Implement daemonization

Now we're a real daemon, yay.

src/kike.c

@@ -1303,6 +1303,41 @@ on_signal_pipe_readable (const struct pollfd *fd, struct server_context *ctx)
 	}
 }
 
+static void
+daemonize (void)
+{
+	// TODO: create and lock a PID file?
+	print_status ("daemonizing...");
+
+	if (chdir ("/"))
+		exit_fatal ("%s: %s", "chdir", strerror (errno));
+
+	pid_t pid;
+	if ((pid = fork ()) < 0)
+		exit_fatal ("%s: %s", "fork", strerror (errno));
+	else if (pid)
+		exit (EXIT_SUCCESS);
+
+	setsid ();
+	signal (SIGHUP, SIG_IGN);
+
+	if ((pid = fork ()) < 0)
+		exit_fatal ("%s: %s", "fork", strerror (errno));
+	else if (pid)
+		exit (EXIT_SUCCESS);
+
+	openlog (PROGRAM_NAME, LOG_NDELAY | LOG_NOWAIT | LOG_PID, 0);
+	g_log_message_real = log_message_syslog;
+
+	// XXX: we may close our own descriptors this way, crippling ourselves
+	for (int i = 0; i < 3; i++)
+		xclose (i);
+
+	int tty = open ("/dev/null", O_RDWR);
+	if (tty != 0 || dup (0) != 1 || dup (0) != 2)
+		exit_fatal ("failed to reopen FD's: %s", strerror (errno));
+}
+
 static void
 print_usage (const char *program_name)
 {
@@ -1396,12 +1431,8 @@ main (int argc, char *argv[])
 		exit (EXIT_FAILURE);
 	}
 
-	// TODO: daemonize
 	if (!g_debug_mode)
-	{
+		daemonize ();
-		openlog (PROGRAM_NAME, LOG_NDELAY | LOG_NOWAIT | LOG_PID, 0);
-		g_log_message_real = log_message_syslog;
-	}
 
 	ctx.polling = true;
 	while (ctx.polling)