2 * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
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 * 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.
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
38 * @(#)bpf.c 7.5 (Berkeley) 7/15/91
41 #if !(defined(lint) || defined(KERNEL) || defined(_KERNEL))
42 static const char rcsid
[] _U_
=
43 "@(#) $Header: /tcpdump/master/libpcap/bpf/net/bpf_filter.c,v 1.46 2008-01-02 04:16:46 guy Exp $ (LBL)";
52 #include <pcap-stdinc.h>
61 #ifdef HAVE_SYS_BITYPES_H
62 #include <sys/bitypes.h>
65 #include <sys/param.h>
66 #include <sys/types.h>
69 #define SOLARIS (defined(sun) && (defined(__SVR4) || defined(__svr4__)))
70 #if defined(__hpux) || SOLARIS
71 # include <sys/sysmacros.h>
72 # include <sys/stream.h>
74 # define m_next b_cont
75 # define MLEN(m) ((m)->b_wptr - (m)->b_rptr)
76 # define mtod(m,t) ((t)(m)->b_rptr)
77 #else /* defined(__hpux) || SOLARIS */
78 # define MLEN(m) ((m)->m_len)
79 #endif /* defined(__hpux) || SOLARIS */
85 #if !defined(KERNEL) && !defined(_KERNEL)
89 #define int32 bpf_int32
90 #define u_int32 bpf_u_int32
94 * XXX - IA-64? If not, this probably won't work on Win64 IA-64
95 * systems, unless LBL_ALIGN is defined elsewhere for them.
96 * XXX - SuperH? If not, this probably won't work on WinCE SuperH
97 * systems, unless LBL_ALIGN is defined elsewhere for them.
99 #if defined(sparc) || defined(__sparc__) || defined(mips) || \
100 defined(ibm032) || defined(__alpha) || defined(__hpux) || \
108 #include <netinet/in.h>
111 #define EXTRACT_SHORT(p) ((u_short)ntohs(*(u_short *)p))
112 #define EXTRACT_LONG(p) (ntohl(*(u_int32 *)p))
114 #define EXTRACT_SHORT(p)\
116 ((u_short)*((u_char *)p+0)<<8|\
117 (u_short)*((u_char *)p+1)<<0))
118 #define EXTRACT_LONG(p)\
119 ((u_int32)*((u_char *)p+0)<<24|\
120 (u_int32)*((u_char *)p+1)<<16|\
121 (u_int32)*((u_char *)p+2)<<8|\
122 (u_int32)*((u_char *)p+3)<<0)
125 #if defined(KERNEL) || defined(_KERNEL)
126 # if !defined(__hpux) && !SOLARIS
127 #include <sys/mbuf.h>
129 #define MINDEX(len, _m, _k) \
132 while ((_k) >= len) { \
134 (_m) = (_m)->m_next; \
143 register struct mbuf
*m
;
144 register int k
, *err
;
147 register u_char
*cp
, *np
;
148 register struct mbuf
*m0
;
151 cp
= mtod(m
, u_char
*) + k
;
154 return EXTRACT_LONG(cp
);
157 if (m0
== 0 || MLEN(m0
) + len
- k
< 4)
160 np
= mtod(m0
, u_char
*);
164 return (cp
[0] << 24) | (np
[0] << 16) | (np
[1] << 8) | np
[2];
167 return (cp
[0] << 24) | (cp
[1] << 16) | (np
[0] << 8) | np
[1];
170 return (cp
[0] << 24) | (cp
[1] << 16) | (cp
[2] << 8) | np
[0];
179 register struct mbuf
*m
;
180 register int k
, *err
;
184 register struct mbuf
*m0
;
187 cp
= mtod(m
, u_char
*) + k
;
190 return EXTRACT_SHORT(cp
);
196 return (cp
[0] << 8) | mtod(m0
, u_char
*)[0];
204 * Execute the filter program starting at pc on the packet p
205 * wirelen is the length of the original packet
206 * buflen is the amount of data present
207 * For the kernel, p is assumed to be a pointer to an mbuf if buflen is 0,
208 * in all other cases, p is a pointer to a buffer and buflen is its size.
