[dns-client] use DecompressRecordData() for broader record type support (openthread#11412)

This commit updates the DNS client to use `DecompressRecordData()`
helper method when processing `QueryRecord()` responses for
arbitrary record types.

This enables decompression of embedded DNS names within the received
record data for a wider range of record types. In particular, name
decompression is now supported for PTR, CNAME, DNAME, NS, SRV, SOA,
MX, RP, AFSDB, RT, PX, KX, and NSEC records.

Author: abtink

include/openthread/dns_client.h

@@ -760,11 +760,11 @@ otError otDnsRecordResponseGetQueryName(const otDnsRecordResponse *aResponse,
  * - The data is copied into `mDataBuffer` (if not `NULL`) up to its capacity specified by `mDataBufferSize`.
  * - `mDataBufferSize` is then updated to reflect the number of bytes actually written into `mDataBuffer`.
  *
- * If the retrieved record type is PTR (12), CNAME (5), DNAME (39), NS (2), or SRV (33), the record data in the
- * received response contains a DNS name which may use DNS name compression. For these specific record types, the
- * record data is first decompressed such that it contains the full uncompressed DNS name. This decompressed data is
- * then provided in `mDataBuffer`, and `mRecordDataLength` will indicate the length of this decompressed data. For all
- * other record types, the record data is read and provided as it appears in the received response message.
+ * If the retrieved record type is NS, CNAME, SOA, PTR, MX, RP, AFSDB, RT, PX, SRV, KX, DNAME, or NSEC, the record
+ * data in the received response contains a DNS name which may use DNS name compression. For these specific record
+ * types, the record data is first decompressed such that it contains the full uncompressed DNS name. This decompressed
+ * data is then provided in `mDataBuffer`, and `mRecordDataLength` will indicate the length of this decompressed data.
+ * For all other record types, the record data is read and provided as it appears in the received response message.
  *
  * @param[in]  aResponse       A pointer to the response.
  * @param[in]  aIndex          The record index to retrieve.
@@ -774,7 +774,7 @@ otError otDnsRecordResponseGetQueryName(const otDnsRecordResponse *aResponse,
  * @retval OT_ERROR_NOT_FOUND  No record in @p aResponse at @p aIndex.
  * @retval OT_ERROR_PARSE      Could not parse the records in the @p aResponse.
  * @retval OT_ERROR_NO_BUFS    The record name does not fit in the provided `mNameBufferSize` in @p aRecordInfo, or
- *                             failed to allocate buffer to decompress a compressed DNS name (PTR, SRV, CNAME).
+ *                             failed to allocate buffer to decompress a compressed DNS name.
  */
 otError otDnsRecordResponseGetRecordInfo(const otDnsRecordResponse *aResponse,
                                          uint16_t                   aIndex,

include/openthread/instance.h

@@ -52,7 +52,7 @@ extern "C" {
  *
  * @note This number versions both OpenThread platform and user APIs.
  */
-#define OPENTHREAD_API_VERSION (501)
+#define OPENTHREAD_API_VERSION (502)
 
 /**
  * @addtogroup api-instance

src/core/net/dns_client.cpp

@@ -378,10 +378,10 @@ Error Client::Response::ReadTxtRecord(Section aSection, const Name &aName, Servi
 
 Error Client::Response::ReadRecordInfo(uint16_t aIndex, RecordInfo &aRecordInfo) const
 {
-    Error          error;
-    uint16_t       offset;
-    ResourceRecord record;
-    Message       *decompressedData = nullptr;
+    Error             error;
+    uint16_t          offset;
+    ResourceRecord    record;
+    OwnedPtr<Message> decompressedData;
 
     if (aIndex < mAnswerRecordCount)
     {
@@ -406,43 +406,12 @@ Error Client::Response::ReadRecordInfo(uint16_t aIndex, RecordInfo &aRecordInfo)
     SuccessOrExit(error = Name::ReadName(*mMessage, offset, aRecordInfo.mNameBuffer, aRecordInfo.mNameBufferSize));
 
     SuccessOrExit(error = mMessage->Read(offset, record));
-    VerifyOrExit(offset + record.GetSize() <= mMessage->GetLength(), error = kErrorParse);
-    offset += sizeof(record);
 
-    aRecordInfo.mRecordType = record.GetType();
-    aRecordInfo.mTtl        = record.GetTtl();
-
-    // We may need to translate the record data for PTR, CNAME, DNAME, NS
-    // and SRV record since the data format contains a DNS name which
-    // may use compression.
-
-    switch (record.GetType())
-    {
-    case ResourceRecord::kTypePtr:
-    case ResourceRecord::kTypeCname:
-    case ResourceRecord::kTypeDname:
-    case ResourceRecord::kTypeNs:
-    case ResourceRecord::kTypeSrv:
-        decompressedData = mMessage->Get<MessagePool>().Allocate(Message::kTypeOther);
-        VerifyOrExit(decompressedData != nullptr, error = kErrorNoBufs);
-
-        if (record.GetType() == ResourceRecord::kTypeSrv)
-        {
-            uint16_t srvMinLength = sizeof(SrvRecord) - sizeof(ResourceRecord);
-
-            VerifyOrExit(record.GetLength() > srvMinLength, error = kErrorParse);
-            SuccessOrExit(error = decompressedData->AppendBytesFromMessage(*mMessage, offset, srvMinLength));
-            offset += srvMinLength;
-        }
-
-        SuccessOrExit(error = Name(*mMessage, offset).AppendTo(*decompressedData));
-        break;
-
-    default:
-        break;
-    }
+    SuccessOrExit(error = ResourceRecord::DecompressRecordData(*mMessage, offset, decompressedData));
 
+    aRecordInfo.mRecordType   = record.GetType();
     aRecordInfo.mRecordLength = (decompressedData != nullptr) ? decompressedData->GetLength() : record.GetLength();
+    aRecordInfo.mTtl          = record.GetTtl();
 
     if (aRecordInfo.mDataBuffer == nullptr)
     {
@@ -458,11 +427,10 @@ Error Client::Response::ReadRecordInfo(uint16_t aIndex, RecordInfo &aRecordInfo)
     }
     else
     {
-        mMessage->ReadBytes(offset, aRecordInfo.mDataBuffer, aRecordInfo.mDataBufferSize);
+        mMessage->ReadBytes(offset + sizeof(ResourceRecord), aRecordInfo.mDataBuffer, aRecordInfo.mDataBufferSize);
     }
 
 exit:
-    FreeMessage(decompressedData);
     return error;
 }