[mle] enhance NewMleMessage() to prepare the MLE header (#7633)

This commit updates `NewMleMessage()` to allocate and also
initialize an MLE message adding MLE header and setting the
`Message::SubType`.

src/core/thread/discover_scanner.cpp

@@ -105,10 +105,8 @@ Error DiscoverScanner::Discover(const Mac::ChannelMask &aScanChannels,
         mScanChannels.Intersect(aScanChannels);
     }
 
-    VerifyOrExit((message = Get<Mle>().NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    message->SetSubType(Message::kSubTypeMleDiscoverRequest);
+    VerifyOrExit((message = Get<Mle>().NewMleMessage(Mle::kCommandDiscoveryRequest)) != nullptr, error = kErrorNoBufs);
     message->SetPanId(aPanId);
-    SuccessOrExit(error = Get<Mle>().AppendHeader(*message, Mle::kCommandDiscoveryRequest));
 
     // Prepare sub-TLV MeshCoP Discovery Request.
     discoveryRequest.Init();

src/core/thread/mle.cpp

@@ -1031,37 +1031,59 @@ const LeaderData &Mle::GetLeaderData(void)
     return mLeaderData;
 }
 
-Message *Mle::NewMleMessage(void)
+Message *Mle::NewMleMessage(Command aCommand)
 {
+    Error             error = kErrorNone;
     Message *         message;
     Message::Settings settings(Message::kNoLinkSecurity, Message::kPriorityNet);
+    Message::SubType  subType;
+    uint8_t           securitySuite;
 
     message = mSocket.NewMessage(0, settings);
-    VerifyOrExit(message != nullptr);
+    VerifyOrExit(message != nullptr, error = kErrorNoBufs);
 
-    message->SetSubType(Message::kSubTypeMleGeneral);
-
-exit:
-    return message;
-}
-
-Error Mle::AppendHeader(Message &aMessage, Command aCommand)
-{
-    Error   error         = kErrorNone;
-    uint8_t securitySuite = k154Security;
+    securitySuite = k154Security;
+    subType       = Message::kSubTypeMleGeneral;
 
     switch (aCommand)
     {
+    case kCommandAnnounce:
+        subType = Message::kSubTypeMleAnnounce;
+        break;
+
     case kCommandDiscoveryRequest:
-    case kCommandDiscoveryResponse:
+        subType       = Message::kSubTypeMleDiscoverRequest;
         securitySuite = kNoSecurity;
         break;
 
+    case kCommandDiscoveryResponse:
+        subType       = Message::kSubTypeMleDiscoverResponse;
+        securitySuite = kNoSecurity;
+        break;
+
+    case kCommandChildUpdateRequest:
+        subType = Message::kSubTypeMleChildUpdateRequest;
+        break;
+
+    case kCommandDataResponse:
+        subType = Message::kSubTypeMleDataResponse;
+        break;
+
+    case kCommandChildIdRequest:
+        subType = Message::kSubTypeMleChildIdRequest;
+        break;
+
+    case kCommandDataRequest:
+        subType = Message::kSubTypeMleDataRequest;
+        break;
+
     default:
         break;
     }
 
-    SuccessOrExit(error = aMessage.Append(securitySuite));
+    message->SetSubType(subType);
+
+    SuccessOrExit(error = message->Append(securitySuite));
 
     if (securitySuite == k154Security)
     {
@@ -1071,13 +1093,14 @@ Error Mle::AppendHeader(Message &aMessage, Command aCommand)
         // message in `SendMessage()` before message is sent.
 
         securityHeader.InitSecurityControl();
-        SuccessOrExit(error = aMessage.Append(securityHeader));
+        SuccessOrExit(error = message->Append(securityHeader));
     }
 
-    error = aMessage.Append<uint8_t>(aCommand);
+    error = message->Append<uint8_t>(aCommand);
 
 exit:
-    return error;
+    FreeAndNullMessageOnError(message, error);
+    return message;
 }
 
