Merge pull request #2069 from GUVWAF/wantAckDM

Flood ACKs on DM back to original sender

src/mesh/FloodingRouter.cpp

@@ -17,7 +17,7 @@ ErrorCode FloodingRouter::send(MeshPacket *p)
     return Router::send(p);
 }
 
-bool FloodingRouter::shouldFilterReceived(MeshPacket *p)
+bool FloodingRouter::shouldFilterReceived(const MeshPacket *p)
 {
     if (wasSeenRecently(p)) { // Note: this will also add a recent packet record
         printPacket("Ignoring incoming msg, because we've already seen it", p);
@@ -34,7 +34,8 @@ void FloodingRouter::sniffReceived(const MeshPacket *p, const Routing *c)
         // do not flood direct message that is ACKed 
         DEBUG_MSG("Receiving an ACK not for me, but don't need to rebroadcast this direct message anymore.\n");
         Router::cancelSending(p->to, p->decoded.request_id);   // cancel rebroadcast for this DM
-    } else if ((p->to != getNodeNum()) && (p->hop_limit > 0) && (getFrom(p) != getNodeNum())) {
+    } 
+    if ((p->to != getNodeNum()) && (p->hop_limit > 0) && (getFrom(p) != getNodeNum())) {
         if (p->id != 0) {
             if (config.device.role != Config_DeviceConfig_Role_CLIENT_MUTE) {
                 MeshPacket *tosend = packetPool.allocCopy(*p); // keep a copy because we will be sending it

src/mesh/FloodingRouter.h

@@ -51,7 +51,7 @@ class FloodingRouter : public Router, protected PacketHistory
      * Called immedately on receiption, before any further processing.
      * @return true to abandon the packet
      */
-    virtual bool shouldFilterReceived(MeshPacket *p) override;
+    virtual bool shouldFilterReceived(const MeshPacket *p) override;
 
     /**
      * Look for broadcasts we need to rebroadcast

src/mesh/MeshModule.cpp

@@ -48,7 +48,7 @@ MeshPacket *MeshModule::allocAckNak(Routing_Error err, NodeNum to, PacketId idFr
 
     p->priority = MeshPacket_Priority_ACK;
 
-    p->hop_limit = 0; // Assume just immediate neighbors for now
+    p->hop_limit = config.lora.hop_limit; // Flood ACK back to original sender
     p->to = to;
     p->decoded.request_id = idFrom;
     p->channel = chIndex;

src/mesh/ReliableRouter.cpp

@@ -27,7 +27,7 @@ ErrorCode ReliableRouter::send(MeshPacket *p)
     return FloodingRouter::send(p);
 }
 
-bool ReliableRouter::shouldFilterReceived(MeshPacket *p)
+bool ReliableRouter::shouldFilterReceived(const MeshPacket *p)
 {
     // Note: do not use getFrom() here, because we want to ignore messages sent from phone
     if (p->from == getNodeNum()) {
@@ -37,9 +37,8 @@ bool ReliableRouter::shouldFilterReceived(MeshPacket *p)
         // If this is the first time we saw this, cancel any retransmissions we have queued up and generate an internal ack for
         // the original sending process.
 
-        // FIXME - we might want to turn off this "optimization", it does save lots of airtime but it assumes that once we've
-        // heard one one adjacent node hear our packet that a) probably other adjacent nodes heard it and b) we can trust those
-        // nodes to reach our destination.  Both of which might be incorrect.
+        // This "optimization", does save lots of airtime. For DMs, you also get a real ACK back
+	// from the intended recipient.
         auto key = GlobalPacketId(getFrom(p), p->id);
         auto old = findPendingPacket(key);
         if (old) {
@@ -54,16 +53,11 @@ bool ReliableRouter::shouldFilterReceived(MeshPacket *p)
         }
     }
 
-    /* send acks for repeated packets that want acks and are destined for us
-     * this way if an ACK is dropped and a packet is resent we'll ACK the resent packet
-     * make sure wasSeenRecently _doesn't_ update
-     * finding the channel requires decoding the packet. */
-    if (p->want_ack && (p->to == getNodeNum()) && wasSeenRecently(p, false) && !MeshModule::currentReply) {
-        if (perhapsDecode(p)) {
-            sendAckNak(Routing_Error_NONE, getFrom(p), p->id, p->channel);
-            DEBUG_MSG("acking a repeated want_ack packet\n");
-        }
-    } else if (wasSeenRecently(p, false) && p->hop_limit == HOP_RELIABLE && !MeshModule::currentReply && p->to != nodeDB.getNodeNum()) {
+    /* Resend implicit ACKs for repeated packets (assuming the original packet was sent with HOP_RELIABLE)
+    * this way if an implicit ACK is dropped and a packet is resent we'll rebroadcast again.
+    * Resending real ACKs is omitted, as you might receive a packet multiple times due to flooding and 
+    * flooding this ACK back to the original sender already adds redundancy. */ 
+    if (wasSeenRecently(p, false) && p->hop_limit == HOP_RELIABLE && !MeshModule::currentReply && p->to != nodeDB.getNodeNum()) {
         // retransmission on broadcast has hop_limit still equal to HOP_RELIABLE
         DEBUG_MSG("Resending implicit ack for a repeated floodmsg\n");
         MeshPacket *tosend = packetPool.allocCopy(*p);

src/mesh/ReliableRouter.h

@@ -96,7 +96,7 @@ class ReliableRouter : public FloodingRouter
     /**
      * We hook this method so we can see packets before FloodingRouter says they should be discarded
      */
-    virtual bool shouldFilterReceived(MeshPacket *p) override;
+    virtual bool shouldFilterReceived(const MeshPacket *p) override;
 
     /**
      * Add p to the list of packets to retransmit occasionally.  We will free it once we stop retransmitting.

src/mesh/Router.h

@@ -90,7 +90,7 @@ class Router : protected concurrency::OSThread
      * Called immedately on receiption, before any further processing.
      * @return true to abandon the packet
      */
-    virtual bool shouldFilterReceived(MeshPacket *p) { return false; }
+    virtual bool shouldFilterReceived(const MeshPacket *p) { return false; }
 
     /**
      * Every (non duplicate) packet this node receives will be passed through this method.  This allows subclasses to