/*-
 * Copyright (c) 1990, 1991, 1992, 1993
 *	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
 *
 */

/*
 * Changed for MintNet
 * 1995, Kay Roemer.
 */

# include "global.h"
# include "util.h"

# include "if.h"
# include "in.h"
# include "bpf.h"

# include <mint/file.h>


# define BPF_ALIGN

# ifdef BPF_ALIGN
# define EXTRACT_SHORT(p) \
	((ushort)(((uchar *)(p))[0]) << 8 | \
	 (ushort)(((uchar *)(p))[1]) << 0)
# define EXTRACT_LONG(p) \
	((ulong)(((uchar *)(p))[0]) << 24 | \
	 (ulong)(((uchar *)(p))[1]) << 16 | \
	 (ulong)(((uchar *)(p))[2]) <<  8 | \
	 (ulong)(((uchar *)(p))[3]) <<  0)
# else
# define EXTRACT_SHORT(p)	(ntohs (*(ushort *) p))
# define EXTRACT_LONG(p)	(ntohl (*(ulong *) p))
# endif

/*
 * 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
 */
ulong
bpf_filter (struct bpf_insn *pc, register uchar *p, ulong wirelen, ulong buflen)
{
	register long A, X;
	register long k;
	long mem[BPF_MEMWORDS];
	
	if (pc == 0)
		/*
		 * No filter means accept all.
		 */
		return (ulong) -1;
	
	A = 0;
	X = 0;
	
	pc--;
	
	while (1)
	{
		pc++;
		
		switch (pc->code)
		{
			default:
				return 0;
			
			case BPF_RET|BPF_K:
				return (ulong) pc->k;
			
			case BPF_RET|BPF_A:
				return (ulong) A;
			
			case BPF_LD|BPF_W|BPF_ABS:
				k = pc->k;
				if (k + sizeof(long) > buflen)
					return 0;
				A = EXTRACT_LONG(&p[k]);
				continue;
			
			case BPF_LD|BPF_H|BPF_ABS:
				k = pc->k;
				if (k + sizeof(short) > buflen)
					return 0;
				A = EXTRACT_SHORT(&p[k]);
				continue;
			
			case BPF_LD|BPF_B|BPF_ABS:
				k = pc->k;
				if (k >= buflen)
					return 0;
				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(long) > buflen)
					return 0;
				A = EXTRACT_LONG(&p[k]);
				continue;
			
			case BPF_LD|BPF_H|BPF_IND:
				k = X + pc->k;
				if (k + sizeof(short) > buflen)
					return 0;
				A = EXTRACT_SHORT(&p[k]);
				continue;
			
			case BPF_LD|BPF_B|BPF_IND:
				k = X + pc->k;
				if (k >= buflen)
					return 0;
				A = p[k];
				continue;
			
			case BPF_LDX|BPF_MSH|BPF_B:
				k = pc->k;
				if (k >= buflen)
					return 0;
				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.  The code must terminate with either an accept or reject. 
 * 'valid' is an array for use by the routine (it must be at least
 * 'len' bytes long).  
 *
 * The kernel needs to be able to verify an application's filter code.
 * Otherwise, a bogus program could easily crash the system.
 */
long
bpf_validate (struct bpf_insn *f, long len)
{
	register int i;
	register struct bpf_insn *p;
	
	for (i = 0; i < len; i++)
	{
		/*
		 * Check that that jumps are forward, and within 
		 * the code block.
		 */
		p = &f[i];
		if (BPF_CLASS(p->code) == BPF_JMP)
		{
			register int from = i + 1;
			
			if (BPF_OP(p->code) == BPF_JA)
			{
				if (from + p->k >= len)
					return 0;
			}
			else if (from + p->jt >= len || from + p->jf >= len)
				return 0;
		}
		
		/*
		 * Check that memory operations use valid addresses.
		 */
		if ((BPF_CLASS(p->code) == BPF_ST ||
		     (BPF_CLASS(p->code) == BPF_LD && 
		      (p->code & 0xe0) == BPF_MEM)) &&
		    (p->k >= BPF_MEMWORDS || p->k < 0))
			return 0;
		
		/*
		 * Check for constant division by 0.
		 */
		if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0)
			return 0;
	}
	
	return BPF_CLASS(f[len - 1].code) == BPF_RET;
}
