bpf_filter.c - net/ipfilter - Rivoreo Source Code Repositories

 /*-
  * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
  *	The Regents of the University of California.  All rights reserved.
  *
  * This code is derived from the Stanford/CMU enet packet filter,
  * (net/enet.c) distributed as part of 4.3BSD, and code contributed
  * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
  * Berkeley Laboratory.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. All advertising materials mentioning features or use of this software
  *    must display the following acknowledgement:
  *	This product includes software developed by the University of
  *	California, Berkeley and its contributors.
  * 4. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  *	@(#)bpf.c	7.5 (Berkeley) 7/15/91
  */

 #if !(defined(lint) || defined(KERNEL) || defined(_KERNEL))
 static const char rcsid[] =
     "@(#) $Header$ (LBL)";
 #endif

 #include <sys/param.h>
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/socket.h>

 #include <netinet/in.h>
 #include <net/if.h>

 #include "netinet/ip_compat.h"
 #include "bpf-ipf.h"


 #if (defined(__hpux) || SOLARIS) && (defined(_KERNEL) || defined(KERNEL))
 # include <sys/sysmacros.h>
 # include <sys/stream.h>
 #endif

 #include "pcap-ipf.h"

 #if !defined(KERNEL) && !defined(_KERNEL)
 #include <stdlib.h>
 #endif

 #define int32 bpf_int32
 #define u_int32 bpf_u_int32

 static int m_xword __P((mb_t *, int, int *));
 static int m_xhalf __P((mb_t *, int, int *));

 #ifndef LBL_ALIGN
 /*
  * XXX - IA-64?  If not, this probably won't work on Win64 IA-64
  * systems, unless LBL_ALIGN is defined elsewhere for them.
  * XXX - SuperH?  If not, this probably won't work on WinCE SuperH
  * systems, unless LBL_ALIGN is defined elsewhere for them.
  */
 #if defined(sparc) || defined(__sparc__) || defined(mips) || \
     defined(ibm032) || defined(__alpha) || defined(__hpux) || \
     defined(__arm__)
 #define LBL_ALIGN
 #endif
 #endif

 #ifndef LBL_ALIGN

 #define EXTRACT_SHORT(p)	((u_short)ntohs(*(u_short *)p))
 #define EXTRACT_LONG(p)		(ntohl(*(u_int32 *)p))
 #else
 #define EXTRACT_SHORT(p)\
 	((u_short)\
 		((u_short)*((u_char *)p+0)<<8|\
 		 (u_short)*((u_char *)p+1)<<0))
 #define EXTRACT_LONG(p)\
 		((u_int32)*((u_char *)p+0)<<24|\
 		 (u_int32)*((u_char *)p+1)<<16|\
 		 (u_int32)*((u_char *)p+2)<<8|\
 		 (u_int32)*((u_char *)p+3)<<0)
 #endif

 #define MINDEX(len, _m, _k) \
 { \
 	len = M_LEN(m); \
 	while ((_k) >= len) { \
 		(_k) -= len; \
 		(_m) = (_m)->m_next; \
 		if ((_m) == 0) \
 			return 0; \
 		len = M_LEN(m); \
 	} \
 }

 static int
 m_xword(m, k, err)
 	register mb_t *m;
 	register int k, *err;
 {
 	register int len;
 	register u_char *cp, *np;
 	register mb_t *m0;

 	MINDEX(len, m, k);
 	cp = MTOD(m, u_char *) + k;
 	if (len - k >= 4) {
 		*err = 0;
 		return EXTRACT_LONG(cp);
 	}
 	m0 = m->m_next;
 	if (m0 == 0 || M_LEN(m0) + len - k < 4)
 		goto bad;
 	*err = 0;
 	np = MTOD(m0, u_char *);
 	switch (len - k) {

 	case 1:
 		return (cp[0] << 24) | (np[0] << 16) | (np[1] << 8) | np[2];

 	case 2:
 		return (cp[0] << 24) | (cp[1] << 16) | (np[0] << 8) | np[1];

 	default:
 		return (cp[0] << 24) | (cp[1] << 16) | (cp[2] << 8) | np[0];
 	}
     bad:
 	*err = 1;
 	return 0;
 }

 static int
 m_xhalf(m, k, err)
 	register mb_t *m;
 	register int k, *err;
 {
 	register int len;
 	register u_char *cp;
 	register mb_t *m0;

