1 /*-
2  * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
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.c	7.5 (Berkeley) 7/15/91
39  */
40 
41 #ifdef HAVE_CONFIG_H
42 #include "config.h"
43 #endif
44 
45 #ifdef WIN32
46 
47 #include <pcap-stdinc.h>
48 
49 #else /* WIN32 */
50 
51 #if HAVE_INTTYPES_H
52 #include <inttypes.h>
53 #elif HAVE_STDINT_H
54 #include <stdint.h>
55 #endif
56 #ifdef HAVE_SYS_BITYPES_H
57 #include <sys/bitypes.h>
58 #endif
59 
60 #include <sys/param.h>
61 #include <sys/types.h>
62 #include <sys/time.h>
63 
64 #define	SOLARIS	(defined(sun) && (defined(__SVR4) || defined(__svr4__)))
65 #if defined(__hpux) || SOLARIS
66 # include <sys/sysmacros.h>
67 # include <sys/stream.h>
68 # define	mbuf	msgb
69 # define	m_next	b_cont
70 # define	MLEN(m)	((m)->b_wptr - (m)->b_rptr)
71 # define	mtod(m,t)	((t)(m)->b_rptr)
72 #else /* defined(__hpux) || SOLARIS */
73 # define	MLEN(m)	((m)->m_len)
74 #endif /* defined(__hpux) || SOLARIS */
75 
76 #endif /* WIN32 */
77 
78 #include <pcap/bpf.h>
79 
80 #if !defined(KERNEL) && !defined(_KERNEL)
81 #include <stdlib.h>
82 #endif
83 
84 #define int32 bpf_int32
85 #define u_int32 bpf_u_int32
86 
87 #ifndef LBL_ALIGN
88 /*
89  * XXX - IA-64?  If not, this probably won't work on Win64 IA-64
90  * systems, unless LBL_ALIGN is defined elsewhere for them.
91  * XXX - SuperH?  If not, this probably won't work on WinCE SuperH
92  * systems, unless LBL_ALIGN is defined elsewhere for them.
93  */
94 #if defined(sparc) || defined(__sparc__) || defined(mips) || \
95     defined(ibm032) || defined(__alpha) || defined(__hpux) || \
96     defined(__arm__)
97 #define LBL_ALIGN
98 #endif
99 #endif
100 
101 #ifndef LBL_ALIGN
102 #ifndef WIN32
103 #include <netinet/in.h>
104 #endif
105 
106 #define EXTRACT_SHORT(p)	((u_short)ntohs(*(u_short *)p))
107 #define EXTRACT_LONG(p)		(ntohl(*(u_int32 *)p))
108 #else
109 #define EXTRACT_SHORT(p)\
110 	((u_short)\
111 		((u_short)*((u_char *)p+0)<<8|\
112 		 (u_short)*((u_char *)p+1)<<0))
113 #define EXTRACT_LONG(p)\
114 		((u_int32)*((u_char *)p+0)<<24|\
115 		 (u_int32)*((u_char *)p+1)<<16|\
116 		 (u_int32)*((u_char *)p+2)<<8|\
117 		 (u_int32)*((u_char *)p+3)<<0)
118 #endif
119 
120 #if defined(KERNEL) || defined(_KERNEL)
121 # if !defined(__hpux) && !SOLARIS
122 #include <sys/mbuf.h>
123 # endif
124 #define MINDEX(len, _m, _k) \
125 { \
126 	len = MLEN(m); \
127 	while ((_k) >= len) { \
128 		(_k) -= len; \
129 		(_m) = (_m)->m_next; \
130 		if ((_m) == 0) \
131 			return 0; \
132 		len = MLEN(m); \
133 	} \
134 }
135 
136 static int
m_xword(m,k,err)137 m_xword(m, k, err)
138 	register struct mbuf *m;
139 	register int k, *err;
140 {
141 	register int len;
