If a packet is heard multiple times, rebroadcast using the highest hop limit

src/mesh/FloodingRouter.cpp

@@ -29,6 +29,13 @@ bool FloodingRouter::shouldFilterReceived(const meshtastic_MeshPacket *p)
             // cancel rebroadcast of this message *if* there was already one, unless we're a router/repeater!
             if (Router::cancelSending(p->from, p->id))
                 txRelayCanceled++;
+        } else if (iface && p->hop_limit > 0) {
+            // If we overhear a duplicate copy of the packet with more hops left than the one we are waiting to
+            // rebroadcast, then remove the packet currently sitting in the TX queue and use this one instead.
+            if (iface->removePendingTXPacket(getFrom(p), p->id, p->hop_limit - 1)) {
+                LOG_DEBUG("Processing packet %d again for rebroadcast with with better hop limit (%d)", p->hop_limit - 1);
+                return false;
+            }
         }
         if (config.device.role == meshtastic_Config_DeviceConfig_Role_ROUTER_LATE && iface) {
             iface->clampToLateRebroadcastWindow(getFrom(p), p->id);

src/mesh/MeshPacketQueue.cpp

@@ -99,12 +99,26 @@ meshtastic_MeshPacket *MeshPacketQueue::getFront()
     return p;
 }
 
+/** Attempt to find a packet in this queue. Returns a pointer to the found packet, or NULL if not found. */
+meshtastic_MeshPacket *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 p;
+        }
+    }
+
+    return NULL;
+}
+
 /** Attempt to find and remove a packet from this queue.  Returns a pointer to the removed packet, or NULL if not found */
-meshtastic_MeshPacket *MeshPacketQueue::remove(NodeNum from, PacketId id, bool tx_normal, bool tx_late)
+meshtastic_MeshPacket *MeshPacketQueue::remove(NodeNum from, PacketId id, bool tx_normal, bool tx_late, uint8_t hop_limit_lt)
 {
     for (auto it = queue.begin(); it != queue.end(); it++) {
         auto p = (*it);
-        if (getFrom(p) == from && p->id == id && ((tx_normal && !p->tx_after) || (tx_late && p->tx_after))) {
+        if (getFrom(p) == from && p->id == id && ((tx_normal && !p->tx_after) || (tx_late && p->tx_after)) &&
+            (!hop_limit_lt || p->hop_limit < hop_limit_lt)) {
             queue.erase(it);
             return p;
         }

src/mesh/MeshPacketQueue.h

@@ -35,6 +35,10 @@ class MeshPacketQueue
 
     meshtastic_MeshPacket *getFront();
 
+    /** Attempt to find a packet in this queue. Returns a pointer to the found packet, or NULL if not found. */
+    meshtastic_MeshPacket *find(NodeNum from, PacketId id);
+
     /** 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, bool tx_normal = true, bool tx_late = true);
+    meshtastic_MeshPacket *remove(NodeNum from, PacketId id, bool tx_normal = true, bool tx_late = true,
+                                  uint8_t hop_limit_lt = 0);
 };

src/mesh/RadioInterface.h

@@ -185,6 +185,12 @@ class RadioInterface
     /** If the packet is not already in the late rebroadcast window, move it there */
     virtual void clampToLateRebroadcastWindow(NodeNum from, PacketId id) { return; }
 
+    /**
+     * If there is a packet pending TX in the queue with a worse hop limit, remove it pending replacement with a better version
+     * @return Whether a pending packet was removed
+     */
+    bool removePendingTXPacket(NodeNum from, PacketId id, uint32_t hop_limit_lt) { return false; }
+
     /**
      * Calculate airtime per
      * https://www.rs-online.com/designspark/rel-assets/ds-assets/uploads/knowledge-items/application-notes-for-the-internet-of-things/LoRa%20Design%20Guide.pdf

src/mesh/RadioLibInterface.cpp

@@ -344,6 +344,26 @@ void RadioLibInterface::clampToLateRebroadcastWindow(NodeNum from, PacketId id)
     }
 }
 
+/**
+ * If there is a packet pending TX in the queue with a worse hop limit, remove it pending replacement with a better version
+ * @return Whether a pending packet was removed
+ */
+bool RadioLibInterface::removePendingTXPacket(NodeNum from, PacketId id, uint32_t hop_limit_lt)
+{
+    meshtastic_MeshPacket *p = txQueue.remove(from, id, true, true, hop_limit_lt);
+    if (p) {
+        LOG_DEBUG("Dropping pending-TX packet %d with hop limit %d", p->id, p->hop_limit);
+        packetPool.release(p);
+        return true;
+    }
+    return false;
+}
+
+/**
+ * Remove a packet that is eligible for replacement from the TX queue
+ */
+// void RadioLibInterface::removePending
+
 void RadioLibInterface::handleTransmitInterrupt()
 {
     // This can be null if we forced the device to enter standby mode.  In that case

src/mesh/RadioLibInterface.h

@@ -204,4 +204,10 @@ class RadioLibInterface : public RadioInterface, protected concurrency::Notified
      * If the packet is not already in the late rebroadcast window, move it there
      */
     void clampToLateRebroadcastWindow(NodeNum from, PacketId id);
+
+    /**
+     * If there is a packet pending TX in the queue with a worse hop limit, remove it pending replacement with a better version
+     * @return Whether a pending packet was removed
+     */
+    bool removePendingTXPacket(NodeNum from, PacketId id, uint32_t hop_limit_lt);
 };