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/mesh/MeshModule.cpp

@@ -32,7 +32,8 @@ MeshModule::~MeshModule()
     assert(0); // FIXME - remove from list of modules once someone needs this feature
 }
 
-meshtastic_MeshPacket *MeshModule::allocAckNak(meshtastic_Routing_Error err, NodeNum to, PacketId idFrom, ChannelIndex chIndex)
+meshtastic_MeshPacket *MeshModule::allocAckNak(meshtastic_Routing_Error err, NodeNum to, PacketId idFrom, ChannelIndex chIndex,
+                                               uint8_t hopStart, uint8_t hopLimit)
 {
     meshtastic_Routing c = meshtastic_Routing_init_default;
 
@@ -49,7 +50,7 @@ meshtastic_MeshPacket *MeshModule::allocAckNak(meshtastic_Routing_Error err, Nod
 
     p->priority = meshtastic_MeshPacket_Priority_ACK;
 
-    p->hop_limit = config.lora.hop_limit; // Flood ACK back to original sender
+    p->hop_limit = routingModule->getHopLimitForResponse(hopStart, hopLimit); // Flood ACK back to original sender
     p->to = to;
     p->decoded.request_id = idFrom;
     p->channel = chIndex;
@@ -176,7 +177,8 @@ void MeshModule::callPlugins(meshtastic_MeshPacket &mp, RxSource src)
             // SECURITY NOTE! I considered sending back a different error code if we didn't find the psk (i.e. !isDecoded)
             // but opted NOT TO.  Because it is not a good idea to let remote nodes 'probe' to find out which PSKs were "good" vs
             // bad.
-            routingModule->sendAckNak(meshtastic_Routing_Error_NO_RESPONSE, getFrom(&mp), mp.id, mp.channel);
+            routingModule->sendAckNak(meshtastic_Routing_Error_NO_RESPONSE, getFrom(&mp), mp.id, mp.channel, mp.hop_start,
+                                      mp.hop_limit);
         }
     }
 
@@ -217,6 +219,7 @@ void setReplyTo(meshtastic_MeshPacket *p, const meshtastic_MeshPacket &to)
     assert(p->which_payload_variant == meshtastic_MeshPacket_decoded_tag); // Should already be set by now
     p->to = getFrom(&to);    // Make sure that if we are sending to the local node, we use our local node addr, not 0
     p->channel = to.channel; // Use the same channel that the request came in on
+    p->hop_limit = routingModule->getHopLimitForResponse(to.hop_start, to.hop_limit);
 
     // No need for an ack if we are just delivering locally (it just generates an ignored ack)
     p->want_ack = (to.from != 0) ? to.want_ack : false;

src/mesh/MeshModule.h

@@ -153,7 +153,8 @@ class MeshModule
     virtual bool wantUIFrame() { return false; }
     virtual Observable<const UIFrameEvent *> *getUIFrameObservable() { return NULL; }
 
-    meshtastic_MeshPacket *allocAckNak(meshtastic_Routing_Error err, NodeNum to, PacketId idFrom, ChannelIndex chIndex);
+    meshtastic_MeshPacket *allocAckNak(meshtastic_Routing_Error err, NodeNum to, PacketId idFrom, ChannelIndex chIndex,
+                                       uint8_t hopStart = 0, uint8_t hopLimit = 0);
 
     /// Send an error response for the specified packet.
     meshtastic_MeshPacket *allocErrorResponse(meshtastic_Routing_Error err, const meshtastic_MeshPacket *p);

src/mesh/NodeDB.cpp

@@ -875,6 +875,12 @@ void NodeDB::updateFrom(const meshtastic_MeshPacket &mp)
 
         if (mp.rx_snr)
             info->snr = mp.rx_snr; // keep the most recent SNR we received for this node.
+
+        info->via_mqtt = mp.via_mqtt; // Store if we received this packet via MQTT
+
+        // If hopStart was set and there wasn't someone messing with the limit in the middle, add hopsAway
+        if (mp.hop_start != 0 && mp.hop_limit <= mp.hop_start)
+            info->hops_away = mp.hop_start - mp.hop_limit;
     }
 }
 

