[485589] Close stdin etc. when daemonised.

Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=485589

ChangeLog.txt

@@ -5,6 +5,7 @@ Broker:
   mount point. This is only affects brokers where the mount_point option is in
   use. Closes #487178.
 - Fix detection of broken connections on Windows. Closes #485143.
+- Close stdin etc. when daemonised. Closes #485589.
 
 Client library:
 - mosq->want_write should be cleared immediately before a call to SSL_write,

src/mosquitto.c

@@ -21,6 +21,7 @@ Contributors:
 #  define _BSD_SOURCE
 #  include <unistd.h>
 #  include <grp.h>
+#  include <assert.h>
 #endif
 
 #ifndef WIN32
@@ -175,6 +176,35 @@ void handle_sigusr1(int signal)
 #endif
 }
 
+void mosquitto__daemonise(void)
+{
+#ifndef WIN32
+	char err[256];
+	pid_t pid;
+
+	pid = fork();
+	if(pid < 0){
+		strerror_r(errno, err, 256);
+		_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error in fork: %s", err);
+		exit(1);
+	}
+	if(pid > 0){
+		exit(0);
+	}
+	if(setsid() < 0){
+		strerror_r(errno, err, 256);
+		_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error in setsid: %s", err);
+		exit(1);
+	}
+
+	assert(freopen("/dev/null", "r", stdin));
+	assert(freopen("/dev/null", "w", stdout));
+	assert(freopen("/dev/null", "w", stderr));
+#else
+	_mosquitto_log_printf(NULL, MOSQ_LOG_WARNING, "Warning: Can't start in daemon mode in Windows.");
+#endif
+}
+
 /* Signal handler for SIGUSR2 - vacuum the db. */
 void handle_sigusr2(int signal)
 {
@@ -197,7 +227,6 @@ int main(int argc, char *argv[])
 #ifdef WIN32
 	SYSTEMTIME st;
 #else
-	char err[256];
 	struct timeval tv;
 #endif
 	struct mosquitto *ctxt, *ctxt_tmp;
@@ -236,20 +265,7 @@ int main(int argc, char *argv[])
 	int_db.config = &config;
 
 	if(config.daemon){
-#ifndef WIN32
-		switch(fork()){
-			case 0:
-				break;
-			case -1:
-				strerror_r(errno, err, 256);
-			_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error in fork: %s", err);
-				return 1;
-			default:
-				return MOSQ_ERR_SUCCESS;
-		}
-#else
-		_mosquitto_log_printf(NULL, MOSQ_LOG_WARNING, "Warning: Can't start in daemon mode in Windows.");
-#endif
+		mosquitto__daemonise();
 	}
 
 	if(config.daemon && config.pid_file){