[border-router] manage RxRaTracker state via multiple requesters (#12050)

This change introduces a mechanism to control the `RxRaTracker` from
multiple sources.

A new method `RxRaTracker::SetEnabled()` is added, which accepts a
`Requester` enum. The tracker now maintains separate enable flags for
each requester (e.g., `RoutingManager`).

The `RxRaTracker` will start only when at least one requester has
enabled it AND the infrastructure interface is initialized and running.
It stops when all requesters have disabled it or when the interface
goes down.

The `Start()` and `Stop()` methods are now private, managed by a new
`UpdateState()` method to centralize the state logic. `InfraIf` is
updated to notify `RxRaTracker` of state changes.

src/core/border_router/infra_if.cpp

@@ -167,6 +167,7 @@ Error InfraIf::HandleStateChanged(uint32_t aIfIndex, bool aIsRunning)
 
     mIsRunning = aIsRunning;
 
+    Get<RxRaTracker>().HandleInfraIfStateChanged();
     Get<RoutingManager>().HandleInfraIfStateChanged();
 
 #if OPENTHREAD_CONFIG_SRP_SERVER_ADVERTISING_PROXY_ENABLE

src/core/border_router/routing_manager.cpp

@@ -260,7 +260,7 @@ void RoutingManager::Start(void)
         LogInfo("Starting");
 
         mIsRunning = true;
-        Get<RxRaTracker>().Start();
+        Get<RxRaTracker>().SetEnabled(true, RxRaTracker::kRequesterRoutingManager);
         mOnLinkPrefixManager.Start();
         mOmrPrefixManager.Start();
         mRoutePublisher.Start();
@@ -294,7 +294,7 @@ void RoutingManager::Stop(void)
 
     SendRouterAdvertisement(kInvalidateAllPrevPrefixes);
 
-    Get<RxRaTracker>().Stop();
+    Get<RxRaTracker>().SetEnabled(false, RxRaTracker::kRequesterRoutingManager);
 
     mTxRaInfo.mTxCount = 0;
 

src/core/border_router/rx_ra_tracker.cpp

@@ -48,6 +48,9 @@ RegisterLogModule("BorderRouting");
 
 RxRaTracker::RxRaTracker(Instance &aInstance)
     : InstanceLocator(aInstance)
+    , mRoutingManagerEnabled(false)
+    , mMultiAilDetectorEnabled(false)
+    , mIsRunning(false)
     , mRsSender(aInstance)
     , mExpirationTimer(aInstance)
     , mStaleTimer(aInstance)
@@ -59,14 +62,50 @@ RxRaTracker::RxRaTracker(Instance &aInstance)
     mLocalRaHeader.Clear();
 }
 
+void RxRaTracker::SetEnabled(bool aEnable, Requester aRequester)
+{
+    switch (aRequester)
+    {
+    case kRequesterRoutingManager:
+        mRoutingManagerEnabled = aEnable;
+        break;
+    case kRequesterMultiAilDetector:
+        mMultiAilDetectorEnabled = aEnable;
+        break;
+    }
+
+    UpdateState();
+}
+
+void RxRaTracker::UpdateState(void)
+{
+    if ((mRoutingManagerEnabled || mMultiAilDetectorEnabled) && Get<InfraIf>().IsRunning())
+    {
+        Start();
+    }
+    else
+    {
+        Stop();
+    }
+}
+
 void RxRaTracker::Start(void)
 {
+    VerifyOrExit(!mIsRunning);
+    mIsRunning = true;
+
     mRsSender.Start();
     HandleNetDataChange();
+
+exit:
+    return;
 }
 
 void RxRaTracker::Stop(void)
 {
+    VerifyOrExit(mIsRunning);
+    mIsRunning = false;
+
     mRouters.Free();
     mIfAddresses.Free();
     mLocalRaHeader.Clear();
@@ -78,6 +117,9 @@ void RxRaTracker::Stop(void)
     mRdnssAddrTimer.Stop();
 
     mRsSender.Stop();
+
+exit:
+    return;
 }
 
 void RxRaTracker::HandleRsSenderFinished(TimeMilli aStartTime)

src/core/border_router/rx_ra_tracker.hpp

@@ -74,6 +74,7 @@ class RxRaTracker : public InstanceLocator
 {
     friend class NetDataBrTracker;
     friend class ot::Notifier;
+    friend class InfraIf;
 
 public:
     /**
@@ -86,6 +87,15 @@ public:
         kThisBrOtherEntity,    ///< From this Border Router, generated by another software entity.
     };
 
+    /**
+     * Represents an entity requesting to enable/disable the `RxRaTracker`.
+     */
+    enum Requester : uint8_t
+    {
+        kRequesterRoutingManager,   ///< Requested by `RoutingManager`.
+        kRequesterMultiAilDetector, ///< Requested by `MultiAilDetector`.
+    };
+
     /**
      * Initializes the `RxRaTracker` object.
      *
@@ -94,14 +104,15 @@ public:
     explicit RxRaTracker(Instance &aInstance);
 
     /**
-     * Starts the RA tracker.
+     * Enables or disables the `RxRaTracker`.
+     *
+     * The `RxRaTracker` can be enabled by multiple requesters (see `Requester`). It remains enabled as long as
+     * at least one requester has it enabled. It is disabled only when all requesters have disabled it.
+     *
+     * @param[in] aEnable      A boolean to enable/disable the  Tracker.
+     * @param[in] aRequester   The entity requesting to enable/disable.
      */
-    void Start(void);
-
-    /**
-     * Stops the RA tracker.
-     */
-    void Stop(void);
+    void SetEnabled(bool aEnable, Requester aRequester);
 
     /**
      * Indicates whether the Router Solicitation (RS) transmission process is in progress.
@@ -532,6 +543,9 @@ private:
 
     //-  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -
 
+    void UpdateState(void);
+    void Start(void);
+    void Stop(void);
     void HandleRsSenderFinished(TimeMilli aStartTime);
     void ProcessRaHeader(const RouterAdvert::Header &aRaHeader, Router &aRouter, RouterAdvOrigin aRaOrigin);
     void ProcessPrefixInfoOption(const PrefixInfoOption &aPio, Router &aRouter);
@@ -552,6 +566,9 @@ private:
     void HandleNotifierEvents(Events aEvents);
     void HandleNetDataChange(void);
 
+    // Callback from `InfraIf`
+    void HandleInfraIfStateChanged(void) { UpdateState(); }
+
     // Tasklet or timer callbacks
     void HandleSignalTask(void);
     void HandleRdnssAddrTask(void);
@@ -576,6 +593,9 @@ private:
     using IfAddressList   = OwningList<Entry<IfAddress>>;
     using RdnssCallback   = Callback<RdnssAddrCallback>;
 
+    bool                 mRoutingManagerEnabled : 1;
+    bool                 mMultiAilDetectorEnabled : 1;
+    bool                 mIsRunning : 1;
     RsSender             mRsSender;
     DecisionFactors      mDecisionFactors;
     RouterList           mRouters;