 	MINDEX(len, m, k);
 	cp = MTOD(m, u_char *) + k;
 	if (len - k >= 2) {
 		*err = 0;
 		return EXTRACT_SHORT(cp);
 	}
 	m0 = m->m_next;
 	if (m0 == 0)
 		goto bad;
 	*err = 0;
 	return (cp[0] << 8) | MTOD(m0, u_char *)[0];
  bad:
 	*err = 1;
 	return 0;
 }

 /*
  * Execute the filter program starting at pc on the packet p
  * wirelen is the length of the original packet
  * buflen is the amount of data present
  * For the kernel, p is assumed to be a pointer to an mbuf if buflen is 0,
  * in all other cases, p is a pointer to a buffer and buflen is its size.
  */
 u_int
 bpf_filter(pc, p, wirelen, buflen)
 	register struct bpf_insn *pc;
 	register u_char *p;
 	u_int wirelen;
 	register u_int buflen;
 {
 	register u_int32 A, X;
 	register int k;
 	int32 mem[BPF_MEMWORDS];
 	mb_t *m, *n;
 	int merr, len;

 	if (buflen == 0) {
 		m = (mb_t *)p;
 		p = MTOD(m, u_char *);
 		buflen = M_LEN(m);
 	} else
 		m = NULL;

 	if (pc == 0)
 		/*
 		 * No filter means accept all.
 		 */
 		return (u_int)-1;
 	A = 0;
 	X = 0;
 	--pc;
 	while (1) {
 		++pc;
 		switch (pc->code) {

 		default:
 			return 0;
 		case BPF_RET|BPF_K:
 			return (u_int)pc->k;

 		case BPF_RET|BPF_A:
 			return (u_int)A;

 		case BPF_LD|BPF_W|BPF_ABS:
 			k = pc->k;
 			if (k + sizeof(int32) > buflen) {
 				if (m == NULL)
 					return 0;
 				A = m_xword(m, k, &merr);
 				if (merr != 0)
 					return 0;
 				continue;
 			}
 			A = EXTRACT_LONG(&p[k]);
 			continue;

 		case BPF_LD|BPF_H|BPF_ABS:
 			k = pc->k;
 			if (k + sizeof(short) > buflen) {
 				if (m == NULL)
 					return 0;
 				A = m_xhalf(m, k, &merr);
 				if (merr != 0)
 					return 0;
 				continue;
 			}
 			A = EXTRACT_SHORT(&p[k]);
 			continue;

 		case BPF_LD|BPF_B|BPF_ABS:
 			k = pc->k;
 			if (k >= buflen) {
 				if (m == NULL)
 					return 0;
 				n = m;
 				MINDEX(len, n, k);
 				A = MTOD(n, u_char *)[k];
 				continue;
 			}
 			A = p[k];
 			continue;

 		case BPF_LD|BPF_W|BPF_LEN:
 			A = wirelen;
 			continue;

 		case BPF_LDX|BPF_W|BPF_LEN:
 			X = wirelen;
 			continue;

 		case BPF_LD|BPF_W|BPF_IND:
 			k = X + pc->k;
 			if (k + sizeof(int32) > buflen) {
 				if (m == NULL)
 					return 0;
 				A = m_xword(m, k, &merr);
 				if (merr != 0)
 					return 0;
 				continue;
 			}
 			A = EXTRACT_LONG(&p[k]);
 			continue;

 		case BPF_LD|BPF_H|BPF_IND:
 			k = X + pc->k;
 			if (k + sizeof(short) > buflen) {
 				if (m == NULL)
 					return 0;
 				A = m_xhalf(m, k, &merr);
 				if (merr != 0)
 					return 0;
 				continue;
 			}
 			A = EXTRACT_SHORT(&p[k]);
 			continue;