 Error Mle::AppendSourceAddress(Message &aMessage) const
@@ -2117,8 +2140,7 @@ void Mle::SendParentRequest(ParentRequestType aType)
         break;
     }
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = AppendHeader(*message, kCommandParentRequest));
+    VerifyOrExit((message = NewMleMessage(kCommandParentRequest)) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendMode(*message, mDeviceMode));
     SuccessOrExit(error = AppendChallenge(*message, mParentRequestChallenge));
     SuccessOrExit(error = AppendScanMask(*message, scanMask));
@@ -2180,9 +2202,7 @@ Error Mle::SendChildIdRequest(void)
         }
     }
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    message->SetSubType(Message::kSubTypeMleChildIdRequest);
-    SuccessOrExit(error = AppendHeader(*message, kCommandChildIdRequest));
+    VerifyOrExit((message = NewMleMessage(kCommandChildIdRequest)) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendResponse(*message, mParentCandidateChallenge));
     SuccessOrExit(error = AppendLinkFrameCounter(*message));
     SuccessOrExit(error = AppendMleFrameCounter(*message));
@@ -2234,9 +2254,7 @@ Error Mle::SendDataRequest(const Ip6::Address &aDestination,
 
     RemoveDelayedDataRequestMessage(aDestination);
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    message->SetSubType(Message::kSubTypeMleDataRequest);
-    SuccessOrExit(error = AppendHeader(*message, kCommandDataRequest));
+    VerifyOrExit((message = NewMleMessage(kCommandDataRequest)) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendTlvRequest(*message, aTlvs, aTlvsLength));
 
     if (aExtraTlvs != nullptr && aExtraTlvsLength > 0)
@@ -2419,9 +2437,7 @@ Error Mle::SendChildUpdateRequest(void)
     mChildUpdateRequestState = kChildUpdateRequestActive;
     ScheduleMessageTransmissionTimer();
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    message->SetSubType(Message::kSubTypeMleChildUpdateRequest);
-    SuccessOrExit(error = AppendHeader(*message, kCommandChildUpdateRequest));
+    VerifyOrExit((message = NewMleMessage(kCommandChildUpdateRequest)) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendMode(*message, mDeviceMode));
 
     switch (mRole)
@@ -2488,8 +2504,7 @@ Error Mle::SendChildUpdateResponse(const uint8_t *aTlvs, uint8_t aNumTlvs, const
     Message *    message;
     bool         checkAddress = false;
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = AppendHeader(*message, kCommandChildUpdateResponse));
+    VerifyOrExit((message = NewMleMessage(kCommandChildUpdateResponse)) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendSourceAddress(*message));
     SuccessOrExit(error = AppendLeaderData(*message));
 
@@ -2574,11 +2589,9 @@ void Mle::SendAnnounce(uint8_t aChannel, const Ip6::Address &aDestination, Annou
     Message *          message = nullptr;
 
     VerifyOrExit(Get<Mac::Mac>().GetSupportedChannelMask().ContainsChannel(aChannel), error = kErrorInvalidArgs);
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
+    VerifyOrExit((message = NewMleMessage(kCommandAnnounce)) != nullptr, error = kErrorNoBufs);
     message->SetLinkSecurityEnabled(true);
-    message->SetSubType(Message::kSubTypeMleAnnounce);
     message->SetChannel(aChannel);
-    SuccessOrExit(error = AppendHeader(*message, kCommandAnnounce));
 
     channel.Init();
     channel.SetChannelPage(0);
@@ -2639,8 +2652,7 @@ Error Mle::SendLinkMetricsManagementResponse(const Ip6::Address &aDestination, L
     Tlv      tlv;
     ot::Tlv  statusSubTlv;
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = AppendHeader(*message, kCommandLinkMetricsManagementResponse));
+    VerifyOrExit((message = NewMleMessage(kCommandLinkMetricsManagementResponse)) != nullptr, error = kErrorNoBufs);
 