211 bpf_filter(pc
, p
, wirelen
, buflen
)
212 register const struct bpf_insn
*pc
;
213 register const u_char
*p
;
215 register u_int buflen
;
217 register u_int32 A
, X
;
219 int32 mem
[BPF_MEMWORDS
];
220 #if defined(KERNEL) || defined(_KERNEL)
225 m
= (struct mbuf
*)p
;
226 p
= mtod(m
, u_char
*);
234 * No filter means accept all.
245 #if defined(KERNEL) || defined(_KERNEL)
256 case BPF_LD
|BPF_W
|BPF_ABS
:
258 if (k
+ sizeof(int32
) > buflen
) {
259 #if defined(KERNEL) || defined(_KERNEL)
262 A
= m_xword(m
, k
, &merr
);
270 A
= EXTRACT_LONG(&p
[k
]);
273 case BPF_LD
|BPF_H
|BPF_ABS
:
275 if (k
+ sizeof(short) > buflen
) {
276 #if defined(KERNEL) || defined(_KERNEL)
279 A
= m_xhalf(m
, k
, &merr
);
287 A
= EXTRACT_SHORT(&p
[k
]);
290 case BPF_LD
|BPF_B
|BPF_ABS
:
293 #if defined(KERNEL) || defined(_KERNEL)
298 A
= mtod(n
, u_char
*)[k
];
307 case BPF_LD
|BPF_W
|BPF_LEN
:
311 case BPF_LDX
|BPF_W
|BPF_LEN
:
315 case BPF_LD
|BPF_W
|BPF_IND
:
317 if (k
+ sizeof(int32
) > buflen
) {
318 #if defined(KERNEL) || defined(_KERNEL)
321 A
= m_xword(m
, k
, &merr
);
329 A
= EXTRACT_LONG(&p
[k
]);
332 case BPF_LD
|BPF_H
|BPF_IND
:
334 if (k
+ sizeof(short) > buflen
) {
335 #if defined(KERNEL) || defined(_KERNEL)
338 A
= m_xhalf(m
, k
, &merr
);
346 A
= EXTRACT_SHORT(&p
[k
]);
349 case BPF_LD
|BPF_B
|BPF_IND
:
352 #if defined(KERNEL) || defined(_KERNEL)
357 A
= mtod(n
, u_char
*)[k
];
366 case BPF_LDX
|BPF_MSH
|BPF_B
:
369 #if defined(KERNEL) || defined(_KERNEL)
374 X
= (mtod(n
, char *)[k
] & 0xf) << 2;
380 X
= (p
[pc
->k
] & 0xf) << 2;
387 case BPF_LDX
|BPF_IMM
:
395 case BPF_LDX
|BPF_MEM
:
408 #if defined(KERNEL) || defined(_KERNEL)
410 * No backward jumps allowed.
415 * XXX - we currently implement "ip6 protochain"
416 * with backward jumps, so sign-extend pc->k.
418 pc
+= (bpf_int32
)pc
->k
;
422 case BPF_JMP
|BPF_JGT
|BPF_K
:
423 pc
+= (A
> pc
->k
) ? pc
->jt
: pc
->jf
;
426 case BPF_JMP
|BPF_JGE
|BPF_K
:
427 pc
+= (A
>= pc
->k
) ? pc
->jt
: pc
->jf
;
430 case BPF_JMP
|BPF_JEQ
|BPF_K
:
431 pc
+= (A
== pc
->k
) ? pc
->jt
: pc
->jf
;
434 case BPF_JMP
|BPF_JSET
|BPF_K
:
435 pc
+= (A
& pc
->k
) ? pc
->jt
: pc
->jf
;
438 case BPF_JMP
|BPF_JGT
|BPF_X
:
439 pc
+= (A
> X
) ? pc
->jt
: pc
->jf
;
442 case BPF_JMP
|BPF_JGE
|BPF_X
:
443 pc
+= (A
>= X
) ? pc
->jt
: pc
->jf
;
446 case BPF_JMP
|BPF_JEQ
|BPF_X
:
447 pc
+= (A
== X
) ? pc
->jt
: pc
->jf
;
450 case BPF_JMP
|BPF_JSET
|BPF_X
:
451 pc
+= (A
& X
) ? pc
->jt
: pc
->jf
;
454 case BPF_ALU
|BPF_ADD
|BPF_X
:
458 case BPF_ALU
|BPF_SUB
|BPF_X
:
462 case BPF_ALU
|BPF_MUL
|BPF_X
:
466 case BPF_ALU
|BPF_DIV
|BPF_X
:
472 case BPF_ALU
|BPF_AND
|BPF_X
:
476 case BPF_ALU
|BPF_OR
|BPF_X
:
480 case BPF_ALU
|BPF_LSH
|BPF_X
:
484 case BPF_ALU
|BPF_RSH
|BPF_X
:
488 case BPF_ALU
|BPF_ADD
|BPF_K
:
492 case BPF_ALU
|BPF_SUB
|BPF_K
:
496 case BPF_ALU
|BPF_MUL
|BPF_K