 		case BPF_LD|BPF_B|BPF_IND:
 			k = X + pc->k;
 			if (k >= buflen) {
 				if (m == NULL)
 					return 0;
 				n = m;
 				MINDEX(len, n, k);
 				A = MTOD(n, u_char *)[k];
 				continue;
 			}
 			A = p[k];
 			continue;

 		case BPF_LDX|BPF_MSH|BPF_B:
 			k = pc->k;
 			if (k >= buflen) {
 				if (m == NULL)
 					return 0;
 				n = m;
 				MINDEX(len, n, k);
 				X = (MTOD(n, char *)[k] & 0xf) << 2;
 				continue;
 			}
 			X = (p[pc->k] & 0xf) << 2;
 			continue;

 		case BPF_LD|BPF_IMM:
 			A = pc->k;
 			continue;

 		case BPF_LDX|BPF_IMM:
 			X = pc->k;
 			continue;

 		case BPF_LD|BPF_MEM:
 			A = mem[pc->k];
 			continue;

 		case BPF_LDX|BPF_MEM:
 			X = mem[pc->k];
 			continue;

 		case BPF_ST:
 			mem[pc->k] = A;
 			continue;

 		case BPF_STX:
 			mem[pc->k] = X;
 			continue;

 		case BPF_JMP|BPF_JA:
 			pc += pc->k;
 			continue;

 		case BPF_JMP|BPF_JGT|BPF_K:
 			pc += (A > pc->k) ? pc->jt : pc->jf;
 			continue;

 		case BPF_JMP|BPF_JGE|BPF_K:
 			pc += (A >= pc->k) ? pc->jt : pc->jf;
 			continue;

 		case BPF_JMP|BPF_JEQ|BPF_K:
 			pc += (A == pc->k) ? pc->jt : pc->jf;
 			continue;

 		case BPF_JMP|BPF_JSET|BPF_K:
 			pc += (A & pc->k) ? pc->jt : pc->jf;
 			continue;

 		case BPF_JMP|BPF_JGT|BPF_X:
 			pc += (A > X) ? pc->jt : pc->jf;
 			continue;

 		case BPF_JMP|BPF_JGE|BPF_X:
 			pc += (A >= X) ? pc->jt : pc->jf;
 			continue;

 		case BPF_JMP|BPF_JEQ|BPF_X:
 			pc += (A == X) ? pc->jt : pc->jf;
 			continue;

 		case BPF_JMP|BPF_JSET|BPF_X:
 			pc += (A & X) ? pc->jt : pc->jf;
 			continue;

 		case BPF_ALU|BPF_ADD|BPF_X:
 			A += X;
 			continue;

 		case BPF_ALU|BPF_SUB|BPF_X:
 			A -= X;
 			continue;

 		case BPF_ALU|BPF_MUL|BPF_X:
 			A *= X;
 			continue;

 		case BPF_ALU|BPF_DIV|BPF_X:
 			if (X == 0)
 				return 0;
 			A /= X;
 			continue;

 		case BPF_ALU|BPF_AND|BPF_X:
 			A &= X;
 			continue;

 		case BPF_ALU|BPF_OR|BPF_X:
 			A |= X;
 			continue;

 		case BPF_ALU|BPF_LSH|BPF_X:
 			A <<= X;
 			continue;

 		case BPF_ALU|BPF_RSH|BPF_X:
 			A >>= X;
 			continue;

 		case BPF_ALU|BPF_ADD|BPF_K:
 			A += pc->k;
 			continue;

 		case BPF_ALU|BPF_SUB|BPF_K:
 			A -= pc->k;
 			continue;

 		case BPF_ALU|BPF_MUL|BPF_K:
 			A *= pc->k;
 			continue;

 		case BPF_ALU|BPF_DIV|BPF_K:
 			A /= pc->k;
 			continue;

 		case BPF_ALU|BPF_AND|BPF_K:
 			A &= pc->k;
 			continue;

