[trel] introduce Trel::PeerDiscoverer class (openthread#11493)

This commit introduces `PeerDiscoverer` as a class responsible for
TREL peer discovery, separating this logic from `Trel::Interface`.
The new class currently handles the preparation of TXT data, calling
the platform API to register the TREL service, and handling callbacks
from the platform layer with newly discovered or updated peer
information.

This separation helps with TREL module organization and enables future
extensions, such as performing discovery using the native OpenThread
mDNS module or the platform-specific DNS-SD (`otPlatDnssd`) module,
in addition to the existing approach where discovery is delegated to
the platform layer.

Author: abtink

src/core/BUILD.gn

@@ -619,6 +619,8 @@ openthread_core_files = [
   "radio/trel_packet.hpp",
   "radio/trel_peer.cpp",
   "radio/trel_peer.hpp",
+  "radio/trel_peer_discoverer.cpp",
+  "radio/trel_peer_discoverer.hpp",
   "thread/address_resolver.cpp",
   "thread/address_resolver.hpp",
   "thread/announce_begin_server.cpp",

src/core/CMakeLists.txt

@@ -204,6 +204,7 @@ set(COMMON_SOURCES
     radio/trel_link.cpp
     radio/trel_packet.cpp
     radio/trel_peer.cpp
+    radio/trel_peer_discoverer.cpp
     thread/address_resolver.cpp
     thread/announce_begin_server.cpp
     thread/announce_sender.cpp

src/core/instance/instance.hpp

@@ -801,6 +801,8 @@ template <> inline Trel::Link &Instance::Get(void) { return mMac.mLinks.mTrel; }
 template <> inline Trel::Interface &Instance::Get(void) { return mMac.mLinks.mTrel.mInterface; }
 
 template <> inline Trel::PeerTable &Instance::Get(void) { return mMac.mLinks.mTrel.mPeerTable; }
+
+template <> inline Trel::PeerDiscoverer &Instance::Get(void) { return mMac.mLinks.mTrel.mPeerDiscoverer; }
 #endif
 
 #if OPENTHREAD_CONFIG_MAC_FILTER_ENABLE

src/core/radio/trel_interface.cpp

@@ -41,15 +41,11 @@ namespace Trel {
 
 RegisterLogModule("TrelInterface");
 
-const char Interface::kTxtRecordExtAddressKey[] = "xa";
-const char Interface::kTxtRecordExtPanIdKey[]   = "xp";
-
 Interface::Interface(Instance &aInstance)
     : InstanceLocator(aInstance)
     , mInitialized(false)
     , mEnabled(false)
     , mFiltered(false)
-    , mRegisterServiceTask(aInstance)
 {
 }
 
@@ -86,9 +82,9 @@ void Interface::Enable(void)
     VerifyOrExit(mInitialized);
 
     otPlatTrelEnable(&GetInstance(), &mUdpPort);
+    Get<PeerDiscoverer>().Start();
 
     LogInfo("Enabled interface, local port:%u", mUdpPort);
-    mRegisterServiceTask.Post();
 
 exit:
     return;
@@ -102,188 +98,14 @@ void Interface::Disable(void)
     VerifyOrExit(mInitialized);
 
