Merge pull request #90 from athombv/fix/multiple-interfaces

Improvements in connection logic

Author: ttherbrink

lib/KNXInterface.js

@@ -7,7 +7,7 @@ const util = require('util');
 
 class KNXInterface extends EventEmitter {
 
-  constructor(knxInterface) {
+  constructor(knxInterface, options = {}) {
     super();
 
     // Setting object parameters from parameters from the interfacemanager
@@ -16,6 +16,11 @@ class KNXInterface extends EventEmitter {
     this.macAddress = knxInterface.interfaceMac;
     this.knxAddress = knxInterface.knxAddress;
 
+    // Resolver (from the interface manager) that maps the gateway IP to the local OS
+    // interface name sharing its subnet. Re-run on every connect so a reboot that
+    // reorders interfaces can't leave the tunnel bound to the wrong (V)LAN.
+    this.getLocalInterfaceName = options.getLocalInterfaceName;
+
     // KNX interface settings/variabeles
     this.isConnected = false; // Boolean to keep track of the connection status.
     this.isTimedOut = false; // Boolean to keep track of timeout events.
@@ -43,7 +48,13 @@ class KNXInterface extends EventEmitter {
     // The KNX tunnel connection itself through the knx library
     if (this.isConnected === true && !this.isTimedOut) return; // Skip re-initializing when already connected and healthy.
     try {
-      this.knxConnection = new knx.Connection({
+      // Resolve which local interface routes to this gateway. When it can't be
+      // determined we omit the option so the knx lib keeps its default behaviour.
+      const localInterface = typeof this.getLocalInterfaceName === 'function'
+        ? this.getLocalInterfaceName(this.ipAddress)
+        : undefined;
+
+      const connectionOptions = {
         ipAddr: this.ipAddress, // IP address obtained through interfacemanager
         ipPort: 3671, // Fixed and part of the KNXnet/IP protocol.
         physAddr: this.knxAddress, // KNX address obtained through interfacemanager
@@ -90,7 +101,16 @@ class KNXInterface extends EventEmitter {
             this.log('Error from FSM:', connstatus);
           },
         },
-      });
+      };
+
+      // Bind to the interface on the gateway's subnet so the CONNECT_REQUEST HPAI
+      // carries a routable source address (critical on multi-interface hosts/SHS).
+      if (localInterface) {
+        this.log(`Binding tunnel to local interface ${localInterface}`);
+        connectionOptions.interface = localInterface;
+      }
+
+      this.knxConnection = new knx.Connection(connectionOptions);
     } catch (error) {
       this.log('KNX lib error', error); // This should be able to catch the 'no valid ipv4 interfaces' error
     }