 		case BPF_ALU|BPF_OR|BPF_K:
 			A |= pc->k;
 			continue;

 		case BPF_ALU|BPF_LSH|BPF_K:
 			A <<= pc->k;
 			continue;

 		case BPF_ALU|BPF_RSH|BPF_K:
 			A >>= pc->k;
 			continue;

 		case BPF_ALU|BPF_NEG:
 			A = -A;
 			continue;

 		case BPF_MISC|BPF_TAX:
 			X = A;
 			continue;

 		case BPF_MISC|BPF_TXA:
 			A = X;
 			continue;
 		}
 	}
 }


 /*
  * Return true if the 'fcode' is a valid filter program.
  * The constraints are that each jump be forward and to a valid
  * code, that memory accesses are within valid ranges (to the
  * extent that this can be checked statically; loads of packet
  * data have to be, and are, also checked at run time), and that
  * the code terminates with either an accept or reject.
  *
  * The kernel needs to be able to verify an application's filter code.
  * Otherwise, a bogus program could easily crash the system.
  */
 int
 bpf_validate(f, len)
 	struct bpf_insn *f;
 	int len;
 {
 	u_int i, from;
 	const struct bpf_insn *p;

 	if (len == 0)
 		return 1;

 	if (len < 1 || len > BPF_MAXINSNS)
 		return 0;

 	for (i = 0; i < len; ++i) {
 		p = &f[i];
 		switch (BPF_CLASS(p->code)) {
 		/*
 		 * Check that memory operations use valid addresses.
 		 */
 		case BPF_LD:
 		case BPF_LDX:
 			switch (BPF_MODE(p->code)) {
 			case BPF_IMM:
 				break;
 			case BPF_ABS:
 			case BPF_IND:
 			case BPF_MSH:
 				/*
 				 * More strict check with actual packet length
 				 * is done runtime.
 				 */
 #if 0
 				if (p->k >= bpf_maxbufsize)
 					return 0;
 #endif
 				break;
 			case BPF_MEM:
 				if (p->k >= BPF_MEMWORDS)
 					return 0;
 				break;
 			case BPF_LEN:
 				break;
 			default:
 				return 0;
 			}
 			break;
 		case BPF_ST:
 		case BPF_STX:
 			if (p->k >= BPF_MEMWORDS)
 				return 0;
 			break;
 		case BPF_ALU:
 			switch (BPF_OP(p->code)) {
 			case BPF_ADD:
 			case BPF_SUB:
 			case BPF_OR:
 			case BPF_AND:
 			case BPF_LSH:
 			case BPF_RSH:
 			case BPF_NEG:
 				break;
 			case BPF_DIV:
 				/*
 				 * Check for constant division by 0.
 				 */
 				if (BPF_RVAL(p->code) == BPF_K && p->k == 0)
 					return 0;
 			default:
 				return 0;
 			}
 			break;
 		case BPF_JMP:
 			/*
 			 * Check that jumps are within the code block,
 			 * and that unconditional branches don't go
 			 * backwards as a result of an overflow.
 			 * Unconditional branches have a 32-bit offset,
 			 * so they could overflow; we check to make
 			 * sure they don't.  Conditional branches have
 			 * an 8-bit offset, and the from address is <=
 			 * BPF_MAXINSNS, and we assume that BPF_MAXINSNS
 			 * is sufficiently small that adding 255 to it
 			 * won't overflow.
 			 *
 			 * We know that len is <= BPF_MAXINSNS, and we
 			 * assume that BPF_MAXINSNS is < the maximum size
 			 * of a u_int, so that i + 1 doesn't overflow.
 			 */
 			from = i + 1;
 			switch (BPF_OP(p->code)) {
 			case BPF_JA:
 				if (from + p->k < from || from + p->k >= len)
 					return 0;
 				break;
 			case BPF_JEQ:
 			case BPF_JGT:
 			case BPF_JGE:
 			case BPF_JSET:
 				if (from + p->jt >= len || from + p->jf >= len)
 					return 0;
 				break;
 			default:
 				return 0;
 			}
 			break;
 		case BPF_RET:
 			break;
 		case BPF_MISC:
 			break;
 		default:
 			return 0;
 		}
 	}
 	return BPF_CLASS(f[len - 1].code) == BPF_RET;
 }
	/*-
	* Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
	* The Regents of the University of California. All rights reserved.
	*
	* This code is derived from the Stanford/CMU enet packet filter,
	* (net/enet.c) distributed as part of 4.3BSD, and code contributed
	* to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
	* Berkeley Laboratory.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. All advertising materials mentioning features or use of this software
	* must display the following acknowledgement:
	* This product includes software developed by the University of
	* California, Berkeley and its contributors.
	* 4. Neither the name of the University nor the names of its contributors
	* may be used to endorse or promote products derived from this software
	* without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	* SUCH DAMAGE.
	*
	* @(#)bpf.c 7.5 (Berkeley) 7/15/91
	*/

