Revised BBMD registration functions to return something approximating a goodness value. (Still too happy for invalid BBMDs, but it's a start.)

Fixed handling of bacapp_decode_context_data() for some of the more unusual (empty, etc) cases I've seen.

bacnet-stack/src/bacapp.c

@@ -694,11 +694,14 @@ int bacapp_decode_context_data(
     max_apdu_len = max_apdu_len;
     if (apdu && value && IS_CONTEXT_SPECIFIC(*apdu)) {
         value->context_specific = true;
+        value->next = NULL;
         tag_len =
             decode_tag_number_and_value(&apdu[0], &tag_number,
             &len_value_type);
-        if (tag_len) {
+        apdu_len = tag_len;
-            apdu_len = tag_len;
+        /* Empty construct : (closing tag) => returns NULL value */
+        if (tag_len && tag_len <= max_apdu_len &&
+            !decode_is_closing_tag_number(&apdu[0], tag_number)) {
             value->context_tag = tag_number;
             value->tag = bacapp_context_tag_type(property, tag_number);
             if (value->tag < MAX_BACNET_APPLICATION_TAG) {
@@ -706,11 +709,16 @@ int bacapp_decode_context_data(
                     bacapp_decode_data(&apdu[apdu_len], value->tag,
                     len_value_type, value);
                 apdu_len += len;
+            } else if (len_value_type) {
+                /* Unknown value : non null size (elementary type) */
+                apdu_len += len_value_type;
+                /* SHOULD NOT HAPPEN, EXCEPTED WHEN READING UNKNOWN CONTEXTUAL PROPERTY */
             } else {
                 apdu_len = BACNET_STATUS_ERROR;
             }
         }
-        value->next = NULL;
+        else if ( tag_len == 1 )	/* and is a Closing tag */
+        	apdu_len = 0;			/* Don't advance over that closing tag. */
     }
 
     return apdu_len;

bacnet-stack/src/bvlc.c

@@ -45,12 +45,12 @@
 #endif
 #include "debug.h"
 
-/** @file bvlc.c  Handle the BACnet Virtual Link Control (BVLC) */
+/** @file bvlc.c  Handle the BACnet Virtual Link Control (BVLC), 
+ * which includes: BACnet Broadcast Management Device,
+ * Broadcast Distribution Table, and
+ * Foreign Device Registration. 
+ */
 
-/* Handle the BACnet Virtual Link Control (BVLC), which includes:
-   BACnet Broadcast Management Device,
-   Broadcast Distribution Table, and
-   Foreign Device Registration */
 typedef struct {
     /* true if valid entry - false if not */
     bool valid;
@@ -733,13 +733,24 @@ static void bvlc_fdt_forward_npdu(
     return;
 }
 
-void bvlc_register_with_bbmd(
+
-    uint32_t bbmd_address,      /* in network byte order */
+/** Register as a foreign device with the indicated BBMD. 
-    uint16_t bbmd_port, /* in network byte order */
+ * @param bbmd_address - IPv4 address (long) of BBMD to register with,
+ *                       in network byte order.
+ * @param bbmd_port - Network port of BBMD, in network byte order
+ * @param time_to_live_seconds - Lease time to use when registering.
+ * @return Positive number (of bytes sent) on success, 
+ *         0 if no registration request is sent, or
+ *         -1 if registration fails.
+ */
+int bvlc_register_with_bbmd(
+    uint32_t bbmd_address,
+    uint16_t bbmd_port,
     uint16_t time_to_live_seconds)
 {
     uint8_t mtu[MAX_MPDU] = { 0 };
     uint16_t mtu_len = 0;
+    int retval = 0;
 
     /* Store the BBMD address and port so that we
        won't broadcast locally. */
@@ -752,7 +763,8 @@ void bvlc_register_with_bbmd(
     mtu_len =
         (uint16_t) bvlc_encode_register_foreign_device(&mtu[0],
         time_to_live_seconds);
-    bvlc_send_mpdu(&Remote_BBMD, &mtu[0], mtu_len);
+    retval = bvlc_send_mpdu(&Remote_BBMD, &mtu[0], mtu_len);
+    return retval;
 }
 
 static void bvlc_send_result(