src/mesh/RadioInterface.cpp

@@ -302,6 +302,8 @@ void printPacket(const char *prefix, const meshtastic_MeshPacket *p)
         out += DEBUG_PORT.mt_sprintf(" rxRSSI=%i", p->rx_rssi);
     if (p->via_mqtt != 0)
         out += DEBUG_PORT.mt_sprintf(" via MQTT");
+    if (p->hop_start != 0)
+        out += DEBUG_PORT.mt_sprintf(" hopStart=%d", p->hop_start);
     if (p->priority != 0)
         out += DEBUG_PORT.mt_sprintf(" priority=%d", p->priority);
 
@@ -561,6 +563,7 @@ size_t RadioInterface::beginSending(meshtastic_MeshPacket *p)
         p->hop_limit = HOP_RELIABLE;
     }
     h->flags = p->hop_limit | (p->want_ack ? PACKET_FLAGS_WANT_ACK_MASK : 0) | (p->via_mqtt ? PACKET_FLAGS_VIA_MQTT_MASK : 0);
+    h->flags |= (p->hop_start << PACKET_FLAGS_HOP_START_SHIFT) & PACKET_FLAGS_HOP_START_MASK;
 
     // if the sender nodenum is zero, that means uninitialized
     assert(h->from);
@@ -569,4 +572,4 @@ size_t RadioInterface::beginSending(meshtastic_MeshPacket *p)
 
     sendingPacket = p;
     return p->encrypted.size + sizeof(PacketHeader);
-}
+}

src/mesh/RadioInterface.h

@@ -10,9 +10,11 @@
 
 #define MAX_RHPACKETLEN 256
 
-#define PACKET_FLAGS_HOP_MASK 0x07
+#define PACKET_FLAGS_HOP_LIMIT_MASK 0x07
 #define PACKET_FLAGS_WANT_ACK_MASK 0x08
 #define PACKET_FLAGS_VIA_MQTT_MASK 0x10
+#define PACKET_FLAGS_HOP_START_MASK 0xE0
+#define PACKET_FLAGS_HOP_START_SHIFT 5
 
 /**
  * This structure has to exactly match the wire layout when sent over the radio link.  Used to keep compatibility
@@ -224,4 +226,4 @@ class RadioInterface
 };
 
 /// Debug printing for packets
-void printPacket(const char *prefix, const meshtastic_MeshPacket *p);
+void printPacket(const char *prefix, const meshtastic_MeshPacket *p);

src/mesh/RadioLibInterface.cpp

@@ -359,8 +359,9 @@ void RadioLibInterface::handleReceiveInterrupt()
             mp->to = h->to;
             mp->id = h->id;
             mp->channel = h->channel;
-            assert(HOP_MAX <= PACKET_FLAGS_HOP_MASK); // If hopmax changes, carefully check this code
-            mp->hop_limit = h->flags & PACKET_FLAGS_HOP_MASK;
+            assert(HOP_MAX <= PACKET_FLAGS_HOP_LIMIT_MASK); // If hopmax changes, carefully check this code
+            mp->hop_limit = h->flags & PACKET_FLAGS_HOP_LIMIT_MASK;
+            mp->hop_start = (h->flags & PACKET_FLAGS_HOP_START_MASK) >> PACKET_FLAGS_HOP_START_SHIFT;
             mp->want_ack = !!(h->flags & PACKET_FLAGS_WANT_ACK_MASK);
             mp->via_mqtt = !!(h->flags & PACKET_FLAGS_VIA_MQTT_MASK);
 
@@ -407,4 +408,4 @@ void RadioLibInterface::startSend(meshtastic_MeshPacket *txp)
         // bits
         enableInterrupt(isrTxLevel0);
     }
-}
+}

src/mesh/ReliableRouter.cpp

@@ -71,12 +71,12 @@ bool ReliableRouter::shouldFilterReceived(const meshtastic_MeshPacket *p)
         i->second.nextTxMsec += iface->getPacketTime(p);
     }
 