	#if !(defined(lint) \|\| defined(KERNEL) \|\| defined(_KERNEL))
	static const char rcsid[] =
	"@(#) $Header$ (LBL)";
	#endif

	#include <sys/param.h>
	#include <sys/types.h>
	#include <sys/time.h>
	#include <sys/socket.h>

	#include <netinet/in.h>
	#include <net/if.h>

	#include "netinet/ip_compat.h"
	#include "bpf-ipf.h"


	#if (defined(__hpux) \|\| SOLARIS) && (defined(_KERNEL) \|\| defined(KERNEL))
	# include <sys/sysmacros.h>
	# include <sys/stream.h>
	#endif

	#include "pcap-ipf.h"

	#if !defined(KERNEL) && !defined(_KERNEL)
	#include <stdlib.h>
	#endif

	#define int32 bpf_int32
	#define u_int32 bpf_u_int32

	static int m_xword __P((mb_t , int, int ));
	static int m_xhalf __P((mb_t , int, int ));

	#ifndef LBL_ALIGN
	/*
	* XXX - IA-64? If not, this probably won't work on Win64 IA-64
	* systems, unless LBL_ALIGN is defined elsewhere for them.
	* XXX - SuperH? If not, this probably won't work on WinCE SuperH
	* systems, unless LBL_ALIGN is defined elsewhere for them.
	*/
	#if defined(sparc) \|\| defined(__sparc__) \|\| defined(mips) \|\| \
	defined(ibm032) \|\| defined(__alpha) \|\| defined(__hpux) \|\| \
	defined(__arm__)
	#define LBL_ALIGN
	#endif
	#endif

	#ifndef LBL_ALIGN

	#define EXTRACT_SHORT(p) ((u_short)ntohs((u_short )p))
	#define EXTRACT_LONG(p) (ntohl((u_int32 )p))
	#else
	#define EXTRACT_SHORT(p)\
	((u_short)\
	((u_short)((u_char )p+0)<<8\|\
	(u_short)((u_char )p+1)<<0))
	#define EXTRACT_LONG(p)\
	((u_int32)((u_char )p+0)<<24\|\
	(u_int32)((u_char )p+1)<<16\|\
	(u_int32)((u_char )p+2)<<8\|\
	(u_int32)((u_char )p+3)<<0)
	#endif

	#define MINDEX(len, _m, _k) \
	{ \
	len = M_LEN(m); \
	while ((_k) >= len) { \
	(_k) -= len; \
	(_m) = (_m)->m_next; \
	if ((_m) == 0) \
	return 0; \
	len = M_LEN(m); \
	} \
	}

	static int
	m_xword(m, k, err)
	register mb_t *m;
	register int k, *err;
	{
	register int len;
	register u_char cp, np;
	register mb_t *m0;

