Initial import from FreeBSD RELENG_4:
[dragonfly.git] / sys / net / bpf_filter.c
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984263bc
MD
1/*
2 * Copyright (c) 1990, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from the Stanford/CMU enet packet filter,
6 * (net/enet.c) distributed as part of 4.3BSD, and code contributed
7 * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
8 * Berkeley Laboratory.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the University of
21 * California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
24 * without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 *
38 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93
39 *
40 * $FreeBSD: src/sys/net/bpf_filter.c,v 1.17 1999/12/29 04:38:31 peter Exp $
41 */
42
43#include <sys/param.h>
44
45#ifdef sun
46#include <netinet/in.h>
47#endif
48
49#if defined(sparc) || defined(mips) || defined(ibm032) || defined(__alpha__)
50#define BPF_ALIGN
51#endif
52
53#ifndef BPF_ALIGN
54#define EXTRACT_SHORT(p) ((u_int16_t)ntohs(*(u_int16_t *)p))
55#define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p))
56#else
57#define EXTRACT_SHORT(p)\
58 ((u_int16_t)\
59 ((u_int16_t)*((u_char *)p+0)<<8|\
60 (u_int16_t)*((u_char *)p+1)<<0))
61#define EXTRACT_LONG(p)\
62 ((u_int32_t)*((u_char *)p+0)<<24|\
63 (u_int32_t)*((u_char *)p+1)<<16|\
64 (u_int32_t)*((u_char *)p+2)<<8|\
65 (u_int32_t)*((u_char *)p+3)<<0)
66#endif
67
68#ifdef _KERNEL
69#include <sys/mbuf.h>
70#endif
71#include <net/bpf.h>
72#ifdef _KERNEL
73#define MINDEX(m, k) \
74{ \
75 register int len = m->m_len; \
76 \
77 while (k >= len) { \
78 k -= len; \
79 m = m->m_next; \
80 if (m == 0) \
81 return 0; \
82 len = m->m_len; \
83 } \
84}
85
86static u_int16_t m_xhalf __P((struct mbuf *m, bpf_u_int32 k, int *err));
87static u_int32_t m_xword __P((struct mbuf *m, bpf_u_int32 k, int *err));
88
89static u_int32_t
90m_xword(m, k, err)
91 register struct mbuf *m;
92 register bpf_u_int32 k;
93 register int *err;
94{
95 register size_t len;
96 register u_char *cp, *np;
97 register struct mbuf *m0;
98
99 len = m->m_len;
100 while (k >= len) {
101 k -= len;
102 m = m->m_next;
103 if (m == 0)
104 goto bad;
105 len = m->m_len;
106 }
107 cp = mtod(m, u_char *) + k;
108 if (len - k >= 4) {
109 *err = 0;
110 return EXTRACT_LONG(cp);
111 }
112 m0 = m->m_next;
113 if (m0 == 0 || m0->m_len + len - k < 4)
114 goto bad;
115 *err = 0;
116 np = mtod(m0, u_char *);
117 switch (len - k) {
118
119 case 1:
120 return
121 ((u_int32_t)cp[0] << 24) |
122 ((u_int32_t)np[0] << 16) |
123 ((u_int32_t)np[1] << 8) |
124 (u_int32_t)np[2];
125
126 case 2:
127 return
128 ((u_int32_t)cp[0] << 24) |
129 ((u_int32_t)cp[1] << 16) |
130 ((u_int32_t)np[0] << 8) |
131 (u_int32_t)np[1];
132
133 default:
134 return
135 ((u_int32_t)cp[0] << 24) |
136 ((u_int32_t)cp[1] << 16) |
137 ((u_int32_t)cp[2] << 8) |
138 (u_int32_t)np[0];
139 }
140 bad:
141 *err = 1;
142 return 0;
143}
144
145static u_int16_t
146m_xhalf(m, k, err)
147 register struct mbuf *m;
148 register bpf_u_int32 k;
149 register int *err;
150{
151 register size_t len;
152 register u_char *cp;
153 register struct mbuf *m0;
154
155 len = m->m_len;
156 while (k >= len) {
157 k -= len;
158 m = m->m_next;
159 if (m == 0)
160 goto bad;
161 len = m->m_len;
162 }
163 cp = mtod(m, u_char *) + k;
164 if (len - k >= 2) {
165 *err = 0;
166 return EXTRACT_SHORT(cp);
167 }
168 m0 = m->m_next;
169 if (m0 == 0)
170 goto bad;
171 *err = 0;
172 return (cp[0] << 8) | mtod(m0, u_char *)[0];
173 bad:
174 *err = 1;
175 return 0;
176}
177#endif
178
179/*
180 * Execute the filter program starting at pc on the packet p
181 * wirelen is the length of the original packet
182 * buflen is the amount of data present
183 */
184u_int
185bpf_filter(pc, p, wirelen, buflen)
186 register const struct bpf_insn *pc;
187 register u_char *p;
188 u_int wirelen;
189 register u_int buflen;
190{
191 register u_int32_t A = 0, X = 0;
192 register bpf_u_int32 k;
193 int32_t mem[BPF_MEMWORDS];
194
195 if (pc == 0)
196 /*
197 * No filter means accept all.
