Merge pull request #37 from kohtala/master

isotptun: add option to daemonize (-D)

isotptun.c

@@ -55,6 +55,8 @@
 #include <libgen.h>
 #include <errno.h>
 #include <signal.h>
+#include <stdarg.h>
+#include <syslog.h>
 
 #include <net/if.h>
 #include <sys/types.h>
@@ -65,6 +67,9 @@
 #include <linux/can/isotp.h>
 #include <linux/if_tun.h>
 
+/* Change this to whatever your daemon is called */
+#define DAEMON_NAME "isotptun"
+
 #define NO_CAN_ID 0xFFFFFFFFU
 #define DEFAULT_NAME "ctun%d"
 
@@ -74,6 +79,26 @@
 
 static volatile int running = 1;
 
+static void fake_syslog(int priority, const char *format, ...)
+{
+	va_list ap;
+
+	fprintf(stderr, "[%d] ", priority);
+	va_start(ap, format);
+	vfprintf(stderr, format, ap);
+	va_end(ap);
+	fprintf(stderr, "\n");
+}
+
+typedef void (*syslog_t)(int priority, const char *format, ...);
+static syslog_t syslogger = syslog;
+
+void perror_syslog(const char *s)
+{
+	const char *colon = s ? ": " : "";
+	syslogger(LOG_ERR, "%s%s%s", s, colon, strerror(errno));
+}
+
 void print_usage(char *prg)
 {
 	fprintf(stderr, "\nUsage: %s [options] <CAN interface>\n\n", prg);
@@ -90,6 +115,7 @@ void print_usage(char *prg)
 	fprintf(stderr, "         -b <bs>      (blocksize. 0 = off)\n");
 	fprintf(stderr, "         -m <val>     (STmin in ms/ns. See spec.)\n");
 	fprintf(stderr, "         -w <num>     (max. wait frame transmissions.)\n");
+	fprintf(stderr, "         -D           (daemonize to background when tun device created)\n");
 	fprintf(stderr, "         -h           (half duplex mode.)\n");
 	fprintf(stderr, "         -v           (verbose mode. Print symbols for tunneled msgs.)\n");
 	fprintf(stderr, "\nCAN IDs and addresses are given and expected in hexadecimal values.\n");
@@ -118,14 +144,11 @@ int main(int argc, char **argv)
 	unsigned char buffer[BUF_LEN];
 	static char name[IFNAMSIZ] = DEFAULT_NAME;
 	int nbytes;
-
+	int run_as_daemon = 0;
-	signal(SIGTERM, sigterm);
-	signal(SIGHUP, sigterm);
-	signal(SIGINT, sigterm);
 
 	addr.can_addr.tp.tx_id = addr.can_addr.tp.rx_id = NO_CAN_ID;
 
-	while ((opt = getopt(argc, argv, "s:d:n:x:p:P:t:b:m:whL:v?")) != -1) {
+	while ((opt = getopt(argc, argv, "s:d:n:x:p:P:t:b:m:whL:vD?")) != -1) {
 		switch (opt) {
 		case 's':
 			addr.can_addr.tp.tx_id = strtoul(optarg, (char **)NULL, 16);
@@ -154,9 +177,9 @@ int main(int argc, char **argv)
 			else if (elements == 2)
 				opts.flags |= (CAN_ISOTP_EXTEND_ADDR | CAN_ISOTP_RX_EXT_ADDR);
 			else {
-				printf("incorrect extended addr values '%s'.\n", optarg);
+				fprintf(stderr, "incorrect extended addr values '%s'.\n", optarg);
 				print_usage(basename(argv[0]));
-				exit(0);
+				exit(EXIT_FAILURE);
 			}
 			break;
 		}
@@ -174,9 +197,9 @@ int main(int argc, char **argv)
 			else if (sscanf(optarg, ":%hhx", &opts.rxpad_content) == 1)
 				opts.flags |= CAN_ISOTP_RX_PADDING;
 			else {
-				printf("incorrect padding values '%s'.\n", optarg);
+				fprintf(stderr, "incorrect padding values '%s'.\n", optarg);
 				print_usage(basename(argv[0]));
-				exit(0);
+				exit(EXIT_FAILURE);
 			}
 			break;
 		}
@@ -189,9 +212,9 @@ int main(int argc, char **argv)
 			else if (optarg[0] == 'a')
 				opts.flags |= (CAN_ISOTP_CHK_PAD_LEN | CAN_ISOTP_CHK_PAD_DATA);
 			else {
-				printf("unknown padding check option '%c'.\n", optarg[0]);
+				fprintf(stderr, "unknown padding check option '%c'.\n", optarg[0]);
 				print_usage(basename(argv[0]));
-				exit(0);
+				exit(EXIT_FAILURE);
 			}
 			break;
 
@@ -220,9 +243,9 @@ int main(int argc, char **argv)
 				   &llopts.mtu,
 				   &llopts.tx_dl,
 				   &llopts.tx_flags) != 3) {
-				printf("unknown link layer options '%s'.\n", optarg);
+				fprintf(stderr, "unknown link layer options '%s'.\n", optarg);
 				print_usage(basename(argv[0]));
-				exit(0);
+				exit(EXIT_FAILURE);
 			}
 			break;
 
