libuuid is used to generate client ids, where it is available, when an MQTT v3.1.1 client connects with a zero length client id.

ChangeLog.txt

@@ -29,6 +29,8 @@ Broker:
 - When a durable client reconnects, its queued messages are now checked
   against ACLs in case of a change in username/ACL state since it last
   connected.
+- libuuid is used to generate client ids, where it is available, when an MQTT
+  v3.1.1 client connects with a zero length client id.
 
 Clients:
 - Both clients can now load default configuration options from a file.

config.mk

@@ -117,8 +117,9 @@ LIB_LIBS:=
 PASSWD_LIBS:=
 
 ifeq ($(UNAME),Linux)
-	BROKER_LIBS:=$(BROKER_LIBS) -lrt
+	BROKER_LIBS:=$(BROKER_LIBS) -lrt -luuid
 	LIB_LIBS:=$(LIB_LIBS) -lrt
+	BROKER_CFLAGS:=$(BROKER_CFLAGS) -DWITH_UUID
 endif
 
 CLIENT_LDFLAGS:=$(LDFLAGS) -L../lib ../lib/libmosquitto.so.${SOVERSION}

src/CMakeLists.txt

@@ -98,6 +98,13 @@ if (${WITH_WEBSOCKETS} STREQUAL ON)
 	set (MOSQ_LIBS ${MOSQ_LIBS} websockets)
 endif (${WITH_WEBSOCKETS} STREQUAL ON)
 
+# Simple detect libuuid
+FIND_PATH(UUID_HEADER uuid/uuid.h)
+if (UUID_HEADER)
+	add_definitions(-DWITH_UUID)
+	set (MOSQ_LIBS ${MOSQ_LIBS} uuid)
+endif (UUID_HEADER)
+
 target_link_libraries(mosquitto ${MOSQ_LIBS})
 
 install(TARGETS mosquitto RUNTIME DESTINATION ${SBINDIR} LIBRARY DESTINATION ${LIBDIR})

src/read_handle_server.c

@@ -27,6 +27,10 @@ Contributors:
 #include <tls_mosq.h>
 #include <util_mosq.h>
 
+#ifdef WITH_UUID
+#  include <uuid/uuid.h>
+#endif
+
 #ifdef WITH_SYS_TREE
 extern unsigned int g_connection_count;
 #endif
@@ -34,17 +38,35 @@ extern unsigned int g_connection_count;
 static char *client_id_gen(struct mosquitto_db *db)
 {
 	char *client_id;
+#ifdef WITH_UUID
+	uuid_t uuid;
+#else
 	int i;
+#endif
 
+#ifdef WITH_UUID
+	client_id = (char *)_mosquitto_calloc(37 + db->config->auto_id_prefix_len, sizeof(char));
+	if(!client_id){
+		return NULL;
+	}
+	if(db->config->auto_id_prefix){
+		memcpy(client_id, db->config->auto_id_prefix, db->config->auto_id_prefix_len);
+	}
+	uuid_generate_random(uuid);
+	uuid_unparse_lower(uuid, &client_id[db->config->auto_id_prefix_len]);
+#else
 	client_id = (char *)_mosquitto_calloc(65 + db->config->auto_id_prefix_len, sizeof(char));
 	if(!client_id){
 		return NULL;
 	}
-	memcpy(client_id, db->config->auto_id_prefix, db->config->auto_id_prefix_len);
+	if(db->config->auto_id_prefix){
+		memcpy(client_id, db->config->auto_id_prefix, db->config->auto_id_prefix_len);
+	}
 	for(i=0; i<64; i++){
 		client_id[i+db->config->auto_id_prefix_len] = (rand()%73)+48;
 	}
 	client_id[i] = '\0';
+#endif
 	return client_id;
 }