[mle] add TxMessage::AppendSteeringData() (#9559)

src/core/thread/mle.cpp

@@ -4963,6 +4963,28 @@ Error Mle::TxMessage::AppendPendingDatasetTlv(void)
     return Get<MeshCoP::PendingDatasetManager>().AppendMleDatasetTlv(*this);
 }
 
+Error Mle::TxMessage::AppendSteeringDataTlv(void)
+{
+    Error                 error = kErrorNone;
+    MeshCoP::SteeringData steeringData;
+
+#if OPENTHREAD_CONFIG_MLE_STEERING_DATA_SET_OOB_ENABLE
+    if (!Get<MleRouter>().mSteeringData.IsEmpty())
+    {
+        steeringData = Get<MleRouter>().mSteeringData;
+    }
+    else
+#endif
+    {
+        SuccessOrExit(Get<NetworkData::Leader>().FindSteeringData(steeringData));
+    }
+
+    error = Tlv::Append<MeshCoP::SteeringDataTlv>(*this, steeringData.GetData(), steeringData.GetLength());
+
+exit:
+    return error;
+}
+
 #endif // OPENTHREAD_FTD
 
 //---------------------------------------------------------------------------------------------------------------------

src/core/thread/mle.hpp

@@ -1017,6 +1017,7 @@ private:
         Error AppendActiveDatasetTlv(void);
         Error AppendPendingDatasetTlv(void);
         Error AppendConnectivityTlv(void);
+        Error AppendSteeringDataTlv(void);
         Error AppendAddressRegistrationTlv(Child &aChild);
 #endif
         template <uint8_t kArrayLength> Error AppendTlvRequestTlv(const uint8_t (&aTlvArray)[kArrayLength])

src/core/thread/mle_router.cpp

@@ -2810,26 +2810,7 @@ Error MleRouter::SendDiscoveryResponse(const Ip6::Address &aDestination, const M
     networkNameTlv.SetNetworkName(Get<MeshCoP::NetworkNameManager>().GetNetworkName().GetAsData());
     SuccessOrExit(error = networkNameTlv.AppendTo(*message));
 
-#if OPENTHREAD_CONFIG_MLE_STEERING_DATA_SET_OOB_ENABLE
-    // If steering data is set out of band, use that value.
-    // Otherwise use the one from commissioning data.
-    if (!mSteeringData.IsEmpty())
-    {
-        SuccessOrExit(error = Tlv::Append<MeshCoP::SteeringDataTlv>(*message, mSteeringData.GetData(),
-                                                                    mSteeringData.GetLength()));
-    }
-    else
-#endif
-    {
-        const MeshCoP::SteeringDataTlv *steeringDataTlv;
-
-        steeringDataTlv = Get<NetworkData::Leader>().FindInCommissioningData<MeshCoP::SteeringDataTlv>();
-
-        if (steeringDataTlv != nullptr)
-        {
-            SuccessOrExit(error = steeringDataTlv->AppendTo(*message));
-        }
-    }
+    SuccessOrExit(error = message->AppendSteeringDataTlv());
 
     SuccessOrExit(
         error = Tlv::Append<MeshCoP::JoinerUdpPortTlv>(*message, Get<MeshCoP::JoinerRouter>().GetJoinerUdpPort()));