made the datalink generic while adding datalink for MS/TP

bacnet-stack/Makefile

@@ -6,12 +6,14 @@ BASEDIR = .
 #CFLAGS  = -Wall -I. -O2 -g
 # Note: you can strip out symbols using the strip command
 # to get an idea of how big the compile really is.
-#CFLAGS  = -Wall -I. -g -DBACDL_ETHERNET=1
+#CFLAGS  = -Wall -I. -Iports/linux -g -DBACDL_MSTP=1
+#CFLAGS  = -Wall -I. -Iports/linux -g -DBACDL_ETHERNET=1
 CFLAGS  = -Wall -I. -Iports/linux -g -DBACDL_BIP=1
 
 SRCS = ports/linux/main.c \
        ports/linux/ethernet.c \
        ports/linux/bip.c \
+       dlmstp.c \
        handlers.c \
        bacdcode.c \
        bigend.c \

bacnet-stack/datalink.c

@@ -46,14 +46,14 @@ int datalink_send_pdu(
   uint8_t *pdu, // any data to be sent - may be null
   unsigned pdu_len) // number of bytes of data
 {
-#ifdef BACDL_ETHERNET
-  return ethernet_send_pdu(
+#ifdef BACDL_MSTP
+  return dlmstp_send_pdu(
     dest,
     pdu,
     pdu_len);
 #endif
-#ifdef BACDL_MSTP
-  return mstp_send_pdu(
+#ifdef BACDL_ETHERNET
+  return ethernet_send_pdu(
     dest,
     pdu,
     pdu_len);
@@ -66,15 +66,45 @@ int datalink_send_pdu(
 #endif
 }
 
+// returns the number of octets in the PDU, or zero on failure
+uint16_t datalink_receive(
+  BACNET_ADDRESS *src,  // source address
+  uint8_t *pdu, // PDU data
+  uint16_t max_pdu, // amount of space available in the PDU 
+  unsigned timeout) // number of milliseconds to wait for a packet
+{
+  #ifdef BACDL_MSTP
+  return dlmstp_receive(
+    src,
+    pdu,
+    max_pdu,
+    timeout);
+  #endif
+  #ifdef BACDL_ETHERNET
+  return ethernet_receive(
+    src,
+    pdu,
+    max_pdu,
+    timeout);
+  #endif
+  #ifdef BACDL_BIP
+  return bip_receive(
+    src,
+    pdu,
+    max_pdu,
+    timeout);
+  #endif
+}
+
 void datalink_get_broadcast_address(
   BACNET_ADDRESS *dest) // destination address
 {
+#ifdef BACDL_MSTP
+  dlmstp_get_broadcast_address(dest);
+#endif
 #ifdef BACDL_ETHERNET
   ethernet_get_broadcast_address(dest);
 #endif
-#ifdef BACDL_MSTP
-  mstp_get_broadcast_address(dest);
-#endif
 #ifdef BACDL_BIP
   bip_get_broadcast_address(dest);
 #endif
@@ -83,12 +113,12 @@ void datalink_get_broadcast_address(
 void datalink_get_my_address(
   BACNET_ADDRESS *my_address)
 {
+#ifdef BACDL_MSTP
+  dlmstp_get_my_address(my_address);
+#endif
 #ifdef BACDL_ETHERNET
   ethernet_get_my_address(my_address);
 #endif
-#ifdef BACDL_MSTP
-  mstp_get_my_address(my_address);
-#endif
 #ifdef BACDL_BIP
   bip_get_my_address(my_address);
 #endif

bacnet-stack/datalink.h

@@ -44,7 +44,7 @@
 #endif
 
 #ifdef BACDL_MSTP
-#include "mstp.h"
+#include "dlmstp.h"
 #endif
 
 #ifdef BACDL_BIP
@@ -57,6 +57,13 @@ int datalink_send_pdu(
   uint8_t *pdu, // any data to be sent - may be null
   unsigned pdu_len); // number of bytes of data
 
+// returns the number of octets in the PDU, or zero on failure
+uint16_t datalink_receive(
+  BACNET_ADDRESS *src,  // source address
+  uint8_t *pdu, // PDU data
+  uint16_t max_pdu, // amount of space available in the PDU 
+  unsigned timeout); // number of milliseconds to wait for a packet
+
 void datalink_get_broadcast_address(
   BACNET_ADDRESS *dest); // destination address
 

bacnet-stack/mstp.h

@@ -40,10 +40,7 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include "bacdef.h"
-
-// defines specific to MS/TP
-#define MAX_HEADER (2+1+1+1+2+1+2+1)
-#define MAX_MPDU (MAX_HEADER+MAX_PDU)
+#include "dlmstp.h"
 
 //  The value 255 is used to denote broadcast when used as a
 // destination address but is not allowed as a value for a station.

bacnet-stack/ports/linux/main.c

@@ -39,12 +39,7 @@
 #include "tsm.h"
 #include "device.h"
 #include "bacfile.h"
-#ifdef BACDL_ETHERNET
-  #include "ethernet.h"
-#endif
-#ifdef BACDL_BIP
-  #include "bip.h"
-#endif
+#include "datalink.h"
 #include "net.h"
 
 // This is an example application using the BACnet Stack on Linux
@@ -329,20 +324,11 @@ int main(int argc, char *argv[])
     // input
     new_time = time(NULL);
     // returns 0 bytes on timeout
-    #ifdef BACDL_ETHERNET
-    pdu_len = ethernet_receive(
+    pdu_len = datalink_receive(
       &src,
       &Rx_Buf[0],
       MAX_MPDU,
       timeout);
-    #endif
-    #ifdef BACDL_BIP
-    pdu_len = bip_receive(
-      &src,
-      &Rx_Buf[0],
-      MAX_MPDU,
-      timeout);
-    #endif
 
     // process
     if (pdu_len)