isc-dhcp/common/socket.c

/* socket.c

   BSD socket interface code... */

/*
 * Copyright (c) 1995, 1996 The Internet Software Consortium.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of The Internet Software Consortium nor the names
 *    of its contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
 * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * This software has been written for the Internet Software Consortium
 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
 * Enterprises.  To learn more about the Internet Software Consortium,
 * see ``http://www.vix.com/isc''.  To learn more about Vixie
 * Enterprises, see ``http://www.vix.com''.
 */

/* SO_BINDTODEVICE support added by Elliot Poger (poger@leland.stanford.edu).
 * This sockopt allows a socket to be bound to a particular interface,
 * thus enabling the use of DHCPD on a multihomed host.
 * If SO_BINDTODEVICE is defined in your system header files, the use of
 * this sockopt will be automatically enabled. 
 * I have implemented it under Linux; other systems should be doable also.
 */

#ifndef lint
static char copyright[] =
"$Id: socket.c,v 1.18 1997/02/18 14:30:13 mellon Exp $ Copyright (c) 1995, 1996 The Internet Software Consortium.  All rights reserved.\n";
#endif /* not lint */

#include "dhcpd.h"

#ifdef USE_SOCKET_FALLBACK
#  define USE_SOCKET_SEND
#  define if_register_send if_register_fallback
#  define send_packet send_fallback
#endif

#if defined (USE_SOCKET_SEND) || defined (USE_SOCKET_RECEIVE)
/* Generic interface registration routine... */
int if_register_socket (info, interface)
	struct interface_info *info;
	struct ifreq *interface;
{
	struct sockaddr_in name;
	int sock;
	int flag;

#ifndef SO_BINDTODEVICE
	static int once = 0;

	/* Make sure only one interface is registered. */
	if (once)
		error ("The standard socket API can only support %s%s%s%s%s",
		       "hosts with a single network interface.   If you must ",
		       "run dhcpd on a host with multiple interfaces, ",
		       "you must compile in BPF or NIT support.   If neither ",
		       "option is supported on your system, please let us ",
		       "know.");
	once = 1;
#endif

	/* Set up the address we're going to bind to. */
	name.sin_family = AF_INET;
	name.sin_port = local_port;
	name.sin_addr.s_addr = INADDR_ANY;
	memset (name.sin_zero, 0, sizeof (name.sin_zero));

	/* Make a socket... */
	if ((sock = socket (AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
		error ("Can't create dhcp socket: %m");

	/* Set the REUSEADDR option so that we don't fail to start if
	   we're being restarted. */
	flag = 1;
	if (setsockopt (sock, SOL_SOCKET, SO_REUSEADDR,
			(char *)&flag, sizeof flag) < 0)
		error ("Can't set SO_REUSEADDR option on dhcp socket: %m");

	/* Set the BROADCAST option so that we can broadcast DHCP responses. */
	if (setsockopt (sock, SOL_SOCKET, SO_BROADCAST,
			(char *)&flag, sizeof flag) < 0)
		error ("Can't set SO_BROADCAST option on dhcp socket: %m");

#ifndef USE_SOCKET_FALLBACK
	/* The following will make all-ones broadcasts go out this interface
	 * on those platforms which use the standard sockets API (assuming 
	 * the OS-specific routines called by enable_sending() are present
	 * for this platform). */
	if_enable (info);
#endif
 
	/* Bind the socket to this interface's IP address. */
	if (bind (sock, (struct sockaddr *)&name, sizeof name) < 0)
		error ("Can't bind to dhcp address: %m");

#ifdef SO_BINDTODEVICE
	/* Bind this socket to this interface. */
	if (setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
		       (char *)interface, sizeof(*interface)) < 0) {
		error("setting SO_BINDTODEVICE");
	}
#endif

	return sock;
}
#endif /* USE_SOCKET_SEND || USE_SOCKET_RECEIVE */

#ifdef USE_SOCKET_SEND
void if_register_send (info, interface)
	struct interface_info *info;
	struct ifreq *interface;

{
#ifndef USE_SOCKET_RECEIVE
	info -> wfdesc = if_register_socket (info, interface);
#else
	info -> wfdesc = info -> rfdesc;
#endif
	note ("Sending on   Socket/%s/%s",
	      info -> name,
	      (info -> shared_network ?
	       info -> shared_network -> name : "unattached"));

}
#endif /* USE_SOCKET_SEND */

#ifdef USE_SOCKET_RECEIVE
void if_register_receive (info, interface)
	struct interface_info *info;
	struct ifreq *interface;
{
	/* If we're using the socket API for sending and receiving,
	   we don't need to register this interface twice. */
	info -> rfdesc = if_register_socket (info, interface);
	note ("Listening on Socket/%s/%s",
	      info -> name,
	      (info -> shared_network ?
	       info -> shared_network -> name : "unattached"));
}
#endif /* USE_SOCKET_RECEIVE */

#ifdef USE_SOCKET_SEND
size_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;
{
	return sendto (interface -> wfdesc, (char *)raw, len, 0,
		       (struct sockaddr *)to, sizeof *to);
}
#endif /* USE_SOCKET_SEND */

#ifdef USE_SOCKET_RECEIVE
size_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 flen = sizeof *from;

	return recvfrom (interface -> rfdesc, buf, len, 0,
			 (struct sockaddr *)from, &flen);
}
#endif /* USE_SOCKET_RECEIVE */

#ifdef USE_SOCKET_FALLBACK
/* This just reads in a packet and silently discards it. */

size_t fallback_discard (interface)
	struct interface_info *interface;
{
	char buf [1540];
	struct sockaddr_in from;
	int flen = sizeof from;

	return recvfrom (interface -> wfdesc, buf, sizeof buf, 0,
			 (struct sockaddr *)&from, &flen);
}
#endif /* USE_SOCKET_RECEIVE */

#if defined (USE_SOCKET_SEND) && !defined (USE_SOCKET_FALLBACK)
/* If we're using the standard socket API without SO_BINDTODEVICE,
 * we need this kludge to force DHCP broadcasts to go out
 * this interface, even though it's not available for general
 * use until we get a lease!
 * This should work _OK_, but it will cause ALL all-ones
 * broadcasts on this host to go out this interface--it
 * could interfere with other interfaces.  And God help you
 * if you run this on multiple interfaces simultaneously.
 * SO_BINDTODEVICE really is better! */
void if_enable (interface)
     struct interface_info *interface;
{
#ifndef SO_BINDTODEVICE
	struct in_addr broad_addr;
	broad_addr.s_addr = htonl(INADDR_BROADCAST);

	/* Delete old routes for broadcast address. */
	remove_routes(NULL, &broad_addr);

	/* Add a route for broadcast address to this interface. */
	/* POTENTIAL PROBLEM: Don't do this to more than one interface! */
	add_route_direct(interface, &broad_addr);
#endif
}
#endif