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[dns] introduce DecompressRecordData() and use it in mDNS (#11408)

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This commit updates the mDNS `RecordQuerier` to handle record types
where the RDATA contains one or more potentially compressed DNS
names. For these types, the reported record data is now decompressed
to include the full DNS names. This enhancement applies to the
following record types: NS, CNAME, SOA, PTR, MX, RP, AFSDB, RT, PX,
SRV, KX, DNAME, and NSEC.

To achieve this, a helper `ResourceRecord::DecompressRecordData()`
method is introduced. This method uses a "recipe" formula specific
to each supported record type. The recipe defines the number of
prefix bytes before the first embedded name, the number of DNS
names, and the minimum number of suffix bytes after the names. A
common implementation then uses this recipe to parse and decompress
the RDATA. This approach makes the implementation flexible and allows
for easier addition of new record types and formats in the future.

Unit test `test_dns` is updated to validate the newly added method.
This commit is contained in:
Abtin Keshavarzian
2025-04-21 14:29:09 -07:00
committed by GitHub
parent 7536e3c73b
commit 2e73358f9d
6 changed files with 264 additions and 38 deletions
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tests/unit/test_dns.cpp
+93 -25
View File
@@ -1122,7 +1122,7 @@ void TestHeaderAndResourceRecords(void)
kHeaderOffset = 0,
kQuestionCount = 1,
kAnswerCount = 2,
kAdditionalCount = 5,
kAdditionalCount = 6,
kTtl = 7200,
kTxtTtl = 7300,
kSrvPort = 1234,
@@ -1146,30 +1146,34 @@ void TestHeaderAndResourceRecords(void)
const char *kInstanceLabels[] = {kInstance1Label, kInstance2Label};
const char *kInstanceNames[] = {kInstance1Name, kInstance2Name};
Instance *instance;
MessagePool *messagePool;
Message *message;
Dns::Header header;
uint16_t messageId;
uint16_t headerOffset;
uint16_t offset;
uint16_t numRecords;
uint16_t len;
uint16_t serviceNameOffset;
uint16_t hostNameOffset;
uint16_t answerSectionOffset;
uint16_t additionalSectionOffset;
uint16_t index;
Dns::PtrRecord ptrRecord;
Dns::SrvRecord srvRecord;
Dns::TxtRecord txtRecord;
Dns::AaaaRecord aaaaRecord;
Dns::ResourceRecord record;
Ip6::Address hostAddress;
Dns::Name::LabelBuffer label;
Dns::Name::Buffer name;
uint8_t buffer[kMaxSize];
Instance *instance;
MessagePool *messagePool;
Message *message;
Dns::Header header;
uint16_t messageId;
uint16_t headerOffset;
uint16_t offset;
uint16_t numRecords;
uint16_t len;
uint16_t serviceNameOffset;
uint16_t hostNameOffset;
uint16_t answerSectionOffset;
uint16_t additionalSectionOffset;
uint16_t index;
Dns::PtrRecord ptrRecord;
Dns::SrvRecord srvRecord;
Dns::TxtRecord txtRecord;
Dns::AaaaRecord aaaaRecord;
Dns::NsecRecord nsecRecord;
Dns::NsecRecord::TypeBitMap nsecBitmap;
Dns::ResourceRecord record;
Ip6::Address hostAddress;
Dns::Name::LabelBuffer label;
Dns::Name::Buffer name;
uint8_t buffer[kMaxSize];
uint8_t *bytes;
OwnedPtr<Message> dataMsg;
uint16_t dataOffset;
printf("================================================================\n");
printf("TestHeaderAndResourceRecords()\n");
@@ -1259,6 +1263,19 @@ void TestHeaderAndResourceRecords(void)
aaaaRecord.SetAddress(hostAddress);
SuccessOrQuit(message->Append(aaaaRecord));
nsecRecord.Init();
nsecRecord.SetTtl(kTtl);
nsecBitmap.Clear();
nsecBitmap.AddType(Dns::ResourceRecord::kTypeAaaa);
SuccessOrQuit(Dns::Name::AppendPointerLabel(hostNameOffset, *message));
offset = message->GetLength();
SuccessOrQuit(message->Append(nsecRecord));
SuccessOrQuit(Dns::Name::AppendPointerLabel(hostNameOffset, *message));
SuccessOrQuit(message->AppendBytes(&nsecBitmap, nsecBitmap.GetSize()));
nsecRecord.SetLength(message->GetLength() - offset - sizeof(Dns::ResourceRecord));
message->Write(offset, nsecRecord);
// Dump the entire message
VerifyOrQuit(message->GetLength() < kMaxSize, "Message is too long");
@@ -1301,6 +1318,13 @@ void TestHeaderAndResourceRecords(void)
for (const char *instanceLabel : kInstanceLabels)
{
SuccessOrQuit(Dns::Name::CompareName(*message, offset, kServiceName));