198 */
199 return (u_int)-1;
200
201 --pc;
202 while (1) {
203 ++pc;
204 switch (pc->code) {
205
206 default:
207#ifdef _KERNEL
208 return 0;
209#else
210 abort();
211#endif
212 case BPF_RET|BPF_K:
213 return (u_int)pc->k;
214
215 case BPF_RET|BPF_A:
216 return (u_int)A;
217
218 case BPF_LD|BPF_W|BPF_ABS:
219 k = pc->k;
220 if (k > buflen || sizeof(int32_t) > buflen - k) {
221#ifdef _KERNEL
222 int merr;
223
224 if (buflen != 0)
225 return 0;
226 A = m_xword((struct mbuf *)p, k, &merr);
227 if (merr != 0)
228 return 0;
229 continue;
230#else
231 return 0;
232#endif
233 }
234#ifdef BPF_ALIGN
235 if (((intptr_t)(p + k) & 3) != 0)
236 A = EXTRACT_LONG(&p[k]);
237 else
238#endif
239 A = ntohl(*(int32_t *)(p + k));
240 continue;
241
242 case BPF_LD|BPF_H|BPF_ABS:
243 k = pc->k;
244 if (k > buflen || sizeof(int16_t) > buflen - k) {
245#ifdef _KERNEL
246 int merr;
247
248 if (buflen != 0)
249 return 0;
250 A = m_xhalf((struct mbuf *)p, k, &merr);
251 continue;
252#else
253 return 0;
254#endif
255 }
256 A = EXTRACT_SHORT(&p[k]);
257 continue;
258
259 case BPF_LD|BPF_B|BPF_ABS:
260 k = pc->k;
261 if (k >= buflen) {
262#ifdef _KERNEL
263 register struct mbuf *m;
264
265 if (buflen != 0)
266 return 0;
267 m = (struct mbuf *)p;
268 MINDEX(m, k);
269 A = mtod(m, u_char *)[k];
270 continue;
271#else
272 return 0;
273#endif
274 }
275 A = p[k];
276 continue;
277
278 case BPF_LD|BPF_W|BPF_LEN:
279 A = wirelen;
280 continue;
281
282 case BPF_LDX|BPF_W|BPF_LEN:
283 X = wirelen;
284 continue;
285
286 case BPF_LD|BPF_W|BPF_IND:
287 k = X + pc->k;
288 if (pc->k > buflen || X > buflen - pc->k ||
289 sizeof(int32_t) > buflen - k) {
290#ifdef _KERNEL
291 int merr;
292
293 if (buflen != 0)
294 return 0;
295 A = m_xword((struct mbuf *)p, k, &merr);
296 if (merr != 0)
297 return 0;
298 continue;
299#else
300 return 0;
301#endif
302 }
303#ifdef BPF_ALIGN
304 if (((intptr_t)(p + k) & 3) != 0)
305 A = EXTRACT_LONG(&p[k]);
306 else
307#endif
308 A = ntohl(*(int32_t *)(p + k));
309 continue;
310
311 case BPF_LD|BPF_H|BPF_IND:
312 k = X + pc->k;
313 if (X > buflen || pc->k > buflen - X ||
314 sizeof(int16_t) > buflen - k) {
315#ifdef _KERNEL
316 int merr;
317
318 if (buflen != 0)
319 return 0;
320 A = m_xhalf((struct mbuf *)p, k, &merr);
321 if (merr != 0)
322 return 0;
323 continue;
324#else
325 return 0;
326#endif
327 }
328 A = EXTRACT_SHORT(&p[k]);
329 continue;
330
331 case BPF_LD|BPF_B|BPF_IND:
332 k = X + pc->k;
333 if (pc->k >= buflen || X >= buflen - pc->k) {
334#ifdef _KERNEL
335 register struct mbuf *m;
336
337 if (buflen != 0)
338 return 0;
339 m = (struct mbuf *)p;
340 MINDEX(m, k);
341 A = mtod(m, char *)[k];
342 continue;
343#else
344 return 0;
345#endif
346 }
347 A = p[k];
348 continue;
349
350 case BPF_LDX|BPF_MSH|BPF_B:
351 k = pc->k;
352 if (k >= buflen) {
353#ifdef _KERNEL
354 register struct mbuf *m;
355
356 if (buflen != 0)
357 return 0;
358 m = (struct mbuf *)p;
359 MINDEX(m, k);
360 X = (mtod(m, char *)[k] & 0xf) << 2;
361 continue;
362#else
363 return 0;
364#endif
365 }
366 X = (p[pc->k] & 0xf) << 2;
367 continue;
368
369 case BPF_LD|BPF_IMM:
370 A = pc->k;
371 continue;
372
373 case BPF_LDX|BPF_IMM:
374 X = pc->k;
375 continue;
376
377 case BPF_LD|BPF_MEM:
378 A = mem[pc->k];
379 continue;
380
381 case BPF_LDX|BPF_MEM:
382 X = mem[pc->k];
383 continue;
384
385 case BPF_ST:
386 mem[pc->k] = A;
387 continue;
388
389 case BPF_STX:
