385 lines
12 KiB
C
385 lines
12 KiB
C
/* bpf.c
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BPF socket interface code, originally contributed by Archie Cobbs. */
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/*
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* Copyright (c) 1995, 1996 The Internet Software Consortium.
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* All rights reserved.
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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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*
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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. Neither the name of The Internet Software Consortium nor the names
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* of its contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
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* CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* 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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* This software has been written for the Internet Software Consortium
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* by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
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* Enterprises. To learn more about the Internet Software Consortium,
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* see ``http://www.vix.com/isc''. To learn more about Vixie
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* Enterprises, see ``http://www.vix.com''.
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*/
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#ifndef lint
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static char copyright[] =
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"$Id: bpf.c,v 1.1.1.2 1997/06/08 04:54:00 mellon Exp $ Copyright (c) 1995, 1996 The Internet Software Consortium. All rights reserved.\n";
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#endif /* not lint */
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#include "dhcpd.h"
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#if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE)
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#include <sys/ioctl.h>
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#include <sys/uio.h>
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#include <net/bpf.h>
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#ifdef NEED_OSF_PFILT_HACKS
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#include <net/pfilt.h>
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#endif
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#include <netinet/in_systm.h>
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#include "includes/netinet/ip.h"
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#include "includes/netinet/udp.h"
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#include "includes/netinet/if_ether.h"
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/* Reinitializes the specified interface after an address change. This
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is not required for packet-filter APIs. */
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#ifdef USE_BPF_SEND
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void if_reinitialize_send (info)
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struct interface_info *info;
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{
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}
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#endif
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#ifdef USE_BPF_RECEIVE
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void if_reinitialize_receive (info)
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struct interface_info *info;
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{
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}
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#endif
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/* Called by get_interface_list for each interface that's discovered.
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Opens a packet filter for each interface and adds it to the select
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mask. */
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int if_register_bpf (info)
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struct interface_info *info;
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{
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int sock;
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char filename[50];
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int b;
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/* Open a BPF device */
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for (b = 0; 1; b++) {
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#ifndef NO_SNPRINTF
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snprintf(filename, sizeof(filename), BPF_FORMAT, b);
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#else
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sprintf(filename, BPF_FORMAT, b);
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#endif
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sock = open (filename, O_RDWR, 0);
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if (sock < 0) {
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if (errno == EBUSY) {
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continue;
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} else {
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error ("Can't find free bpf: %m");
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}
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} else {
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break;
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}
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}
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/* Set the BPF device to point at this interface. */
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if (ioctl (sock, BIOCSETIF, info -> ifp) < 0)
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error ("Can't attach interface %s to bpf device %s: %m",
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info -> name, filename);
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return sock;
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}
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#endif /* USE_BPF_SEND || USE_BPF_RECEIVE */
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#ifdef USE_BPF_SEND
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void if_register_send (info)
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struct interface_info *info;
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{
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/* If we're using the bpf API for sending and receiving,
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we don't need to register this interface twice. */
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#ifndef USE_BPF_RECEIVE
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info -> wfdesc = if_register_bpf (info, interface);
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#else
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info -> wfdesc = info -> rfdesc;
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#endif
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note ("Sending on BPF/%s/%s/%s",
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info -> name,
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print_hw_addr (info -> hw_address.htype,
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info -> hw_address.hlen,
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info -> hw_address.haddr),
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(info -> shared_network ?
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info -> shared_network -> name : "unattached"));
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}
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#endif /* USE_BPF_SEND */
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#ifdef USE_BPF_RECEIVE
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/* Packet filter program...
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XXX Changes to the filter program may require changes to the constant
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offsets used in if_register_send to patch the BPF program! XXX */
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struct bpf_insn 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, 67, 0, 1), /* patch */
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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, (u_int)-1),
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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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void if_register_receive (info)
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struct interface_info *info;
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{
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int flag = 1;
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struct bpf_version v;
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u_int32_t addr;
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struct bpf_program p;
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u_int32_t bits;
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/* Open a BPF device and hang it on this interface... */
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info -> rfdesc = if_register_bpf (info);
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/* Make sure the BPF version is in range... */
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if (ioctl (info -> rfdesc, BIOCVERSION, &v) < 0)
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error ("Can't get BPF version: %m");
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if (v.bv_major != BPF_MAJOR_VERSION ||
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v.bv_minor < BPF_MINOR_VERSION)
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error ("Kernel BPF version out of range - recompile dhcpd!");
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/* Set immediate mode so that reads return as soon as a packet
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comes in, rather than waiting for the input buffer to fill with
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packets. */
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if (ioctl (info -> rfdesc, BIOCIMMEDIATE, &flag) < 0)
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error ("Can't set immediate mode on bpf device: %m");
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#ifdef NEED_OSF_PFILT_HACKS
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/* Allow the copyall flag to be set... */
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if (ioctl(info -> rfdesc, EIOCALLOWCOPYALL, &flag) < 0)
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error ("Can't set ALLOWCOPYALL: %m");
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/* Clear all the packet filter mode bits first... */
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bits = 0;
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if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0)
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error ("Can't clear pfilt bits: %m");
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/* Set the ENBATCH, ENCOPYALL, ENBPFHDR bits... */
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bits = ENBATCH | ENCOPYALL | ENBPFHDR;
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if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0)
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error ("Can't set ENBATCH|ENCOPYALL|ENBPFHDR: %m");
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#endif
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/* Get the required BPF buffer length from the kernel. */
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if (ioctl (info -> rfdesc, BIOCGBLEN, &info -> rbuf_max) < 0)
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error ("Can't get bpf buffer length: %m");
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info -> rbuf = malloc (info -> rbuf_max);
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if (!info -> rbuf)
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error ("Can't allocate %d bytes for bpf input buffer.");
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info -> rbuf_offset = 0;
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info -> rbuf_len = 0;
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/* Set up the bpf filter program structure. */
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p.bf_len = sizeof filter / sizeof (struct bpf_insn);
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p.bf_insns = filter;
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/* Patch the server port into the BPF program...
