bpf.c

/* bpf.c

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

/*
 * Copyright (C) 2004-2022 Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 1996-2003 by Internet Software Consortium
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * 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.
 *   PO Box 360
 *   Newmarket, NH 03857 USA
 *   <info@isc.org>
 *   https://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.
 */

#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

#if defined(USE_BPF_SEND) || defined(USE_BPF_RECEIVE) || defined(USE_BPF_HWADDR)
#include <net/if_types.h>
#include <ifaddrs.h>
#endif

#include <errno.h>

/* 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);

	get_hw_addr(info->name, &info->hw_address);

	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(RELAY_PORT)
/*
 * For relay port extension
 */
struct bpf_insn dhcp_bpf_relay_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, 10),

	/* 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, 8),

	/* 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, 6, 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, 2, 0),             /* patch */

	/* relay can have an alternative 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),
};

int dhcp_bpf_relay_filter_len =
	sizeof dhcp_bpf_relay_filter / sizeof (struct bpf_insn);
#endif

#if defined (DEC_FDDI)
struct bpf_insn *bpf_fddi_filter = NULL;
#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;
	struct bpf_program p;
#ifdef NEED_OSF_PFILT_HACKS
	u_int32_t bits;
#endif
#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;

#ifdef DEC_FDDI
	/* See if this is an FDDI interface, flag it for later. */
	if (ioctl(info -> rfdesc, BIOCGDLT, &link_layer) >= 0 &&
	    link_layer == DLT_FDDI) {
		if (!bpf_fddi_filter) {
			bpf_fddi_filter = dmalloc (sizeof dhcp_bpf_filter,
						    MDL);
			if (!bpf_fddi_filter)
				log_fatal ("No memory for FDDI filter.");
			memcpy (bpf_fddi_filter,
				dhcp_bpf_filter, sizeof dhcp_bpf_filter);
			/* Patch the BPF program to account for the difference
			   in length between ethernet headers (14), FDDI and
			   802.2 headers (16 +8=24, +10).
			   XXX changes to filter program may require changes to
			   XXX the insn number(s) used below! */
			bpf_fddi_filter[0].k += 10;
			bpf_fddi_filter[2].k += 10;
			bpf_fddi_filter[4].k += 10;
			bpf_fddi_filter[6].k += 10;
			bpf_fddi_filter[7].k += 10;
		}
		p.bf_insns = bpf_fddi_filter;
	} else
#endif /* DEC_FDDI */
	p.bf_insns = dhcp_bpf_filter;

        /* Patch the server port into the BPF  program...
	   XXX changes to filter program may require changes
	   to the insn number(s) used below! XXX */
#if defined(RELAY_PORT)
	if (relay_port) {
		/*
		 * If user defined relay UDP port, we need to filter
		 * also on the user UDP port.
		 */
		p.bf_len = dhcp_bpf_relay_filter_len;
		p.bf_insns = dhcp_bpf_relay_filter;

		dhcp_bpf_relay_filter [10].k = ntohs (relay_port);
	}
#endif
	p.bf_insns [8].k = ntohs (local_port);

	if (ioctl (info -> rfdesc, BIOCSETF, &p) < 0)
		log_fatal ("Can't install packet filter program: %m");
	if (!quiet_interface_discovery)
		log_info ("Listening 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_receive (info)
	struct interface_info *info;
{
	close (info -> rfdesc);
	info -> rfdesc = -1;

	if (!quiet_interface_discovery)
		log_info ("Disabling input 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_RECEIVE */

#ifdef USE_BPF_SEND
ssize_t send_packet (interface, packet, raw, len, from, to, hto)
	struct interface_info *interface;
	struct packet *packet;
	struct dhcp_packet *raw;
	size_t len;
	struct in_addr from;
	struct sockaddr_in *to;
	struct hardware *hto;
{
	unsigned hbufp = 0, ibufp = 0;
	double hw [4];
	double ip [32];
	struct iovec iov [3];
	int result;

	if (!strcmp (interface -> name, "fallback"))
		return send_fallback (interface, packet, raw,
				      len, from, to, hto);

	if (hto == NULL && interface->anycast_mac_addr.hlen)
		hto = &interface->anycast_mac_addr;

