bpf.c

DHCP服务器源码

/* bpf.c

   BPF socket interface code, originally contributed by Archie Cobbs. */

/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 1996-2003 by Internet Software Consortium
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 *   Internet Systems Consortium, Inc.
 *   950 Charter Street
 *   Redwood City, CA 94063
 *   <[e-mail]>
 *   http://www.isc.org/
 *
 * This software was contributed to Internet Systems Consortium
 * by Archie Cobbs.
 *
 * Patches for FDDI support on Digital Unix were written by Bill
 * Stapleton, and maintained for a while by Mike Meredith before he
 * managed to get me to integrate them.
 */

#ifndef lint
static char copyright[] =
"$Id: bpf.c,v 1.48.2.6 2004/06/17 20:54:38 dhankins Exp $ Copyright (c) 2004 Internet Systems Consortium.  All rights reserved.\n";
#endif /* not lint */

#include "dhcpd.h"
#if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE)	\
				|| defined (USE_LPF_RECEIVE)
# if defined (USE_LPF_RECEIVE)
#  include <asm/types.h>
#  include <linux/filter.h>
#  define bpf_insn sock_filter /* Linux: dare to be gratuitously different. */
# else
#  include <sys/ioctl.h>
#  include <sys/uio.h>
#  include <net/bpf.h>
#  if defined (NEED_OSF_PFILT_HACKS)
#   include <net/pfilt.h>
#  endif
# endif

#include <netinet/in_systm.h>
#include "includes/netinet/ip.h"
#include "includes/netinet/udp.h"
#include "includes/netinet/if_ether.h"
#endif

/* Reinitializes the specified interface after an address change.   This
   is not required for packet-filter APIs. */

#ifdef USE_BPF_SEND
void if_reinitialize_send (info)
	struct interface_info *info;
{
}
#endif

#ifdef USE_BPF_RECEIVE
void if_reinitialize_receive (info)
	struct interface_info *info;
{
}
#endif

/* Called by get_interface_list for each interface that's discovered.
   Opens a packet filter for each interface and adds it to the select
   mask. */

#if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE)
int if_register_bpf (info)
	struct interface_info *info;
{
	int sock;
	char filename[50];
	int b;

	/* Open a BPF device */
	for (b = 0; 1; b++) {
		/* %Audit% 31 bytes max. %2004.06.17,Safe% */
		sprintf(filename, BPF_FORMAT, b);
		sock = open (filename, O_RDWR, 0);
		if (sock < 0) {
			if (errno == EBUSY) {
				continue;
			} else {
				if (!b)
					log_fatal ("No bpf devices.%s%s%s",
					       "   Please read the README",
					       " section for your operating",
					       " system.");
				log_fatal ("Can't find free bpf: %m");
			}
		} else {
			break;
		}
	}

	/* Set the BPF device to point at this interface. */
	if (ioctl (sock, BIOCSETIF, info -> ifp) < 0)
		log_fatal ("Can't attach interface %s to bpf device %s: %m",
		       info -> name, filename);

	return sock;
}
#endif /* USE_BPF_SEND || USE_BPF_RECEIVE */

#ifdef USE_BPF_SEND
void if_register_send (info)
	struct interface_info *info;
{
	/* If we're using the bpf API for sending and receiving,
	   we don't need to register this interface twice. */
#ifndef USE_BPF_RECEIVE
	info -> wfdesc = if_register_bpf (info, interface);
#else
	info -> wfdesc = info -> rfdesc;
#endif
	if (!quiet_interface_discovery)
		log_info ("Sending on   BPF/%s/%s%s%s",
		      info -> name,
		      print_hw_addr (info -> hw_address.hbuf [0],
				     info -> hw_address.hlen - 1,
				     &info -> hw_address.hbuf [1]),
		      (info -> shared_network ? "/" : ""),
		      (info -> shared_network ?
		       info -> shared_network -> name : ""));
}

void if_deregister_send (info)
	struct interface_info *info;
{
	/* If we're using the bpf API for sending and receiving,
	   we don't need to register this interface twice. */
#ifndef USE_BPF_RECEIVE
	close (info -> wfdesc);
#endif
	info -> wfdesc = -1;

	if (!quiet_interface_discovery)
		log_info ("Disabling output on BPF/%s/%s%s%s",
		      info -> name,
		      print_hw_addr (info -> hw_address.hbuf [0],
				     info -> hw_address.hlen - 1,
				     &info -> hw_address.hbuf [1]),
		      (info -> shared_network ? "/" : ""),
		      (info -> shared_network ?
		       info -> shared_network -> name : ""));
}
#endif /* USE_BPF_SEND */