     otPlatTrelDisable(&GetInstance());
-    Get<PeerTable>().Clear();
-    LogDebg("Disabled interface");
-
-exit:
-    return;
-}
-
-void Interface::NotifyPeerSocketAddressDifference(const Ip6::SockAddr &aPeerSockAddr, const Ip6::SockAddr &aRxSockAddr)
-{
-    otPlatTrelNotifyPeerSocketAddressDifference(&GetInstance(), &aPeerSockAddr, &aRxSockAddr);
-}
-
-void Interface::HandleExtAddressChange(void)
-{
-    VerifyOrExit(mInitialized && mEnabled);
-    LogDebg("Extended Address changed, re-registering DNS-SD service");
-    mRegisterServiceTask.Post();
-
-exit:
-    return;
-}
-
-void Interface::HandleExtPanIdChange(void)
-{
-    VerifyOrExit(mInitialized && mEnabled);
-    LogDebg("Extended PAN ID changed, re-registering DNS-SD service");
-    mRegisterServiceTask.Post();
-
-exit:
-    return;
-}
-
-void Interface::RegisterService(void)
-{
-    // TXT data consists of two entries: the length fields, the
-    // "key" string, "=" char, and binary representation of the MAC
-    // or Extended PAN ID values.
-    static constexpr uint8_t kTxtDataSize =
-        /* ExtAddr  */ sizeof(uint8_t) + sizeof(kTxtRecordExtAddressKey) - 1 + sizeof(char) + sizeof(Mac::ExtAddress) +
-        /* ExtPanId */ sizeof(uint8_t) + sizeof(kTxtRecordExtPanIdKey) - 1 + sizeof(char) +
-        sizeof(MeshCoP::ExtendedPanId);
-
-    uint8_t             txtData[kTxtDataSize];
-    Dns::TxtDataEncoder encoder(txtData, sizeof(txtData));
-
-    VerifyOrExit(mInitialized && mEnabled);
-
-    SuccessOrAssert(encoder.AppendEntry(kTxtRecordExtAddressKey, Get<Mac::Mac>().GetExtAddress()));
-    SuccessOrAssert(encoder.AppendEntry(kTxtRecordExtPanIdKey, Get<MeshCoP::ExtendedPanIdManager>().GetExtPanId()));
-
-    LogInfo("Registering DNS-SD service: port:%u, txt:\"%s=%s, %s=%s\"", mUdpPort, kTxtRecordExtAddressKey,
-            Get<Mac::Mac>().GetExtAddress().ToString().AsCString(), kTxtRecordExtPanIdKey,
-            Get<MeshCoP::ExtendedPanIdManager>().GetExtPanId().ToString().AsCString());
-
-    otPlatTrelRegisterService(&GetInstance(), mUdpPort, txtData, static_cast<uint8_t>(encoder.GetLength()));
-
-exit:
-    return;
-}
-
-extern "C" void otPlatTrelHandleDiscoveredPeerInfo(otInstance *aInstance, const otPlatTrelPeerInfo *aInfo)
-{
-    Instance &instance = AsCoreType(aInstance);
-
-    VerifyOrExit(instance.IsInitialized());
-    instance.Get<Interface>().HandleDiscoveredPeerInfo(*static_cast<const Interface::PeerInfo *>(aInfo));
-
-exit:
-    return;
-}
-
-void Interface::HandleDiscoveredPeerInfo(const PeerInfo &aInfo)
-{
-    Peer                  *peer;
-    Mac::ExtAddress        extAddress;
-    MeshCoP::ExtendedPanId extPanId;
-    bool                   isNew = false;
-
-    VerifyOrExit(mInitialized && mEnabled);
+    Get<PeerDiscoverer>().Stop();
 
-    SuccessOrExit(aInfo.ParseTxtData(extAddress, extPanId));
-
-    VerifyOrExit(extAddress != Get<Mac::Mac>().GetExtAddress());
-
-    if (aInfo.IsRemoved())
-    {
-        Get<PeerTable>().RemoveAndFreeAllMatching(extAddress);
-        ExitNow();
-    }
-
-    // It is a new entry or an update to an existing entry. First
-    // check whether we have an existing entry that matches the same
-    // socket address, and remove it if it is associated with a
-    // different Extended MAC address. This ensures that we do not
-    // keep stale entries in the peer table.
-
-    peer = Get<PeerTable>().FindMatching(aInfo.GetSockAddr());
-
-    if ((peer != nullptr) && !peer->Matches(extAddress))
-    {
-        Get<PeerTable>().RemoveMatching(aInfo.GetSockAddr());
-        peer = nullptr;
-    }
-
-    if (peer == nullptr)
-    {
-        peer = Get<PeerTable>().FindMatching(extAddress);
-    }
-
-    if (peer == nullptr)
-    {
-        peer = Get<PeerTable>().AllocateAndAddNewPeer();
-        VerifyOrExit(peer != nullptr);
-
-        peer->SetExtAddress(extAddress);
-        isNew = true;
-    }
-
-    if (!isNew)
-    {
-        VerifyOrExit((peer->GetExtPanId() != extPanId) || (peer->GetSockAddr() != aInfo.GetSockAddr()));
-    }
-
-    peer->SetExtPanId(extPanId);
-    peer->SetSockAddr(aInfo.GetSockAddr());
-
-    peer->Log(isNew ? Peer::kAdded : Peer::kUpdated);
+    LogDebg("Disabled interface");
 
