Resend implicit ACK for a repeated broadcast (#1628)

src/mesh/ReliableRouter.cpp

@@ -67,6 +67,12 @@ bool ReliableRouter::shouldFilterReceived(MeshPacket *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) {
+        // 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);
+        tosend->hop_limit--; // bump down the hop count
+        Router::send(tosend);
     }
 
     return FloodingRouter::shouldFilterReceived(p);