Add original hop limit to header to determine hops used (#3321)

* Set `hop_start` in header to determine how many hops each packet traveled

* Set hopLimit of response according to hops used by request

* Identify neighbors based on `hopStart` and `hopLimit`

* NeighborInfo: get all packets and assume a default broadcast interval

* Add fail-safe in case node in between is running modified firmware

* Add `viaMQTT` and `hopsAway` to NodeInfo

* Replace `HOP_RELIABLE` with hopStart for repeated packet

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/modules/NeighborInfoModule.cpp

@@ -95,6 +95,7 @@ NeighborInfoModule::NeighborInfoModule()
     ourPortNum = meshtastic_PortNum_NEIGHBORINFO_APP;
 
     if (moduleConfig.neighbor_info.enabled) {
+        isPromiscuous = true; // Update neighbors from all packets
         this->loadProtoForModule();
         setIntervalFromNow(35 * 1000);
     } else {
@@ -202,9 +203,12 @@ Pass it to an upper client; do not persist this data on the mesh
 */
 bool NeighborInfoModule::handleReceivedProtobuf(const meshtastic_MeshPacket &mp, meshtastic_NeighborInfo *np)
 {
-    if (enabled) {
+    if (np) {
         printNeighborInfo("RECEIVED", np);
         updateNeighbors(mp, np);
+    } else if (mp.hop_start != 0 && mp.hop_start == mp.hop_limit) {
+        // If the hopLimit is the same as hopStart, then it is a neighbor
+        getOrCreateNeighbor(mp.from, mp.from, 0, mp.rx_snr); // Set the broadcast interval to 0, as we don't know it
     }
     // Allow others to handle this packet
     return false;
@@ -261,7 +265,7 @@ meshtastic_Neighbor *NeighborInfoModule::getOrCreateNeighbor(NodeNum originalSen
             nbr->snr = snr;
             nbr->last_rx_time = getTime();
             // Only if this is the original sender, the broadcast interval corresponds to it
-            if (originalSender == n)
+            if (originalSender == n && node_broadcast_interval_secs != 0)
                 nbr->node_broadcast_interval_secs = node_broadcast_interval_secs;
             saveProtoForModule(); // Save the updated neighbor
             return nbr;
@@ -277,8 +281,10 @@ meshtastic_Neighbor *NeighborInfoModule::getOrCreateNeighbor(NodeNum originalSen
     new_nbr->snr = snr;
     new_nbr->last_rx_time = getTime();
     // Only if this is the original sender, the broadcast interval corresponds to it
-    if (originalSender == n)
+    if (originalSender == n && node_broadcast_interval_secs != 0)
         new_nbr->node_broadcast_interval_secs = node_broadcast_interval_secs;
+    else // Assume the same broadcast interval as us for the neighbor if we don't know it
+        new_nbr->node_broadcast_interval_secs = moduleConfig.neighbor_info.update_interval;
     saveProtoForModule(); // Save the new neighbor
     return new_nbr;
 }

src/modules/NeighborInfoModule.h

@@ -75,6 +75,9 @@ class NeighborInfoModule : public ProtobufModule<meshtastic_NeighborInfo>, priva
     /* Does our periodic broadcast */
     int32_t runOnce() override;
 
+    // Override wantPacket to say we want to see all packets when enabled, not just those for our port number
+    virtual bool wantPacket(const meshtastic_MeshPacket *p) override { return enabled; }
+
     /* These are for debugging only */
     void printNeighborInfo(const char *header, const meshtastic_NeighborInfo *np);
     void printNodeDBNodes(const char *header);

src/modules/RoutingModule.cpp

@@ -36,13 +36,28 @@ meshtastic_MeshPacket *RoutingModule::allocReply()
     return NULL;
 }
 
-void RoutingModule::sendAckNak(meshtastic_Routing_Error err, NodeNum to, PacketId idFrom, ChannelIndex chIndex)
+void RoutingModule::sendAckNak(meshtastic_Routing_Error err, NodeNum to, PacketId idFrom, ChannelIndex chIndex, uint8_t hopStart,
+                               uint8_t hopLimit)
 {
-    auto p = allocAckNak(err, to, idFrom, chIndex);
+    auto p = allocAckNak(err, to, idFrom, chIndex, hopStart, hopLimit);
 
     router->sendLocal(p); // we sometimes send directly to the local node
 }
 
+uint8_t RoutingModule::getHopLimitForResponse(uint8_t hopStart, uint8_t hopLimit)
+{
+    if (hopStart != 0) {
+        // Hops used by the request. If somebody in between running modified firmware modified it, ignore it
+        uint8_t hopsUsed = hopStart < hopLimit ? config.lora.hop_limit : hopStart - hopLimit;
+        if (hopsUsed > config.lora.hop_limit) {
+            return hopsUsed; // If the request used more hops than the limit, use the same amount of hops
+        } else if (hopsUsed + 2 < config.lora.hop_limit) {
+            return hopsUsed + 2; // Use only the amount of hops needed with some margin as the way back may be different
+        }
+    }
+    return config.lora.hop_limit; // Use the default hop limit
+}
+
 RoutingModule::RoutingModule() : ProtobufModule("routing", meshtastic_PortNum_ROUTING_APP, &meshtastic_Routing_msg)
 {
     isPromiscuous = true;

src/modules/RoutingModule.h

@@ -13,7 +13,11 @@ class RoutingModule : public ProtobufModule<meshtastic_Routing>
      */
     RoutingModule();
 
-    void sendAckNak(meshtastic_Routing_Error err, NodeNum to, PacketId idFrom, ChannelIndex chIndex);
+    void sendAckNak(meshtastic_Routing_Error err, NodeNum to, PacketId idFrom, ChannelIndex chIndex, uint8_t hopStart = 0,
+                    uint8_t hopLimit = 0);
+
+    // Given the hopStart and hopLimit upon reception of a request, return the hop limit to use for the response
+    uint8_t getHopLimitForResponse(uint8_t hopStart, uint8_t hopLimit);
 
   protected:
     friend class Router;