142 	register u_char *cp, *np;
143 	register struct mbuf *m0;
144 
145 	MINDEX(len, m, k);
146 	cp = mtod(m, u_char *) + k;
147 	if (len - k >= 4) {
148 		*err = 0;
149 		return EXTRACT_LONG(cp);
150 	}
151 	m0 = m->m_next;
152 	if (m0 == 0 || MLEN(m0) + len - k < 4)
153 		goto bad;
154 	*err = 0;
155 	np = mtod(m0, u_char *);
156 	switch (len - k) {
157 
158 	case 1:
159 		return (cp[0] << 24) | (np[0] << 16) | (np[1] << 8) | np[2];
160 
161 	case 2:
162 		return (cp[0] << 24) | (cp[1] << 16) | (np[0] << 8) | np[1];
163 
164 	default:
165 		return (cp[0] << 24) | (cp[1] << 16) | (cp[2] << 8) | np[0];
166 	}
167     bad:
168 	*err = 1;
169 	return 0;
170 }
171 
172 static int
m_xhalf(m,k,err)173 m_xhalf(m, k, err)
174 	register struct mbuf *m;
175 	register int k, *err;
176 {
177 	register int len;
178 	register u_char *cp;
179 	register struct mbuf *m0;
180 
181 	MINDEX(len, m, k);
182 	cp = mtod(m, u_char *) + k;
183 	if (len - k >= 2) {
184 		*err = 0;
185 		return EXTRACT_SHORT(cp);
186 	}
187 	m0 = m->m_next;
188 	if (m0 == 0)
189 		goto bad;
190 	*err = 0;
191 	return (cp[0] << 8) | mtod(m0, u_char *)[0];
192  bad:
193 	*err = 1;
194 	return 0;
195 }
196 #endif
197 
198 #ifdef __linux__
199 #include <linux/types.h>
200 #include <linux/if_packet.h>
201 #include <linux/filter.h>
202 #endif
203 
204 enum {
205         BPF_S_ANC_NONE,
206         BPF_S_ANC_VLAN_TAG,
207         BPF_S_ANC_VLAN_TAG_PRESENT,
208 };
209 
210 /*
211  * Execute the filter program starting at pc on the packet p
212  * wirelen is the length of the original packet
213  * buflen is the amount of data present
214  * aux_data is auxiliary data, currently used only when interpreting
215  * filters intended for the Linux kernel in cases where the kernel
216  * rejects the filter; it contains VLAN tag information
217  * For the kernel, p is assumed to be a pointer to an mbuf if buflen is 0,
218  * in all other cases, p is a pointer to a buffer and buflen is its size.
219  */
220 u_int
bpf_filter_with_aux_data(pc,p,wirelen,buflen,aux_data)221 bpf_filter_with_aux_data(pc, p, wirelen, buflen, aux_data)
222 	register const struct bpf_insn *pc;
223 	register const u_char *p;
224 	u_int wirelen;
225 	register u_int buflen;
226 	register const struct bpf_aux_data *aux_data;
227 {
228 	register u_int32 A, X;
229 	register bpf_u_int32 k;
230 	u_int32 mem[BPF_MEMWORDS];
231 #if defined(KERNEL) || defined(_KERNEL)
232 	struct mbuf *m, *n;
233 	int merr, len;
234 
235 	if (buflen == 0) {
236 		m = (struct mbuf *)p;
237 		p = mtod(m, u_char *);
238 		buflen = MLEN(m);
239 	} else
240 		m = NULL;
241 #endif
242 
243 	if (pc == 0)
244 		/*
245 		 * No filter means accept all.