     tlv.SetType(Tlv::kLinkMetricsManagement);
     statusSubTlv.SetType(LinkMetrics::SubTlv::kStatus);
@@ -2666,8 +2678,7 @@ Error Mle::SendLinkProbe(const Ip6::Address &aDestination, uint8_t aSeriesId, ui
     Message *message;
     Tlv      tlv;
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = AppendHeader(*message, kCommandLinkProbe));
+    VerifyOrExit((message = NewMleMessage(kCommandLinkProbe)) != nullptr, error = kErrorNoBufs);
 
     tlv.SetType(Tlv::kLinkProbe);
     tlv.SetLength(sizeof(aSeriesId) + aLength);
@@ -4666,8 +4677,7 @@ Error Mle::SendLinkMetricsManagementRequest(const Ip6::Address &aDestination, co
     Message *message;
     Tlv      tlv;
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = AppendHeader(*message, kCommandLinkMetricsManagementRequest));
+    VerifyOrExit((message = NewMleMessage(kCommandLinkMetricsManagementRequest)) != nullptr, error = kErrorNoBufs);
 
     // Link Metrics Management TLV
     tlv.SetType(Tlv::kLinkMetricsManagement);

src/core/thread/mle.hpp

@@ -975,12 +975,14 @@ protected:
     };
 
     /**
-     * This method allocates a new message buffer for preparing an MLE message.
+     * This method allocates and initializes new MLE message for a given command.
+     *
+     * @param[in] aCommand   The MLE command.
      *
      * @returns A pointer to the message or `nullptr` if insufficient message buffers are available.
      *
      */
-    Message *NewMleMessage(void);
+    Message *NewMleMessage(Command aCommand);
 
     /**
      * This method sets the device role.
@@ -1006,18 +1008,6 @@ protected:
      */
     void SetAttachState(AttachState aState);
 
-    /**
-     * This method appends an MLE header to a message.
-     *
-     * @param[in]  aMessage  A reference to the message.
-     * @param[in]  aCommand  The MLE Command Type.
-     *
-     * @retval kErrorNone    Successfully appended the header.
-     * @retval kErrorNoBufs  Insufficient buffers available to append the header.
-     *
-     */
-    Error AppendHeader(Message &aMessage, Command aCommand);
-
     /**
      * This method appends a Source Address TLV to a message.
      *

src/core/thread/mle_router.cpp

@@ -496,8 +496,7 @@ void MleRouter::SendAdvertisement(void)
     // children to detach.
     VerifyOrExit(!mAddressSolicitPending);
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = AppendHeader(*message, kCommandAdvertisement));
+    VerifyOrExit((message = NewMleMessage(kCommandAdvertisement)) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendSourceAddress(*message));
     SuccessOrExit(error = AppendLeaderData(*message));
 
@@ -538,8 +537,7 @@ Error MleRouter::SendLinkRequest(Neighbor *aNeighbor)
 
     destination.Clear();
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = AppendHeader(*message, kCommandLinkRequest));
+    VerifyOrExit((message = NewMleMessage(kCommandLinkRequest)) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendVersion(*message));
 
     switch (mRole)
@@ -735,8 +733,7 @@ Error MleRouter::SendLinkAccept(const Ip6::MessageInfo &aMessageInfo,
 
     command = (aNeighbor == nullptr || aNeighbor->IsStateValid()) ? kCommandLinkAccept : kCommandLinkAcceptAndRequest;
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = AppendHeader(*message, command));
+    VerifyOrExit((message = NewMleMessage(command)) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendVersion(*message));
     SuccessOrExit(error = AppendSourceAddress(*message));
     SuccessOrExit(error = AppendResponse(*message, aChallenge));
@@ -1954,10 +1951,9 @@ void MleRouter::SendParentResponse(Child *aChild, const Challenge &aChallenge, b
     Message *    message;
     uint16_t     delay;
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
+    VerifyOrExit((message = NewMleMessage(kCommandParentResponse)) != nullptr, error = kErrorNoBufs);
     message->SetDirectTransmission();
 
