[mle] simplify parsing of Address Registration TLV entries (#8963)

This commit adds `ProcessAddressRegistrationTlv()` method which
finds an Address Registration TLV in a received MLE messages from
a child and processes its entries updating the child's registered
addresses.

src/core/thread/mle_router.cpp

@@ -1785,26 +1785,28 @@ exit:
 }
 #endif
 
-Error MleRouter::UpdateChildAddresses(const Message &aMessage, uint16_t aOffset, uint16_t aLength, Child &aChild)
+Error MleRouter::ProcessAddressRegistrationTlv(RxInfo &aRxInfo, Child &aChild)
 {
-    Error                    error = kErrorNone;
+    Error    error;
-    AddressRegistrationEntry entry;
+    uint16_t offset;
-    Ip6::Address             address;
+    uint16_t length;
-    Lowpan::Context          context;
+    uint16_t endOffset;
-    uint8_t                  registeredCount = 0;
+    uint8_t  count       = 0;
-    uint8_t                  storedCount     = 0;
+    uint8_t  storedCount = 0;
-    uint16_t                 end             = aOffset + aLength;
 #if OPENTHREAD_CONFIG_TMF_PROXY_DUA_ENABLE
     Ip6::Address        oldDua;
     const Ip6::Address *oldDuaPtr = nullptr;
     bool                hasDua    = false;
 #endif
-
 #if OPENTHREAD_CONFIG_TMF_PROXY_MLR_ENABLE
     Ip6::Address oldMlrRegisteredAddresses[kMaxChildIpAddresses - 1];
     uint16_t     oldMlrRegisteredAddressNum = 0;
 #endif
 
+    SuccessOrExit(error = Tlv::FindTlvValueOffset(aRxInfo.mMessage, Tlv::kAddressRegistration, offset, length));
+
+    endOffset = offset + length;
+
 #if OPENTHREAD_CONFIG_TMF_PROXY_DUA_ENABLE
     if ((oldDuaPtr = aChild.GetDomainUnicastAddress()) != nullptr)
     {
@@ -1831,36 +1833,47 @@ Error MleRouter::UpdateChildAddresses(const Message &aMessage, uint16_t aOffset,
 
     aChild.ClearIp6Addresses();
 
-    while (aOffset < end)
+    while (offset < endOffset)
     {
-        uint8_t len;
+        uint8_t      controlByte;
+        Ip6::Address address;
 
-        // read out the control field
+        // Read out the control byte (first byte in entry)
-        SuccessOrExit(error = aMessage.Read(aOffset, &entry, sizeof(uint8_t)));
+        SuccessOrExit(error = aRxInfo.mMessage.Read(offset, controlByte));
+        offset++;
+        count++;
 
-        len = entry.GetLength();
+        address.Clear();
 
-        SuccessOrExit(error = aMessage.Read(aOffset, &entry, len));
+        if (AddressRegistrationTlv::IsEntryCompressed(controlByte))
-
-        aOffset += len;
-        registeredCount++;
-
-        if (entry.IsCompressed())
         {
-            if (Get<NetworkData::Leader>().GetContext(entry.GetContextId(), context) != kErrorNone)
+            // Compressed entry contains IID with the 64-bit prefix
+            // determined from 6LoWPAN context identifier (from
+            // the control byte).
+
+            uint8_t         contextId = AddressRegistrationTlv::GetContextId(controlByte);
+            Lowpan::Context context;
+
+            VerifyOrExit(offset + sizeof(Ip6::InterfaceIdentifier) <= endOffset, error = kErrorParse);
+            IgnoreError(aRxInfo.mMessage.Read(offset, address.GetIid()));
+            offset += sizeof(Ip6::InterfaceIdentifier);
+
+            if (Get<NetworkData::Leader>().GetContext(contextId, context) != kErrorNone)
             {
-                LogWarn("Failed to get context %u for compressed address from child 0x%04x", entry.GetContextId(),
+                LogWarn("Failed to get context %u for compressed address from child 0x%04x", contextId,
                         aChild.GetRloc16());
                 continue;
             }
 
-            address.Clear();
             address.SetPrefix(context.mPrefix);
-            address.SetIid(entry.GetIid());
         }
         else
         {
-            address = entry.GetIp6Address();
+            // Uncompressed entry contains the full IPv6 address.
+
+            VerifyOrExit(offset + sizeof(Ip6::Address) <= endOffset, error = kErrorParse);
+            IgnoreError(aRxInfo.mMessage.Read(offset, address));
+            offset += sizeof(Ip6::Address);
         }
 