	MINDEX(len, m, k);
	cp = MTOD(m, u_char *) + k;
	if (len - k >= 4) {
	*err = 0;
	return EXTRACT_LONG(cp);
	}
	m0 = m->m_next;
	if (m0 == 0 \|\| M_LEN(m0) + len - k < 4)
	goto bad;
	*err = 0;
	np = MTOD(m0, u_char *);
	switch (len - k) {

	case 1:
	return (cp[0] << 24) \| (np[0] << 16) \| (np[1] << 8) \| np[2];

	case 2:
	return (cp[0] << 24) \| (cp[1] << 16) \| (np[0] << 8) \| np[1];

	default:
	return (cp[0] << 24) \| (cp[1] << 16) \| (cp[2] << 8) \| np[0];
	}
	bad:
	*err = 1;
	return 0;
	}

	static int
	m_xhalf(m, k, err)
	register mb_t *m;
	register int k, *err;
	{
	register int len;
	register u_char *cp;
	register mb_t *m0;

	MINDEX(len, m, k);
	cp = MTOD(m, u_char *) + k;
	if (len - k >= 2) {
	*err = 0;
	return EXTRACT_SHORT(cp);
	}
	m0 = m->m_next;
	if (m0 == 0)
	goto bad;
	*err = 0;
	return (cp[0] << 8) \| MTOD(m0, u_char *)[0];
	bad:
	*err = 1;
	return 0;
	}

	/*
	* Execute the filter program starting at pc on the packet p
	* wirelen is the length of the original packet
	* buflen is the amount of data present
	* For the kernel, p is assumed to be a pointer to an mbuf if buflen is 0,
	* in all other cases, p is a pointer to a buffer and buflen is its size.
	*/
	u_int
	bpf_filter(pc, p, wirelen, buflen)
	register struct bpf_insn *pc;
	register u_char *p;
	u_int wirelen;
	register u_int buflen;
	{
	register u_int32 A, X;
	register int k;
	int32 mem[BPF_MEMWORDS];
	mb_t m, n;
	int merr, len;

	if (buflen == 0) {
	m = (mb_t *)p;
	p = MTOD(m, u_char *);
	buflen = M_LEN(m);
	} else
	m = NULL;

	if (pc == 0)
	/*
	* No filter means accept all.
	*/
	return (u_int)-1;
	A = 0;
	X = 0;
	--pc;
	while (1) {
	++pc;
	switch (pc->code) {

	default:
	return 0;
	case BPF_RET\|BPF_K:
	return (u_int)pc->k;

	case BPF_RET\|BPF_A:
	return (u_int)A;

	case BPF_LD\|BPF_W\|BPF_ABS:
	k = pc->k;
	if (k + sizeof(int32) > buflen) {
	if (m == NULL)
	return 0;
	A = m_xword(m, k, &merr);
	if (merr != 0)
	return 0;
	continue;
	}
	A = EXTRACT_LONG(&p[k]);
	continue;

	case BPF_LD\|BPF_H\|BPF_ABS:
	k = pc->k;
	if (k + sizeof(short) > buflen) {
	if (m == NULL)
	return 0;
	A = m_xhalf(m, k, &merr);
	if (merr != 0)
	return 0;
	continue;
	}
	A = EXTRACT_SHORT(&p[k]);
	continue;

	case BPF_LD\|BPF_B\|BPF_ABS:
	k = pc->k;
	if (k >= buflen) {
	if (m == NULL)
	return 0;
	n = m;
	MINDEX(len, n, k);
	A = MTOD(n, u_char *)[k];
	continue;
	}
	A = p[k];
	continue;

	case BPF_LD\|BPF_W\|BPF_LEN:
	A = wirelen;
	continue;

	case BPF_LDX\|BPF_W\|BPF_LEN:
	X = wirelen;
	continue;

	case BPF_LD\|BPF_W\|BPF_IND:
	k = X + pc->k;
	if (k + sizeof(int32) > buflen) {
	if (m == NULL)
	return 0;
	A = m_xword(m, k, &merr);
	if (merr != 0)
	return 0;
	continue;
	}
	A = EXTRACT_LONG(&p[k]);
	continue;