-    SuccessOrExit(error = AppendHeader(*message, kCommandParentResponse));
     SuccessOrExit(error = AppendSourceAddress(*message));
     SuccessOrExit(error = AppendLeaderData(*message));
     SuccessOrExit(error = AppendLinkFrameCounter(*message));
@@ -2961,8 +2957,7 @@ Error MleRouter::SendDiscoveryResponse(const Ip6::Address &aDestination, const M
     MeshCoP::NetworkNameTlv       networkName;
     uint16_t                      delay;
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    message->SetSubType(Message::kSubTypeMleDiscoverResponse);
+    VerifyOrExit((message = NewMleMessage(kCommandDiscoveryResponse)) != nullptr, error = kErrorNoBufs);
     message->SetPanId(aDiscoverRequestMessage.GetPanId());
 #if OPENTHREAD_CONFIG_MULTI_RADIO
     // Send the MLE Discovery Response message on same radio link
@@ -2970,8 +2965,6 @@ Error MleRouter::SendDiscoveryResponse(const Ip6::Address &aDestination, const M
     message->SetRadioType(aDiscoverRequestMessage.GetRadioType());
 #endif
 
-    SuccessOrExit(error = AppendHeader(*message, kCommandDiscoveryResponse));
-
     // Discovery TLV
     tlv.SetType(Tlv::kDiscovery);
     SuccessOrExit(error = message->Append(tlv));
@@ -3057,8 +3050,7 @@ Error MleRouter::SendChildIdResponse(Child &aChild)
     Ip6::Address destination;
     Message *    message;
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = AppendHeader(*message, kCommandChildIdResponse));
+    VerifyOrExit((message = NewMleMessage(kCommandChildIdResponse)) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendSourceAddress(*message));
     SuccessOrExit(error = AppendLeaderData(*message));
     SuccessOrExit(error = AppendActiveTimestamp(*message));
@@ -3171,9 +3163,7 @@ Error MleRouter::SendChildUpdateRequest(Child &aChild)
         }
     }
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    message->SetSubType(Message::kSubTypeMleChildUpdateRequest);
-    SuccessOrExit(error = AppendHeader(*message, kCommandChildUpdateRequest));
+    VerifyOrExit((message = NewMleMessage(kCommandChildUpdateRequest)) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendSourceAddress(*message));
     SuccessOrExit(error = AppendLeaderData(*message));
     SuccessOrExit(error = AppendNetworkData(*message, aChild.GetNetworkDataType()));
@@ -3212,8 +3202,7 @@ void MleRouter::SendChildUpdateResponse(Child *                 aChild,
     Error    error = kErrorNone;
     Message *message;
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = AppendHeader(*message, kCommandChildUpdateResponse));
+    VerifyOrExit((message = NewMleMessage(kCommandChildUpdateResponse)) != nullptr, error = kErrorNoBufs);
 
     for (int i = 0; i < aTlvsLength; i++)
     {
@@ -3305,9 +3294,7 @@ void MleRouter::SendDataResponse(const Ip6::Address &aDestination,
         ExitNow();
     }
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    message->SetSubType(Message::kSubTypeMleDataResponse);
-    SuccessOrExit(error = AppendHeader(*message, kCommandDataResponse));
+    VerifyOrExit((message = NewMleMessage(kCommandDataResponse)) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendSourceAddress(*message));
     SuccessOrExit(error = AppendLeaderData(*message));
     SuccessOrExit(error = AppendActiveTimestamp(*message));
@@ -4444,8 +4431,7 @@ Error MleRouter::SendTimeSync(void)
     Ip6::Address destination;
     Message *    message = nullptr;
 
-    VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = AppendHeader(*message, kCommandTimeSync));
+    VerifyOrExit((message = NewMleMessage(kCommandTimeSync)) != nullptr, error = kErrorNoBufs);
 
     message->SetTimeSync(true);