add a refcount to library init/cleanup

Add a refcount around mosquitto_lib_init and mosquitto_lib_cleanup so
that multiple calls to init/cleanup don't trigger memory leaks or
double-frees.

Signed-off-by: Martin Kelly <mkelly@xevo.com>

lib/mosquitto.c

@@ -33,6 +33,7 @@ Contributors:
 #include "packet_mosq.h"
 #include "will_mosq.h"
 
+static unsigned int init_refcount = 0;
 
 void mosquitto__destroy(struct mosquitto *mosq);
 
@@ -46,6 +47,9 @@ int mosquitto_lib_version(int *major, int *minor, int *revision)
 
 int mosquitto_lib_init(void)
 {
+	int rc;
+
+	if (init_refcount == 0) {
 #ifdef WIN32
 		srand(GetTickCount64());
 #elif _POSIX_TIMERS>0 && defined(_POSIX_MONOTONIC_CLOCK)
@@ -65,12 +69,25 @@ int mosquitto_lib_init(void)
 		srand(tv.tv_sec*1000 + tv.tv_usec/1000);
 #endif
 
-	return net__init();
+		rc = net__init();
+		if (rc != MOSQ_ERR_SUCCESS) {
+			return rc;
+		}
+	}
+
+	init_refcount++;
+	return MOSQ_ERR_SUCCESS;
 }
 
 int mosquitto_lib_cleanup(void)
 {
+	if (init_refcount == 1) {
 		net__cleanup();
+	}
+
+	if (init_refcount > 0) {
+		--init_refcount;
+	}
 
 	return MOSQ_ERR_SUCCESS;
 }