Make the 'init <CMD | RUNLEVEL>' commands synchronous.

When a user changes runlevel, or wants to reload the config, we want the
command to return only when the operation has completed.  For instance,
rolling in a new system configuration in runlevel 1 requires that we are
sure we've actually entered that runlevel before rolling it in.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

finit.c

@@ -84,6 +84,8 @@ static int client(int argc, char *argv[])
 {
 	int fd;
 	int c;
+	int result = -1;
+	ssize_t len;
 	struct option long_options[] = {
 		{"debug", 0, NULL, 'd'},
 		{"help", 0, NULL, 'h'},
@@ -94,7 +96,7 @@ static int client(int argc, char *argv[])
 		.cmd = 0
 	};
 
-	while ((c = getopt_long (argc, argv, "h?d", long_options, NULL)) != EOF) {
+	while ((c = getopt_long(argc, argv, "h?d", long_options, NULL)) != EOF) {
 		switch(c) {
 		case 'd':
 			rq.cmd = INIT_CMD_DEBUG;
@@ -123,15 +125,22 @@ static int client(int argc, char *argv[])
 		return 1;
 	}
 
-	fd = open(FINIT_FIFO, O_WRONLY);
+	fd = open(FINIT_FIFO, O_RDWR);
 	if (-1 == fd) {
 		perror("Failed opening " FINIT_FIFO);
 		return 1;
 	}
-	write(fd, &rq, sizeof(rq));
+
+	len = write(fd, &rq, sizeof(rq));
+	if (len == sizeof(rq)) {
+		len = read(fd, &rq, sizeof(rq));
+		if (len == sizeof(rq) && rq.cmd == INIT_CMD_ACK)
+			result = 0;
+	}
+
 	close(fd);
 
-	return 0;
+	return result;
 }
 
 static void banner(void)

finit.h

@@ -76,6 +76,7 @@
 #define INIT_MAGIC		0x03091969
 #define INIT_CMD_RUNLVL		1
 #define INIT_CMD_DEBUG		2
+#define INIT_CMD_ACK		255
 
 struct init_request {
 	int	magic;		/* Magic number			*/

plugins/initctl.c

@@ -45,7 +45,7 @@ static plugin_t plugin = {
 
 static void fifo_open(void)
 {
-	plugin.io.fd = open(FINIT_FIFO, O_RDONLY | O_NONBLOCK | O_CLOEXEC);
+	plugin.io.fd = open(FINIT_FIFO, O_RDWR | O_NONBLOCK | O_CLOEXEC);
 	if (-1 == plugin.io.fd) {
 		_e("Failed opening %s FIFO, error %d: %s", FINIT_FIFO, errno, strerror(errno));
 		return;
@@ -85,7 +85,8 @@ static void parse(void *UNUSED(arg), int fd, int UNUSED(events))
 		}
 
 		_d("Magic OK ...");
-		if (rq.cmd == INIT_CMD_RUNLVL) {
+		switch (rq.cmd) {
+		case INIT_CMD_RUNLVL:
 			switch (rq.runlevel) {
 			case '0':
 				_d("Halting system (SIGUSR2)");
@@ -113,13 +114,30 @@ static void parse(void *UNUSED(arg), int fd, int UNUSED(events))
 				_d("Unsupported runlevel: %d", rq.runlevel);
 				break;
 			}
-		} else if (rq.cmd == INIT_CMD_DEBUG) {
+			break;
+
+		case INIT_CMD_DEBUG:
 			debug = !debug;
-		} else {
+			break;
+
+		case INIT_CMD_ACK:
+			_d("Client failed reading ACK.");
+			goto leave;
+
+		default:
 			_d("Unsupported cmd: %d", rq.cmd);
+			break;
 		}
+
+		rq.cmd = INIT_CMD_ACK;
+		len = write(fd, &rq, sizeof(rq));
+		if (len != sizeof(rq))
+			_d("Failed sending ACK back to client.");
+		else
+			sleep(1); /* Give client time to read FIFO */
 	}
 
+leave:
 	close(fd);
 	fifo_open();
 }