 #if OPENTHREAD_CONFIG_REFERENCE_DEVICE_ENABLE
@@ -1956,14 +1969,14 @@ Error MleRouter::UpdateChildAddresses(const Message &aMessage, uint16_t aOffset,
     Get<MlrManager>().UpdateProxiedSubscriptions(aChild, oldMlrRegisteredAddresses, oldMlrRegisteredAddressNum);
 #endif
 
-    if (registeredCount == 0)
+    if (count == 0)
     {
         LogInfo("Child 0x%04x has no registered IPv6 address", aChild.GetRloc16());
     }
     else
     {
-        LogInfo("Child 0x%04x has %u registered IPv6 address%s, %u address%s stored", aChild.GetRloc16(),
+        LogInfo("Child 0x%04x has %u registered IPv6 address%s, %u address%s stored", aChild.GetRloc16(), count,
-                registeredCount, (registeredCount == 1) ? "" : "es", storedCount, (storedCount == 1) ? "" : "es");
+                (count == 1) ? "" : "es", storedCount, (storedCount == 1) ? "" : "es");
     }
 
     error = kErrorNone;
@@ -2088,11 +2101,7 @@ void MleRouter::HandleChildIdRequest(RxInfo &aRxInfo)
 
     if (!mode.IsFullThreadDevice())
     {
-        uint16_t offset;
+        SuccessOrExit(error = ProcessAddressRegistrationTlv(aRxInfo, *child));
-        uint16_t length;
-
-        SuccessOrExit(error = Tlv::FindTlvValueOffset(aRxInfo.mMessage, Tlv::kAddressRegistration, offset, length));
-        SuccessOrExit(error = UpdateChildAddresses(aRxInfo.mMessage, offset, length, *child));
     }
 
     // Remove from router table
@@ -2182,8 +2191,6 @@ void MleRouter::HandleChildUpdateRequest(RxInfo &aRxInfo)
     DeviceMode      oldMode;
     TlvList         requestedTlvList;
     TlvList         tlvList;
-    uint16_t        addrOffset;
-    uint16_t        addrLength;
     bool            childDidChange = false;
 
     Log(kMessageReceive, kTypeChildUpdateRequestOfChild, aRxInfo.mMessageInfo.GetPeerAddr());
@@ -2246,10 +2253,15 @@ void MleRouter::HandleChildUpdateRequest(RxInfo &aRxInfo)
     }
 
     // IPv6 Address TLV
-    if (Tlv::FindTlvValueOffset(aRxInfo.mMessage, Tlv::kAddressRegistration, addrOffset, addrLength) == kErrorNone)
+    switch (ProcessAddressRegistrationTlv(aRxInfo, *child))
     {
-        SuccessOrExit(error = UpdateChildAddresses(aRxInfo.mMessage, addrOffset, addrLength, *child));
+    case kErrorNone:
         tlvList.Add(Tlv::kAddressRegistration);
+        break;
+    case kErrorNotFound:
+        break;
+    default:
+        ExitNow(error = kErrorParse);
     }
 
     // Leader Data
@@ -2404,8 +2416,6 @@ void MleRouter::HandleChildUpdateResponse(RxInfo &aRxInfo)
     uint32_t   mleFrameCounter;
     LeaderData leaderData;
     Child     *child;
-    uint16_t   addrOffset;
-    uint16_t   addrLength;
 
     if ((aRxInfo.mNeighbor == nullptr) || IsActiveRouter(aRxInfo.mNeighbor->GetRloc16()) ||
         !Get<ChildTable>().Contains(*aRxInfo.mNeighbor))
@@ -2517,9 +2527,13 @@ void MleRouter::HandleChildUpdateResponse(RxInfo &aRxInfo)
     }
 
     // IPv6 Address
-    if (Tlv::FindTlvValueOffset(aRxInfo.mMessage, Tlv::kAddressRegistration, addrOffset, addrLength) == kErrorNone)
+    switch (ProcessAddressRegistrationTlv(aRxInfo, *child))
     {
-        SuccessOrExit(error = UpdateChildAddresses(aRxInfo.mMessage, addrOffset, addrLength, *child));
+    case kErrorNone:
+    case kErrorNotFound:
+        break;
+    default:
+        ExitNow(error = kErrorParse);
     }
 
