[tlvs] change Tlv::AppendTlv value param to be void pointer (#5008)

This commit changes the `Tlv::AppendTlv()` value parameter to use
`void *` as its type. This helps simplify its used in different
modules (we can simply pass a pointer to the object that is to be
appended as the TLV's value and avoid casting or conversion to
`uint8_t *`).

src/core/common/tlvs.cpp

@@ -257,7 +257,7 @@ otError Tlv::AppendUint32Tlv(Message &aMessage, uint8_t aType, uint32_t aValue)
     return tlv32.AppendTo(aMessage);
 }
 
-otError Tlv::AppendTlv(Message &aMessage, uint8_t aType, const uint8_t *aValue, uint8_t aLength)
+otError Tlv::AppendTlv(Message &aMessage, uint8_t aType, const void *aValue, uint8_t aLength)
 {
     otError error = OT_ERROR_NONE;
     Tlv     tlv;

src/core/common/tlvs.hpp

@@ -347,7 +347,7 @@ public:
      * @retval OT_ERROR_NO_BUFS  Insufficient available buffers to grow the message.
      *
      */
-    static otError AppendTlv(Message &aMessage, uint8_t aType, const uint8_t *aValue, uint8_t aLength);
+    static otError AppendTlv(Message &aMessage, uint8_t aType, const void *aValue, uint8_t aLength);
 
 protected:
     enum

src/core/meshcop/border_agent.cpp

@@ -459,8 +459,8 @@ bool BorderAgent::HandleUdpReceive(const Message &aMessage, const Ip6::MessageIn
         aMessage.CopyTo(aMessage.GetOffset(), offset, udpLength, *message);
     }
 
-    SuccessOrExit(error = Tlv::AppendTlv(*message, Tlv::kIPv6Address, aMessageInfo.GetPeerAddr().mFields.m8,
-                                         sizeof(Ip6::Address)));
+    SuccessOrExit(error =
+                      Tlv::AppendTlv(*message, Tlv::kIPv6Address, &aMessageInfo.GetPeerAddr(), sizeof(Ip6::Address)));
 
     SuccessOrExit(error = Get<Coap::CoapSecure>().SendMessage(*message, Get<Coap::CoapSecure>().GetPeerAddress()));
 

src/core/meshcop/dataset_manager.cpp

@@ -486,7 +486,7 @@ otError DatasetManager::SendSetRequest(const otOperationalDataset &aDataset, con
     if (aDataset.mComponents.mIsMasterKeyPresent)
     {
         SuccessOrExit(error =
-                          Tlv::AppendTlv(*message, Tlv::kNetworkMasterKey, aDataset.mMasterKey.m8, sizeof(MasterKey)));
+                          Tlv::AppendTlv(*message, Tlv::kNetworkMasterKey, &aDataset.mMasterKey, sizeof(MasterKey)));
     }
 
     if (aDataset.mComponents.mIsNetworkNamePresent)
@@ -499,13 +499,13 @@ otError DatasetManager::SendSetRequest(const otOperationalDataset &aDataset, con
 
     if (aDataset.mComponents.mIsExtendedPanIdPresent)
     {
-        SuccessOrExit(error = Tlv::AppendTlv(*message, Tlv::kExtendedPanId, aDataset.mExtendedPanId.m8,
+        SuccessOrExit(error = Tlv::AppendTlv(*message, Tlv::kExtendedPanId, &aDataset.mExtendedPanId,
                                              sizeof(Mac::ExtendedPanId)));
     }
 
     if (aDataset.mComponents.mIsMeshLocalPrefixPresent)
     {
-        SuccessOrExit(error = Tlv::AppendTlv(*message, Tlv::kMeshLocalPrefix, aDataset.mMeshLocalPrefix.m8,
+        SuccessOrExit(error = Tlv::AppendTlv(*message, Tlv::kMeshLocalPrefix, &aDataset.mMeshLocalPrefix,
                                              sizeof(otMeshLocalPrefix)));
     }
 

src/core/meshcop/joiner_router.cpp

@@ -358,13 +358,13 @@ Coap::Message *JoinerRouter::PrepareJoinerEntrustMessage(void)
     SuccessOrExit(error = message->SetPayloadMarker());
     message->SetSubType(Message::kSubTypeJoinerEntrust);
 
