Adds network address translation (NAT) handling to BVLC when the device is BBMD.

When the device is behind a NAT enabled IP router, the local subnet is not accessible from the WAN side. This means that the device's local IP address cannot be used by other devices to communicate with it. The router can port forward BACnet packets to one device in the local network, but to do so other devices need to use the global IP for communication. The considerations and limitations for NAT usage are specified in BACnet standard Annex J.7.8. Thank you, Sami Pietikäinen, for the contribution!
2015-02-24 21:54:19 +00:00
parent efdb70b7f9
commit 98207470f4
2 changed files with 386 additions and 66 deletions
@@ -144,6 +144,27 @@ extern "C" {
        BBMD_TABLE_ENTRY* entry);


+    /* NAT handling
+     * If the communication between BBMDs goes through a NAT enabled internet
+     * router, special considerations are needed as stated in Annex J.7.8.
+     *
+     * In short, the local IP address of the BBMD is different than the global
+     * address which is visible to the other BBMDs or foreign devices. This is
+     * why the source address in forwarded messages needs to be changed to the
+     * global IP address.
+     *
+     * For other considerations/limitations see Annex J.7.8.
+     */
+
+    /* Set global IP address of a NAT enabled router which is used in forwarded
+     * messages. Enables NAT handling.
+     */
+    void bvlc_set_global_address_for_nat(const struct in_addr* addr);
+
+    /* Disable NAT handling of BBMD.
+     */
+    void bvlc_disable_nat(void);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */