Handle repeated/fallback to flooding packets properly

First check if it's not still in the TxQueue

src/mesh/FloodingRouter.cpp

@@ -22,23 +22,16 @@ ErrorCode FloodingRouter::send(meshtastic_MeshPacket *p)
 bool FloodingRouter::shouldFilterReceived(const meshtastic_MeshPacket *p)
 {
     if (wasSeenRecently(p)) { // Note: this will also add a recent packet record
-        printPacket("Ignore dupe incoming msg", p);
-        rxDupe++;
-        if (config.device.role != meshtastic_Config_DeviceConfig_Role_ROUTER &&
-            config.device.role != meshtastic_Config_DeviceConfig_Role_REPEATER) {
-            // cancel rebroadcast of this message *if* there was already one, unless we're a router/repeater!
-            if (Router::cancelSending(p->from, p->id))
-                txRelayCanceled++;
-        }
-
         /* If the original transmitter is doing retransmissions (hopStart equals hopLimit) for a reliable transmission, e.g., when
-        the ACK got lost, we will handle the packet again to make sure it gets an ACK to its packet. */
+        the ACK got lost, we will handle the packet again to make sure it gets an implicit ACK. */
         bool isRepeated = p->hop_start > 0 && p->hop_start == p->hop_limit;
         if (isRepeated) {
             LOG_DEBUG("Repeated reliable tx");
-            if (!perhapsRebroadcast(p) && isToUs(p) && p->want_ack) {
-                sendAckNak(meshtastic_Routing_Error_NONE, getFrom(p), p->id, p->channel, 0);
-            }
+            // Check if it's still in the Tx queue, if not, we have to relay it again
+            if (!findInTxQueue(p->from, p->id))
+                perhapsRebroadcast(p);
+        } else {
+            perhapsCancelDupe(p);
         }
 
         return true;
@@ -47,13 +40,25 @@ bool FloodingRouter::shouldFilterReceived(const meshtastic_MeshPacket *p)
     return Router::shouldFilterReceived(p);
 }
 
+void FloodingRouter::perhapsCancelDupe(const meshtastic_MeshPacket *p)
+{
+    printPacket("Ignore dupe incoming msg", p);
+    rxDupe++;
+    if (config.device.role != meshtastic_Config_DeviceConfig_Role_ROUTER &&
+        config.device.role != meshtastic_Config_DeviceConfig_Role_REPEATER) {
+        // cancel rebroadcast of this message *if* there was already one, unless we're a router/repeater!
+        if (Router::cancelSending(p->from, p->id))
+            txRelayCanceled++;
+    }
+}
+
 bool FloodingRouter::isRebroadcaster()
 {
     return config.device.role != meshtastic_Config_DeviceConfig_Role_CLIENT_MUTE &&
            config.device.rebroadcast_mode != meshtastic_Config_DeviceConfig_RebroadcastMode_NONE;
 }
 
-bool FloodingRouter::perhapsRebroadcast(const meshtastic_MeshPacket *p)
+void FloodingRouter::perhapsRebroadcast(const meshtastic_MeshPacket *p)
 {
     if (!isToUs(p) && (p->hop_limit > 0) && !isFromUs(p)) {
         if (p->id != 0) {
@@ -73,8 +78,6 @@ bool FloodingRouter::perhapsRebroadcast(const meshtastic_MeshPacket *p)
                 // Note: we are careful to resend using the original senders node id
                 // We are careful not to call our hooked version of send() - because we don't want to check this again
                 Router::send(tosend);
-
-                return true;
             } else {
                 LOG_DEBUG("No rebroadcast: Role = CLIENT_MUTE or Rebroadcast Mode = NONE");
             }
@@ -82,8 +85,6 @@ bool FloodingRouter::perhapsRebroadcast(const meshtastic_MeshPacket *p)
             LOG_DEBUG("Ignore 0 id broadcast");
         }
     }
-
-    return false;
 }
 
 void FloodingRouter::sniffReceived(const meshtastic_MeshPacket *p, const meshtastic_Routing *c)

src/mesh/FloodingRouter.h

@@ -28,9 +28,8 @@
 class FloodingRouter : public Router
 {
   private:
-    /** Check if we should rebroadcast this packet, and do so if needed
-     * @return true if rebroadcasted */
-    bool perhapsRebroadcast(const meshtastic_MeshPacket *p);
+    /* Check if we should rebroadcast this packet, and do so if needed */
+    void perhapsRebroadcast(const meshtastic_MeshPacket *p);
 
   public:
     /**
@@ -60,6 +59,9 @@ class FloodingRouter : public Router
      */
     virtual void sniffReceived(const meshtastic_MeshPacket *p, const meshtastic_Routing *c) override;
 