-    SuccessOrExit(error = Tlv::AppendTlv(*message, Tlv::kNetworkMasterKey, Get<KeyManager>().GetMasterKey().m8,
-                                         sizeof(MasterKey)));
+    SuccessOrExit(
+        error = Tlv::AppendTlv(*message, Tlv::kNetworkMasterKey, &Get<KeyManager>().GetMasterKey(), sizeof(MasterKey)));
 
-    SuccessOrExit(error = Tlv::AppendTlv(*message, Tlv::kMeshLocalPrefix, Get<Mle::MleRouter>().GetMeshLocalPrefix().m8,
+    SuccessOrExit(error = Tlv::AppendTlv(*message, Tlv::kMeshLocalPrefix, &Get<Mle::MleRouter>().GetMeshLocalPrefix(),
                                          sizeof(otMeshLocalPrefix)));
 
-    SuccessOrExit(error = Tlv::AppendTlv(*message, Tlv::kExtendedPanId, Get<Mac::Mac>().GetExtendedPanId().m8,
+    SuccessOrExit(error = Tlv::AppendTlv(*message, Tlv::kExtendedPanId, &Get<Mac::Mac>().GetExtendedPanId(),
                                          sizeof(Mac::ExtendedPanId)));
 
     networkName.Init();

src/core/thread/address_resolver.cpp

@@ -559,7 +559,7 @@ otError AddressResolver::SendAddressQuery(const Ip6::Address &aEid)
     SuccessOrExit(error = message->AppendUriPathOptions(OT_URI_PATH_ADDRESS_QUERY));
     SuccessOrExit(error = message->SetPayloadMarker());
 
-    SuccessOrExit(error = Tlv::AppendTlv(*message, ThreadTlv::kTarget, aEid.mFields.m8, sizeof(aEid)));
+    SuccessOrExit(error = Tlv::AppendTlv(*message, ThreadTlv::kTarget, &aEid, sizeof(aEid)));
 
     messageInfo.GetPeerAddr().SetToRealmLocalAllRoutersMulticast();
 
@@ -673,7 +673,7 @@ void AddressResolver::SendAddressError(const Ip6::Address &aTarget,
     SuccessOrExit(error = message->AppendUriPathOptions(OT_URI_PATH_ADDRESS_ERROR));
     SuccessOrExit(error = message->SetPayloadMarker());
 
-    SuccessOrExit(error = Tlv::AppendTlv(*message, ThreadTlv::kTarget, aTarget.mFields.m8, sizeof(aTarget)));
+    SuccessOrExit(error = Tlv::AppendTlv(*message, ThreadTlv::kTarget, &aTarget, sizeof(aTarget)));
     SuccessOrExit(error = Tlv::AppendTlv(*message, ThreadTlv::kMeshLocalEid, aMeshLocalIid,
                                          Ip6::Address::kInterfaceIdentifierSize));
 
@@ -843,7 +843,7 @@ void AddressResolver::SendAddressQueryResponse(const Ip6::Address &aTarget,
     SuccessOrExit(error = message->AppendUriPathOptions(OT_URI_PATH_ADDRESS_NOTIFY));
     SuccessOrExit(error = message->SetPayloadMarker());
 
-    SuccessOrExit(error = Tlv::AppendTlv(*message, ThreadTlv::kTarget, aTarget.mFields.m8, sizeof(aTarget)));
+    SuccessOrExit(error = Tlv::AppendTlv(*message, ThreadTlv::kTarget, &aTarget, sizeof(aTarget)));
     SuccessOrExit(error = Tlv::AppendTlv(*message, ThreadTlv::kMeshLocalEid, aMeshLocalIid,
                                          Ip6::Address::kInterfaceIdentifierSize));
     SuccessOrExit(error = Tlv::AppendUint16Tlv(*message, ThreadTlv::kRloc16, Get<Mle::MleRouter>().GetRloc16()));

src/core/thread/network_diagnostic.cpp

@@ -307,7 +307,7 @@ otError NetworkDiagnostic::FillRequestedTlvs(const Message &       aRequest,
         {
         case NetworkDiagnosticTlv::kExtMacAddress:
             SuccessOrExit(
-                error = Tlv::AppendTlv(aResponse, type, Get<Mac::Mac>().GetExtAddress().m8, sizeof(Mac::ExtAddress)));
+                error = Tlv::AppendTlv(aResponse, type, &Get<Mac::Mac>().GetExtAddress(), sizeof(Mac::ExtAddress)));
             break;
 
         case NetworkDiagnosticTlv::kAddress16: