/*	$OpenBSD: dhcrelay.c,v 1.26 2005/11/13 20:26:00 deraadt Exp $ */

/*
 * Copyright (c) 2004 Henning Brauer <henning@cvs.openbsd.org>
 * Copyright (c) 1997, 1998, 1999 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''.
 */

#include "dhcpd.h"

void	 usage(void);
void	 relay(struct interface_info *, struct dhcp_packet *, int,
	    unsigned int, struct iaddr, struct hardware *);
char	*print_hw_addr(int, int, unsigned char *);
void	 got_response(struct protocol *);

time_t cur_time;

int log_perror = 1;

u_int16_t server_port;
u_int16_t client_port;
int log_priority;
struct interface_info *interfaces = NULL;

struct server_list {
	struct server_list *next;
	struct sockaddr_in to;
	int fd;
} *servers;

int
main(int argc, char *argv[])
{
	int			 ch, no_daemon = 0, opt;
	extern char		*__progname;
	struct server_list	*sp = NULL;
	struct passwd		*pw;
	struct sockaddr_in	 laddr;

	/* Initially, log errors to stderr as well as to syslogd. */
	openlog(__progname, LOG_NDELAY, DHCPD_LOG_FACILITY);
	setlogmask(LOG_UPTO(LOG_INFO));

	while ((ch = getopt(argc, argv, "di:")) != -1) {
		switch (ch) {
		case 'd':
			no_daemon = 1;
			break;
		case 'i':
			if (interfaces != NULL)
				usage();
			if ((interfaces = calloc(1,
			    sizeof(struct interface_info))) == NULL)
				error("calloc");
			strlcpy(interfaces->name, optarg,
			    sizeof(interfaces->name));
			break;
		default:
			usage();
			/* not reached */
		}
	}

	argc -= optind;
	argv += optind;

	if (argc < 1)
		usage();

	while (argc > 0) {
		struct hostent		*he;
		struct in_addr		 ia, *iap = NULL;

		if (inet_aton(argv[0], &ia))
			iap = &ia;
		else {
			he = gethostbyname(argv[0]);
			if (!he)
				warn("%s: host unknown", argv[0]);
			else
				iap = ((struct in_addr *)he->h_addr_list[0]);
		}
		if (iap) {
			if ((sp = calloc(1, sizeof *sp)) == NULL)
				error("calloc");
			sp->next = servers;
			servers = sp;
			memcpy(&sp->to.sin_addr, iap, sizeof *iap);
		}
		argc--;
		argv++;
	}

	log_perror = 0;

	if (interfaces == NULL)
		error("no interface given");

	/* Default DHCP/BOOTP ports. */
	server_port = htons(SERVER_PORT);
	client_port = htons(CLIENT_PORT);

	/* We need at least one server. */
	if (!sp)
		usage();

	discover_interfaces(interfaces);

	bzero(&laddr, sizeof laddr);
	laddr.sin_len = sizeof laddr;
	laddr.sin_family = AF_INET;
	laddr.sin_port = server_port;
	laddr.sin_addr.s_addr = interfaces->primary_address.s_addr;
	/* Set up the server sockaddrs. */
	for (sp = servers; sp; sp = sp->next) {
		sp->to.sin_port = server_port;
		sp->to.sin_family = AF_INET;
		sp->to.sin_len = sizeof sp->to;
		sp->fd = socket(AF_INET, SOCK_DGRAM, 0);
		if (sp->fd == -1)
			error("socket: %m");
		opt = 1;
		if (setsockopt(sp->fd, SOL_SOCKET, SO_REUSEPORT,
		    &opt, sizeof(opt)) == -1)
			error("setsockopt: %m");
		if (bind(sp->fd, (struct sockaddr *)&laddr, sizeof laddr) == -1)
			error("bind: %m");
		if (connect(sp->fd, (struct sockaddr *)&sp->to,
		    sizeof sp->to) == -1)
			error("connect: %m");
		add_protocol("server", sp->fd, got_response, sp);
	}

	tzset();

	time(&cur_time);
	bootp_packet_handler = relay;
	if (!no_daemon)
		daemon(0, 0);

	if ((pw = getpwnam("_dhcp")) == NULL)
		error("user \"_dhcp\" not found");
	if (chroot(_PATH_VAREMPTY) == -1)
		error("chroot: %m");
	if (chdir("/") == -1)
		error("chdir(\"/\"): %m");
	if (setgroups(1, &pw->pw_gid) ||
	    setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
	    setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid))
		error("can't drop privileges: %m");

	dispatch();
	/* not reached */

	exit(0);
}

void
relay(struct interface_info *ip, struct dhcp_packet *packet, int length,
    unsigned int from_port, struct iaddr from, struct hardware *hfrom)
{
	struct server_list	*sp;
	struct sockaddr_in	 to;
	struct hardware		 hto;

	if (packet->hlen > sizeof packet->chaddr) {
		note("Discarding packet with invalid hlen.");
		return;
	}

