545 lines
10 KiB
C
545 lines
10 KiB
C
/*
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* Copyright (c) 1990, 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from the Stanford/CMU enet packet filter,
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* (net/enet.c) distributed as part of 4.3BSD, and code contributed
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* to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
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* Berkeley Laboratory.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93
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*
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* $Id: bpf_filter.c,v 1.4 1995/04/01 01:46:27 davidg Exp $
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*/
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#include <sys/param.h>
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#include <sys/types.h>
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#include <sys/time.h>
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#ifdef sun
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#include <netinet/in.h>
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#endif
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#if defined(sparc) || defined(mips) || defined(ibm032)
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#define BPF_ALIGN
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#endif
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#ifndef BPF_ALIGN
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#define EXTRACT_SHORT(p) ((u_short)ntohs(*(u_short *)p))
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#define EXTRACT_LONG(p) (ntohl(*(u_long *)p))
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#else
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#define EXTRACT_SHORT(p)\
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((u_short)\
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((u_short)*((u_char *)p+0)<<8|\
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(u_short)*((u_char *)p+1)<<0))
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#define EXTRACT_LONG(p)\
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((u_long)*((u_char *)p+0)<<24|\
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(u_long)*((u_char *)p+1)<<16|\
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(u_long)*((u_char *)p+2)<<8|\
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(u_long)*((u_char *)p+3)<<0)
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#endif
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#ifdef KERNEL
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#include <sys/mbuf.h>
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#define MINDEX(m, k) \
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{ \
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register int len = m->m_len; \
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\
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while (k >= len) { \
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k -= len; \
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m = m->m_next; \
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if (m == 0) \
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return 0; \
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len = m->m_len; \
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} \
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}
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static int
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m_xword(m, k, err)
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register struct mbuf *m;
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register int k, *err;
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{
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register int len;
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register u_char *cp, *np;
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register struct mbuf *m0;
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len = m->m_len;
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while (k >= len) {
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k -= len;
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m = m->m_next;
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if (m == 0)
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goto bad;
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len = m->m_len;
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}
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cp = mtod(m, u_char *) + k;
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if (len - k >= 4) {
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*err = 0;
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return EXTRACT_LONG(cp);
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}
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m0 = m->m_next;
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if (m0 == 0 || m0->m_len + len - k < 4)
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goto bad;
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*err = 0;
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np = mtod(m0, u_char *);
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switch (len - k) {
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case 1:
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return (cp[0] << 24) | (np[0] << 16) | (np[1] << 8) | np[2];
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case 2:
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return (cp[0] << 24) | (cp[1] << 16) | (np[0] << 8) |
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np[1];
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default:
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return (cp[0] << 24) | (cp[1] << 16) | (cp[2] << 8) |
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np[0];
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}
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bad:
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*err = 1;
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return 0;
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}
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static int
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m_xhalf(m, k, err)
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register struct mbuf *m;
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register int k, *err;
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{
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register int len;
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register u_char *cp;
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register struct mbuf *m0;
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len = m->m_len;
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while (k >= len) {
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k -= len;
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m = m->m_next;
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if (m == 0)
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goto bad;
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len = m->m_len;
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}
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cp = mtod(m, u_char *) + k;
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if (len - k >= 2) {
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*err = 0;
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return EXTRACT_SHORT(cp);
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}
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m0 = m->m_next;
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if (m0 == 0)
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goto bad;
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*err = 0;
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return (cp[0] << 8) | mtod(m0, u_char *)[0];
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bad:
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*err = 1;
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return 0;
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}
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#endif
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#include <net/bpf.h>
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/*
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* Execute the filter program starting at pc on the packet p
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* wirelen is the length of the original packet
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* buflen is the amount of data present
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*/
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u_int
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bpf_filter(pc, p, wirelen, buflen)
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register struct bpf_insn *pc;
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register u_char *p;
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u_int wirelen;
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register u_int buflen;
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{
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register u_long A = 0, X = 0;
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register int k;
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long mem[BPF_MEMWORDS];
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if (pc == 0)
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/*
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* No filter means accept all.