SuccessOrQuit(Dns::ResourceRecord::DecompressRecordData(*message, offset, dataMsg));
VerifyOrQuit(dataMsg != nullptr);
dataOffset = 0;
VerifyOrQuit(Dns::Name::CompareName(*dataMsg, dataOffset, kServiceName));
VerifyOrQuit(dataOffset == dataMsg->GetLength());
SuccessOrQuit(Dns::ResourceRecord::ReadRecord(*message, offset, ptrRecord));
VerifyOrQuit(ptrRecord.GetTtl() == kTtl, "Read PTR is incorrect");
@@ -1374,6 +1398,7 @@ void TestHeaderAndResourceRecords(void)
// SRV record
SuccessOrQuit(Dns::Name::CompareName(*message, offset, instanceName));
savedOffset = offset;
SuccessOrQuit(Dns::ResourceRecord::ReadRecord(*message, offset, srvRecord));
VerifyOrQuit(srvRecord.GetTtl() == kTtl);
VerifyOrQuit(srvRecord.GetPort() == kSrvPort);
@@ -1384,8 +1409,24 @@ void TestHeaderAndResourceRecords(void)
printf(" \"%s\" SRV %u %d %d %d %d \"%s\"\n", instanceName, srvRecord.GetTtl(), srvRecord.GetLength(),
srvRecord.GetPort(), srvRecord.GetWeight(), srvRecord.GetPriority(), name);
// SRV record again using `DecompressRecordData()`
dataMsg.Free();
SuccessOrQuit(Dns::ResourceRecord::DecompressRecordData(*message, savedOffset, dataMsg));
VerifyOrQuit(dataMsg != nullptr);
dataOffset = 0;
len = sizeof(Dns::SrvRecord) - sizeof(Dns::ResourceRecord);
bytes = reinterpret_cast<uint8_t *>(&srvRecord);
bytes += sizeof(Dns::ResourceRecord);
VerifyOrQuit(dataMsg->CompareBytes(dataOffset, bytes, len));
dataOffset += len;
SuccessOrQuit(Dns::Name::CompareName(*dataMsg, dataOffset, kHostName));
VerifyOrQuit(dataOffset == dataMsg->GetLength());
// TXT record
SuccessOrQuit(Dns::Name::CompareName(*message, offset, instanceName));
dataMsg.Free();
SuccessOrQuit(Dns::ResourceRecord::DecompressRecordData(*message, offset, dataMsg));
VerifyOrQuit(dataMsg == nullptr);
SuccessOrQuit(Dns::ResourceRecord::ReadRecord(*message, offset, txtRecord));
VerifyOrQuit(txtRecord.GetTtl() == kTxtTtl);
savedOffset = offset;
@@ -1405,13 +1446,34 @@ void TestHeaderAndResourceRecords(void)
VerifyOrQuit(savedOffset == offset);
}
// AAAA record
SuccessOrQuit(Dns::Name::CompareName(*message, offset, kHostName));
dataMsg.Free();
SuccessOrQuit(Dns::ResourceRecord::DecompressRecordData(*message, offset, dataMsg));
VerifyOrQuit(dataMsg == nullptr);
SuccessOrQuit(Dns::ResourceRecord::ReadRecord(*message, offset, aaaaRecord));
VerifyOrQuit(aaaaRecord.GetTtl() == kTtl);
VerifyOrQuit(aaaaRecord.GetAddress() == hostAddress);
printf(" \"%s\" AAAA %u %d \"%s\"\n", kHostName, aaaaRecord.GetTtl(), aaaaRecord.GetLength(),
aaaaRecord.GetAddress().ToString().AsCString());
// NSEC record
SuccessOrQuit(Dns::Name::CompareName(*message, offset, kHostName));
dataMsg.Free();
SuccessOrQuit(Dns::ResourceRecord::DecompressRecordData(*message, offset, dataMsg));
VerifyOrQuit(dataMsg != nullptr);
dataOffset = 0;
SuccessOrQuit(Dns::Name::CompareName(*dataMsg, dataOffset, kHostName));
VerifyOrQuit(dataMsg->CompareBytes(dataOffset, &nsecBitmap, nsecBitmap.GetSize()));
dataOffset += nsecBitmap.GetSize();
VerifyOrQuit(dataOffset == dataMsg->GetLength());
SuccessOrQuit(Dns::ResourceRecord::ReadRecord(*message, offset, record));
VerifyOrQuit(record.GetType() == Dns::ResourceRecord::kTypeNsec);
VerifyOrQuit(nsecBitmap.ContainsType(Dns::ResourceRecord::kTypeAaaa));
printf(" \"%s\" NSEC %u %d bitmap-size:%d\n", kHostName, record.GetTtl(), record.GetLength(),
nsecBitmap.GetSize());
offset += record.GetLength();
VerifyOrQuit(offset == message->GetLength(), "offset is incorrect after additional section parse");
// Use `ParseRecords()` to parse all records
@@ -1451,6 +1513,12 @@ void TestHeaderAndResourceRecords(void)
SuccessOrQuit(Dns::ResourceRecord::ReadRecord(*message, offset, record));
VerifyOrQuit(record.GetType() == Dns::ResourceRecord::kTypeAaaa);
offset += record.GetLength();
SuccessOrQuit(Dns::ResourceRecord::FindRecord(*message, offset, numRecords, Dns::Name(kHostName)));
SuccessOrQuit(Dns::ResourceRecord::ReadRecord(*message, offset, record));
VerifyOrQuit(record.GetType() == Dns::ResourceRecord::kTypeNsec);
offset += record.GetLength();
VerifyOrQuit(offset == message->GetLength(), "offset is incorrect after additional section parse");
printf("Use FindRecord() to search for specific records:\n");