bpf.c

DHCP服务器源码

#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 bpf_fddi_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 */
	dhcp_bpf_filter [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;
	int fudge;

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

	/* 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;

	/* 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... */

	do {
		/* 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,
						 (omapi_object_t *)0);
				}
				return length;
			}
			interface -> rbuf_offset = 0;
			interface -> rbuf_len = BPF_WORDALIGN (length);
		}

		/* 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,
					       (unsigned char *)0,
					       hdr.bh_caplen);

		/* 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,
			hdr.bh_caplen);
		interface -> rbuf_offset =
			BPF_WORDALIGN (interface -> rbuf_offset +
				       hdr.bh_caplen);
		return hdr.bh_caplen;
	} while (!length);
	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