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*/
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return (u_int)-1;
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--pc;
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while (1) {
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++pc;
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switch (pc->code) {
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default:
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#ifdef KERNEL
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return 0;
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#else
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abort();
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#endif
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case BPF_RET|BPF_K:
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return (u_int)pc->k;
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case BPF_RET|BPF_A:
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return (u_int)A;
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case BPF_LD|BPF_W|BPF_ABS:
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k = pc->k;
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if (k + sizeof(long) > buflen) {
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#ifdef KERNEL
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int merr;
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if (buflen != 0)
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return 0;
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A = m_xword((struct mbuf *)p, k, &merr);
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if (merr != 0)
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return 0;
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continue;
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#else
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return 0;
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#endif
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}
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#ifdef BPF_ALIGN
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if (((int)(p + k) & 3) != 0)
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A = EXTRACT_LONG(&p[k]);
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else
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#endif
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A = ntohl(*(long *)(p + k));
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continue;
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case BPF_LD|BPF_H|BPF_ABS:
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k = pc->k;
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if (k + sizeof(short) > buflen) {
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#ifdef KERNEL
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int merr;
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if (buflen != 0)
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return 0;
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A = m_xhalf((struct mbuf *)p, k, &merr);
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continue;
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#else
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return 0;
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#endif
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}
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A = EXTRACT_SHORT(&p[k]);
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continue;
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case BPF_LD|BPF_B|BPF_ABS:
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k = pc->k;
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if (k >= buflen) {
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#ifdef KERNEL
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register struct mbuf *m;
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if (buflen != 0)
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return 0;
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m = (struct mbuf *)p;
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MINDEX(m, k);
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A = mtod(m, u_char *)[k];
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continue;
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#else
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return 0;
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#endif
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}
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A = p[k];
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continue;
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case BPF_LD|BPF_W|BPF_LEN:
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A = wirelen;
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continue;
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case BPF_LDX|BPF_W|BPF_LEN:
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X = wirelen;
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continue;
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case BPF_LD|BPF_W|BPF_IND:
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k = X + pc->k;
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if (k + sizeof(long) > buflen) {
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#ifdef KERNEL
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int merr;
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if (buflen != 0)
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return 0;
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A = m_xword((struct mbuf *)p, k, &merr);
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if (merr != 0)
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return 0;
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continue;
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#else
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return 0;
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#endif
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}
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#ifdef BPF_ALIGN
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if (((int)(p + k) & 3) != 0)
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A = EXTRACT_LONG(&p[k]);
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else
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#endif
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A = ntohl(*(long *)(p + k));
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continue;
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case BPF_LD|BPF_H|BPF_IND:
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k = X + pc->k;
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if (k + sizeof(short) > buflen) {
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#ifdef KERNEL
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int merr;
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if (buflen != 0)
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return 0;
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A = m_xhalf((struct mbuf *)p, k, &merr);
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if (merr != 0)
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return 0;
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continue;
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#else
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return 0;
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#endif
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}
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A = EXTRACT_SHORT(&p[k]);
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continue;
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case BPF_LD|BPF_B|BPF_IND:
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k = X + pc->k;
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if (k >= buflen) {
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#ifdef KERNEL
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register struct mbuf *m;
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if (buflen != 0)
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return 0;
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m = (struct mbuf *)p;
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MINDEX(m, k);
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A = mtod(m, char *)[k];
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continue;
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#else
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return 0;
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#endif
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}
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A = p[k];
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continue;
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case BPF_LDX|BPF_MSH|BPF_B:
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k = pc->k;
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if (k >= buflen) {
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#ifdef KERNEL
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register struct mbuf *m;
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if (buflen != 0)
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return 0;
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m = (struct mbuf *)p;
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MINDEX(m, k);
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X = (mtod(m, char *)[k] & 0xf) << 2;
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continue;
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#else
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return 0;
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#endif
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}
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X = (p[pc->k] & 0xf) << 2;
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continue;
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case BPF_LD|BPF_IMM:
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A = pc->k;
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continue;
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case BPF_LDX|BPF_IMM:
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X = pc->k;
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continue;
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case BPF_LD|BPF_MEM:
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A = mem[pc->k];
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continue;
