[border-router] send RA immediately when RA parameters are updated (#6565)

src/core/border_router/router_advertisement.cpp

@@ -208,6 +208,12 @@ const RouterAdvMessage &RouterAdvMessage::operator=(const RouterAdvMessage &aOth
     return *this;
 }
 
+bool RouterAdvMessage::operator==(const RouterAdvMessage &aOther) const
+{
+    return memcmp(&mHeader.mData, &aOther.mHeader.mData, sizeof(mHeader.mData)) == 0 &&
+           mReachableTime == aOther.mReachableTime && mRetransTimer == aOther.mRetransTimer;
+}
+
 RouterSolicitMessage::RouterSolicitMessage(void)
 {
     mHeader.Clear();

src/core/border_router/router_advertisement.hpp

@@ -447,6 +447,30 @@ public:
      */
     const RouterAdvMessage &operator=(const RouterAdvMessage &aOther);
 
+    /**
+     * This method overloads operator `==` to evaluate whether or not
+     * two instances of `RouterAdvMessage` are equal.
+     *
+     * @param[in]  aOther  The other `RouterAdvMessage` instance to compare with.
+     *
+     * @retval TRUE   If the two `RouterAdvMessage` instances are equal.
+     * @retval FALSE  If the two `RouterAdvMessage` instances are not equal.
+     *
+     */
+    bool operator==(const RouterAdvMessage &aOther) const;
+
+    /**
+     * This method overloads operator `!=` to evaluate whether or not
+     * two instances of `RouterAdvMessage` are equal.
+     *
+     * @param[in]  aOther  The other `RouterAdvMessage` instance to compare with.
+     *
+     * @retval TRUE   If the two `RouterAdvMessage` instances are not equal.
+     * @retval FALSE  If the two `RouterAdvMessage` instances are equal.
+     *
+     */
+    bool operator!=(const RouterAdvMessage &aOther) const { return !(*this == aOther); }
+
 private:
     enum : uint8_t
     {

src/core/border_router/routing_manager.cpp

@@ -959,16 +959,7 @@ void RoutingManager::HandleRouterAdvertisement(const Ip6::Address &aSrcAddress,
     // initiated from the infra interface.
     if (otPlatInfraIfHasAddress(mInfraIfIndex, &aSrcAddress))
     {
-        if (routerAdvMessage->GetRouterLifetime() == 0)
-        {
-            mRouterAdvMessage.SetToDefault();
-        }
-        else
-        {
-            mRouterAdvMessage = *routerAdvMessage;
-            // TODO: add a timer for invalidating the learned RA parameters
-            // for cases that the other RA daemon crashed or is force killed.
-        }
+        needReevaluate |= UpdateRouterAdvMessage(*routerAdvMessage);
     }
 
     if (needReevaluate)
@@ -1198,6 +1189,27 @@ bool RoutingManager::NetworkDataContainsOmrPrefix(const Ip6::Prefix &aPrefix) co
     return contain;
 }
 
+// Update the `mRouterAdvMessage` with given Router Advertisement message.
+// Returns a boolean which indicates whether there are changes of `mRouterAdvMessage`.
+bool RoutingManager::UpdateRouterAdvMessage(const RouterAdv::RouterAdvMessage &aRouterAdvMessage)
+{
+    RouterAdv::RouterAdvMessage oldRouterAdvMessage;
+
+    oldRouterAdvMessage = mRouterAdvMessage;
+    if (aRouterAdvMessage.GetRouterLifetime() == 0)
+    {
+        mRouterAdvMessage.SetToDefault();
+    }
+    else
+    {
+        mRouterAdvMessage = aRouterAdvMessage;
+        // TODO: add a timer for invalidating the learned RA parameters
+        // for cases that the other RA daemon crashed or is force killed.
+    }
+
+    return (mRouterAdvMessage != oldRouterAdvMessage);
+}
+
 } // namespace BorderRouter
 
 } // namespace ot

src/core/border_router/routing_manager.hpp

@@ -232,6 +232,7 @@ private:
                              uint32_t           aLifetime,
                              otRoutePreference  aRoutePreference = OT_ROUTE_PREFERENCE_MED);
     bool NetworkDataContainsOmrPrefix(const Ip6::Prefix &aPrefix) const;
+    bool UpdateRouterAdvMessage(const RouterAdv::RouterAdvMessage &aRouterAdvMessage);
 
     static bool     IsValidOmrPrefix(const NetworkData::OnMeshPrefixConfig &aOnMeshPrefixConfig);
     static bool     IsValidOmrPrefix(const Ip6::Prefix &aOmrPrefix);

tests/scripts/thread-cert/border_router/test_radvd_coexist.py

@@ -114,7 +114,7 @@ class SingleBorderRouter(thread_cert.TestCase):
         self.assertTrue(host.ping(router.get_ip6_address(config.ADDRESS_TYPE.OMR)[0], backbone=True))
 
         # Stop the radvd service and wait for the Border Router
-        # to start adverting on-link prefix on its own.
+        # to reset the RA parameters.
         br.stop_radvd_service()
         self.simulator.go(15)