#if defined (USE_BPF_RECEIVE) || defined (USE_LPF_RECEIVE)
/* Packet filter program...
   XXX Changes to the filter program may require changes to the constant
   offsets used in if_register_send to patch the BPF program! XXX */

struct bpf_insn dhcp_bpf_filter [] = {
	/* Make sure this is an IP packet... */
	BPF_STMT (BPF_LD + BPF_H + BPF_ABS, 12),
	BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),

	/* Make sure it's a UDP packet... */
	BPF_STMT (BPF_LD + BPF_B + BPF_ABS, 23),
	BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),

	/* Make sure this isn't a fragment... */
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
	BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),

	/* Get the IP header length... */
	BPF_STMT (BPF_LDX + BPF_B + BPF_MSH, 14),

	/* Make sure it's to the right port... */
	BPF_STMT (BPF_LD + BPF_H + BPF_IND, 16),
	BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1),             /* patch */

	/* If we passed all the tests, ask for the whole packet. */
	BPF_STMT(BPF_RET+BPF_K, (u_int)-1),

	/* Otherwise, drop it. */
	BPF_STMT(BPF_RET+BPF_K, 0),
};

#if defined (DEC_FDDI)
struct bpf_insn *bpf_fddi_filter;
#endif

int dhcp_bpf_filter_len = sizeof dhcp_bpf_filter / sizeof (struct bpf_insn);
#if defined (HAVE_TR_SUPPORT)
struct bpf_insn dhcp_bpf_tr_filter [] = {
        /* accept all token ring packets due to variable length header */
        /* if we want to get clever, insert the program here */

	/* If we passed all the tests, ask for the whole packet. */
	BPF_STMT(BPF_RET+BPF_K, (u_int)-1),

	/* Otherwise, drop it. */
	BPF_STMT(BPF_RET+BPF_K, 0),
};

int dhcp_bpf_tr_filter_len = (sizeof dhcp_bpf_tr_filter /
			      sizeof (struct bpf_insn));
#endif /* HAVE_TR_SUPPORT */
#endif /* USE_LPF_RECEIVE || USE_BPF_RECEIVE */

#if defined (USE_BPF_RECEIVE)
void if_register_receive (info)
	struct interface_info *info;
{
	int flag = 1;
	struct bpf_version v;
	u_int32_t addr;
	struct bpf_program p;
	u_int32_t bits;
#ifdef DEC_FDDI
	int link_layer;
#endif /* DEC_FDDI */

	/* Open a BPF device and hang it on this interface... */
	info -> rfdesc = if_register_bpf (info);

	/* Make sure the BPF version is in range... */
	if (ioctl (info -> rfdesc, BIOCVERSION, &v) < 0)
		log_fatal ("Can't get BPF version: %m");

	if (v.bv_major != BPF_MAJOR_VERSION ||
	    v.bv_minor < BPF_MINOR_VERSION)
		log_fatal ("BPF version mismatch - recompile DHCP!");

	/* Set immediate mode so that reads return as soon as a packet
	   comes in, rather than waiting for the input buffer to fill with
	   packets. */
	if (ioctl (info -> rfdesc, BIOCIMMEDIATE, &flag) < 0)
		log_fatal ("Can't set immediate mode on bpf device: %m");

#ifdef NEED_OSF_PFILT_HACKS
	/* Allow the copyall flag to be set... */
	if (ioctl(info -> rfdesc, EIOCALLOWCOPYALL, &flag) < 0)
		log_fatal ("Can't set ALLOWCOPYALL: %m");

	/* Clear all the packet filter mode bits first... */
	bits = 0;
	if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0)
		log_fatal ("Can't clear pfilt bits: %m");

	/* Set the ENBATCH, ENCOPYALL, ENBPFHDR bits... */
	bits = ENBATCH | ENCOPYALL | ENBPFHDR;
	if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0)
		log_fatal ("Can't set ENBATCH|ENCOPYALL|ENBPFHDR: %m");
#endif
	/* Get the required BPF buffer length from the kernel. */
	if (ioctl (info -> rfdesc, BIOCGBLEN, &info -> rbuf_max) < 0)
		log_fatal ("Can't get bpf buffer length: %m");
	info -> rbuf = dmalloc (info -> rbuf_max, MDL);
	if (!info -> rbuf)
		log_fatal ("Can't allocate %ld bytes for bpf input buffer.",
			   (long)(info -> rbuf_max));
	info -> rbuf_offset = 0;
	info -> rbuf_len = 0;

	/* Set up the bpf filter program structure. */
	p.bf_len = dhcp_bpf_filter_len;