2 * Copyright (c) 1990, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
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
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
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 * 4. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93
39 #include <sys/param.h>
42 #include <netinet/in.h>
50 #define EXTRACT_SHORT(p) ((u_int16_t)ntohs(*(u_int16_t *)p))
51 #define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p))
53 #define EXTRACT_SHORT(p)\
55 ((u_int16_t)*((u_char *)p+0)<<8|\
56 (u_int16_t)*((u_char *)p+1)<<0))
57 #define EXTRACT_LONG(p)\
58 ((u_int32_t)*((u_char *)p+0)<<24|\
59 (u_int32_t)*((u_char *)p+1)<<16|\
60 (u_int32_t)*((u_char *)p+2)<<8|\
61 (u_int32_t)*((u_char *)p+3)<<0)
69 #define MINDEX(m, k) \
71 register int len = m->m_len; \
82 static u_int16_t m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err);
83 static u_int32_t m_xword(struct mbuf *m, bpf_u_int32 k, int *err);
86 m_xword(struct mbuf *m, bpf_u_int32 k, int *err)
100 cp = mtod(m, u_char *) + k;
103 return EXTRACT_LONG(cp);
106 if (m0 == 0 || m0->m_len + len - k < 4)
109 np = mtod(m0, u_char *);
113 ((u_int32_t)cp[0] << 24) |
114 ((u_int32_t)np[0] << 16) |
115 ((u_int32_t)np[1] << 8) |
120 ((u_int32_t)cp[0] << 24) |
121 ((u_int32_t)cp[1] << 16) |
122 ((u_int32_t)np[0] << 8) |
127 ((u_int32_t)cp[0] << 24) |
128 ((u_int32_t)cp[1] << 16) |
129 ((u_int32_t)cp[2] << 8) |
138 m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err)
152 cp = mtod(m, u_char *) + k;
155 return (EXTRACT_SHORT(cp));
161 return ((cp[0] << 8) | mtod(m0, u_char *)[0]);
169 * Execute the filter program starting at pc on the packet p
170 * wirelen is the length of the original packet
171 * buflen is the amount of data present
174 bpf_filter(const struct bpf_insn *pc, u_char *p, u_int wirelen, u_int buflen)
176 u_int32_t A = 0, X = 0;
178 u_int32_t mem[BPF_MEMWORDS];
182 * No filter means accept all.
198 return ((u_int)pc->k);
203 case BPF_LD|BPF_W|BPF_ABS:
205 if (k > buflen || sizeof(int32_t) > buflen - k) {
211 A = m_xword((struct mbuf *)p, k, &merr);
220 if (((intptr_t)(p + k) & 3) != 0)
221 A = EXTRACT_LONG(&p[k]);
224 A = ntohl(*(int32_t *)(p + k));
227 case BPF_LD|BPF_H|BPF_ABS:
229 if (k > buflen || sizeof(int16_t) > buflen - k) {
235 A = m_xhalf((struct mbuf *)p, k, &merr);
241 A = EXTRACT_SHORT(&p[k]);
244 case BPF_LD|BPF_B|BPF_ABS:
252 m = (struct mbuf *)p;
254 A = mtod(m, u_char *)[k];
263 case BPF_LD|BPF_W|BPF_LEN:
267 case BPF_LDX|BPF_W|BPF_LEN:
271 case BPF_LD|BPF_W|BPF_IND:
273 if (pc->k > buflen || X > buflen - pc->k ||
274 sizeof(int32_t) > buflen - k) {
280 A = m_xword((struct mbuf *)p, k, &merr);
289 if (((intptr_t)(p + k) & 3) != 0)
290 A = EXTRACT_LONG(&p[k]);
293 A = ntohl(*(int32_t *)(p + k));
296 case BPF_LD|BPF_H|BPF_IND:
298 if (X > buflen || pc->k > buflen - X ||
