Refactor/mstp zero config state machine (#676)

* Changed MS/TP master node self destination checks to be located in receive FSM

* Changed MSTP zero configuration: modified comments for state transition names; modified next station increment; refactored the UUID rand() to not be required by common zero config implementation; added more unit tests.

* Added another context to MS/TP user data to allow additional user data

ports/stm32f4xx/device.c

@@ -81,6 +81,7 @@ static uint32_t Database_Revision;
 static BACNET_REINITIALIZED_STATE Reinitialize_State = BACNET_REINIT_IDLE;
 static const char *Reinit_Password = "stm32f4xx";
 static const char *BACnet_Version = BACNET_VERSION_TEXT;
+static uint8_t Device_UUID[16];
 
 /* These three arrays are used by the ReadPropertyMultiple handler */
 static const int Device_Properties_Required[] = { PROP_OBJECT_IDENTIFIER,
@@ -94,7 +95,8 @@ static const int Device_Properties_Required[] = { PROP_OBJECT_IDENTIFIER,
     PROP_DATABASE_REVISION, -1 };
 
 static const int Device_Properties_Optional[] = { PROP_DESCRIPTION,
-    PROP_LOCATION, PROP_MAX_MASTER, PROP_MAX_INFO_FRAMES, -1 };
+    PROP_LOCATION, PROP_MAX_MASTER, PROP_MAX_INFO_FRAMES, PROP_DEVICE_UUID,
+    -1 };
 
 static const int Device_Properties_Proprietary[] = { -1 };
 
@@ -398,6 +400,71 @@ void Device_Inc_Database_Revision(void)
     Database_Revision++;
 }
 
+/**
+ * @brief Initialize a UUID for storing the unique identifier of this device
+ * @note A Universally Unique IDentifier (UUID) - also called a
+ * Global Unique IDentifier (GUID) - is a 128-bit value, see RFC 4122.
+ *
+ * 4.4.  Algorithms for Creating a UUID from Truly Random or
+ *      Pseudo-Random Numbers
+ *
+ *   The version 4 UUID is meant for generating UUIDs from truly-random or
+ *   pseudo-random numbers.
+ *
+ *   The algorithm is as follows:
+ *
+ *   o  Set the two most significant bits (bits 6 and 7) of the
+ *      clock_seq_hi_and_reserved to zero and one, respectively.
+ *
+ *   o  Set the four most significant bits (bits 12 through 15) of the
+ *      time_hi_and_version field to the 4-bit version number from
+ *      Section 4.1.3.
+ *
+ *   o  Set all the other bits to randomly (or pseudo-randomly) chosen
+ *      values.
+ */
+void Device_UUID_Init(void)
+{
+    unsigned i = 0;
+
+    /* 1. Generate 16 random bytes = 128 bits */
+    for (i = 0; i < sizeof(Device_UUID); i++) {
+        Device_UUID[i] = rand() % 255;
+    }
+    /* 2. Adjust certain bits according to RFC 4122 section 4.4.
+       This just means do the following
+       (a) set the high nibble of the 7th byte equal to 4 and
+       (b) set the two most significant bits of the 9th byte to 10'B,
+       so the high nibble will be one of {8,9,A,B}.
+       From http://www.cryptosys.net/pki/Uuid.c.html */
+    Device_UUID[6] = 0x40 | (Device_UUID[6] & 0x0f);
+    Device_UUID[8] = 0x80 | (Device_UUID[8] & 0x3f);
+}
+
+/**
+ * @brief Set the UUID for this device
+ * @param new_uuid [in] The new UUID to set
+ * @param length [in] The length of the new UUID
+ */
+void Device_UUID_Set(uint8_t *new_uuid, size_t length)
+{
+    if (new_uuid && (length == sizeof(Device_UUID))) {
+        memcpy(Device_UUID, new_uuid, sizeof(Device_UUID));
+    }
+}
+
+/**
+ * @brief Get the UUID for this device
+ * @param uuid [out] The UUID of this device
+ * @param length [in] The length of the UUID
+ */
+void Device_UUID_Get(uint8_t *uuid, size_t length)
+{
+    if (uuid && (length == sizeof(Device_UUID))) {
+        memcpy(uuid, Device_UUID, sizeof(Device_UUID));
+    }
+}
+
 /** Get the total count of objects supported by this Device Object.
  * @note Since many network clients depend on the object list
  *       for discovery, it must be consistent!
@@ -586,6 +653,7 @@ int Device_Read_Property_Local(BACNET_READ_PROPERTY_DATA *rpdata)
     int apdu_len = 0; /* return value */
     BACNET_BIT_STRING bit_string = { 0 };
     BACNET_CHARACTER_STRING char_string = { 0 };
+    BACNET_OCTET_STRING octet_string = { 0 };
     uint32_t i = 0;
     uint32_t count = 0;
     uint8_t *apdu = NULL;
@@ -713,6 +781,10 @@ int Device_Read_Property_Local(BACNET_READ_PROPERTY_DATA *rpdata)
             apdu_len =
                 encode_application_unsigned(&apdu[0], dlmstp_max_master());
             break;
+        case PROP_DEVICE_UUID:
+            octetstring_init(&octet_string, Device_UUID, sizeof(Device_UUID));
+            apdu_len = encode_application_octet_string(&apdu[0], &octet_string);
+            break;
         default:
             rpdata->error_class = ERROR_CLASS_PROPERTY;
             rpdata->error_code = ERROR_CODE_UNKNOWN_PROPERTY;