libuavcan: Proper passive mode handling

libuavcan/include/uavcan/node/abstract_node.hpp

@@ -41,8 +41,9 @@ public:
     /**
      * Sets the Node ID of this node.
      * Node ID can be assigned only once. This method returns true if the Node ID was successfully assigned, otherwise
-     * it returns false (e.g. the argument does not represent a valid Node ID, or it was already assigned earlier).
+     * it returns false.
      * As long as a valid Node ID is not set, the node will remain in passive mode.
+     * Using a non-unicast Node ID puts the node into passive mode (as default).
      */
     bool setNodeID(NodeID nid)
     {

libuavcan/include/uavcan/transport/dispatcher.hpp

@@ -102,6 +102,7 @@ class UAVCAN_EXPORT Dispatcher : Noncopyable
     LoopbackFrameListenerRegistry loopback_listeners_;
 
     NodeID self_node_id_;
+    bool self_node_id_is_set_;
 
     void handleFrame(const CanRxFrame& can_frame);
     void handleLoopbackFrame(const CanRxFrame& can_frame);
@@ -111,6 +112,7 @@ public:
         : canio_(driver, allocator, sysclock)
         , sysclock_(sysclock)
         , outgoing_transfer_reg_(otr)
+        , self_node_id_is_set_(false)
     { }
 
     int spin(MonotonicTime deadline);
@@ -143,6 +145,10 @@ public:
 
     LoopbackFrameListenerRegistry& getLoopbackFrameListenerRegistry() { return loopback_listeners_; }
 
+    /**
+     * Node ID can be set only once.
+     * Non-unicast Node ID puts the node into passive mode.
+     */
     NodeID getNodeID() const { return self_node_id_; }
     bool setNodeID(NodeID nid);
 

libuavcan/src/transport/uc_dispatcher.cpp

@@ -319,9 +319,10 @@ bool Dispatcher::hasServer(DataTypeID dtid) const
 
 bool Dispatcher::setNodeID(NodeID nid)
 {
-    if (nid.isUnicast() && !self_node_id_.isValid())
+    if (!self_node_id_is_set_)
     {
         self_node_id_ = nid;
+        self_node_id_is_set_ = true;
         return true;
     }
     return false;