[mle] add AppendSourceAddressAndLeaderDataTlvs() helper (#12867)

This commit introduces `TxMessage::AppendSourceAddressAndLeaderDataTlvs()`
to consolidate the appending of `Source Address` and `Leader Data` TLVs.

This combination is frequently used together across various MLE messages
to provide the sender's identity and leader data. Centralizing this
into a single helper method improves code consistency.

Additionally, the `TxMessage` methods in `mle.hpp` and `mle.cpp` are
organized into "Appending single TLV" and "Appending multiple TLVs"
sections for better clarity and maintainability. Existing multi-TLV
methods like `AppendLinkAndMleFrameCounterTlvs()` and
`AppendActiveAndPendingTimestampTlvs()` are moved to the new section.

src/core/thread/mle.cpp

@@ -1261,8 +1261,7 @@ Error Mle::SendChildUpdateRequestToParent(ChildUpdateRequestMode aMode)
         break;
 
     case kRoleChild:
-        SuccessOrExit(error = message->AppendSourceAddressTlv());
-        SuccessOrExit(error = message->AppendLeaderDataTlv());
+        SuccessOrExit(error = message->AppendSourceAddressAndLeaderDataTlvs());
         SuccessOrExit(error = message->AppendTimeoutTlv((aMode == kAppendZeroTimeout) ? 0 : mTimeout));
         SuccessOrExit(error = message->AppendSupervisionIntervalTlvIfSleepyChild());
 #if OPENTHREAD_CONFIG_MAC_CSL_RECEIVER_ENABLE
@@ -3545,6 +3544,9 @@ exit:
     return message;
 }
 
+//- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// TxMessage - Append single TLV
+
 Error Mle::TxMessage::AppendSourceAddressTlv(void)
 {
     return Tlv::Append<SourceAddressTlv>(*this, Get<Mle>().GetRloc16());
@@ -3589,17 +3591,6 @@ Error Mle::TxMessage::AppendMleFrameCounterTlv(void)
     return Tlv::Append<MleFrameCounterTlv>(*this, Get<KeyManager>().GetMleFrameCounter());
 }
 
-Error Mle::TxMessage::AppendLinkAndMleFrameCounterTlvs(void)
-{
-    Error error;
-
-    SuccessOrExit(error = AppendLinkFrameCounterTlv());
-    error = AppendMleFrameCounterTlv();
-
-exit:
-    return error;
-}
-
 Error Mle::TxMessage::AppendAddress16Tlv(uint16_t aRloc16) { return Tlv::Append<Address16Tlv>(*this, aRloc16); }
 
 Error Mle::TxMessage::AppendLeaderDataTlv(void)
@@ -3827,17 +3818,6 @@ exit:
     return error;
 }
 
-Error Mle::TxMessage::AppendActiveAndPendingTimestampTlvs(void)
-{
-    Error error;
-
-    SuccessOrExit(error = AppendActiveTimestampTlv());
-    error = AppendPendingTimestampTlv();
-
-exit:
-    return error;
-}
-
 #if OPENTHREAD_CONFIG_MAC_CSL_RECEIVER_ENABLE
 Error Mle::TxMessage::AppendCslChannelTlv(void)
 {
@@ -3873,6 +3853,45 @@ Error Mle::TxMessage::AppendCslClockAccuracyTlv(void)
 }
 #endif
 
+//- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// TxMessage - Append multiple TLVs
+
+Error Mle::TxMessage::AppendLinkAndMleFrameCounterTlvs(void)
+{
+    Error error;
+
+    SuccessOrExit(error = AppendLinkFrameCounterTlv());
+    error = AppendMleFrameCounterTlv();
+
+exit:
+    return error;
+}
+
+Error Mle::TxMessage::AppendSourceAddressAndLeaderDataTlvs(void)
+{
+    Error error;
+
+    SuccessOrExit(error = AppendSourceAddressTlv());
+    error = AppendLeaderDataTlv();
+
+exit:
+    return error;
+}
+
+Error Mle::TxMessage::AppendActiveAndPendingTimestampTlvs(void)
+{
+    Error error;
+
+    SuccessOrExit(error = AppendActiveTimestampTlv());
+    error = AppendPendingTimestampTlv();
+
+exit:
+    return error;
+}
+
+//- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// TxMessage - Misc
+
 Error Mle::TxMessage::SendTo(const Ip6::Address &aDestination)
 {
     Error            error  = kErrorNone;

src/core/thread/mle.hpp

@@ -1556,6 +1556,7 @@ private:
     class TxMessage : public Message
     {
     public:
+        // Appending single TLV
         Error AppendSourceAddressTlv(void);
         Error AppendModeTlv(DeviceMode aMode);
         Error AppendTimeoutTlv(uint32_t aTimeout);
@@ -1563,7 +1564,6 @@ private:
         Error AppendResponseTlv(const RxChallenge &aResponse);
         Error AppendLinkFrameCounterTlv(void);
         Error AppendMleFrameCounterTlv(void);
-        Error AppendLinkAndMleFrameCounterTlvs(void);
         Error AppendAddress16Tlv(uint16_t aRloc16);
         Error AppendNetworkDataTlv(NetworkData::Type aType);
         Error AppendTlvRequestTlv(const uint8_t *aTlvs, uint8_t aTlvsLength);
@@ -1578,7 +1578,6 @@ private:
         Error AppendXtalAccuracyTlv(void);
         Error AppendActiveTimestampTlv(void);
         Error AppendPendingTimestampTlv(void);
-        Error AppendActiveAndPendingTimestampTlvs(void);
 #if OPENTHREAD_CONFIG_TIME_SYNC_ENABLE
         Error AppendTimeRequestTlv(void);
         Error AppendTimeParameterTlv(void);
@@ -1603,6 +1602,11 @@ private:
             return AppendTlvRequestTlv(aTlvArray, kArrayLength);
         }
 
+        // Appending multiple TLVs
+        Error AppendLinkAndMleFrameCounterTlvs(void);
+        Error AppendSourceAddressAndLeaderDataTlvs(void);
+        Error AppendActiveAndPendingTimestampTlvs(void);
+
         Error SendTo(const Ip6::Address &aDestination);
 
     private:

src/core/thread/mle_ftd.cpp

@@ -539,8 +539,7 @@ void Mle::SendAdvertisement(const Ip6::Address &aDestination)
     VerifyOrExit(!mAddressSolicitPending);
 
     VerifyOrExit((message = NewMleMessage(kCommandAdvertisement)) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = message->AppendSourceAddressTlv());
-    SuccessOrExit(error = message->AppendLeaderDataTlv());
+    SuccessOrExit(error = message->AppendSourceAddressAndLeaderDataTlvs());
 
     switch (mRole)
     {
@@ -588,8 +587,7 @@ void Mle::SendLinkRequest(Router *aRouter)
         break;
 
     case kRoleChild:
-        SuccessOrExit(error = message->AppendSourceAddressTlv());
-        SuccessOrExit(error = message->AppendLeaderDataTlv());
+        SuccessOrExit(error = message->AppendSourceAddressAndLeaderDataTlvs());
         break;
 
     case kRoleRouter:
@@ -603,8 +601,7 @@ void Mle::SendLinkRequest(Router *aRouter)
             SuccessOrExit(error = message->AppendTlvRequestTlv(kValidNeighborTlvs));
         }
 
-        SuccessOrExit(error = message->AppendSourceAddressTlv());
-        SuccessOrExit(error = message->AppendLeaderDataTlv());
+        SuccessOrExit(error = message->AppendSourceAddressAndLeaderDataTlvs());
         break;
 
     case kRoleDisabled:
@@ -1800,8 +1797,7 @@ void Mle::SendParentResponse(const ParentResponseInfo &aInfo)
     VerifyOrExit((message = NewMleMessage(kCommandParentResponse)) != nullptr, error = kErrorNoBufs);
     message->SetDirectTransmission();
 
-    SuccessOrExit(error = message->AppendSourceAddressTlv());
-    SuccessOrExit(error = message->AppendLeaderDataTlv());
+    SuccessOrExit(error = message->AppendSourceAddressAndLeaderDataTlvs());
     SuccessOrExit(error = message->AppendLinkAndMleFrameCounterTlvs());
     SuccessOrExit(error = message->AppendResponseTlv(aInfo.mRxChallenge));
 #if OPENTHREAD_CONFIG_TIME_SYNC_ENABLE
@@ -2886,8 +2882,7 @@ Error Mle::SendChildIdResponse(Child &aChild)
     TxMessage   *message;
 
     VerifyOrExit((message = NewMleMessage(kCommandChildIdResponse)) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = message->AppendSourceAddressTlv());
-    SuccessOrExit(error = message->AppendLeaderDataTlv());
+    SuccessOrExit(error = message->AppendSourceAddressAndLeaderDataTlvs());
     SuccessOrExit(error = message->AppendActiveAndPendingTimestampTlvs());
 
     if ((aChild.GetRloc16() == 0) || !HasMatchingRouterIdWith(aChild.GetRloc16()))
@@ -2975,8 +2970,7 @@ Error Mle::SendChildUpdateRequestToChild(Child &aChild)
     Get<MeshForwarder>().RemoveMessagesForChild(aChild, IsMessageChildUpdateRequest);
 
     VerifyOrExit((message = NewMleMessage(kCommandChildUpdateRequest)) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = message->AppendSourceAddressTlv());
-    SuccessOrExit(error = message->AppendLeaderDataTlv());
+    SuccessOrExit(error = message->AppendSourceAddressAndLeaderDataTlvs());
     SuccessOrExit(error = message->AppendNetworkDataTlv(aChild.GetNetworkDataType()));
     SuccessOrExit(error = message->AppendActiveAndPendingTimestampTlvs());
 
@@ -3148,8 +3142,7 @@ void Mle::SendDataResponse(const Ip6::Address &aDestination, const TlvList &aTlv
     }
 
     VerifyOrExit((message = NewMleMessage(kCommandDataResponse)) != nullptr, error = kErrorNoBufs);
-    SuccessOrExit(error = message->AppendSourceAddressTlv());
-    SuccessOrExit(error = message->AppendLeaderDataTlv());
+    SuccessOrExit(error = message->AppendSourceAddressAndLeaderDataTlvs());
     SuccessOrExit(error = message->AppendActiveAndPendingTimestampTlvs());
 
     for (uint8_t tlvType : aTlvList)