Fixed dlmstp ringbuffer initialization corruption (#865)

* Added ringbuf API for testing.

* Fixed basic ms/tp datalink packet ringbuffer initialization buffer overrun.

* Added basic ms/tp datalink unit test

* Added Ringbuf_Initialize() API with buffer size checking.

* Changed examples to use Ringbuf_Initialize() API for buffer size checking.

src/bacnet/basic/client/bac-rw.c

@@ -896,9 +896,10 @@ uint16_t bacnet_read_write_vendor_id_filter(void)
  */
 void bacnet_read_write_init(void)
 {
-    Ringbuf_Init(
+    Ringbuf_Initialize(
         &Target_Data_Queue, (uint8_t *)&Target_Data_Buffer,
-        TARGET_DATA_QUEUE_SIZE, TARGET_DATA_QUEUE_COUNT);
+        sizeof(Target_Data_Buffer), TARGET_DATA_QUEUE_SIZE,
+        TARGET_DATA_QUEUE_COUNT);
     /* handle i-am to support binding to other devices */
     apdu_set_unconfirmed_handler(SERVICE_UNCONFIRMED_I_AM, My_I_Am_Bind);
     /* handle the data coming back from confirmed requests */

src/bacnet/basic/sys/ringbuf.c

@@ -374,6 +374,23 @@ bool Ringbuf_Data_Put(RING_BUFFER *b, const volatile uint8_t *data_element)
     return status;
 }
 
+/**
+ * Gets the data size of each element in the ring buffer
+ *
+ * @param  b - pointer to RING_BUFFER structure
+ * @return size of each element in the ring buffer
+ */
+unsigned Ringbuf_Data_Size(RING_BUFFER const *b)
+{
+    unsigned size = 0;
+
+    if (b) {
+        size = b->element_size;
+    }
+
+    return size;
+}
+
 /**
  * Test that the parameter is a power of two.
  *
@@ -395,8 +412,8 @@ static bool isPowerOfTwo(unsigned int x)
  * @param  buffer - pointer to a data buffer that is used to store the ring data
  * @param  element_size - size of one element in the data block
  * @param  element_count - number elements in the data block
- *
  * @return  true if ring buffer was initialized
+ * @deprecated  Use Ringbuf_Initialize() instead
  */
 bool Ringbuf_Init(
     RING_BUFFER *b,
@@ -419,3 +436,29 @@ bool Ringbuf_Init(
 
     return status;
 }
+
+/**
+ * Configures the ring buffer data buffer.  Note that the element_count
+ * parameter must be a power of two.
+ *
+ * @param  b - pointer to RING_BUFFER structure
+ * @param  buffer - pointer to a data buffer that is used to store the ring data
+ * @param  buffer_size - size of the data buffer
+ * @param  element_size - size of one element in the data block
+ * @param  element_count - number elements in the data block
+ *
+ * @return  true if ring buffer was initialized
+ */
+bool Ringbuf_Initialize(
+    RING_BUFFER *b,
+    volatile uint8_t *buffer,
+    unsigned buffer_size,
+    unsigned element_size,
+    unsigned element_count)
+{
+    if ((element_size * element_count) <= buffer_size) {
+        return Ringbuf_Init(b, buffer, element_size, element_count);
+    }
+
+    return false;
+}

src/bacnet/basic/sys/ringbuf.h

@@ -89,6 +89,8 @@ volatile void *
 Ringbuf_Peek_Next(RING_BUFFER const *b, const uint8_t *data_element);
 BACNET_STACK_EXPORT
 bool Ringbuf_Data_Put(RING_BUFFER *b, const volatile uint8_t *data_element);
+BACNET_STACK_EXPORT
+unsigned Ringbuf_Data_Size(RING_BUFFER const *b);
 /* Note: element_count must be a power of two */
 BACNET_STACK_EXPORT
 bool Ringbuf_Init(
@@ -96,6 +98,13 @@ bool Ringbuf_Init(
     volatile uint8_t *buffer,
     unsigned element_size,
     unsigned element_count);
+BACNET_STACK_EXPORT
+bool Ringbuf_Initialize(
+    RING_BUFFER *b,
+    volatile uint8_t *buffer,
+    unsigned buffer_size,
+    unsigned element_size,
+    unsigned element_count);
 
 #ifdef __cplusplus
 }

src/bacnet/datalink/dlmstp.c

@@ -92,6 +92,7 @@ uint16_t MSTP_Get_Send(struct mstp_port_struct_t *mstp_port, unsigned timeout)
     struct dlmstp_packet *pkt;
     struct dlmstp_user_data_t *user;
 
+    (void)timeout;
     if (!mstp_port) {
         return 0;
     }
@@ -250,6 +251,7 @@ uint16_t MSTP_Get_Reply(struct mstp_port_struct_t *mstp_port, unsigned timeout)
     struct dlmstp_user_data_t *user = NULL;
     struct dlmstp_packet *pkt;
 
+    (void)timeout;
     if (!mstp_port) {
         return 0;
     }
@@ -346,6 +348,7 @@ uint16_t dlmstp_receive(
     uint16_t i;
     uint32_t milliseconds;
 
+    (void)timeout;
     if (!MSTP_Port) {
         return 0;
     }
@@ -993,9 +996,10 @@ bool dlmstp_init(char *ifname)
         MSTP_Port->SilenceTimerReset = dlmstp_silence_reset;
         user = (struct dlmstp_user_data_t *)MSTP_Port->UserData;
         if (user && !user->Initialized) {
-            Ringbuf_Init(
+            Ringbuf_Initialize(
                 &user->PDU_Queue, (volatile uint8_t *)user->PDU_Buffer,
-                sizeof(user->PDU_Buffer), DLMSTP_MAX_INFO_FRAMES);
+                sizeof(user->PDU_Buffer), sizeof(struct dlmstp_packet),
+                DLMSTP_MAX_INFO_FRAMES);
             MSTP_Init(MSTP_Port);
             user->Initialized = true;
         }