 exit:
     return;
 }
 
-Error Interface::PeerInfo::ParseTxtData(Mac::ExtAddress &aExtAddress, MeshCoP::ExtendedPanId &aExtPanId) const
-{
-    Error                   error;
-    Dns::TxtEntry           entry;
-    Dns::TxtEntry::Iterator iterator;
-    bool                    parsedExtAddress = false;
-    bool                    parsedExtPanId   = false;
-
-    aExtPanId.Clear();
-
-    iterator.Init(mTxtData, mTxtLength);
-
-    while ((error = iterator.GetNextEntry(entry)) == kErrorNone)
-    {
-        // If the TXT data happens to have entries with key longer
-        // than `kMaxIterKeyLength`, `mKey` would be `nullptr` and full
-        // entry would be placed in `mValue`. We skip over such
-        // entries.
-        if (entry.mKey == nullptr)
-        {
-            continue;
-        }
-
-        if (StringMatch(entry.mKey, kTxtRecordExtAddressKey))
-        {
-            VerifyOrExit(!parsedExtAddress, error = kErrorParse);
-            VerifyOrExit(entry.mValueLength >= sizeof(Mac::ExtAddress), error = kErrorParse);
-            aExtAddress.Set(entry.mValue);
-            parsedExtAddress = true;
-        }
-        else if (StringMatch(entry.mKey, kTxtRecordExtPanIdKey))
-        {
-            VerifyOrExit(!parsedExtPanId, error = kErrorParse);
-            VerifyOrExit(entry.mValueLength >= sizeof(MeshCoP::ExtendedPanId), error = kErrorParse);
-            memcpy(aExtPanId.m8, entry.mValue, sizeof(MeshCoP::ExtendedPanId));
-            parsedExtPanId = true;
-        }
-
-        // Skip over and ignore any unknown keys.
-    }
-
-    VerifyOrExit(error == kErrorNotFound);
-    error = kErrorNone;
-
-    VerifyOrExit(parsedExtAddress && parsedExtPanId, error = kErrorParse);
-
-exit:
-    return error;
-}
-
 const Counters *Interface::GetCounters(void) const { return otPlatTrelGetCounters(&GetInstance()); }
 
 void Interface::ResetCounters(void) { otPlatTrelResetCounters(&GetInstance()); }

src/core/radio/trel_interface.hpp

@@ -41,26 +41,19 @@
 #include <openthread/trel.h>
 #include <openthread/platform/trel.h>
 
-#include "common/linked_list.hpp"
 #include "common/locator.hpp"
-#include "common/pool.hpp"
-#include "common/tasklet.hpp"
-#include "common/time.hpp"
+#include "net/socket.hpp"
 #include "radio/trel_packet.hpp"
-#include "radio/trel_peer.hpp"
 
 namespace ot {
 namespace Trel {
 
 class Link;
-class Interface;
 
 extern "C" void otPlatTrelHandleReceived(otInstance       *aInstance,
                                          uint8_t          *aBuffer,
                                          uint16_t          aLength,
                                          const otSockAddr *aSenderAddr);
-extern "C" void otPlatTrelHandleDiscoveredPeerInfo(otInstance *aInstance, const otPlatTrelPeerInfo *aInfo);
-
 /**
  * Represents a group of TREL counters.
  */
@@ -76,7 +69,6 @@ class Interface : public InstanceLocator
                                          uint8_t          *aBuffer,
                                          uint16_t          aLength,
                                          const otSockAddr *aSenderAddr);
-    friend void otPlatTrelHandleDiscoveredPeerInfo(otInstance *aInstance, const otPlatTrelPeerInfo *aInfo);
 
 public:
     /**
@@ -152,54 +144,21 @@ class Interface : public InstanceLocator
      */
     uint16_t GetUdpPort(void) const { return mUdpPort; }
 