246 		 */
247 		return (u_int)-1;
248 	A = 0;
249 	X = 0;
250 	--pc;
251 	while (1) {
252 		++pc;
253 		switch (pc->code) {
254 
255 		default:
256 #if defined(KERNEL) || defined(_KERNEL)
257 			return 0;
258 #else
259 			abort();
260 #endif
261 		case BPF_RET|BPF_K:
262 			return (u_int)pc->k;
263 
264 		case BPF_RET|BPF_A:
265 			return (u_int)A;
266 
267 		case BPF_LD|BPF_W|BPF_ABS:
268 			k = pc->k;
269 			if (k > buflen || sizeof(int32_t) > buflen - k) {
270 #if defined(KERNEL) || defined(_KERNEL)
271 				if (m == NULL)
272 					return 0;
273 				A = m_xword(m, k, &merr);
274 				if (merr != 0)
275 					return 0;
276 				continue;
277 #else
278 				return 0;
279 #endif
280 			}
281 			A = EXTRACT_LONG(&p[k]);
282 			continue;
283 
284 		case BPF_LD|BPF_H|BPF_ABS:
285 			k = pc->k;
286 			if (k > buflen || sizeof(int16_t) > buflen - k) {
287 #if defined(KERNEL) || defined(_KERNEL)
288 				if (m == NULL)
289 					return 0;
290 				A = m_xhalf(m, k, &merr);
291 				if (merr != 0)
292 					return 0;
293 				continue;
294 #else
295 				return 0;
296 #endif
297 			}
298 			A = EXTRACT_SHORT(&p[k]);
299 			continue;
300 
301 		case BPF_LD|BPF_B|BPF_ABS:
302 			{
303 #if defined(SKF_AD_VLAN_TAG) && defined(SKF_AD_VLAN_TAG_PRESENT)
304 				int code = BPF_S_ANC_NONE;
305 #define ANCILLARY(CODE) case SKF_AD_OFF + SKF_AD_##CODE:		\
306 				code = BPF_S_ANC_##CODE;		\
307                                         if (!aux_data)                  \
308                                                 return 0;               \
309                                         break;
310 
311 				switch (pc->k) {
312 					ANCILLARY(VLAN_TAG);
313 					ANCILLARY(VLAN_TAG_PRESENT);
314 				default :
315 #endif
316 					k = pc->k;
317 					if (k >= buflen) {
318 #if defined(KERNEL) || defined(_KERNEL)
319 						if (m == NULL)
320 							return 0;
321 						n = m;
322 						MINDEX(len, n, k);
323 						A = mtod(n, u_char *)[k];
324 						continue;
325 #else
326 						return 0;
327 #endif
328 					}
329 					A = p[k];
330 #if defined(SKF_AD_VLAN_TAG) && defined(SKF_AD_VLAN_TAG_PRESENT)
331 				}
332 				switch (code) {
333 				case BPF_S_ANC_VLAN_TAG:
334 					if (aux_data)
335 						A = aux_data->vlan_tag;
336 					break;
337 
338 				case BPF_S_ANC_VLAN_TAG_PRESENT:
339 					if (aux_data)
340 						A = aux_data->vlan_tag_present;
341 					break;
342 				}
343 #endif
344 				continue;
345 			}
346 		case BPF_LD|BPF_W|BPF_LEN:
347 			A = wirelen;
348 			continue;
349 
350 		case BPF_LDX|BPF_W|BPF_LEN:
351 			X = wirelen;
352 			continue;
353 
354 		case BPF_LD|BPF_W|BPF_IND:
355 			k = X + pc->k;
356 			if (pc->k > buflen || X > buflen - pc->k ||
357 			    sizeof(int32_t) > buflen - k) {
358 #if defined(KERNEL) || defined(_KERNEL)
359 				if (m == NULL)
360 					return 0;
361 				A = m_xword(m, k, &merr);
362 				if (merr != 0)
363 					return 0;
364 				continue;
365 #else
366 				return 0;
367 #endif
368 			}
