Feat/0-cost hops for favorite routers (#7992)

* feat: implement router hop preservation for router-to-router communication

- Preserve hop_limit when both local device and previous relay are routers/CLIENT_BASE
- Only preserve hops for favorite routers to prevent abuse
- Apply to both FloodingRouter and NextHopRouter
- Update hop counting logic in MeshService for router-to-router communication

This allows routers to communicate over longer distances without
consuming hop limits, improving mesh network efficiency for
infrastructure nodes.

* chore: update protobufs submodule to latest

* Optimized to check friend list first before nodedb.

* Reverting unintended changes

* revert: remove protobufs submodule update

This reverts the protobufs submodule back to a84657c22 to remove
unintended changes from this branch.

* Slight rewrite to remove flawed NO_RELAY_NODE logic and added logic to add isFirstHop. If isFirstHop, always decrease hop_limit to avoid retry logic.

* DRY code. Remove NodeInfo logic that was left over.

* Trunk formatting

src/mesh/FloodingRouter.cpp

@@ -1,5 +1,6 @@
 #include "FloodingRouter.h"
-
+#include "MeshTypes.h"
+#include "NodeDB.h"
 #include "configuration.h"
 #include "mesh-pb-constants.h"
 
@@ -90,7 +91,12 @@ void FloodingRouter::perhapsRebroadcast(const meshtastic_MeshPacket *p)
             if (isRebroadcaster()) {
                 meshtastic_MeshPacket *tosend = packetPool.allocCopy(*p); // keep a copy because we will be sending it
 
-                tosend->hop_limit--; // bump down the hop count
+                // Use shared logic to determine if hop_limit should be decremented
+                if (shouldDecrementHopLimit(p)) {
+                    tosend->hop_limit--; // bump down the hop count
+                } else {
+                    LOG_INFO("favorite-ROUTER/CLIENT_BASE-to-ROUTER/CLIENT_BASE flood: preserving hop_limit");
+                }
 #if USERPREFS_EVENT_MODE
                 if (tosend->hop_limit > 2) {
                     // if we are "correcting" the hop_limit, "correct" the hop_start by the same amount to preserve hops away.
@@ -98,6 +104,7 @@ void FloodingRouter::perhapsRebroadcast(const meshtastic_MeshPacket *p)
                     tosend->hop_limit = 2;
                 }
 #endif
+
                 tosend->next_hop = NO_NEXT_HOP_PREFERENCE; // this should already be the case, but just in case
 
                 LOG_INFO("Rebroadcast received floodmsg");

src/mesh/NextHopRouter.cpp

@@ -1,4 +1,5 @@
 #include "NextHopRouter.h"
+#include "NodeDB.h"
 
 NextHopRouter::NextHopRouter() {}
 
@@ -108,7 +109,13 @@ bool NextHopRouter::perhapsRelay(const meshtastic_MeshPacket *p)
                 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
+                // Use shared logic to determine if hop_limit should be decremented
+                if (shouldDecrementHopLimit(p)) {
+                    tosend->hop_limit--; // bump down the hop count
+                } else {
+                    LOG_INFO("Router/CLIENT_BASE-to-favorite-router/CLIENT_BASE relay: preserving hop_limit");
+                }
+
                 NextHopRouter::send(tosend);
 
                 return true;

src/mesh/Router.cpp

@@ -69,6 +69,58 @@ Router::Router() : concurrency::OSThread("Router"), fromRadioQueue(MAX_RX_FROMRA
     cryptLock = new concurrency::Lock();
 }
 
+bool Router::shouldDecrementHopLimit(const meshtastic_MeshPacket *p)
+{
+    // First hop MUST always decrement to prevent retry issues
+    bool isFirstHop = (p->hop_start != 0 && p->hop_start == p->hop_limit);
+    if (isFirstHop) {
+        return true; // Always decrement on first hop
+    }
+
+    // Check if both local device and previous relay are routers (including CLIENT_BASE)
+    bool localIsRouter =
+        IS_ONE_OF(config.device.role, meshtastic_Config_DeviceConfig_Role_ROUTER, meshtastic_Config_DeviceConfig_Role_ROUTER_LATE,
+                  meshtastic_Config_DeviceConfig_Role_CLIENT_BASE);
+
+    // If local device isn't a router, always decrement
+    if (!localIsRouter) {
+        return true;
+    }
+
+    // For subsequent hops, check if previous relay is a favorite router
+    // Optimized search for favorite routers with matching last byte
+    // Check ordering optimized for IoT devices (cheapest checks first)
+    for (int i = 0; i < nodeDB->getNumMeshNodes(); i++) {
+        meshtastic_NodeInfoLite *node = nodeDB->getMeshNodeByIndex(i);
+        if (!node)
+            continue;
+
+        // Check 1: is_favorite (cheapest - single bool)
+        if (!node->is_favorite)
+            continue;
+
+        // Check 2: has_user (cheap - single bool)
+        if (!node->has_user)
+            continue;
+
+        // Check 3: role check (moderate cost - multiple comparisons)
+        if (!IS_ONE_OF(node->user.role, meshtastic_Config_DeviceConfig_Role_ROUTER,
+                       meshtastic_Config_DeviceConfig_Role_ROUTER_LATE, meshtastic_Config_DeviceConfig_Role_CLIENT_BASE)) {
+            continue;
+        }
+
+        // Check 4: last byte extraction and comparison (most expensive)
+        if (nodeDB->getLastByteOfNodeNum(node->num) == p->relay_node) {
+            // Found a favorite router match
+            LOG_DEBUG("Identified favorite relay router 0x%x from last byte 0x%x", node->num, p->relay_node);
+            return false; // Don't decrement hop_limit
+        }
+    }
+
+    // No favorite router match found, decrement hop_limit
+    return true;
+}
+
 /**
  * do idle processing
  * Mostly looking in our incoming rxPacket queue and calling handleReceived.

src/mesh/Router.h

@@ -104,6 +104,18 @@ class Router : protected concurrency::OSThread, protected PacketHistory
      */
     virtual bool shouldFilterReceived(const meshtastic_MeshPacket *p) { return false; }
 
+    /**
+     * Determine if hop_limit should be decremented for a relay operation.
+     * Returns false (preserve hop_limit) only if all conditions are met:
+     * - It's NOT the first hop (first hop must always decrement)
+     * - Local device is a ROUTER, ROUTER_LATE, or CLIENT_BASE
+     * - Previous relay is a favorite ROUTER, ROUTER_LATE, or CLIENT_BASE
+     *
+     * @param p The packet being relayed
+     * @return true if hop_limit should be decremented, false to preserve it
+     */
+    bool shouldDecrementHopLimit(const meshtastic_MeshPacket *p);
+
     /**
      * 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)