	/* Assemble the headers... */
	assemble_hw_header (interface, (unsigned char *)hw, &hbufp, hto);
	assemble_udp_ip_header (interface,
				(unsigned char *)ip, &ibufp, from.s_addr,
				to -> sin_addr.s_addr, to -> sin_port,
				(unsigned char *)raw, len);

	/* Fire it off */
	iov [0].iov_base = ((char *)hw);
	iov [0].iov_len = hbufp;
	iov [1].iov_base = ((char *)ip);
	iov [1].iov_len = ibufp;
	iov [2].iov_base = (char *)raw;
	iov [2].iov_len = len;

	result = writev(interface -> wfdesc, iov, 3);
	if (result < 0)
		log_error ("send_packet: %m");
	return result;
}
#endif /* USE_BPF_SEND */

#ifdef USE_BPF_RECEIVE
ssize_t receive_packet (interface, buf, len, from, hfrom)
	struct interface_info *interface;
	unsigned char *buf;
	size_t len;
	struct sockaddr_in *from;
	struct hardware *hfrom;
{
	int length = 0;
	int offset = 0;
	struct bpf_hdr hdr;
	unsigned paylen;

	/* All this complexity is because BPF doesn't guarantee
	   that only one packet will be returned at a time.   We're
	   getting what we deserve, though - this is a terrible abuse
	   of the BPF interface.   Sigh. */

	/* Process packets until we get one we can return or until we've
	   done a read and gotten nothing we can return... */

	/* If the buffer is empty, fill it. */
	if (interface->rbuf_offset >= interface->rbuf_len) {
		length = read(interface->rfdesc, interface->rbuf,
			      (size_t)interface->rbuf_max);
		if (length <= 0) {
#ifdef __FreeBSD__
			if (errno == ENXIO) {
#else
			if (errno == EIO) {
#endif
				dhcp_interface_remove
					((omapi_object_t *)interface, NULL);
			}
			return (length);
		}
		interface->rbuf_offset = 0;
		interface->rbuf_len = BPF_WORDALIGN(length);
	}

	do {
		/* If there isn't room for a whole bpf header, something went
		   wrong, but we'll ignore it and hope it goes away... XXX */
		if (interface->rbuf_len -
		    interface->rbuf_offset < sizeof hdr) {
			interface->rbuf_offset = interface->rbuf_len;
			continue;
		}

		/* Copy out a bpf header... */
		memcpy(&hdr, &interface->rbuf[interface->rbuf_offset],
		       sizeof hdr);

		/* If the bpf header plus data doesn't fit in what's left
		   of the buffer, stick head in sand yet again... */
		if (interface->rbuf_offset +
		    hdr.bh_hdrlen + hdr.bh_caplen > interface->rbuf_len) {
			interface->rbuf_offset = interface->rbuf_len;
			continue;
		}

		/* If the captured data wasn't the whole packet, or if
		   the packet won't fit in the input buffer, all we
		   can do is drop it. */
		if (hdr.bh_caplen != hdr.bh_datalen) {
			interface->rbuf_offset =
				BPF_WORDALIGN(interface->rbuf_offset +
					      hdr.bh_hdrlen + hdr.bh_caplen);
			continue;
		}

		/* Skip over the BPF header... */
		interface->rbuf_offset += hdr.bh_hdrlen;

		/* Decode the physical header... */
		offset = decode_hw_header(interface, interface->rbuf,
					  interface->rbuf_offset, hfrom);

		/* If a physical layer checksum failed (dunno of any
		   physical layer that supports this, but WTH), skip this
		   packet. */
		if (offset < 0) {
			interface->rbuf_offset =
				BPF_WORDALIGN(interface->rbuf_offset +
					      hdr.bh_caplen);
			continue;
		}
		interface->rbuf_offset += offset;
		hdr.bh_caplen -= offset;

		/* Decode the IP and UDP headers... */
		offset = decode_udp_ip_header(interface, interface->rbuf,
					      interface->rbuf_offset,
                                              from, hdr.bh_caplen, &paylen, 1);