-    /**
-     * Notifies platform that a TREL packet is received from a peer using a different socket address than the one
-     * reported earlier.
-     *
-     * @param[in] aPeerSockAddr   The previously reported peer sock addr.
-     * @param[in] aRxSockAddr     The address of received packet from the same peer.
-     */
-    void NotifyPeerSocketAddressDifference(const Ip6::SockAddr &aPeerSockAddr, const Ip6::SockAddr &aRxSockAddr);
-
 private:
-#if OPENTHREAD_CONFIG_TREL_PEER_TABLE_SIZE != 0
-    static constexpr uint16_t kPeerPoolSize = OPENTHREAD_CONFIG_TREL_PEER_TABLE_SIZE;
-#else
-    static constexpr uint16_t kExtraEntries = 32;
-    static constexpr uint16_t kPeerPoolSize = Mle::kMaxRouters + Mle::kMaxChildren + kExtraEntries;
-#endif
-    static const char kTxtRecordExtAddressKey[];
-    static const char kTxtRecordExtPanIdKey[];
-
-    struct PeerInfo : public otPlatTrelPeerInfo
-    {
-        bool                 IsRemoved(void) const { return mRemoved; }
-        const Ip6::SockAddr &GetSockAddr(void) const { return AsCoreType(&mSockAddr); }
-        Error                ParseTxtData(Mac::ExtAddress &aExtAddress, MeshCoP::ExtendedPanId &aExtPanId) const;
-    };
-
     explicit Interface(Instance &aInstance);
 
     // Methods used by `Trel::Link`.
     void  Init(void);
-    void  HandleExtAddressChange(void);
-    void  HandleExtPanIdChange(void);
     Error Send(const Packet &aPacket, bool aIsDiscovery = false);
 
     // Callbacks from `otPlatTrel`.
     void HandleReceived(uint8_t *aBuffer, uint16_t aLength, const Ip6::SockAddr &aSenderAddr);
-    void HandleDiscoveredPeerInfo(const PeerInfo &aInfo);
-
-    void RegisterService(void);
-
-    using RegisterServiceTask = TaskletIn<Interface, &Interface::RegisterService>;
 
-    bool                mInitialized : 1;
-    bool                mEnabled : 1;
-    bool                mFiltered : 1;
-    RegisterServiceTask mRegisterServiceTask;
-    uint16_t            mUdpPort;
-    Packet              mRxPacket;
+    bool     mInitialized : 1;
+    bool     mEnabled : 1;
+    bool     mFiltered : 1;
+    uint16_t mUdpPort;
+    Packet   mRxPacket;
 };
 
 } // namespace Trel

src/core/radio/trel_link.cpp

@@ -51,6 +51,7 @@ Link::Link(Instance &aInstance)
     , mTimer(aInstance)
     , mInterface(aInstance)
     , mPeerTable(aInstance)
+    , mPeerDiscoverer(aInstance)
 {
     ClearAllBytes(mTxFrame);
     ClearAllBytes(mRxFrame);
@@ -409,7 +410,7 @@ void Link::CheckPeerAddrOnRxSuccess(PeerSockAddrUpdateMode aMode)
         mRxPacketPeer->SetSockAddr(mRxPacketSenderAddr);
     }
 
-    Get<Interface>().NotifyPeerSocketAddressDifference(prevSockAddr, mRxPacketSenderAddr);
+    mPeerDiscoverer.NotifyPeerSocketAddressDifference(prevSockAddr, mRxPacketSenderAddr);
 
 exit:
     mRxPacketPeer = nullptr;
@@ -496,7 +497,7 @@ void Link::HandleNotifierEvents(Events aEvents)
 {
     if (aEvents.Contains(kEventThreadExtPanIdChanged))
     {
-        mInterface.HandleExtPanIdChange();
+        mPeerDiscoverer.HandleExtPanIdChange();
     }
 }