+    /* Call when receiving a duplicate packet to check whether we should cancel a packet in the Tx queue */
+    void perhapsCancelDupe(const meshtastic_MeshPacket *p);
+
     // Return true if we are a rebroadcaster
     bool isRebroadcaster();
 };

src/mesh/MeshPacketQueue.cpp

@@ -107,6 +107,19 @@ meshtastic_MeshPacket *MeshPacketQueue::remove(NodeNum from, PacketId id)
     return NULL;
 }
 
+/* Attempt to find a packet from this queue. Return true if it was found. */
+bool MeshPacketQueue::find(NodeNum from, PacketId id)
+{
+    for (auto it = queue.begin(); it != queue.end(); it++) {
+        auto p = (*it);
+        if (getFrom(p) == from && p->id == id) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
 /** Attempt to find and remove a packet from this queue.  Returns the packet which was removed from the queue */
 bool MeshPacketQueue::replaceLowerPriorityPacket(meshtastic_MeshPacket *p)
 {

src/mesh/MeshPacketQueue.h

@@ -37,4 +37,7 @@ class MeshPacketQueue
 
     /** Attempt to find and remove a packet from this queue.  Returns the packet which was removed from the queue */
     meshtastic_MeshPacket *remove(NodeNum from, PacketId id);
-};
+
+    /* Attempt to find a packet from this queue. Return true if it was found. */
+    bool find(NodeNum from, PacketId id);
+};

src/mesh/NextHopRouter.cpp

@@ -30,15 +30,25 @@ ErrorCode NextHopRouter::send(meshtastic_MeshPacket *p)
 
 bool NextHopRouter::shouldFilterReceived(const meshtastic_MeshPacket *p)
 {
-    if (wasSeenRecently(p)) { // Note: this will return false for a fallback to flooding
-        printPacket("Already seen, try stop re-Tx and cancel sending", p);
-        rxDupe++;
+    bool wasFallback = false;
+    if (wasSeenRecently(p, true, &wasFallback)) { // Note: this will also add a recent packet record
         stopRetransmission(p->from, p->id);
-        if (config.device.role != meshtastic_Config_DeviceConfig_Role_ROUTER &&
-            config.device.role != meshtastic_Config_DeviceConfig_Role_REPEATER) {
-            // cancel rebroadcast of this message *if* there was already one, unless we're a router/repeater!
-            if (Router::cancelSending(p->from, p->id))
-                txRelayCanceled++;
+
+        // If it was a fallback to flooding, try to relay again
+        if (wasFallback) {
+            LOG_INFO("Fallback to flooding from relay_node=0x%x", p->relay_node);
+            // Check if it's still in the Tx queue, if not, we have to relay it again
+            if (!findInTxQueue(p->from, p->id))
+                perhapsRelay(p);
+        } else {
+            bool isRepeated = p->hop_start > 0 && p->hop_start == p->hop_limit;
+            // If repeated and not in Tx queue anymore, try relaying again, or if we are the destination, send the ACK again
+            if (isRepeated) {
+                if (!findInTxQueue(p->from, p->id) && !perhapsRelay(p) && isToUs(p) && p->want_ack)
+                    sendAckNak(meshtastic_Routing_Error_NONE, getFrom(p), p->id, p->channel, 0);
+            } else {
+                perhapsCancelDupe(p); // If it's a dupe, cancel relay
+            }
         }
         return true;
     }
@@ -75,21 +85,32 @@ void NextHopRouter::sniffReceived(const meshtastic_MeshPacket *p, const meshtast
         }
     }
 