		/* If the IP or UDP checksum was bad, skip the packet... */
		if (offset < 0) {
			interface->rbuf_offset =
				BPF_WORDALIGN(interface->rbuf_offset +
					      hdr.bh_caplen);
			continue;
		}
		interface->rbuf_offset = interface->rbuf_offset + offset;
		hdr.bh_caplen -= offset;

		/* If there's not enough room to stash the packet data,
		   we have to skip it (this shouldn't happen in real
		   life, though). */
		if (hdr.bh_caplen > len) {
			interface->rbuf_offset =
				BPF_WORDALIGN(interface->rbuf_offset +
					       hdr.bh_caplen);
			continue;
		}

		/* Copy out the data in the packet... */
		memcpy(buf, interface->rbuf + interface->rbuf_offset, paylen);
		interface->rbuf_offset =
			BPF_WORDALIGN(interface->rbuf_offset + hdr.bh_caplen);
		return paylen;
	} while (interface->rbuf_offset < interface->rbuf_len);

	return (0);
}

int can_unicast_without_arp (ip)
	struct interface_info *ip;
{
	return 1;
}

int can_receive_unicast_unconfigured (ip)
	struct interface_info *ip;
{
	return 1;
}

int supports_multiple_interfaces (ip)
	struct interface_info *ip;
{
	return 1;
}

void maybe_setup_fallback ()
{
	isc_result_t status;
	struct interface_info *fbi = (struct interface_info *)0;
	if (setup_fallback (&fbi, MDL)) {
		if_register_fallback (fbi);
		status = omapi_register_io_object ((omapi_object_t *)fbi,
						   if_readsocket, 0,
						   fallback_discard, 0, 0);
		if (status != ISC_R_SUCCESS)
			log_fatal ("Can't register I/O handle for %s: %s",
				   fbi -> name, isc_result_totext (status));
		interface_dereference (&fbi, MDL);
	}
}
#endif

#if defined(USE_BPF_RECEIVE) || defined(USE_BPF_HWADDR)
void
get_hw_addr(const char *name, struct hardware *hw) {
	struct ifaddrs *ifa;
	struct ifaddrs *p;
	struct sockaddr_dl *sa;

	if (getifaddrs(&ifa) != 0) {
		log_fatal("Error getting interface information; %m");
	}

	/*
	 * Loop through our interfaces finding a match.
	 */
	sa = NULL;
	for (p=ifa; (p != NULL) && (sa == NULL); p = p->ifa_next) {
		if ((p->ifa_addr->sa_family == AF_LINK) &&
		    !strcmp(p->ifa_name, name)) {
		    	sa = (struct sockaddr_dl *)p->ifa_addr;
		}
	}
	if (sa == NULL) {
		log_fatal("No interface called '%s'", name);
	}

	/*
	 * Pull out the appropriate information.
	 */
        switch (sa->sdl_type) {
                case IFT_ETHER:
#if defined (IFT_L2VLAN)
		case IFT_L2VLAN:
#endif
                        hw->hlen = sa->sdl_alen + 1;
                        hw->hbuf[0] = HTYPE_ETHER;
                        memcpy(&hw->hbuf[1], LLADDR(sa), sa->sdl_alen);
                        break;
		case IFT_ISO88023:
		case IFT_ISO88024: /* "token ring" */
		case IFT_ISO88025:
		case IFT_ISO88026:
                        hw->hlen = sa->sdl_alen + 1;
                        hw->hbuf[0] = HTYPE_IEEE802;
                        memcpy(&hw->hbuf[1], LLADDR(sa), sa->sdl_alen);
                        break;
#ifdef IFT_FDDI
                case IFT_FDDI:
                        hw->hlen = sa->sdl_alen + 1;
                        hw->hbuf[0] = HTYPE_FDDI;
                        memcpy(&hw->hbuf[1], LLADDR(sa), sa->sdl_alen);
                        break;
#endif /* IFT_FDDI */
                default:
                        log_fatal("Unsupported device type %d for \"%s\"",
                                  sa->sdl_type, name);
        }

	freeifaddrs(ifa);
}
#endif