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[mdns] update 'TxtEntry' to handle boolean attribute
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This commit updates `TxtEntry`, `EncodeTxtData()`, and `DecodeTxtData()`
to support boolean attributes, which are encoded as `key` string
without the `=` character. It also ensures that `EncodeTxtData()`
will generate valid TXT data (containing a single zero byte) when
given an empty `TxtList`. Additionally, this commit updates
`AdvertisingProxy::MakeTxtList()` to use `DecodeTxtData()`, and adds
a test to validate the encoder and decoder behavior.
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@abtink
abtink committed Sep 5, 2023
1 parent 0cd0b9a commit d419073
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Showing 7 changed files with 154 additions and 50 deletions.
7 changes: 4 additions & 3 deletions src/border_agent/border_agent.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -343,10 +343,11 @@ void AppendVendorTxtEntries(const std::map<std::string, std::vector<uint8_t>> &a

for (auto &addedEntry : aTxtList)
{
if (addedEntry.mName == key)
if (addedEntry.mKey == key)
{
addedEntry.mValue = value;
found = true;
addedEntry.mValue = value;
addedEntry.mIsBooleanAttribute = false;
found = true;
break;
}
}
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54 changes: 38 additions & 16 deletions src/mdns/mdns.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -99,18 +99,32 @@ otbrError Publisher::EncodeTxtData(const TxtList &aTxtList, std::vector<uint8_t>
{
otbrError error = OTBR_ERROR_NONE;

for (const auto &txtEntry : aTxtList)
aTxtData.clear();

for (const TxtEntry &txtEntry : aTxtList)
{
const auto &name = txtEntry.mName;
const auto &value = txtEntry.mValue;
const size_t entryLength = name.length() + 1 + value.size();
size_t entryLength = txtEntry.mKey.length();

if (!txtEntry.mIsBooleanAttribute)
{
entryLength += txtEntry.mValue.size() + sizeof(uint8_t); // for `=` char.
}

VerifyOrExit(entryLength <= kMaxTextEntrySize, error = OTBR_ERROR_INVALID_ARGS);

aTxtData.push_back(static_cast<uint8_t>(entryLength));
aTxtData.insert(aTxtData.end(), name.begin(), name.end());
aTxtData.push_back('=');
aTxtData.insert(aTxtData.end(), value.begin(), value.end());
aTxtData.insert(aTxtData.end(), txtEntry.mKey.begin(), txtEntry.mKey.end());

if (!txtEntry.mIsBooleanAttribute)
{
aTxtData.push_back('=');
aTxtData.insert(aTxtData.end(), txtEntry.mValue.begin(), txtEntry.mValue.end());
}
}

if (aTxtData.empty())
{
aTxtData.push_back(0);
}

exit:
Expand All @@ -121,30 +135,39 @@ otbrError Publisher::DecodeTxtData(Publisher::TxtList &aTxtList, const uint8_t *
{
otbrError error = OTBR_ERROR_NONE;

aTxtList.clear();

for (uint16_t r = 0; r < aTxtLength;)
{
uint16_t entrySize = aTxtData[r];
uint16_t keyStart = r + 1;
uint16_t entryEnd = keyStart + entrySize;
uint16_t keyEnd = keyStart;
uint16_t valStart;

VerifyOrExit(entryEnd <= aTxtLength, error = OTBR_ERROR_PARSE);

while (keyEnd < entryEnd && aTxtData[keyEnd] != '=')
{
keyEnd++;
}

valStart = keyEnd;
if (valStart < entryEnd && aTxtData[valStart] == '=')
if (keyEnd == entryEnd)
{
valStart++;
if (keyEnd > keyStart)
{
// No `=`, treat as a boolean attribute.
aTxtList.emplace_back(reinterpret_cast<const char *>(&aTxtData[keyStart]), keyEnd - keyStart);
}
}
else
{
uint16_t valStart = keyEnd + 1; // To skip over `=`

aTxtList.emplace_back(reinterpret_cast<const char *>(&aTxtData[keyStart]), keyEnd - keyStart,
&aTxtData[valStart], entryEnd - valStart);
aTxtList.emplace_back(reinterpret_cast<const char *>(&aTxtData[keyStart]), keyEnd - keyStart,
&aTxtData[valStart], entryEnd - valStart);
}

r += entrySize + 1;
VerifyOrExit(r <= aTxtLength, error = OTBR_ERROR_PARSE);
}

exit:
Expand Down Expand Up @@ -260,7 +283,7 @@ Publisher::SubTypeList Publisher::SortSubTypeList(SubTypeList aSubTypeList)
Publisher::TxtList Publisher::SortTxtList(TxtList aTxtList)
{
std::sort(aTxtList.begin(), aTxtList.end(),
[](const TxtEntry &aLhs, const TxtEntry &aRhs) { return aLhs.mName < aRhs.mName; });
[](const TxtEntry &aLhs, const TxtEntry &aRhs) { return aLhs.mKey < aRhs.mKey; });
return aTxtList;
}

