/* 
 * Copyright © 2005-2008  Red Hat, Inc. All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions of the
 * GNU General Public License v.2.  This program is distributed in the hope
 * that it will be useful, but WITHOUT ANY WARRANTY expressed or implied,
 * including the implied warranties of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE. See the GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. Any Red Hat
 * trademarks that are incorporated in the source code or documentation are not
 * subject to the GNU General Public License and may only be used or replicated
 * with the express permission of Red Hat, Inc.
 *
 * Red Hat Author(s): Nathan Straz <nstraz@redhat.com>
 *                    Dean Jansa <djansa@redhat.com>
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include "btime_int.h"

static int same_addr(struct sockaddr_in *a, struct sockaddr_in *b);
static void gen_cookie(char *s);
/*
 * btime --
 * 
 *	Return the boot time of a remote host if that host is running the
 *	btimed deamon.
 *
 * Returns:
 *	btime, or 0 on failure.
 */

unsigned int
btime(const char *host)
{
	int sd;
	char cookie[BTIME_MSGLEN];
	char response[BTIME_MSGLEN];
	struct sockaddr_in serv_addr;
	struct sockaddr_in my_addr;
	struct sockaddr_in resp_addr;
	socklen_t serv_addr_len;
	socklen_t resp_addr_len;
	struct hostent *hostent;
	in_addr_t inaddr;
	unsigned int btime = 0;
	ssize_t nbytes;	
	int retry;
	fd_set sdset;
	struct timeval timeout;

	if ((sd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
		fprintf(stderr, "Could not create socket: %s\n", 
		        strerror(errno));
		return 0;
	}

	memset(&serv_addr, 0, sizeof serv_addr);
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_port = htons(BTIME_PORT);

	if ((inaddr = inet_addr(host)) != INADDR_NONE) {
		memcpy(&serv_addr.sin_addr, &inaddr, sizeof inaddr);
	} else {
		if ((hostent = gethostbyname(host)) == NULL) {
			return 0;
		}

		memcpy(&serv_addr.sin_addr, hostent->h_addr, hostent->h_length);
	}

	memset(&my_addr, 0, sizeof my_addr);
	my_addr.sin_family = AF_INET;
	my_addr.sin_addr.s_addr = htonl(INADDR_ANY);
	my_addr.sin_port = htons(0);
	if (bind(sd, (struct sockaddr *)&my_addr, sizeof my_addr) < 0) {
		fprintf(stderr, "Could not bind to local address: %s\n", 
		        strerror(errno));
		return 0;
	}

	memset(cookie, 0, BTIME_MSGLEN);
	gen_cookie(cookie);
	for (retry = 0; retry < MAX_RETRY; retry++) {
		serv_addr_len = sizeof serv_addr;
		if ((nbytes = sendto(sd, &cookie, BTIME_MSGLEN, MSG_DONTWAIT,
	       	 (struct sockaddr *)&serv_addr, serv_addr_len)) < 0) {
			if (errno == EAGAIN) {
				usleep(retry * 100);
			} else {
				/* Non EAGAIN error... */
				break;
			}
		} else {
			break;
		}
	}
	
	FD_ZERO(&sdset);
	FD_SET(sd, &sdset);
	do {
		retry = 0;

		timeout.tv_sec = 0;
		timeout.tv_usec = 250000;

		if (select(sd + 1, &sdset, NULL, NULL, &timeout) != 1) {
			/* Either an error or a timeout, we don't need to retry */
			break;
		}

		memset(&resp_addr, 0, sizeof resp_addr);
		memset(response, 0, BTIME_MSGLEN);
		resp_addr_len = sizeof resp_addr;
		nbytes = recvfrom(sd, &response, BTIME_MSGLEN, MSG_DONTWAIT, 
				(struct sockaddr *)&resp_addr, &resp_addr_len);
		if (nbytes == 0) {
			/* Nothing received */
			continue;
		} else if (response[0] == 'B' && response[1] == 'T') {
			/* Check for new style cookie */
			if (memcmp(cookie, response, COOKIE_LEN) == 0) {
				btime = strtoul(response+COOKIE_LEN, NULL, 10);
				break;
			} else {
				/* ignore the invalid btime cookie */
				retry = 1;
				continue;
			}
		} else if (!same_addr(&serv_addr, &resp_addr)) {
			/* If no cookie, check peer */
			char *rstr = strdup(inet_ntoa(resp_addr.sin_addr));
			char *sstr = strdup(inet_ntoa(serv_addr.sin_addr));
			fprintf(stderr, "Got response from %s instead of %s\n",
					rstr, sstr);
			free(rstr);
			free(sstr);
			retry = 1;
			continue;
		} else {
			/* If peer matches, accept the bare btime */
			btime = strtoul(response, (char **)NULL, 10);
			break;
		}
	} while (retry);

	close(sd);

	return btime;
}

/* same_addr
 *
 * 	Compare to struct sockaddr_in's
 *
 * Returns:
 * 	1 if the addresses match
 * 	0 if the addresses are different
 */
static int
same_addr(struct sockaddr_in *a, struct sockaddr_in *b)
{
	if (a->sin_family != b->sin_family) {
		return 0;
	} else if (a->sin_addr.s_addr != b->sin_addr.s_addr) {
		return 0;
	} else {
		return 1;
	}
}
/* gen_cookie
 *
 * 	Generate a random string that btimed will send back to us.
 */
static void gen_cookie(char *s)
{
	char *a = s;
	int i;

	*a++ = 'B';
	*a++ = 'T';
	for (i = 0; i < COOKIE_RANDOM_PARTS; i++) {
		*(int32_t *)a = (int32_t)random();
		a += sizeof(int32_t);
	}
	*a = '\n';
}