	case BPF_LD\|BPF_H\|BPF_IND:
	k = X + pc->k;
	if (k + sizeof(short) > buflen) {
	if (m == NULL)
	return 0;
	A = m_xhalf(m, k, &merr);
	if (merr != 0)
	return 0;
	continue;
	}
	A = EXTRACT_SHORT(&p[k]);
	continue;

	case BPF_LD\|BPF_B\|BPF_IND:
	k = X + pc->k;
	if (k >= buflen) {
	if (m == NULL)
	return 0;
	n = m;
	MINDEX(len, n, k);
	A = MTOD(n, u_char *)[k];
	continue;
	}
	A = p[k];
	continue;

	case BPF_LDX\|BPF_MSH\|BPF_B:
	k = pc->k;
	if (k >= buflen) {
	if (m == NULL)
	return 0;
	n = m;
	MINDEX(len, n, k);
	X = (MTOD(n, char *)[k] & 0xf) << 2;
	continue;
	}
	X = (p[pc->k] & 0xf) << 2;
	continue;

	case BPF_LD\|BPF_IMM:
	A = pc->k;
	continue;

	case BPF_LDX\|BPF_IMM:
	X = pc->k;
	continue;

	case BPF_LD\|BPF_MEM:
	A = mem[pc->k];
	continue;

	case BPF_LDX\|BPF_MEM:
	X = mem[pc->k];
	continue;

	case BPF_ST:
	mem[pc->k] = A;
	continue;

	case BPF_STX:
	mem[pc->k] = X;
	continue;

	case BPF_JMP\|BPF_JA:
	pc += pc->k;
	continue;

	case BPF_JMP\|BPF_JGT\|BPF_K:
	pc += (A > pc->k) ? pc->jt : pc->jf;
	continue;

	case BPF_JMP\|BPF_JGE\|BPF_K:
	pc += (A >= pc->k) ? pc->jt : pc->jf;
	continue;

	case BPF_JMP\|BPF_JEQ\|BPF_K:
	pc += (A == pc->k) ? pc->jt : pc->jf;
	continue;

	case BPF_JMP\|BPF_JSET\|BPF_K:
	pc += (A & pc->k) ? pc->jt : pc->jf;
	continue;

	case BPF_JMP\|BPF_JGT\|BPF_X:
	pc += (A > X) ? pc->jt : pc->jf;
	continue;

	case BPF_JMP\|BPF_JGE\|BPF_X:
	pc += (A >= X) ? pc->jt : pc->jf;
	continue;

	case BPF_JMP\|BPF_JEQ\|BPF_X:
	pc += (A == X) ? pc->jt : pc->jf;
	continue;

	case BPF_JMP\|BPF_JSET\|BPF_X:
	pc += (A & X) ? pc->jt : pc->jf;
	continue;

	case BPF_ALU\|BPF_ADD\|BPF_X:
	A += X;
	continue;

	case BPF_ALU\|BPF_SUB\|BPF_X:
	A -= X;
	continue;

	case BPF_ALU\|BPF_MUL\|BPF_X:
	A *= X;
	continue;

	case BPF_ALU\|BPF_DIV\|BPF_X:
	if (X == 0)
	return 0;
	A /= X;
	continue;

	case BPF_ALU\|BPF_AND\|BPF_X:
	A &= X;
	continue;

	case BPF_ALU\|BPF_OR\|BPF_X:
	A \|= X;
	continue;

	case BPF_ALU\|BPF_LSH\|BPF_X:
	A <<= X;
	continue;

	case BPF_ALU\|BPF_RSH\|BPF_X:
	A >>= X;
	continue;

	case BPF_ALU\|BPF_ADD\|BPF_K:
	A += pc->k;
	continue;

	case BPF_ALU\|BPF_SUB\|BPF_K:
	A -= pc->k;
	continue;

	case BPF_ALU\|BPF_MUL\|BPF_K:
	A *= pc->k;
	continue;

	case BPF_ALU\|BPF_DIV\|BPF_K:
	A /= pc->k;
	continue;

	case BPF_ALU\|BPF_AND\|BPF_K:
	A &= pc->k;
	continue;