	/* If it's a bootreply, forward it to the client. */
	if (packet->op == BOOTREPLY) {
		bzero(&to, sizeof(to));
		if (!(packet->flags & htons(BOOTP_BROADCAST))) {
			to.sin_addr = packet->yiaddr;
			to.sin_port = client_port;
		} else {
			to.sin_addr.s_addr = htonl(INADDR_BROADCAST);
			to.sin_port = client_port;
		}
		to.sin_family = AF_INET;
		to.sin_len = sizeof to;

		/* Set up the hardware destination address. */
		hto.hlen = packet->hlen;
		if (hto.hlen > sizeof hto.haddr)
			hto.hlen = sizeof hto.haddr;
		memcpy(hto.haddr, packet->chaddr, hto.hlen);
		hto.htype = packet->htype;

		if (send_packet(interfaces, packet, length,
		    interfaces->primary_address, &to, &hto) != -1)
			debug("forwarded BOOTREPLY for %s to %s",
			    print_hw_addr(packet->htype, packet->hlen,
			    packet->chaddr), inet_ntoa(to.sin_addr));
		return;
	}

	if (ip == NULL) {
		note("ignoring non BOOTREPLY from server");
		return;
	}

	/* If giaddr is set on a BOOTREQUEST, ignore it - it's already
	   been gatewayed. */
	if (packet->giaddr.s_addr) {
		note("ignoring BOOTREQUEST with giaddr of %s\n",
		    inet_ntoa(packet->giaddr));
		return;
	}

	/* Set the giaddr so the server can figure out what net it's
	   from and so that we can later forward the response to the
	   correct net. */
	packet->giaddr = ip->primary_address;

	/* Otherwise, it's a BOOTREQUEST, so forward it to all the
	   servers. */
	for (sp = servers; sp; sp = sp->next) {
		if (send(sp->fd, packet, length, 0) != -1) {
			debug("forwarded BOOTREQUEST for %s to %s",
			    print_hw_addr(packet->htype, packet->hlen,
			    packet->chaddr), inet_ntoa(sp->to.sin_addr));
		}
	}

}

void
usage(void)
{
	extern char	*__progname;

	fprintf(stderr, "Usage: %s [-d] ", __progname);
	fprintf(stderr, "-i interface server1 [... serverN]\n");
	exit(1);
}

char *
print_hw_addr(int htype, int hlen, unsigned char *data)
{
	static char	 habuf[49];
	char		*s = habuf;
	int		 i, j, slen = sizeof(habuf);

	if (htype == 0 || hlen == 0) {
bad:
		strlcpy(habuf, "<null>", sizeof habuf);
		return habuf;
	}

	for (i = 0; i < hlen; i++) {
		j = snprintf(s, slen, "%02x", data[i]);
		if (j <= 0 || j >= slen)
			goto bad;
		j = strlen (s);
		s += j;
		slen -= (j + 1);
		*s++ = ':';
	}
	*--s = '\0';
	return habuf;
}

void
got_response(struct protocol *l)
{
	ssize_t result;
	struct iaddr ifrom;
	union {
		/*
		 * Packet input buffer.  Must be as large as largest
		 * possible MTU.
		 */
		unsigned char packbuf[4095];
		struct dhcp_packet packet;
	} u;
	struct server_list *sp = l->local;

	if ((result = recv(l->fd, u.packbuf, sizeof(u), 0)) == -1 &&
	    errno != ECONNREFUSED) {
		/*
		 * Ignore ECONNREFUSED as to many dhcp server send a bogus
		 * icmp unreach for every request.
		 */
		warn("recv failed for %s: %m",
		    inet_ntoa(sp->to.sin_addr));
		return;
	}
	if (result == 0)
		return;

	if (result < BOOTP_MIN_LEN) {
		note("Discarding packet with invalid size.");
		return;
	}

	if (bootp_packet_handler) {
		ifrom.len = 4;
		memcpy(ifrom.iabuf, &sp->to.sin_addr, ifrom.len);

		(*bootp_packet_handler)(NULL, &u.packet, result,
		    sp->to.sin_port, ifrom, NULL);
	}
}