369 			A = EXTRACT_LONG(&p[k]);
370 			continue;
371 
372 		case BPF_LD|BPF_H|BPF_IND:
373 			k = X + pc->k;
374 			if (X > buflen || pc->k > buflen - X ||
375 			    sizeof(int16_t) > buflen - k) {
376 #if defined(KERNEL) || defined(_KERNEL)
377 				if (m == NULL)
378 					return 0;
379 				A = m_xhalf(m, k, &merr);
380 				if (merr != 0)
381 					return 0;
382 				continue;
383 #else
384 				return 0;
385 #endif
386 			}
387 			A = EXTRACT_SHORT(&p[k]);
388 			continue;
389 
390 		case BPF_LD|BPF_B|BPF_IND:
391 			k = X + pc->k;
392 			if (pc->k >= buflen || X >= buflen - pc->k) {
393 #if defined(KERNEL) || defined(_KERNEL)
394 				if (m == NULL)
395 					return 0;
396 				n = m;
397 				MINDEX(len, n, k);
398 				A = mtod(n, u_char *)[k];
399 				continue;
400 #else
401 				return 0;
402 #endif
403 			}
404 			A = p[k];
405 			continue;
406 
407 		case BPF_LDX|BPF_MSH|BPF_B:
408 			k = pc->k;
409 			if (k >= buflen) {
410 #if defined(KERNEL) || defined(_KERNEL)
411 				if (m == NULL)
412 					return 0;
413 				n = m;
414 				MINDEX(len, n, k);
415 				X = (mtod(n, char *)[k] & 0xf) << 2;
416 				continue;
417 #else
418 				return 0;
419 #endif
420 			}
421 			X = (p[pc->k] & 0xf) << 2;
422 			continue;
423 
424 		case BPF_LD|BPF_IMM:
425 			A = pc->k;
426 			continue;
427 
428 		case BPF_LDX|BPF_IMM:
429 			X = pc->k;
430 			continue;
431 
432 		case BPF_LD|BPF_MEM:
433 			A = mem[pc->k];
434 			continue;
435 
436 		case BPF_LDX|BPF_MEM:
437 			X = mem[pc->k];
438 			continue;
439 
440 		case BPF_ST:
441 			mem[pc->k] = A;
442 			continue;
443 
444 		case BPF_STX:
445 			mem[pc->k] = X;
446 			continue;
447 
448 		case BPF_JMP|BPF_JA:
449 #if defined(KERNEL) || defined(_KERNEL)
450 			/*
451 			 * No backward jumps allowed.
452 			 */
453 			pc += pc->k;
454 #else
455 			/*
456 			 * XXX - we currently implement "ip6 protochain"
457 			 * with backward jumps, so sign-extend pc->k.
458 			 */
459 			pc += (bpf_int32)pc->k;
460 #endif
461 			continue;
462 
463 		case BPF_JMP|BPF_JGT|BPF_K:
464 			pc += (A > pc->k) ? pc->jt : pc->jf;
465 			continue;
466 
467 		case BPF_JMP|BPF_JGE|BPF_K:
468 			pc += (A >= pc->k) ? pc->jt : pc->jf;
469 			continue;
470 
471 		case BPF_JMP|BPF_JEQ|BPF_K:
472 			pc += (A == pc->k) ? pc->jt : pc->jf;
473 			continue;
474 
475 		case BPF_JMP|BPF_JSET|BPF_K:
476 			pc += (A & pc->k) ? pc->jt : pc->jf;
477 			continue;
478 
479 		case BPF_JMP|BPF_JGT|BPF_X:
480 			pc += (A > X) ? pc->jt : pc->jf;
481 			continue;
482 
483 		case BPF_JMP|BPF_JGE|BPF_X:
484 			pc += (A >= X) ? pc->jt : pc->jf;
485 			continue;
486 
487 		case BPF_JMP|BPF_JEQ|BPF_X:
488 			pc += (A == X) ? pc->jt : pc->jf;
489 			continue;
490 
491 		case BPF_JMP|BPF_JSET|BPF_X:
492 			pc += (A & X) ? pc->jt : pc->jf;
493 			continue;
494 
495 		case BPF_ALU|BPF_ADD|BPF_X:
496 			A += X;
497 			continue;
498 
499 		case BPF_ALU|BPF_SUB|BPF_X:
500 			A -= X;
501 			continue;
502 
503 		case BPF_ALU|BPF_MUL|BPF_X:
504 			A *= X;
505 			continue;
506 
507 		case BPF_ALU|BPF_DIV|BPF_X:
508 			if (X == 0)
509 				return 0;
510 			A /= X;
511 			continue;
512 
513 		case BPF_ALU|BPF_MOD|BPF_X:
514 			if (X == 0)
515 				return 0;
516 			A %= X;
517 			continue;
518 
519 		case BPF_ALU|BPF_AND|BPF_X:
520 			A &= X;
521 			continue;
522 
523 		case BPF_ALU|BPF_OR|BPF_X:
524 			A |= X;
525 			continue;
526 
527 		case BPF_ALU|BPF_XOR|BPF_X:
528 			A ^= X;
529 			continue;
530 
531 		case BPF_ALU|BPF_LSH|BPF_X:
532 			A <<= X;
533 			continue;
534 
535 		case BPF_ALU|BPF_RSH|BPF_X:
536 			A >>= X;
537 			continue;
538 
539 		case BPF_ALU|BPF_ADD|BPF_K:
540 			A += pc->k;
541 			continue;
542 
543 		case BPF_ALU|BPF_SUB|BPF_K:
544 			A -= pc->k;
545 			continue;
546 
547 		case BPF_ALU|BPF_MUL|BPF_K:
548 			A *= pc->k;
549 			continue;
550 
551 		case BPF_ALU|BPF_DIV|BPF_K:
552 			A /= pc->k;
553 			continue;
554 
555 		case BPF_ALU|BPF_MOD|BPF_K:
556 			A %= pc->k;
557 			continue;
558 
559 		case BPF_ALU|BPF_AND|BPF_K:
560 			A &= pc->k;
561 			continue;
562 
563 		case BPF_ALU|BPF_OR|BPF_K:
564 			A |= pc->k;
565 			continue;
566 
567 		case BPF_ALU|BPF_XOR|BPF_K:
568 			A ^= pc->k;
569 			continue;
570 
571 		case BPF_ALU|BPF_LSH|BPF_K:
572 			A <<= pc->k;
573 			continue;
574 
575 		case BPF_ALU|BPF_RSH|BPF_K:
576 			A >>= pc->k;
577 			continue;
578 
579 		case BPF_ALU|BPF_NEG:
580 			A = -A;
581 			continue;
582 
583 		case BPF_MISC|BPF_TAX:
584 			X = A;
585 			continue;
586 
587 		case BPF_MISC|BPF_TXA:
588 			A = X;
589 			continue;
590 		}
591 	}
592 }
593 
594 u_int
bpf_filter(pc,p,wirelen,buflen)595 bpf_filter(pc, p, wirelen, buflen)
596 	register const struct bpf_insn *pc;
597 	register const u_char *p;
598 	u_int wirelen;
599 	register u_int buflen;
600 {
601 	return bpf_filter_with_aux_data(pc, p, wirelen, buflen, NULL);
602 }
603 
604 
605 /*
606  * Return true if the 'fcode' is a valid filter program.
607  * The constraints are that each jump be forward and to a valid
608  * code, that memory accesses are within valid ranges (to the
609  * extent that this can be checked statically; loads of packet
610  * data have to be, and are, also checked at run time), and that
611  * the code terminates with either an accept or reject.
612  *
613  * The kernel needs to be able to verify an application's filter code.
614  * Otherwise, a bogus program could easily crash the system.
615  */
616 int
bpf_validate(f,len)617 bpf_validate(f, len)
618 	const struct bpf_insn *f;
619 	int len;
620 {
621 	u_int i, from;
622 	const struct bpf_insn *p;
623 
624 	if (len < 1)
625 		return 0;
626 	/*
627 	 * There's no maximum program length in userland.
628 	 */
629 #if defined(KERNEL) || defined(_KERNEL)
630 	if (len > BPF_MAXINSNS)
631 		return 0;
632 #endif
633 
634 	for (i = 0; i < len; ++i) {
635 		p = &f[i];
636 		switch (BPF_CLASS(p->code)) {
637 		/*
638 		 * Check that memory operations use valid addresses.
