[border-routing] decide Router Solicitation state with IsRouterSolicitationInProgress (#7242)

src/core/border_router/routing_manager.cpp

@@ -499,7 +499,7 @@ const Ip6::Prefix *RoutingManager::EvaluateOnLinkPrefix(void)
     const Ip6::Prefix *smallestOnLinkPrefix = nullptr;
 
     // We don't evaluate on-link prefix if we are doing Router Solicitation.
-    VerifyOrExit(!mRouterSolicitTimer.IsRunning(),
+    VerifyOrExit(!IsRouterSolicitationInProgress(),
                  newOnLinkPrefix = (mIsAdvertisingLocalOnLinkPrefix ? &mLocalOnLinkPrefix : nullptr));
 
     for (const ExternalPrefix &prefix : mDiscoveredPrefixes)
@@ -636,7 +636,9 @@ void RoutingManager::StartRouterSolicitationDelay(void)
 {
     uint32_t randomDelay;
 
-    VerifyOrExit(!mRouterSolicitTimer.IsRunning() && mRouterSolicitCount == 0);
+    VerifyOrExit(!IsRouterSolicitationInProgress());
+
+    OT_ASSERT(mRouterSolicitCount == 0);
 
     mVicariousRouterSolicitTimer.Stop();
 
@@ -651,6 +653,11 @@ exit:
     return;
 }
 
+bool RoutingManager::IsRouterSolicitationInProgress(void) const
+{
+    return mRouterSolicitTimer.IsRunning() || mRouterSolicitCount > 0;
+}
+
 Error RoutingManager::SendRouterSolicitation(void)
 {
     Ip6::Address                    destAddress;
@@ -898,9 +905,10 @@ void RoutingManager::HandleRouterSolicitTimer(void)
             UpdateRouterAdvMessage(/* aRouterAdvMessage */ nullptr);
         }
 
+        mRouterSolicitCount = 0;
+
         // Re-evaluate our routing policy and send Router Advertisement if necessary.
         EvaluateRoutingPolicy();
-        mRouterSolicitCount = 0;
     }
 }
 
@@ -940,7 +948,7 @@ void RoutingManager::HandleRouterSolicit(const Ip6::Address &aSrcAddress,
     OT_UNUSED_VARIABLE(aBuffer);
     OT_UNUSED_VARIABLE(aBufferLength);
 
-    VerifyOrExit(!mRouterSolicitTimer.IsRunning());
+    VerifyOrExit(!IsRouterSolicitationInProgress());
     otLogInfoBr("Received Router Solicitation from %s on interface %u", aSrcAddress.ToString().AsCString(),
                 mInfraIfIndex);
 

src/core/border_router/routing_manager.hpp

@@ -288,6 +288,7 @@ private:
     void  StartRouterSolicitationDelay(void);
     Error SendRouterSolicitation(void);
     void  SendRouterAdvertisement(const OmrPrefixArray &aNewOmrPrefixes, const Ip6::Prefix *aNewOnLinkPrefix);
+    bool  IsRouterSolicitationInProgress(void) const;
 
     static void HandleRouterAdvertisementTimer(Timer &aTimer);
     void        HandleRouterAdvertisementTimer(void);