-    /* Resend implicit ACKs for repeated packets (assuming the original packet was sent with HOP_RELIABLE)
+    /* Resend implicit ACKs for repeated packets (hopStart equals hopLimit);
      * 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
+    bool isRepeated = p->hop_start == 0 ? (p->hop_limit == HOP_RELIABLE) : (p->hop_start == p->hop_limit);
+    if (wasSeenRecently(p, false) && isRepeated && !MeshModule::currentReply && p->to != nodeDB.getNodeNum()) {
         LOG_DEBUG("Resending implicit ack for a repeated floodmsg\n");
         meshtastic_MeshPacket *tosend = packetPool.allocCopy(*p);
         tosend->hop_limit--; // bump down the hop count
@@ -107,10 +107,11 @@ void ReliableRouter::sniffReceived(const meshtastic_MeshPacket *p, const meshtas
             if (MeshModule::currentReply) {
                 LOG_DEBUG("Some other module has replied to this message, no need for a 2nd ack\n");
             } else if (p->which_payload_variant == meshtastic_MeshPacket_decoded_tag) {
-                sendAckNak(meshtastic_Routing_Error_NONE, getFrom(p), p->id, p->channel);
+                sendAckNak(meshtastic_Routing_Error_NONE, getFrom(p), p->id, p->channel, p->hop_start, p->hop_limit);
             } else {
                 // Send a 'NO_CHANNEL' error on the primary channel if want_ack packet destined for us cannot be decoded
-                sendAckNak(meshtastic_Routing_Error_NO_CHANNEL, getFrom(p), p->id, channels.getPrimaryIndex());
+                sendAckNak(meshtastic_Routing_Error_NO_CHANNEL, getFrom(p), p->id, channels.getPrimaryIndex(), p->hop_start,
+                           p->hop_limit);
             }
         }
 
@@ -255,4 +256,4 @@ void ReliableRouter::setNextTx(PendingPacket *pending)
     LOG_DEBUG("Setting next retransmission in %u msecs: ", d);
     printPacket("", pending->packet);
     setReceivedMessage(); // Run ASAP, so we can figure out our correct sleep time
-}
+}

src/mesh/Router.cpp

@@ -132,9 +132,10 @@ meshtastic_MeshPacket *Router::allocForSending()
 /**
  * Send an ack or a nak packet back towards whoever sent idFrom
  */
-void Router::sendAckNak(meshtastic_Routing_Error err, NodeNum to, PacketId idFrom, ChannelIndex chIndex)
+void Router::sendAckNak(meshtastic_Routing_Error err, NodeNum to, PacketId idFrom, ChannelIndex chIndex, uint8_t hopStart,
+                        uint8_t hopLimit)
 {
-    routingModule->sendAckNak(err, to, idFrom, chIndex);
+    routingModule->sendAckNak(err, to, idFrom, chIndex, hopStart, hopLimit);
 }
 
 void Router::abortSendAndNak(meshtastic_Routing_Error err, meshtastic_MeshPacket *p)
@@ -240,6 +241,10 @@ ErrorCode Router::send(meshtastic_MeshPacket *p)
     // the lora we need to make sure we have replaced it with our local address
     p->from = getFrom(p);
 
+    // If we are the original transmitter, set the hop limit with which we start
+    if (p->from == getNodeNum())
+        p->hop_start = p->hop_limit;
+
     // If the packet hasn't yet been encrypted, do so now (it might already be encrypted if we are just forwarding it)
 
     assert(p->which_payload_variant == meshtastic_MeshPacket_encrypted_tag ||

src/mesh/Router.h

@@ -104,7 +104,8 @@ class Router : protected concurrency::OSThread
     /**
      * Send an ack or a nak packet back towards whoever sent idFrom
      */
-    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);
 
   private:
     /**

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;