->ph_in;
334 ph->ph_in = list_in;
335 }
336 if (list_out != NULL) {
337 old_list_out = ph->ph_out;
338 ph->ph_out = list_out;
339 }
340
341 /*
342 * Wait until everyone has finished the old lists iteration
343 */
344 if (TAILQ_EMPTY(ph->ph_in) && TAILQ_EMPTY(ph->ph_out))
345 ph->ph_hashooks = 0;
346 netmsg_service_sync();
347
348 /*
349 * Now it is safe to free the old lists, since no one sees it
350 */
351 if (old_list_in != NULL)
352 pfil_list_free(old_list_in);
353 if (old_list_out != NULL)
354 pfil_list_free(old_list_out);
355 reply:
356 lwkt_replymsg(&nmsg->base.lmsg, err);
357 }
358
359 /*
360 * pfil_remove_hook removes a specific function from the packet filter
361 * hook list.
362 */
363 int
pfil_remove_hook(pfil_func_t func,void * arg,int flags,struct pfil_head * ph)364 pfil_remove_hook(pfil_func_t func, void *arg, int flags, struct pfil_head *ph)
365 {
366 struct netmsg_pfil pfilmsg;
367 netmsg_base_t nmsg;
368
369 nmsg = &pfilmsg.base;
370 netmsg_init(nmsg, NULL, &curthread->td_msgport,
371 0, pfil_remove_hook_dispatch);
372 pfilmsg.pfil_func = func;
373 pfilmsg.pfil_arg = arg;
374 pfilmsg.pfil_flags = flags;
375 pfilmsg.pfil_ph = ph;
376
377 return lwkt_domsg(PFIL_CFGPORT, &nmsg->lmsg, 0);
378 }
379
380 static void
pfil_list_add(pfil_list_t * list,pfil_func_t func,void * arg,int flags)381 pfil_list_add(pfil_list_t *list, pfil_func_t func, void *arg, int flags)
382 {
383 struct packet_filter_hook *pfh;
384
385 KKASSERT(&curthread->td_msgport == PFIL_CFGPORT);
386
387 pfh = kmalloc(sizeof(*pfh), M_IFADDR, M_WAITOK);
388
389 pfh->pfil_func = func;
390 pfh->pfil_arg = arg;
391 pfh->pfil_flags = flags;
392
393 /*
394 * Insert the input list in reverse order of the output list
395 * so that the same path is followed in or out of the kernel.
396 */
397 if (flags & PFIL_IN)
398 TAILQ_INSERT_HEAD(list, pfh, pfil_link);
399 else
400 TAILQ_INSERT_TAIL(list, pfh, pfil_link);
401 }
402
403 static void
pfil_list_dup(const pfil_list_t * from,pfil_list_t * to,const struct packet_filter_hook * skip)404 pfil_list_dup(const pfil_list_t *from, pfil_list_t *to,
405 const struct packet_filter_hook *skip)
406 {
407 struct packet_filter_hook *pfh_to, *pfh_from;
408
409 KKASSERT(&curthread->td_msgport == PFIL_CFGPORT);
410 KKASSERT(TAILQ_EMPTY(to));
411
412 TAILQ_FOREACH(pfh_from, from, pfil_link) {
413 if (pfh_from == skip)
414 continue;
415
416 pfh_to = kmalloc(sizeof(*pfh_to), M_IFADDR, M_WAITOK);
417 bcopy(pfh_from, pfh_to, sizeof(*pfh_to));
418
419 TAILQ_INSERT_TAIL(to, pfh_to, pfil_link);
420 }
421 }
422
423 static pfil_list_t *
pfil_list_alloc(void)424 pfil_list_alloc(void)
425 {
426 pfil_list_t *list;
427
428 list = kmalloc(sizeof(*list), M_IFADDR, M_WAITOK);
429 TAILQ_INIT(list);
430 return list;
431 }
432
433 static void
pfil_list_free(pfil_list_t * list)434 pfil_list_free(pfil_list_t *list)
435 {
436 struct packet_filter_hook *pfh;
437
438 while ((pfh = TAILQ_FIRST(list)) != NULL) {
439 TAILQ_REMOVE(list, pfh, pfil_link);
440 kfree(pfh, M_IFADDR);
441 }
442 kfree(list, M_IFADDR);
443 }
444
445 static struct packet_filter_hook *
pfil_list_find(const pfil_list_t * list,pfil_func_t func,const void * arg)446 pfil_list_find(const pfil_list_t *list, pfil_func_t func, const void *arg)
447 {
448 struct packet_filter_hook *pfh;
449
450 KKASSERT(&curthread->td_msgport == PFIL_CFGPORT);
451
452 TAILQ_FOREACH(pfh, list, pfil_link) {
453 if (pfh->pfil_func == func && pfh->pfil_arg == arg)
454 return pfh;
455 }
456 return NULL;
457 }
458