@@ -230,15 +253,19 @@ int main(int argc, char **argv)
 			verbose = 1;
 			break;
 
+		case 'D':
+			run_as_daemon = 1;
+			break;
+
 		case '?':
 			print_usage(basename(argv[0]));
-			exit(0);
+			exit(EXIT_SUCCESS);
 			break;
 
 		default:
 			fprintf(stderr, "Unknown option %c\n", opt);
 			print_usage(basename(argv[0]));
-			exit(1);
+			exit(EXIT_FAILURE);
 			break;
 		}
 	}
@@ -247,12 +274,18 @@ int main(int argc, char **argv)
 	    (addr.can_addr.tp.tx_id == NO_CAN_ID) ||
 	    (addr.can_addr.tp.rx_id == NO_CAN_ID)) {
 		print_usage(basename(argv[0]));
-		exit(1);
+		exit(EXIT_FAILURE);
 	}
   
+	if (!run_as_daemon)
+		syslogger = fake_syslog;
+
+	/* Initialize the logging interface */
+	openlog(DAEMON_NAME, LOG_PID, LOG_LOCAL5);
+
 	if ((s = socket(PF_CAN, SOCK_DGRAM, CAN_ISOTP)) < 0) {
-		perror("socket");
+		perror_syslog("socket");
-		exit(1);
+		exit(EXIT_FAILURE);
 	}
 
 	setsockopt(s, SOL_CAN_ISOTP, CAN_ISOTP_OPTS, &opts, sizeof(opts));
@@ -260,33 +293,33 @@ int main(int argc, char **argv)
 
 	if (llopts.tx_dl) {
 		if (setsockopt(s, SOL_CAN_ISOTP, CAN_ISOTP_LL_OPTS, &llopts, sizeof(llopts)) < 0) {
-			perror("link layer sockopt");
+			perror_syslog("link layer sockopt");
-			exit(1);
+			exit(EXIT_FAILURE);
 		}
 	}
 
 	strncpy(ifr.ifr_name, argv[optind], IFNAMSIZ);
 	ifr.ifr_ifindex = if_nametoindex(ifr.ifr_name);
 	if (!ifr.ifr_ifindex) {
-		perror("if_nametoindex");
+		perror_syslog("if_nametoindex");
 		close(s);
-		exit(1);
+		exit(EXIT_FAILURE);
 	}
 
 	addr.can_family = AF_CAN;
 	addr.can_ifindex = ifr.ifr_ifindex;
 
 	if (bind(s, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
-		perror("bind");
+		perror_syslog("bind");
 		close(s);
-		exit(1);
+		exit(EXIT_FAILURE);
 	}
 
 	if ((t = open("/dev/net/tun", O_RDWR)) < 0) {
-		perror("open tunfd");
+		perror_syslog("open tunfd");
 		close(s);
 		close(t);
-		exit(1);
+		exit(EXIT_FAILURE);
 	}
 
 	memset(&ifr, 0, sizeof(ifr));
@@ -295,12 +328,25 @@ int main(int argc, char **argv)
 	ifr.ifr_name[IFNAMSIZ - 1] = '\0';
 
 	if (ioctl(t, TUNSETIFF, (void *) &ifr) < 0) {
-		perror("ioctl tunfd");
+		perror_syslog("ioctl tunfd");
 		close(s);
 		close(t);
-		exit(1);
+		exit(EXIT_FAILURE);
 	}
 
+	/* Now the tun device exists. We can daemonize to let the
+	 * parent continue and use the network interface. */
+	if (run_as_daemon) {
+		if (daemon(0, 0)) {
+			syslogger(LOG_ERR, "failed to daemonize");
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	signal(SIGTERM, sigterm);
+	signal(SIGHUP, sigterm);
+	signal(SIGINT, sigterm);
+
 	while (running) {
 
 		FD_ZERO(&rdfs);
@@ -308,14 +354,14 @@ int main(int argc, char **argv)
 		FD_SET(t, &rdfs);
 
 		if ((ret = select(t+1, &rdfs, NULL, NULL, NULL)) < 0) {
-			perror("select");
+			perror_syslog("select");
 			continue;
 		}
 
 		if (FD_ISSET(s, &rdfs)) {
 			nbytes = read(s, buffer, BUF_LEN);
 			if (nbytes < 0) {
-				perror("read isotp socket");
+				perror_syslog("read isotp socket");
 				return -1;
 			}
 			if (nbytes > MAX_PDU_LENGTH)
@@ -333,7 +379,7 @@ int main(int argc, char **argv)
 		if (FD_ISSET(t, &rdfs)) {
 			nbytes = read(t, buffer, BUF_LEN);
 			if (nbytes < 0) {
-				perror("read tunfd");
+				perror_syslog("read tunfd");
 				return -1;
 			}
 			if (nbytes > MAX_PDU_LENGTH)
@@ -351,5 +397,5 @@ int main(int argc, char **argv)
 
 	close(s);
 	close(t);
-	return 0;
+	return EXIT_SUCCESS;
 }