299 sizeof(int16_t) > buflen - k) {
305 A = m_xhalf((struct mbuf *)p, k, &merr);
313 A = EXTRACT_SHORT(&p[k]);
316 case BPF_LD|BPF_B|BPF_IND:
318 if (pc->k >= buflen || X >= buflen - pc->k) {
324 m = (struct mbuf *)p;
326 A = mtod(m, u_char *)[k];
335 case BPF_LDX|BPF_MSH|BPF_B:
339 register struct mbuf *m;
343 m = (struct mbuf *)p;
345 X = (mtod(m, u_char *)[k] & 0xf) << 2;
351 X = (p[pc->k] & 0xf) << 2;
358 case BPF_LDX|BPF_IMM:
366 case BPF_LDX|BPF_MEM:
382 case BPF_JMP|BPF_JGT|BPF_K:
383 pc += (A > pc->k) ? pc->jt : pc->jf;
386 case BPF_JMP|BPF_JGE|BPF_K:
387 pc += (A >= pc->k) ? pc->jt : pc->jf;
390 case BPF_JMP|BPF_JEQ|BPF_K:
391 pc += (A == pc->k) ? pc->jt : pc->jf;
394 case BPF_JMP|BPF_JSET|BPF_K:
395 pc += (A & pc->k) ? pc->jt : pc->jf;
398 case BPF_JMP|BPF_JGT|BPF_X:
399 pc += (A > X) ? pc->jt : pc->jf;
402 case BPF_JMP|BPF_JGE|BPF_X:
403 pc += (A >= X) ? pc->jt : pc->jf;
406 case BPF_JMP|BPF_JEQ|BPF_X:
407 pc += (A == X) ? pc->jt : pc->jf;
410 case BPF_JMP|BPF_JSET|BPF_X:
411 pc += (A & X) ? pc->jt : pc->jf;
414 case BPF_ALU|BPF_ADD|BPF_X:
418 case BPF_ALU|BPF_SUB|BPF_X:
422 case BPF_ALU|BPF_MUL|BPF_X:
426 case BPF_ALU|BPF_DIV|BPF_X:
432 case BPF_ALU|BPF_AND|BPF_X:
436 case BPF_ALU|BPF_OR|BPF_X:
440 case BPF_ALU|BPF_LSH|BPF_X:
444 case BPF_ALU|BPF_RSH|BPF_X:
448 case BPF_ALU|BPF_ADD|BPF_K:
452 case BPF_ALU|BPF_SUB|BPF_K:
456 case BPF_ALU|BPF_MUL|BPF_K:
460 case BPF_ALU|BPF_DIV|BPF_K:
464 case BPF_ALU|BPF_AND|BPF_K:
468 case BPF_ALU|BPF_OR|BPF_K:
472 case BPF_ALU|BPF_LSH|BPF_K:
476 case BPF_ALU|BPF_RSH|BPF_K:
480 case BPF_ALU|BPF_NEG:
484 case BPF_MISC|BPF_TAX:
488 case BPF_MISC|BPF_TXA:
497 * Return true if the 'fcode' is a valid filter program.
498 * The constraints are that each jump be forward and to a valid
499 * code. The code must terminate with either an accept or reject.
501 * The kernel needs to be able to verify an application's filter code.
502 * Otherwise, a bogus program could easily crash the system.
506 const struct bpf_insn *f;
510 register const struct bpf_insn *p;
512 /* Do not accept negative length filter. */
516 /* An empty filter means accept all. */
520 for (i = 0; i < len; ++i) {
522 * Check that that jumps are forward, and within
526 if (BPF_CLASS(p->code) == BPF_JMP) {
527 register int from = i + 1;
529 if (BPF_OP(p->code) == BPF_JA) {
530 if (from >= len || p->k >= len - from)
533 else if (from >= len || p->jt >= len - from ||
538 * Check that memory operations use valid addresses.
540 if ((BPF_CLASS(p->code) == BPF_ST ||
541 BPF_CLASS(p->code) == BPF_STX ||
542 ((BPF_CLASS(p->code) == BPF_LD ||
543 BPF_CLASS(p->code) == BPF_LDX) &&
544 (p->code & 0xe0) == BPF_MEM)) &&
545 p->k >= BPF_MEMWORDS)
548 * Check for constant division by 0.
550 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0)
553 return BPF_CLASS(f[len - 1].code) == BPF_RET;