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72 lines
2.8 KiB
C
72 lines
2.8 KiB
C
/*
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* dhcpcd - DHCP client daemon
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* Copyright 2006-2008 Roy Marples <roy@marples.name>
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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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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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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/* Credit where credit is due :)
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* The below BPF filter is taken from ISC DHCP */
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static struct bpf_insn dhcp_bpf_filter [] = {
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/* Make sure this is an IP packet... */
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BPF_STMT (BPF_LD + BPF_H + BPF_ABS, 12),
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BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
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/* Make sure it's a UDP packet... */
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BPF_STMT (BPF_LD + BPF_B + BPF_ABS, 23),
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BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
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/* Make sure this isn't a fragment... */
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BPF_STMT (BPF_LD + BPF_H + BPF_ABS, 20),
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BPF_JUMP (BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
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/* Get the IP header length... */
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BPF_STMT (BPF_LDX + BPF_B + BPF_MSH, 14),
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/* Make sure it's to the right port... */
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BPF_STMT (BPF_LD + BPF_H + BPF_IND, 16),
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BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, DHCP_CLIENT_PORT, 0, 1),
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/* If we passed all the tests, ask for the whole packet. */
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BPF_STMT (BPF_RET + BPF_K, ~0U),
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/* Otherwise, drop it. */
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BPF_STMT (BPF_RET + BPF_K, 0),
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};
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/* This, however, is mine */
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static struct bpf_insn arp_bpf_filter [] = {
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/* Make sure this is an ARP packet... */
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BPF_STMT (BPF_LD + BPF_H + BPF_ABS, 12),
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BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_ARP, 0, 3),
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/* Make sure this is an ARP REPLY... */
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BPF_STMT (BPF_LD + BPF_H + BPF_ABS, 20),
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BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REPLY, 0, 1),
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/* If we passed all the tests, ask for the whole packet. */
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BPF_STMT (BPF_RET + BPF_K, ~0U),
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/* Otherwise, drop it. */
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BPF_STMT (BPF_RET + BPF_K, 0),
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};
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