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case BPF_LDX|BPF_MEM:
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X = mem[pc->k];
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continue;
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case BPF_ST:
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mem[pc->k] = A;
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continue;
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case BPF_STX:
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mem[pc->k] = X;
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continue;
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case BPF_JMP|BPF_JA:
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pc += pc->k;
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continue;
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case BPF_JMP|BPF_JGT|BPF_K:
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pc += (A > pc->k) ? pc->jt : pc->jf;
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continue;
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case BPF_JMP|BPF_JGE|BPF_K:
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pc += (A >= pc->k) ? pc->jt : pc->jf;
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continue;
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case BPF_JMP|BPF_JEQ|BPF_K:
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pc += (A == pc->k) ? pc->jt : pc->jf;
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continue;
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case BPF_JMP|BPF_JSET|BPF_K:
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pc += (A & pc->k) ? pc->jt : pc->jf;
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continue;
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case BPF_JMP|BPF_JGT|BPF_X:
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pc += (A > X) ? pc->jt : pc->jf;
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continue;
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case BPF_JMP|BPF_JGE|BPF_X:
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pc += (A >= X) ? pc->jt : pc->jf;
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continue;
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case BPF_JMP|BPF_JEQ|BPF_X:
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pc += (A == X) ? pc->jt : pc->jf;
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continue;
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case BPF_JMP|BPF_JSET|BPF_X:
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pc += (A & X) ? pc->jt : pc->jf;
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continue;
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case BPF_ALU|BPF_ADD|BPF_X:
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A += X;
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continue;
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case BPF_ALU|BPF_SUB|BPF_X:
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A -= X;
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continue;
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case BPF_ALU|BPF_MUL|BPF_X:
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A *= X;
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continue;
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case BPF_ALU|BPF_DIV|BPF_X:
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if (X == 0)
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return 0;
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A /= X;
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continue;
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case BPF_ALU|BPF_AND|BPF_X:
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A &= X;
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continue;
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case BPF_ALU|BPF_OR|BPF_X:
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A |= X;
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continue;
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case BPF_ALU|BPF_LSH|BPF_X:
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A <<= X;
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continue;
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case BPF_ALU|BPF_RSH|BPF_X:
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A >>= X;
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continue;
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case BPF_ALU|BPF_ADD|BPF_K:
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A += pc->k;
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continue;
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case BPF_ALU|BPF_SUB|BPF_K:
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A -= pc->k;
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continue;
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case BPF_ALU|BPF_MUL|BPF_K:
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A *= pc->k;
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continue;
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case BPF_ALU|BPF_DIV|BPF_K:
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A /= pc->k;
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continue;
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case BPF_ALU|BPF_AND|BPF_K:
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A &= pc->k;
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continue;
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case BPF_ALU|BPF_OR|BPF_K:
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A |= pc->k;
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continue;
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case BPF_ALU|BPF_LSH|BPF_K:
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A <<= pc->k;
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continue;
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case BPF_ALU|BPF_RSH|BPF_K:
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A >>= pc->k;
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continue;
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case BPF_ALU|BPF_NEG:
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A = -A;
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continue;
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case BPF_MISC|BPF_TAX:
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X = A;
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continue;
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case BPF_MISC|BPF_TXA:
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A = X;
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continue;
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}
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}
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}
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#ifdef KERNEL
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/*
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* Return true if the 'fcode' is a valid filter program.
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* The constraints are that each jump be forward and to a valid
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* code. The code must terminate with either an accept or reject.
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* 'valid' is an array for use by the routine (it must be at least
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* 'len' bytes long).
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*
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* The kernel needs to be able to verify an application's filter code.
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* Otherwise, a bogus program could easily crash the system.
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*/
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int
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bpf_validate(f, len)
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struct bpf_insn *f;
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int len;
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{
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register int i;
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register struct bpf_insn *p;
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for (i = 0; i < len; ++i) {
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/*
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* Check that that jumps are forward, and within
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* the code block.
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*/
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p = &f[i];
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if (BPF_CLASS(p->code) == BPF_JMP) {
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register int from = i + 1;
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if (BPF_OP(p->code) == BPF_JA) {
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if (from + p->k >= len)
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return 0;
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}
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else if (from + p->jt >= len || from + p->jf >= len)
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return 0;
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}
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/*
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* Check that memory operations use valid addresses.
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*/
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if ((BPF_CLASS(p->code) == BPF_ST ||
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(BPF_CLASS(p->code) == BPF_LD &&
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(p->code & 0xe0) == BPF_MEM)) &&
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(p->k >= BPF_MEMWORDS || p->k < 0))
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return 0;
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/*
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* Check for constant division by 0.
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*/
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if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0)
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return 0;
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}
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return BPF_CLASS(f[len - 1].code) == BPF_RET;
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}
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#endif
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