isc-dhcp/common/nit.c

/* nit.c

   Network Interface Tap (NIT) network interface code, by Ted Lemon
   with one crucial tidbit of help from Stu Grossmen. */

/*
 * 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/
 *
 */

#include "dhcpd.h"
#if defined (USE_NIT_SEND) || defined (USE_NIT_RECEIVE)
#include <sys/ioctl.h>
#include <sys/uio.h>

#include <sys/time.h>
#include <net/nit.h>
#include <net/nit_if.h>
#include <net/nit_pf.h>
#include <net/nit_buf.h>
#include <sys/stropts.h>
#include <net/packetfilt.h>

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

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

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

#ifdef USE_NIT_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. */

int if_register_nit (info)
	struct interface_info *info;
{
	int sock;
	char filename[50];
	struct ifreq ifr;
	struct strioctl sio;

	/* Open a NIT device */
	sock = open ("/dev/nit", O_RDWR);
	if (sock < 0)
		log_fatal ("Can't open NIT device for %s: %m", info -> name);

	/* Set the NIT device to point at this interface. */
	sio.ic_cmd = NIOCBIND;
	sio.ic_len = sizeof *(info -> ifp);
	sio.ic_dp = (char *)(info -> ifp);
	sio.ic_timout = INFTIM;
	if (ioctl (sock, I_STR, &sio) < 0)
		log_fatal ("Can't attach interface %s to nit device: %m",
		       info -> name);

	/* Get the low-level address... */
	sio.ic_cmd = SIOCGIFADDR;
	sio.ic_len = sizeof ifr;
	sio.ic_dp = (char *)&ifr;
	sio.ic_timout = INFTIM;
	if (ioctl (sock, I_STR, &sio) < 0)
		log_fatal ("Can't get physical layer address for %s: %m",
		       info -> name);

	/* XXX code below assumes ethernet interface! */
	info -> hw_address.hlen = 7;
	info -> hw_address.hbuf [0] = ARPHRD_ETHER;
	memcpy (&info -> hw_address.hbuf [1],
		ifr.ifr_ifru.ifru_addr.sa_data, 6);

	if (ioctl (sock, I_PUSH, "pf") < 0)
		log_fatal ("Can't push packet filter onto NIT for %s: %m",
		       info -> name);

	return sock;
}
#endif /* USE_NIT_SEND || USE_NIT_RECEIVE */

#ifdef USE_NIT_SEND
void if_register_send (info)
	struct interface_info *info;
{
	/* If we're using the nit API for sending and receiving,
	   we don't need to register this interface twice. */
#ifndef USE_NIT_RECEIVE
	struct packetfilt pf;
	struct strioctl sio;

	info -> wfdesc = if_register_nit (info);

	pf.Pf_Priority = 0;
	pf.Pf_FilterLen = 1;
	pf.Pf_Filter [0] = ENF_PUSHZERO;

	/* Set up an NIT filter that rejects everything... */
	sio.ic_cmd = NIOCSETF;
	sio.ic_len = sizeof pf;
	sio.ic_dp = (char *)&pf;
	sio.ic_timout = INFTIM;
	if (ioctl (info -> wfdesc, I_STR, &sio) < 0)
		log_fatal ("Can't set NIT filter: %m");
#else
	info -> wfdesc = info -> rfdesc;
#endif
        if (!quiet_interface_discovery)
		log_info ("Sending on   NIT/%s%s%s",
		      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 nit API for sending and receiving,
	   we don't need to register this interface twice. */
#ifndef USE_NIT_RECEIVE
	close (info -> wfdesc);
#endif
	info -> wfdesc = -1;
        if (!quiet_interface_discovery)
		log_info ("Disabling output on NIT/%s%s%s",
		      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_NIT_SEND */

#ifdef USE_NIT_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 NIT program! XXX */

#if defined(RELAY_PORT)
#error "Relay port is not yet supported for NIT"
#endif

void if_register_receive (info)
	struct interface_info *info;
{
	int flag = 1;
	u_int32_t x;
	struct packetfilt pf;
	struct strioctl sio;
	u_int16_t addr [2];
	struct timeval t;

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

	/* Set the snap length to 0, which means always take the whole
	   packet. */
	x = 0;
	if (ioctl (info -> rfdesc, NIOCSSNAP, &x) < 0)
		log_fatal ("Can't set NIT snap length on %s: %m", info -> name);

	/* Set the stream to byte stream mode */
	if (ioctl (info -> rfdesc, I_SRDOPT, RMSGN) != 0)
		log_info ("I_SRDOPT failed on %s: %m", info -> name);

#if 0
	/* Push on the chunker... */
	if (ioctl (info -> rfdesc, I_PUSH, "nbuf") < 0)
		log_fatal ("Can't push chunker onto NIT STREAM: %m");

	/* Set the timeout to zero. */
	t.tv_sec = 0;
	t.tv_usec = 0;
	if (ioctl (info -> rfdesc, NIOCSTIME, &t) < 0)
		log_fatal ("Can't set chunk timeout: %m");
#endif

	/* Ask for no header... */
	x = 0;
	if (ioctl (info -> rfdesc, NIOCSFLAGS, &x) < 0)
		log_fatal ("Can't set NIT flags on %s: %m", info -> name);

	/* Set up the NIT filter program. */
	/* XXX Unlike the BPF filter program, this one won't work if the
	   XXX IP packet is fragmented or if there are options on the IP
	   XXX header. */
	pf.Pf_Priority = 0;
	pf.Pf_FilterLen = 0;

	pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHWORD + 6;
	pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHLIT + ENF_CAND;
	pf.Pf_Filter [pf.Pf_FilterLen++] = htons (ETHERTYPE_IP);
	pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHLIT;
	pf.Pf_Filter [pf.Pf_FilterLen++] = htons (IPPROTO_UDP);
	pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHWORD + 11;
	pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHLIT + ENF_AND;
	pf.Pf_Filter [pf.Pf_FilterLen++] = htons (0xFF);
	pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_CAND;
	pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHWORD + 18;
	pf.Pf_Filter [pf.Pf_FilterLen++] = ENF_PUSHLIT + ENF_CAND;
	pf.Pf_Filter [pf.Pf_FilterLen++] = local_port;

	/* Install the filter... */
	sio.ic_cmd = NIOCSETF;
	sio.ic_len = sizeof pf;
	sio.ic_dp = (char *)&pf;
	sio.ic_timout = INFTIM;
	if (ioctl (info -> rfdesc, I_STR, &sio) < 0)
		log_fatal ("Can't set NIT filter on %s: %m", info -> name);

        if (!quiet_interface_discovery)
		log_info ("Listening on NIT/%s%s%s",
		      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;
{
	/* If we're using the nit API for sending and receiving,
	   we don't need to register this interface twice. */
	close (info -> rfdesc);
	info -> rfdesc = -1;

        if (!quiet_interface_discovery)
		log_info ("Disabling input on NIT/%s%s%s",
		      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_NIT_RECEIVE */

#ifdef USE_NIT_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, ibufp;
	double hh [16];
	double ih [1536 / sizeof (double)];
	unsigned char *buf = (unsigned char *)ih;
	struct sockaddr *junk;
	struct strbuf ctl, data;
	struct sockaddr_in foo;
	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;

	/* Start with the sockaddr struct... */
	junk = (struct sockaddr *)&hh [0];
	hbufp = (((unsigned char *)&junk -> sa_data [0]) -
		 (unsigned char *)&hh[0]);
	ibufp = 0;

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

	/* Copy the data into the buffer (yuk). */
	memcpy (buf + ibufp, raw, len);

	/* Set up the sockaddr structure... */
#if USE_SIN_LEN
	junk -> sa_len = hbufp - 2; /* XXX */
#endif
	junk -> sa_family = AF_UNSPEC;

	/* Set up the msg_buf structure... */
	ctl.buf = (char *)&hh [0];
	ctl.maxlen = ctl.len = hbufp;
	data.buf = (char *)&ih [0];
	data.maxlen = data.len = ibufp + len;

	result = putmsg (interface -> wfdesc, &ctl, &data, 0);
	if (result < 0)
		log_error ("send_packet: %m");
	return result;
}
#endif /* USE_NIT_SEND */

#ifdef USE_NIT_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 nread;
	int length = 0;
	int offset = 0;
	unsigned char ibuf [1536];
	int bufix = 0;
	unsigned paylen;

	length = read (interface -> rfdesc, ibuf, sizeof ibuf);
	if (length <= 0)
		return length;

	/* Decode the physical header... */
	offset = decode_hw_header (interface, ibuf, bufix, hfrom);

	/* If a physical layer checksum failed (dunno of any
	   physical layer that supports this, but WTH), skip this
	   packet. */
	if (offset < 0) {
		return 0;
	}

	bufix += offset;
	length -= offset;

	/* Decode the IP and UDP headers... */
	offset = decode_udp_ip_header (interface, ibuf, bufix,
				       from, length, &paylen, 1);

	/* If the IP or UDP checksum was bad, skip the packet... */
	if (offset < 0)
		return 0;

	bufix += offset;
	length -= offset;

	if (length < paylen)
		log_fatal("Internal inconsistency at %s:%d.", MDL);

	/* Copy out the data in the packet... */
	memcpy(buf, &ibuf[bufix], paylen);
	return paylen;
}

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