:
500 case BPF_ALU
|BPF_DIV
|BPF_K
:
504 case BPF_ALU
|BPF_AND
|BPF_K
:
508 case BPF_ALU
|BPF_OR
|BPF_K
:
512 case BPF_ALU
|BPF_LSH
|BPF_K
:
516 case BPF_ALU
|BPF_RSH
|BPF_K
:
520 case BPF_ALU
|BPF_NEG
:
524 case BPF_MISC
|BPF_TAX
:
528 case BPF_MISC
|BPF_TXA
:
536 * Return true if the 'fcode' is a valid filter program.
537 * The constraints are that each jump be forward and to a valid
538 * code, that memory accesses are within valid ranges (to the
539 * extent that this can be checked statically; loads of packet
540 * data have to be, and are, also checked at run time), and that
541 * the code terminates with either an accept or reject.
543 * The kernel needs to be able to verify an application's filter code.
544 * Otherwise, a bogus program could easily crash the system.
548 const struct bpf_insn
*f
;
552 const struct bpf_insn
*p
;
557 * There's no maximum program length in userland.
559 #if defined(KERNEL) || defined(_KERNEL)
560 if (len
> BPF_MAXINSNS
)
564 for (i
= 0; i
< len
; ++i
) {
566 switch (BPF_CLASS(p
->code
)) {
568 * Check that memory operations use valid addresses.
572 switch (BPF_MODE(p
->code
)) {
579 * There's no maximum packet data size
580 * in userland. The runtime packet length
583 #if defined(KERNEL) || defined(_KERNEL)
585 * More strict check with actual packet length
588 if (p
->k
>= bpf_maxbufsize
)
593 if (p
->k
>= BPF_MEMWORDS
)
604 if (p
->k
>= BPF_MEMWORDS
)
608 switch (BPF_OP(p
->code
)) {
620 * Check for constant division by 0.
622 if (BPF_SRC(p
->code
) == BPF_K
&& p
->k
== 0)
631 * Check that jumps are within the code block,
632 * and that unconditional branches don't go
633 * backwards as a result of an overflow.
634 * Unconditional branches have a 32-bit offset,
635 * so they could overflow; we check to make
636 * sure they don't. Conditional branches have
637 * an 8-bit offset, and the from address is <=
638 * BPF_MAXINSNS, and we assume that BPF_MAXINSNS
639 * is sufficiently small that adding 255 to it
642 * We know that len is <= BPF_MAXINSNS, and we
643 * assume that BPF_MAXINSNS is < the maximum size
644 * of a u_int, so that i + 1 doesn't overflow.
646 * For userland, we don't know that the from
647 * or len are <= BPF_MAXINSNS, but we know that
648 * from <= len, and, except on a 64-bit system,
649 * it's unlikely that len, if it truly reflects
650 * the size of the program we've been handed,
651 * will be anywhere near the maximum size of
652 * a u_int. We also don't check for backward
653 * branches, as we currently support them in
654 * userland for the protochain operation.
657 switch (BPF_OP(p
->code
)) {
659 #if defined(KERNEL) || defined(_KERNEL)
660 if (from
+ p
->k
< from
|| from
+ p
->k
>= len
)
662 if (from
+ p
->k
>= len
)
670 if (from
+ p
->jt
>= len
|| from
+ p
->jf
>= len
)
685 return BPF_CLASS(f
[len
- 1].code
) == BPF_RET
;