Changed the MSTP_MASTER_STATE_ANSWER_DATA_REQUEST state to always send a REPLY_POSTPONED by

commenting out the section that checks for new packets to send.  It was not the intent of the BACnet standard, but it makes the Master Node FSM compliant.  It's either that or re-parse the message for a matching apdu and invoke id, and then defer if the next message does not match.  The problem happens when an unconfirmed request (i.e. WhoIs) is followed immediated by a confirmed request (i.e. ReadProperty) before the device can respond to the unconfirmed request (i.e. the I-Am is queued in the Transmit buffer).

bacnet-stack/ports/win32/dlmstp.c

@@ -42,11 +42,14 @@
 /* Number of MS/TP Packets Rx/Tx */
 uint16_t MSTP_Packets = 0;
 
-/* receive buffer */
-static DLMSTP_PACKET Receive_Buffer;
-/* temp buffer for NPDU insertion */
+/* packet queues */
+static DLMSTP_PACKET Receive_Packet;
+static DLMSTP_PACKET Transmit_Packet;
 /* local MS/TP port data - shared with RS-485 */
 volatile struct mstp_port_struct_t MSTP_Port;
+/* buffers needed by mstp port struct */
+static uint8_t TxBuffer[MAX_MPDU];
+static uint8_t RxBuffer[MAX_MPDU];
 
 #define INCREMENT_AND_LIMIT_UINT16(x) {if (x < 0xFFFF) x++;}
 
@@ -76,13 +79,12 @@ int dlmstp_send_pdu(BACNET_ADDRESS * dest,      /* destination address */
 {                               /* number of bytes of data */
     int bytes_sent = 0;
     uint8_t destination = 0;    /* destination address */
-    BACNET_ADDRESS src;
 
-    if (MSTP_Port.TxReady == false) {
+    if (!Transmit_Packet.ready) {
         if (npdu_data->data_expecting_reply)
-            MSTP_Port.TxFrameType = FRAME_TYPE_BACNET_DATA_EXPECTING_REPLY;
+            Transmit_Packet.frame_type = FRAME_TYPE_BACNET_DATA_EXPECTING_REPLY;
         else
-            MSTP_Port.TxFrameType =
+            Transmit_Packet.frame_type =
                 FRAME_TYPE_BACNET_DATA_NOT_EXPECTING_REPLY;
 
         /* load destination MAC address */
@@ -91,17 +93,17 @@ int dlmstp_send_pdu(BACNET_ADDRESS * dest,      /* destination address */
         } else {
             return -2;
         }
-        dlmstp_get_my_address(&src);
         if ((8 /* header len */  + pdu_len) > MAX_MPDU) {
             return -4;
         }
-        bytes_sent = MSTP_Create_Frame(
-            (uint8_t *) & MSTP_Port.TxBuffer[0],
-            sizeof(MSTP_Port.TxBuffer),
-            MSTP_Port.TxFrameType,
-            destination, MSTP_Port.This_Station, pdu, pdu_len);
-        MSTP_Port.TxLength = bytes_sent;
-        MSTP_Port.TxReady = true;
+        Transmit_Packet.pdu_len = MSTP_Create_Frame(
+            (uint8_t *) & Transmit_Packet.pdu[0],
+            sizeof(Transmit_Packet.pdu),
+            Transmit_Packet.frame_type,
+            destination,
+            MSTP_Port.This_Station,
+            pdu, pdu_len);
+        Transmit_Packet.ready = true;
         MSTP_Packets++;
     }
 
@@ -118,22 +120,22 @@ uint16_t dlmstp_receive(
 
     /* see if there is a packet available, and a place
        to put the reply (if necessary) and process it */
-    if (Receive_Buffer.ready) {
-        if (Receive_Buffer.pdu_len) {
+    if (Receive_Packet.ready) {
+        if (Receive_Packet.pdu_len) {
             MSTP_Packets++;
             if (src) {
                 memmove(src,
-                    &Receive_Buffer.address,
-                    sizeof(Receive_Buffer.address));
+                    &Receive_Packet.address,
+                    sizeof(Receive_Packet.address));
             }
             if (pdu) {
                 memmove(pdu,
-                    &Receive_Buffer.pdu,
-                    sizeof(Receive_Buffer.pdu));
+                    &Receive_Packet.pdu,
+                    sizeof(Receive_Packet.pdu));
             }
-            pdu_len = Receive_Buffer.pdu_len;
+            pdu_len = Receive_Packet.pdu_len;
         }
-        Receive_Buffer.ready = false;
+        Receive_Packet.ready = false;
     }
 
     return pdu_len;
@@ -210,10 +212,10 @@ uint16_t dlmstp_put_receive(uint8_t src,        /* source MS/TP address */
     uint8_t * pdu,              /* PDU data */
     uint16_t pdu_len)
 {                               /* amount of PDU data */
-    /* PDU is already in the Receive_Buffer */
-    dlmstp_fill_bacnet_address(&Receive_Buffer.address, src);
-    Receive_Buffer.pdu_len = pdu_len;
-    Receive_Buffer.ready = true;
+    /* PDU is already in the Receive_Packet */
+    dlmstp_fill_bacnet_address(&Receive_Packet.address, src);
+    Receive_Packet.pdu_len = pdu_len;
+    Receive_Packet.ready = true;
 
     return pdu_len;
 }
@@ -229,11 +231,15 @@ uint16_t dlmstp_get_send(
     uint16_t pdu_len = 0;
 
     (void)src;
-    (void)max_pdu;
-    if (MSTP_Port.TxReady) {
-        memmove(&pdu[0],(void *)&MSTP_Port.TxBuffer[0],sizeof(MSTP_Port.TxBuffer));
-        pdu_len = MSTP_Port.TxLength;
-        MSTP_Port.TxReady = false;
+    (void)timeout;
+    if (Transmit_Packet.ready) {
+        if (Transmit_Packet.pdu_len <= max_pdu) {
+            memmove(&pdu[0],
+                (void *) & Transmit_Packet.pdu[0],
+                Transmit_Packet.pdu_len);
+            pdu_len = Transmit_Packet.pdu_len;
+        }
+        Transmit_Packet.ready = false;
     }
 
     return pdu_len;
@@ -361,9 +367,9 @@ bool dlmstp_init(char *ifname)
     unsigned long hThread = 0;
     uint32_t arg_value = 0;
 
-    /* initialize buffer */
-    Receive_Buffer.ready = false;
-    Receive_Buffer.pdu_len = 0;
+    /* initialize packet queue */
+    Receive_Packet.ready = false;
+    Receive_Packet.pdu_len = 0;
     /* initialize hardware */
     /* initialize hardware */
     if (ifname) {
@@ -373,6 +379,10 @@ bool dlmstp_init(char *ifname)
 #endif
     }
     RS485_Initialize();
+    MSTP_Port.InputBuffer = &RxBuffer[0];
+    MSTP_Port.InputBufferSize = sizeof(RxBuffer);
+    MSTP_Port.OutputBuffer = &TxBuffer[0];
+    MSTP_Port.OutputBufferSize = sizeof(TxBuffer);
     MSTP_Init(&MSTP_Port);
 #if 0
     uint8_t data;