/*
 * Emergency remote reboot switch, telnet to port, insert challenge and reboot
 * instantly, created for the use of remote embedded development nodes which
 * tend to run out of usefull interactive deamons due to swap, memory issues.
 * Causing great pain when trying to reboot.
 *
 * Rick van der Zwet <info@rickvanderzwet.nl>
 * License: BSDLike - http://rickvanderzwet.nl/license
 */

/* Version: $Id$ */
/* XXX: Some signal handeling to nicely close connections on failure */

#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <strings.h>
#include <string.h>
#include <sys/reboot.h>
#include <sysexits.h>

#include <sys/socket.h>
#include <netinet/in.h>

#define PORT_NUMBER 666
#define CHALLENGE "reboot"
#define PIDFILE "/var/run/rebootd.pid"

void error(const char * message) {
	perror(message);
	exit(EX_OSERR);
}

void init_reboot(const int dryrun) {
	if (dryrun == 1) {
		fprintf(stderr, "Reboot call detected\n");
		return;
	}

	reboot(RB_AUTOBOOT); 
}

void usage() {
	fprintf(stderr,"rebootd [-fn] [-c challenge] [-p pidfile] [-d port]\n \
Arguments: \n\
\tf         = run in foreground [off] \n\
\tn         = dry run, no actual reboot [off] \n\
\tpidfile   = pid file to use [%s] \n\
\tport      = tcp port to use [%i] \n\
\tchallenge = verification password [%s] \n",PIDFILE , PORT_NUMBER, CHALLENGE);
	exit(EX_USAGE);
}

int main (int argc, char * argv[]) {
	char * challenge = CHALLENGE;
	char * pidfile = PIDFILE;
	char buffer[256];
	int port_number = PORT_NUMBER;
	int nodeamon_flag = 0;
	int dryrun_flag = 0;
	int sockfd, newsockfd, ch;
	pid_t pid;
	struct sockaddr_in serv_addr, cli_addr;

	while ((ch = getopt(argc, argv, "c:d:hfnp:")) != -1) {
		switch(ch) {
			case 'c':
				challenge = optarg;
				break;
			case 'd':
				port_number = atoi(optarg);
				if (port_number == 0) {
					usage();
				}
				break;
			case 'f':
				nodeamon_flag = 1;
				break;
			case 'n':
				dryrun_flag = 1;
				break;
			case 'p':
				pidfile = optarg;
				break;
			case 'h':
			case '?':
			default:
				usage();
		}
	}
	if (getuid() > 0) {
		fprintf(stderr,"Sorry, rebootd requires superuser power\n");
		exit(EX_USAGE);
	}
	
	if (nodeamon_flag == 0) {
		pid = fork();
		if (pid < 0) {
			exit(EX_OSERR);
		} else if (pid > 0) {
			FILE * pidhandle;
			pidhandle = fopen(pidfile, "w");
			if (pidhandle) {
				fprintf(pidhandle, "%i", pid);
				fclose(pidhandle);
			}
			exit(EX_OK);
		}
	}

	sockfd = socket(AF_INET, SOCK_STREAM, 0);
	if (sockfd < 0)
		error("ERROR opening socket");
	bzero((char *) &serv_addr, sizeof(serv_addr));
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_addr.s_addr = INADDR_ANY;
	serv_addr.sin_port = htons(PORT_NUMBER);

	if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
		error("ERROR on binding");
	}
	listen(sockfd,5);
	while ( 1 ) {
		newsockfd = accept(sockfd, NULL, NULL); 
		bzero(buffer,256);
		read(newsockfd,buffer,255);
		if (strncmp(buffer, "PING",4) == 0) {
			write(newsockfd,"ACK\n",4);
		} else if (strncmp(buffer, CHALLENGE, strlen(CHALLENGE)) == 0) {
			write(newsockfd,"OK - rebooting\n",15);
			init_reboot(dryrun_flag);
		} else {
			write(newsockfd,"ERROR - invalid command\n",25);
		}
		close(newsockfd);
	}

	return(EX_OK);
}