+    perhapsRelay(p);
+
+    // handle the packet as normal
+    Router::sniffReceived(p, c);
+}
+
+/* Check if we should be relaying this packet if so, do so. */
+bool NextHopRouter::perhapsRelay(const meshtastic_MeshPacket *p)
+{
     if (!isToUs(p) && !isFromUs(p) && p->hop_limit > 0) {
-        if (p->next_hop == NO_NEXT_HOP_PREFERENCE || p->next_hop == ourRelayID) {
+        if (p->next_hop == NO_NEXT_HOP_PREFERENCE || p->next_hop == nodeDB->getLastByteOfNodeNum(getNodeNum())) {
             if (isRebroadcaster()) {
                 meshtastic_MeshPacket *tosend = packetPool.allocCopy(*p); // keep a copy because we will be sending it
                 LOG_INFO("Relaying received message coming from %x", p->relay_node);
 
                 tosend->hop_limit--; // bump down the hop count
                 NextHopRouter::send(tosend);
+
+                return true;
             } else {
                 LOG_DEBUG("Not rebroadcasting: Role = CLIENT_MUTE or Rebroadcast Mode = NONE");
             }
         }
     }
-    // handle the packet as normal
-    Router::sniffReceived(p, c);
+
+    return false;
 }
 
 /**

src/mesh/NextHopRouter.h

@@ -144,4 +144,8 @@ class NextHopRouter : public FloodingRouter
      * @return the node number of the next hop, 0 if no preference (fallback to FloodingRouter)
      */
     uint8_t getNextHop(NodeNum to, uint8_t relay_node);
+
+    /** Check if we should be relaying this packet if so, do so.
+     *  @return true if we did relay */
+    bool perhapsRelay(const meshtastic_MeshPacket *p);
 };

src/mesh/PacketHistory.cpp

@@ -16,7 +16,7 @@ PacketHistory::PacketHistory()
 /**
  * Update recentBroadcasts and return true if we have already seen this packet
  */
-bool PacketHistory::wasSeenRecently(const meshtastic_MeshPacket *p, bool withUpdate)
+bool PacketHistory::wasSeenRecently(const meshtastic_MeshPacket *p, bool withUpdate, bool *wasFallback)
 {
     if (p->id == 0) {
         LOG_DEBUG("Ignore message with zero id");
@@ -41,21 +41,19 @@ bool PacketHistory::wasSeenRecently(const meshtastic_MeshPacket *p, bool withUpd
         seenRecently = false;
     }
 
-    if (seenRecently) {
-        // If it was seen with a next-hop not set to us and now it's NO_NEXT_HOP_PREFERENCE, and the relayer relayed already
-        // before, it's a fallback to flooding. If we didn't already relay and the next-hop neither, consider it unseen because we
-        // might need to handle it now
-        uint8_t ourRelayID = nodeDB->getLastByteOfNodeNum(nodeDB->getNodeNum());
-        if (found->sender != nodeDB->getNodeNum() && found->next_hop != NO_NEXT_HOP_PREFERENCE && found->next_hop != ourRelayID &&
-            p->next_hop == NO_NEXT_HOP_PREFERENCE && wasRelayer(p->relay_node, found) && !wasRelayer(ourRelayID, found) &&
-            !wasRelayer(found->next_hop, found)) {
-            LOG_INFO("Fallback to flooding, consider unseen relay_node=0x%x", p->relay_node);
-            seenRecently = false;
-        }
-    }
-
     if (seenRecently) {
         LOG_DEBUG("Found existing packet record for fr=0x%x,to=0x%x,id=0x%x", p->from, p->to, p->id);
+        if (wasFallback) {
+            // If it was seen with a next-hop not set to us and now it's NO_NEXT_HOP_PREFERENCE, and the relayer relayed already
+            // before, it's a fallback to flooding. If we didn't already relay and the next-hop neither, we might need to handle
+            // it now.
+            uint8_t ourRelayID = nodeDB->getLastByteOfNodeNum(nodeDB->getNodeNum());
+            if (found->sender != nodeDB->getNodeNum() && found->next_hop != NO_NEXT_HOP_PREFERENCE &&
+                found->next_hop != ourRelayID && p->next_hop == NO_NEXT_HOP_PREFERENCE && wasRelayer(p->relay_node, found) &&
+                !wasRelayer(ourRelayID, found) && !wasRelayer(found->next_hop, found)) {
+                *wasFallback = true;
+            }
+        }
     }
 
     if (withUpdate) {

src/mesh/PacketHistory.h

@@ -45,8 +45,9 @@ class PacketHistory
      * Update recentBroadcasts and return true if we have already seen this packet
      *
      * @param withUpdate if true and not found we add an entry to recentPackets
+     * @param wasFallback if not nullptr, packet will be checked for fallback to flooding and value will be set to true if so
      */
-    bool wasSeenRecently(const meshtastic_MeshPacket *p, bool withUpdate = true);
+    bool wasSeenRecently(const meshtastic_MeshPacket *p, bool withUpdate = true, bool *wasFallback = nullptr);
 
