Address review comments.

Author: bzbarsky-apple

src/app/CASEClient.cpp

@@ -50,10 +50,9 @@ CHIP_ERROR CASEClient::EstablishSession(const CASEClientInitParams & params, con
     VerifyOrReturnError(exchange != nullptr, CHIP_ERROR_INTERNAL);
 
     mCASESession.SetGroupDataProvider(params.groupDataProvider);
-    // EstablishSession defaults to using the local MRP config, which is what we want.
     ReturnErrorOnFailure(mCASESession.EstablishSession(*params.sessionManager, params.fabricTable, peer, exchange,
                                                        params.sessionResumptionStorage, params.certificateValidityPolicy, delegate,
-                                                       NullOptional));
+                                                       params.mrpLocalConfig));
 
     return CHIP_NO_ERROR;
 }

src/app/CASEClient.h

@@ -35,6 +35,11 @@ struct CASEClientInitParams
     FabricTable * fabricTable                                          = nullptr;
     Credentials::GroupDataProvider * groupDataProvider                 = nullptr;
 
+    // mrpLocalConfig should not generally be set to anything other than
+    // NullOptional.  Doing that can lead to different parts of the system
+    // claiming different MRP parameters for the same node.
+    Optional<ReliableMessageProtocolConfig> mrpLocalConfig = NullOptional;
+
     CHIP_ERROR Validate() const
     {
         // sessionResumptionStorage can be nullptr when resumption is disabled.

src/app/server/Server.cpp

@@ -313,6 +313,9 @@ CHIP_ERROR Server::Init(const ServerInitParams & initParams)
             .exchangeMgr       = &mExchangeMgr,
             .fabricTable       = &mFabrics,
             .groupDataProvider = mGroupsProvider,
+            // Don't provide an MRP local config, so each CASE initiation will use
+            // the then-current value.
+            .mrpLocalConfig = NullOptional,
         },
         .clientPool            = &mCASEClientPool,
         .sessionSetupPool      = &mSessionSetupPool,

src/controller/CHIPDeviceControllerFactory.cpp

@@ -270,6 +270,9 @@ CHIP_ERROR DeviceControllerFactory::InitSystemState(FactoryInitParams params)
         .exchangeMgr               = stateParams.exchangeMgr,
         .fabricTable               = stateParams.fabricTable,
         .groupDataProvider         = stateParams.groupDataProvider,
+        // Don't provide an MRP local config, so each CASE initiation will use
+        // the then-current value.
+        .mrpLocalConfig = NullOptional,
     };
 
     CASESessionManagerConfig sessionManagerConfig = {