390 mem[pc->k] = X;
391 continue;
392
393 case BPF_JMP|BPF_JA:
394 pc += pc->k;
395 continue;
396
397 case BPF_JMP|BPF_JGT|BPF_K:
398 pc += (A > pc->k) ? pc->jt : pc->jf;
399 continue;
400
401 case BPF_JMP|BPF_JGE|BPF_K:
402 pc += (A >= pc->k) ? pc->jt : pc->jf;
403 continue;
404
405 case BPF_JMP|BPF_JEQ|BPF_K:
406 pc += (A == pc->k) ? pc->jt : pc->jf;
407 continue;
408
409 case BPF_JMP|BPF_JSET|BPF_K:
410 pc += (A & pc->k) ? pc->jt : pc->jf;
411 continue;
412
413 case BPF_JMP|BPF_JGT|BPF_X:
414 pc += (A > X) ? pc->jt : pc->jf;
415 continue;
416
417 case BPF_JMP|BPF_JGE|BPF_X:
418 pc += (A >= X) ? pc->jt : pc->jf;
419 continue;
420
421 case BPF_JMP|BPF_JEQ|BPF_X:
422 pc += (A == X) ? pc->jt : pc->jf;
423 continue;
424
425 case BPF_JMP|BPF_JSET|BPF_X:
426 pc += (A & X) ? pc->jt : pc->jf;
427 continue;
428
429 case BPF_ALU|BPF_ADD|BPF_X:
430 A += X;
431 continue;
432
433 case BPF_ALU|BPF_SUB|BPF_X:
434 A -= X;
435 continue;
436
437 case BPF_ALU|BPF_MUL|BPF_X:
438 A *= X;
439 continue;
440
441 case BPF_ALU|BPF_DIV|BPF_X:
442 if (X == 0)
443 return 0;
444 A /= X;
445 continue;
446
447 case BPF_ALU|BPF_AND|BPF_X:
448 A &= X;
449 continue;
450
451 case BPF_ALU|BPF_OR|BPF_X:
452 A |= X;
453 continue;
454
455 case BPF_ALU|BPF_LSH|BPF_X:
456 A <<= X;
457 continue;
458
459 case BPF_ALU|BPF_RSH|BPF_X:
460 A >>= X;
461 continue;
462
463 case BPF_ALU|BPF_ADD|BPF_K:
464 A += pc->k;
465 continue;
466
467 case BPF_ALU|BPF_SUB|BPF_K:
468 A -= pc->k;
469 continue;
470
471 case BPF_ALU|BPF_MUL|BPF_K:
472 A *= pc->k;
473 continue;
474
475 case BPF_ALU|BPF_DIV|BPF_K:
476 A /= pc->k;
477 continue;
478
479 case BPF_ALU|BPF_AND|BPF_K:
480 A &= pc->k;
481 continue;
482
483 case BPF_ALU|BPF_OR|BPF_K:
484 A |= pc->k;
485 continue;
486
487 case BPF_ALU|BPF_LSH|BPF_K:
488 A <<= pc->k;
489 continue;
490
491 case BPF_ALU|BPF_RSH|BPF_K:
492 A >>= pc->k;
493 continue;
494
495 case BPF_ALU|BPF_NEG:
496 A = -A;
497 continue;
498
499 case BPF_MISC|BPF_TAX:
500 X = A;
501 continue;
502
503 case BPF_MISC|BPF_TXA:
504 A = X;
505 continue;
506 }
507 }
508}
509
510#ifdef _KERNEL
511/*
512 * Return true if the 'fcode' is a valid filter program.
513 * The constraints are that each jump be forward and to a valid
514 * code. The code must terminate with either an accept or reject.
515 *
516 * The kernel needs to be able to verify an application's filter code.
517 * Otherwise, a bogus program could easily crash the system.
518 */
519int
520bpf_validate(f, len)
521 const struct bpf_insn *f;
522 int len;
523{
524 register int i;
525 register const struct bpf_insn *p;
526
527 for (i = 0; i < len; ++i) {
528 /*
529 * Check that that jumps are forward, and within
530 * the code block.
531 */
532 p = &f[i];
533 if (BPF_CLASS(p->code) == BPF_JMP) {
534 register int from = i + 1;
535
536 if (BPF_OP(p->code) == BPF_JA) {
537 if (from >= len || p->k >= len - from)
538 return 0;
539 }
540 else if (from >= len || p->jt >= len - from ||
541 p->jf >= len - from)
542 return 0;
543 }
544 /*
545 * Check that memory operations use valid addresses.
546 */
547 if ((BPF_CLASS(p->code) == BPF_ST ||
548 (BPF_CLASS(p->code) == BPF_LD &&
549 (p->code & 0xe0) == BPF_MEM)) &&
550 p->k >= BPF_MEMWORDS)
551 return 0;
552 /*
553 * Check for constant division by 0.
554 */
555 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0)
556 return 0;
557 }
558 return BPF_CLASS(f[len - 1].code) == BPF_RET;
559}
560#endif