     /* Check if a certain node was a relayer of a packet in the history given an ID and sender
      * @return true if node was indeed a relayer, false if not */

src/mesh/RadioInterface.h

@@ -155,6 +155,9 @@ class RadioInterface
     /** 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; }
 
+    /** Attempt to find a packet in the TxQueue. Returns true if the packet was found. */
+    virtual bool findInTxQueue(NodeNum from, PacketId id) { return false; }
+
     // methods from radiohead
 
     /// Initialise the Driver transport hardware and software.

src/mesh/RadioLibInterface.cpp

@@ -246,6 +246,12 @@ bool RadioLibInterface::cancelSending(NodeNum from, PacketId id)
     return result;
 }
 
+/** Attempt to find a packet in the TxQueue. Returns true if the packet was found. */
+bool RadioLibInterface::findInTxQueue(NodeNum from, PacketId id)
+{
+    return txQueue.find(from, id);
+}
+
 /** radio helper thread callback.
 We never immediately transmit after any operation (either Rx or Tx). Instead we should wait a random multiple of
 'slotTimes' (see definition in RadioInterface.h) taken from a contention window (CW) to lower the chance of collision.

src/mesh/RadioLibInterface.h

@@ -142,6 +142,9 @@ class RadioLibInterface : public RadioInterface, protected concurrency::Notified
     /** Attempt to cancel a previously sent packet.  Returns true if a packet was found we could cancel */
     virtual bool cancelSending(NodeNum from, PacketId id) override;
 
+    /** Attempt to find a packet in the TxQueue. Returns true if the packet was found. */
+    virtual bool findInTxQueue(NodeNum from, PacketId id) override;
+
   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

@@ -299,6 +299,12 @@ bool Router::cancelSending(NodeNum from, PacketId id)
     return false;
 }
 
+/** Attempt to find a packet in the TxQueue. Returns true if the packet was found. */
+bool Router::findInTxQueue(NodeNum from, PacketId id)
+{
+    return iface->findInTxQueue(from, id);
+}
+
 /**
  * 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

@@ -51,6 +51,9 @@ class Router : protected concurrency::OSThread, protected PacketHistory
     /** Attempt to cancel a previously sent packet.  Returns true if a packet was found we could cancel */
     bool cancelSending(NodeNum from, PacketId id);
 
+    /** Attempt to find a packet in the TxQueue. Returns true if the packet was found. */
+    bool findInTxQueue(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
      */

src/platform/portduino/SimRadio.cpp

@@ -133,6 +133,12 @@ bool SimRadio::cancelSending(NodeNum from, PacketId id)
     return result;
 }
 
+/** Attempt to find a packet in the TxQueue. Returns true if the packet was found. */
+bool SimRadio::findInTxQueue(NodeNum from, PacketId id)
+{
+    return txQueue.find(from, id);
+}
+
 void SimRadio::onNotify(uint32_t notification)
 {
     switch (notification) {
@@ -265,4 +271,4 @@ int16_t SimRadio::readData(uint8_t *data, size_t len)
     }
 
     return state;
-}
+}

src/platform/portduino/SimRadio.h

@@ -38,6 +38,9 @@ class SimRadio : public RadioInterface, protected concurrency::NotifiedWorkerThr
     /** Attempt to cancel a previously sent packet.  Returns true if a packet was found we could cancel */
     virtual bool cancelSending(NodeNum from, PacketId id) override;
 
+    /** Attempt to find a packet in the TxQueue. Returns true if the packet was found. */
+    virtual bool findInTxQueue(NodeNum from, PacketId id) override;
+
     /**
      * Start waiting to receive a message
      *