Expand Down Expand Up @@ -577,5 +600,4 @@ void Publisher::UpdateHostResolutionEmaLatency(const std::string &aHostName, otb
}

} // namespace Mdns

} // namespace otbr
39 changes: 28 additions & 11 deletions src/mdns/mdns.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -70,31 +70,48 @@ class Publisher : private NonCopyable
{
public:
/**
* This structure represents a name/value pair of the TXT record.
* This structure represents a key/value pair of the TXT record.
*
*/
struct TxtEntry
{
std::string mName; ///< The name of the TXT entry.
std::vector<uint8_t> mValue; ///< The value of the TXT entry.
std::string mKey; ///< The key of the TXT entry.
std::vector<uint8_t> mValue; ///< The value of the TXT entry. Can be empty.
bool mIsBooleanAttribute; ///< This entry is boolean attribute (encoded as `key` without `=`).

TxtEntry(const char *aName, const char *aValue)
: TxtEntry(aName, reinterpret_cast<const uint8_t *>(aValue), strlen(aValue))
TxtEntry(const char *aKey, const char *aValue)
: TxtEntry(aKey, reinterpret_cast<const uint8_t *>(aValue), strlen(aValue))
{
}

TxtEntry(const char *aName, const uint8_t *aValue, size_t aValueLength)
: TxtEntry(aName, strlen(aName), aValue, aValueLength)
TxtEntry(const char *aKey, const uint8_t *aValue, size_t aValueLength)
: TxtEntry(aKey, strlen(aKey), aValue, aValueLength)
{
}

TxtEntry(const char *aName, size_t aNameLength, const uint8_t *aValue, size_t aValueLength)
: mName(aName, aNameLength)
TxtEntry(const char *aKey, size_t aKeyLength, const uint8_t *aValue, size_t aValueLength)
: mKey(aKey, aKeyLength)
, mValue(aValue, aValue + aValueLength)
, mIsBooleanAttribute(false)
{
}

bool operator==(const TxtEntry &aOther) const { return mName == aOther.mName && mValue == aOther.mValue; }
TxtEntry(const char *aKey)
: TxtEntry(aKey, strlen(aKey))
{
}

TxtEntry(const char *aKey, size_t aKeyLength)
: mKey(aKey, aKeyLength)
, mIsBooleanAttribute(true)
{
}

bool operator==(const TxtEntry &aOther) const
{
return (mKey == aOther.mKey) && (mValue == aOther.mValue) &&
(mIsBooleanAttribute == aOther.mIsBooleanAttribute);
}
};

typedef std::vector<TxtEntry> TxtList;
Expand Down Expand Up @@ -356,7 +373,7 @@ class Publisher : private NonCopyable
* See RFC 6763 for details: https://tools.ietf.org/html/rfc6763#section-6.
*
* @param[in] aTxtList A TXT entry list.
* @param[out] aTxtData A TXT data buffer.
* @param[out] aTxtData A TXT data buffer. Will be cleared.
*
* @retval OTBR_ERROR_NONE Successfully write the TXT entry list.
* @retval OTBR_ERROR_INVALID_ARGS The @p aTxtList includes invalid TXT entry.
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32 changes: 22 additions & 10 deletions src/mdns/mdns_avahi.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -803,24 +803,36 @@ otbrError PublisherAvahi::TxtListToAvahiStringList(const TxtList &aTxtList,
aHead = nullptr;
for (const auto &txtEntry : aTxtList)
{
const char *name = txtEntry.mName.c_str();
size_t nameLength = txtEntry.mName.length();
const char *key = txtEntry.mKey.c_str();
size_t keyLength = txtEntry.mKey.length();
const uint8_t *value = txtEntry.mValue.data();
size_t valueLength = txtEntry.mValue.size();
// +1 for the size of "=", avahi doesn't need '\0' at the end of the entry
size_t needed = sizeof(AvahiStringList) - sizeof(AvahiStringList::text) + nameLength + valueLength + 1;
size_t needed = sizeof(AvahiStringList) - sizeof(AvahiStringList::text) + keyLength;
const uint8_t *next;

if (!txtEntry.mIsBooleanAttribute)
{
needed += valueLength + 1; // +1 is for `=` character.
}