     // Leader Data

src/core/thread/mle_router.hpp

@@ -630,6 +630,7 @@ private:
     void  SetStateRouterOrLeader(DeviceRole aRole, uint16_t aRloc16, LeaderStartMode aStartMode);
     void  StopLeader(void);
     void  SynchronizeChildNetworkData(void);
+    Error ProcessAddressRegistrationTlv(RxInfo &aRxInfo, Child &aChild);
     Error UpdateChildAddresses(const Message &aMessage, uint16_t aOffset, uint16_t aLength, Child &aChild);
     bool  HasNeighborWithGoodLinkQuality(void) const;
 

src/core/thread/mle_tlvs.hpp

@@ -999,6 +999,27 @@ public:
      */
     static uint8_t ControlByteFor(uint8_t aContextId) { return kCompressed | (aContextId & kContextIdMask); }
 
+    /**
+     * This static method indicates whether or not an address entry is using compressed format.
+     *
+     * @param[in] aControlByte  The control byte (the first byte in the entry).
+     *
+     * @retval TRUE   If the entry uses compressed format.
+     * @retval FALSE  If the entry uses uncompressed format.
+     *
+     */
+    static bool IsEntryCompressed(uint8_t aControlByte) { return (aControlByte & kCompressed); }
+
+    /**
+     * This static method gets the context ID in a compressed entry.
+     *
+     * @param[in] aControlByte  The control byte (the first byte in the entry).
+     *
+     * @returns The 6LoWPAN context ID.
+     *
+     */
+    static uint8_t GetContextId(uint8_t aControlByte) { return (aControlByte & kContextIdMask); }
+
     AddressRegistrationTlv(void) = delete;
 
 private:
@@ -1006,98 +1027,6 @@ private:
     static constexpr uint8_t kContextIdMask = 0xf;
 };
 
-/**
- * This class implements Address Registration Entry generation and parsing.
- *
- */
-OT_TOOL_PACKED_BEGIN
-class AddressRegistrationEntry
-{
-public:
-    /**
-     * This method returns the IPv6 address or IID length.
-     *
-     * @returns The IPv6 address length if the Compressed bit is clear, or the IID length if the Compressed bit is
-     *          set.
-     *
-     */
-    uint8_t GetLength(void) const { return sizeof(mControl) + (IsCompressed() ? sizeof(mIid) : sizeof(mIp6Address)); }
-
-    /**
-     * This method indicates whether or not the Compressed flag is set.
-     *
-     * @retval TRUE   If the Compressed flag is set.
-     * @retval FALSE  If the Compressed flag is not set.
-     *
-     */
-    bool IsCompressed(void) const { return (mControl & kCompressed) != 0; }
-
-    /**
-     * This method sets the Uncompressed flag.
-     *
-     */
-    void SetUncompressed(void) { mControl = 0; }
-
-    /**
-     * This method returns the Context ID for the compressed form.
-     *
-     * @returns The Context ID value.
-     *
-     */
-    uint8_t GetContextId(void) const { return mControl & kCidMask; }
-
-    /**
-     * This method sets the Context ID value.
-     *
-     * @param[in]  aContextId  The Context ID value.
-     *
-     */
-    void SetContextId(uint8_t aContextId) { mControl = kCompressed | aContextId; }
-
-    /**
-     * This method returns the IID value.
-     *
-     * @returns The IID value.
-     *
-     */
-    const Ip6::InterfaceIdentifier &GetIid(void) const { return mIid; }
-
-    /**
-     * This method sets the IID value.
-     *
-     * @param[in]  aIid  The IID value.
-     *
-     */
-    void SetIid(const Ip6::InterfaceIdentifier &aIid) { mIid = aIid; }
-
-    /**
-     * This method returns the IPv6 Address value.
-     *
-     * @returns The IPv6 Address value.
-     *
-     */
-    const Ip6::Address &GetIp6Address(void) const { return mIp6Address; }
-
-    /**
-     * This method sets the IPv6 Address value.
-     *
-     * @param[in]  aAddress  A reference to the IPv6 Address value.
-     *
-     */
-    void SetIp6Address(const Ip6::Address &aAddress) { mIp6Address = aAddress; }
-
-private:
-    static constexpr uint8_t kCompressed = 1 << 7;
-    static constexpr uint8_t kCidMask    = 0xf;
-
-    uint8_t mControl;
-    union
-    {
-        Ip6::InterfaceIdentifier mIid;
-        Ip6::Address             mIp6Address;
-    } OT_TOOL_PACKED_FIELD;
-} OT_TOOL_PACKED_END;
-
 /**
  * This class implements Channel TLV generation and parsing.
  *