639 		 */
640 		case BPF_LD:
641 		case BPF_LDX:
642 			switch (BPF_MODE(p->code)) {
643 			case BPF_IMM:
644 				break;
645 			case BPF_ABS:
646 			case BPF_IND:
647 			case BPF_MSH:
648 				/*
649 				 * There's no maximum packet data size
650 				 * in userland.  The runtime packet length
651 				 * check suffices.
652 				 */
653 #if defined(KERNEL) || defined(_KERNEL)
654 				/*
655 				 * More strict check with actual packet length
656 				 * is done runtime.
657 				 */
658 				if (p->k >= bpf_maxbufsize)
659 					return 0;
660 #endif
661 				break;
662 			case BPF_MEM:
663 				if (p->k >= BPF_MEMWORDS)
664 					return 0;
665 				break;
666 			case BPF_LEN:
667 				break;
668 			default:
669 				return 0;
670 			}
671 			break;
672 		case BPF_ST:
673 		case BPF_STX:
674 			if (p->k >= BPF_MEMWORDS)
675 				return 0;
676 			break;
677 		case BPF_ALU:
678 			switch (BPF_OP(p->code)) {
679 			case BPF_ADD:
680 			case BPF_SUB:
681 			case BPF_MUL:
682 			case BPF_OR:
683 			case BPF_AND:
684 			case BPF_XOR:
685 			case BPF_LSH:
686 			case BPF_RSH:
687 			case BPF_NEG:
688 				break;
689 			case BPF_DIV:
690 			case BPF_MOD:
691 				/*
692 				 * Check for constant division or modulus
693 				 * by 0.
694 				 */
695 				if (BPF_SRC(p->code) == BPF_K && p->k == 0)
696 					return 0;
697 				break;
698 			default:
699 				return 0;
700 			}
701 			break;
702 		case BPF_JMP:
703 			/*
704 			 * Check that jumps are within the code block,
705 			 * and that unconditional branches don't go
706 			 * backwards as a result of an overflow.
707 			 * Unconditional branches have a 32-bit offset,
708 			 * so they could overflow; we check to make
709 			 * sure they don't.  Conditional branches have
710 			 * an 8-bit offset, and the from address is <=
711 			 * BPF_MAXINSNS, and we assume that BPF_MAXINSNS
712 			 * is sufficiently small that adding 255 to it
713 			 * won't overflow.
714 			 *
715 			 * We know that len is <= BPF_MAXINSNS, and we
716 			 * assume that BPF_MAXINSNS is < the maximum size
717 			 * of a u_int, so that i + 1 doesn't overflow.
718 			 *
719 			 * For userland, we don't know that the from
720 			 * or len are <= BPF_MAXINSNS, but we know that
721 			 * from <= len, and, except on a 64-bit system,
722 			 * it's unlikely that len, if it truly reflects
723 			 * the size of the program we've been handed,
724 			 * will be anywhere near the maximum size of
725 			 * a u_int.  We also don't check for backward
726 			 * branches, as we currently support them in
727 			 * userland for the protochain operation.
728 			 */
729 			from = i + 1;
730 			switch (BPF_OP(p->code)) {
731 			case BPF_JA:
732 #if defined(KERNEL) || defined(_KERNEL)
733 				if (from + p->k < from || from + p->k >= len)
734 #else
735 				if (from + p->k >= len)
736 #endif
737 					return 0;
738 				break;
739 			case BPF_JEQ:
740 			case BPF_JGT:
741 			case BPF_JGE:
742 			case BPF_JSET:
743 				if (from + p->jt >= len || from + p->jf >= len)
744 					return 0;
745 				break;
746 			default:
747 				return 0;
748 			}
749 			break;
750 		case BPF_RET:
751 			break;
752 		case BPF_MISC:
753 			break;
754 		default:
755 			return 0;
756 		}
757 	}
758 	return BPF_CLASS(f[len - 1].code) == BPF_RET;
759 }
760