VerifyOrExit(used + needed <= aBufferSize, error = OTBR_ERROR_INVALID_ARGS);
curr->next = last;
last = curr;
memcpy(curr->text, name, nameLength);
curr->text[nameLength] = '=';
memcpy(curr->text + nameLength + 1, value, valueLength);
curr->size = nameLength + valueLength + 1;
memcpy(curr->text, key, keyLength);

if (!txtEntry.mIsBooleanAttribute)
{
const uint8_t *next = curr->text + curr->size;
curr = OTBR_ALIGNED(next, AvahiStringList *);
curr->text[keyLength] = '=';
memcpy(curr->text + keyLength + 1, value, valueLength);
curr->size = keyLength + valueLength + 1;
}
else
{
curr->size = keyLength;
}

next = curr->text + curr->size;
curr = OTBR_ALIGNED(next, AvahiStringList *);
used = static_cast<size_t>(reinterpret_cast<uint8_t *>(curr) - reinterpret_cast<uint8_t *>(aBuffer));
}
SuccessOrExit(error);
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10 changes: 1 addition & 9 deletions src/sdp_proxy/advertising_proxy.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -342,18 +342,10 @@ Mdns::Publisher::TxtList AdvertisingProxy::MakeTxtList(const otSrpServerService
{
const uint8_t *txtData;
uint16_t txtDataLength = 0;
otDnsTxtEntryIterator iterator;
otDnsTxtEntry txtEntry;
Mdns::Publisher::TxtList txtList;

txtData = otSrpServerServiceGetTxtData(aSrpService, &txtDataLength);

otDnsInitTxtEntryIterator(&iterator, txtData, txtDataLength);

while (otDnsGetNextTxtEntry(&iterator, &txtEntry) == OT_ERROR_NONE)
{
txtList.emplace_back(txtEntry.mKey, txtEntry.mValue, txtEntry.mValueLength);
}
Mdns::Publisher::DecodeTxtData(txtList, txtData, txtDataLength);

return txtList;
}
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7 changes: 6 additions & 1 deletion src/trel_dnssd/trel_dnssd.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -495,7 +495,12 @@ void TrelDnssd::Peer::ReadExtAddrFromTxtData(void)

for (const auto &txtEntry : txtEntries)
{
if (StringUtils::EqualCaseInsensitive(txtEntry.mName, kTxtRecordExtAddressKey))
if (txtEntry.mIsBooleanAttribute)
{
continue;
}

if (StringUtils::EqualCaseInsensitive(txtEntry.mKey, kTxtRecordExtAddressKey))
{
VerifyOrExit(txtEntry.mValue.size() == sizeof(mExtAddr));

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55 changes: 55 additions & 0 deletions tests/mdns/main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -410,10 +410,65 @@ otbrError TestStopService(void)
return ret;
}

otbrError CheckTxtDataEncoderDecoder(void)
{
otbrError error = OTBR_ERROR_NONE;
Mdns::Publisher::TxtList txtList;
Mdns::Publisher::TxtList parsedTxtList;
std::vector<uint8_t> txtData;

// Encode empty `TxtList`

SuccessOrExit(error = Mdns::Publisher::EncodeTxtData(txtList, txtData));
VerifyOrExit(txtData.size() == 1, error = OTBR_ERROR_PARSE);
VerifyOrExit(txtData[0] == 0, error = OTBR_ERROR_PARSE);

SuccessOrExit(error = Mdns::Publisher::DecodeTxtData(parsedTxtList, txtData.data(), txtData.size()));
VerifyOrExit(parsedTxtList.size() == 0, error = OTBR_ERROR_PARSE);

// TxtList with one bool attribute

txtList.clear();
txtList.emplace_back("b1");

SuccessOrExit(error = Mdns::Publisher::EncodeTxtData(txtList, txtData));
SuccessOrExit(error = Mdns::Publisher::DecodeTxtData(parsedTxtList, txtData.data(), txtData.size()));
VerifyOrExit(parsedTxtList == txtList, error = OTBR_ERROR_PARSE);

// TxtList with one one key/value

txtList.clear();
txtList.emplace_back("k1", "v1");

SuccessOrExit(error = Mdns::Publisher::EncodeTxtData(txtList, txtData));
SuccessOrExit(error = Mdns::Publisher::DecodeTxtData(parsedTxtList, txtData.data(), txtData.size()));
VerifyOrExit(parsedTxtList == txtList, error = OTBR_ERROR_PARSE);

// TxtList with multiple entries

txtList.clear();
txtList.emplace_back("k1", "v1");
txtList.emplace_back("b1");
txtList.emplace_back("b2");
txtList.emplace_back("k2", "valu2");

SuccessOrExit(error = Mdns::Publisher::EncodeTxtData(txtList, txtData));
SuccessOrExit(error = Mdns::Publisher::DecodeTxtData(parsedTxtList, txtData.data(), txtData.size()));
VerifyOrExit(parsedTxtList == txtList, error = OTBR_ERROR_PARSE);

exit:
return error;
}

int main(int argc, char *argv[])
{
int ret = 0;

if (CheckTxtDataEncoderDecoder() != OTBR_ERROR_NONE)
{
return 1;
}

if (argc < 2)
{
return 1;
Expand Down

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