	case BPF_ALU\|BPF_OR\|BPF_K:
	A \|= pc->k;
	continue;

	case BPF_ALU\|BPF_LSH\|BPF_K:
	A <<= pc->k;
	continue;

	case BPF_ALU\|BPF_RSH\|BPF_K:
	A >>= pc->k;
	continue;

	case BPF_ALU\|BPF_NEG:
	A = -A;
	continue;

	case BPF_MISC\|BPF_TAX:
	X = A;
	continue;

	case BPF_MISC\|BPF_TXA:
	A = X;
	continue;
	}
	}
	}


	/*
	* Return true if the 'fcode' is a valid filter program.
	* The constraints are that each jump be forward and to a valid
	* code, that memory accesses are within valid ranges (to the
	* extent that this can be checked statically; loads of packet
	* data have to be, and are, also checked at run time), and that
	* the code terminates with either an accept or reject.
	*
	* The kernel needs to be able to verify an application's filter code.
	* Otherwise, a bogus program could easily crash the system.
	*/
	int
	bpf_validate(f, len)
	struct bpf_insn *f;
	int len;
	{
	u_int i, from;
	const struct bpf_insn *p;

	if (len == 0)
	return 1;

	if (len < 1 \|\| len > BPF_MAXINSNS)
	return 0;

	for (i = 0; i < len; ++i) {
	p = &f[i];
	switch (BPF_CLASS(p->code)) {
	/*
	* Check that memory operations use valid addresses.
	*/
	case BPF_LD:
	case BPF_LDX:
	switch (BPF_MODE(p->code)) {
	case BPF_IMM:
	break;
	case BPF_ABS:
	case BPF_IND:
	case BPF_MSH:
	/*
	* More strict check with actual packet length
	* is done runtime.
	*/
	#if 0
	if (p->k >= bpf_maxbufsize)
	return 0;
	#endif
	break;
	case BPF_MEM:
	if (p->k >= BPF_MEMWORDS)
	return 0;
	break;
	case BPF_LEN:
	break;
	default:
	return 0;
	}
	break;
	case BPF_ST:
	case BPF_STX:
	if (p->k >= BPF_MEMWORDS)
	return 0;
	break;
	case BPF_ALU:
	switch (BPF_OP(p->code)) {
	case BPF_ADD:
	case BPF_SUB:
	case BPF_OR:
	case BPF_AND:
	case BPF_LSH:
	case BPF_RSH:
	case BPF_NEG:
	break;
	case BPF_DIV:
	/*
	* Check for constant division by 0.
	*/
	if (BPF_RVAL(p->code) == BPF_K && p->k == 0)
	return 0;
	default:
	return 0;
	}
	break;
	case BPF_JMP:
	/*
	* Check that jumps are within the code block,
	* and that unconditional branches don't go
	* backwards as a result of an overflow.
	* Unconditional branches have a 32-bit offset,
	* so they could overflow; we check to make
	* sure they don't. Conditional branches have
	* an 8-bit offset, and the from address is <=
	* BPF_MAXINSNS, and we assume that BPF_MAXINSNS
	* is sufficiently small that adding 255 to it
	* won't overflow.
	*
	* We know that len is <= BPF_MAXINSNS, and we
	* assume that BPF_MAXINSNS is < the maximum size
	* of a u_int, so that i + 1 doesn't overflow.
	*/
	from = i + 1;
	switch (BPF_OP(p->code)) {
	case BPF_JA:
	if (from + p->k < from \|\| from + p->k >= len)
	return 0;
	break;
	case BPF_JEQ:
	case BPF_JGT:
	case BPF_JGE:
	case BPF_JSET:
	if (from + p->jt >= len \|\| from + p->jf >= len)
	return 0;
	break;
	default:
	return 0;
	}
	break;
	case BPF_RET:
	break;
	case BPF_MISC:
	break;
	default:
	return 0;
	}
	}
	return BPF_CLASS(f[len - 1].code) == BPF_RET;
	}