partial for #681: Never let stale nodeinfos/positions stay in xmit queue

src/mesh/MeshService.cpp

@@ -169,6 +169,11 @@ void MeshService::handleToRadio(MeshPacket &p)
     }
 }
 
+/** Attempt to cancel a previously sent packet from this _local_ node.  Returns true if a packet was found we could cancel */
+bool MeshService::cancelSending(PacketId id) {
+    return router->cancelSending(nodeDB.getNodeNum(), id);
+}
+
 void MeshService::sendToMesh(MeshPacket *p)
 {
     nodeDB.updateFrom(*p); // update our local DB for this packet (because phone might have sent position packets etc...)

src/mesh/MeshService.h

@@ -79,6 +79,9 @@ class MeshService
     /// cache
     void sendToMesh(MeshPacket *p);
 
+    /** Attempt to cancel a previously sent packet from this _local_ node.  Returns true if a packet was found we could cancel */
+    bool cancelSending(PacketId id);
+
     /// Pull the latest power and time info into my nodeinfo
     NodeInfo *refreshMyNodeInfo();
 

src/mesh/RadioInterface.h

@@ -105,6 +105,9 @@ class RadioInterface
      */
     virtual ErrorCode send(MeshPacket *p) = 0;
 
+    /** Attempt to cancel a previously sent packet.  Returns true if a packet was found we could cancel */
+    virtual bool cancelSending(NodeNum from, PacketId id) { return false; }
+
     // methods from radiohead
 
     /// Initialise the Driver transport hardware and software.

src/mesh/RadioLibInterface.cpp

@@ -132,6 +132,13 @@ bool RadioLibInterface::canSleep()
     return res;
 }
 
+/** Attempt to cancel a previously sent packet.  Returns true if a packet was found we could cancel */
+bool RadioLibInterface::cancelSending(NodeNum from, PacketId id) {
+    assert(0);
+    return false;
+}
+
+
 /** radio helper thread callback.
 
 We never immediately transmit after any operation (either rx or tx).  Instead we should start receiving and

src/mesh/RadioLibInterface.h

@@ -136,6 +136,9 @@ class RadioLibInterface : public RadioInterface, protected concurrency::Notified
      */
     virtual bool isActivelyReceiving() = 0;
 
+    /** Attempt to cancel a previously sent packet.  Returns true if a packet was found we could cancel */
+    virtual bool cancelSending(NodeNum from, PacketId id);
+    
   private:
     /** if we have something waiting to send, start a short random timer so we can come check for collision before actually doing
      * the transmit

src/mesh/Router.cpp

@@ -124,6 +124,8 @@ void Router::sendAckNak(ErrorReason err, NodeNum to, PacketId idFrom)
     sendLocal(p); // we sometimes send directly to the local node
 }
 
+
+
 ErrorCode Router::sendLocal(MeshPacket *p)
 {
     // No need to deliver externally if the destination is the local node
@@ -199,6 +201,13 @@ ErrorCode Router::send(MeshPacket *p)
     } */
 }
 
+/** Attempt to cancel a previously sent packet.  Returns true if a packet was found we could cancel */
+bool Router::cancelSending(NodeNum from, PacketId id) {
+    return iface ? iface->cancelSending(from, id) : false;
+}
+
+
+
 /**
  * Every (non duplicate) packet this node receives will be passed through this method.  This allows subclasses to
  * update routing tables etc... based on what we overhear (even for messages not destined to our node)

src/mesh/Router.h

@@ -55,7 +55,12 @@ class Router : protected concurrency::OSThread
      */
     ErrorCode sendLocal(MeshPacket *p);
 
-    /// Allocate and return a meshpacket which defaults as send to broadcast from the current node.
+    /** Attempt to cancel a previously sent packet.  Returns true if a packet was found we could cancel */
+    bool cancelSending(NodeNum from, PacketId id);    
+
+    /** Allocate and return a meshpacket which defaults as send to broadcast from the current node.
+     * The returned packet is guaranteed to have a unique packet ID already assigned
+     */
     MeshPacket *allocForSending();
 
     /**