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XXX changes to filter program may require changes
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to the insn number(s) used below! XXX */
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filter [8].k = ntohs (local_port);
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if (ioctl (info -> rfdesc, BIOCSETF, &p) < 0)
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error ("Can't install packet filter program: %m");
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note ("Listening on BPF/%s/%s/%s",
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info -> name,
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print_hw_addr (info -> hw_address.htype,
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info -> hw_address.hlen,
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info -> hw_address.haddr),
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(info -> shared_network ?
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info -> shared_network -> name : "unattached"));
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}
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#endif /* USE_BPF_RECEIVE */
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#ifdef USE_BPF_SEND
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ssize_t send_packet (interface, packet, raw, len, from, to, hto)
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struct interface_info *interface;
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struct packet *packet;
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struct dhcp_packet *raw;
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size_t len;
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struct in_addr from;
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struct sockaddr_in *to;
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struct hardware *hto;
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{
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int bufp = 0;
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unsigned char buf [256];
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struct iovec iov [2];
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/* Assemble the headers... */
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assemble_hw_header (interface, buf, &bufp, hto);
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assemble_udp_ip_header (interface, buf, &bufp, from.s_addr,
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to -> sin_addr.s_addr, to -> sin_port,
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(unsigned char *)raw, len);
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/* Fire it off */
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iov [0].iov_base = (char *)buf;
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iov [0].iov_len = bufp;
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iov [1].iov_base = (char *)raw;
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iov [1].iov_len = len;
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return writev(interface -> wfdesc, iov, 2);
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}
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#endif /* USE_BPF_SEND */
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#ifdef USE_BPF_RECEIVE
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ssize_t receive_packet (interface, buf, len, from, hfrom)
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struct interface_info *interface;
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unsigned char *buf;
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size_t len;
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struct sockaddr_in *from;
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struct hardware *hfrom;
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{
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int length = 0;
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int offset = 0;
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struct bpf_hdr hdr;
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/* All this complexity is because BPF doesn't guarantee
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that only one packet will be returned at a time. We're
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getting what we deserve, though - this is a terrible abuse
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of the BPF interface. Sigh. */
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/* Process packets until we get one we can return or until we've
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done a read and gotten nothing we can return... */
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do {
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/* If the buffer is empty, fill it. */
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if (interface -> rbuf_offset == interface -> rbuf_len) {
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length = read (interface -> rfdesc,
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interface -> rbuf,
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interface -> rbuf_max);
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if (length <= 0)
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return length;
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interface -> rbuf_offset = 0;
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interface -> rbuf_len = length;
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}
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/* If there isn't room for a whole bpf header, something went
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wrong, but we'll ignore it and hope it goes away... XXX */
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if (interface -> rbuf_len -
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interface -> rbuf_offset < sizeof hdr) {
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interface -> rbuf_offset = interface -> rbuf_len;
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continue;
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}
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/* Copy out a bpf header... */
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memcpy (&hdr, &interface -> rbuf [interface -> rbuf_offset],
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sizeof hdr);
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/* If the bpf header plus data doesn't fit in what's left
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of the buffer, stick head in sand yet again... */
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if (interface -> rbuf_offset +
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hdr.bh_hdrlen + hdr.bh_caplen > interface -> rbuf_len) {
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interface -> rbuf_offset = interface -> rbuf_len;
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continue;
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}
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/* If the captured data wasn't the whole packet, or if
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the packet won't fit in the input buffer, all we
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can do is drop it. */
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if (hdr.bh_caplen != hdr.bh_datalen) {
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interface -> rbuf_offset +=
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hdr.bh_hdrlen = hdr.bh_caplen;
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continue;
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}
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/* Skip over the BPF header... */
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interface -> rbuf_offset += hdr.bh_hdrlen;
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/* Decode the physical header... */
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offset = decode_hw_header (interface,
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interface -> rbuf,
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interface -> rbuf_offset,
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hfrom);
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/* If a physical layer checksum failed (dunno of any
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physical layer that supports this, but WTH), skip this
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packet. */
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if (offset < 0) {
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interface -> rbuf_offset += hdr.bh_caplen;
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continue;
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}
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interface -> rbuf_offset += offset;
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hdr.bh_caplen -= offset;
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/* Decode the IP and UDP headers... */
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offset = decode_udp_ip_header (interface,
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interface -> rbuf,
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interface -> rbuf_offset,
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from,
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(unsigned char *)0,
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hdr.bh_caplen);
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/* If the IP or UDP checksum was bad, skip the packet... */
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if (offset < 0) {
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interface -> rbuf_offset += hdr.bh_caplen;
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continue;
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}
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interface -> rbuf_offset += offset;
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hdr.bh_caplen -= offset;
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/* If there's not enough room to stash the packet data,
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we have to skip it (this shouldn't happen in real
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life, though). */
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if (hdr.bh_caplen > len) {
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interface -> rbuf_offset += hdr.bh_caplen;
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continue;
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}
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/* Copy out the data in the packet... */
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memcpy (buf, interface -> rbuf + interface -> rbuf_offset,
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hdr.bh_caplen);
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interface -> rbuf_offset += hdr.bh_caplen;
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return hdr.bh_caplen;
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} while (!length);
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return 0;
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}
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#endif
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