[udp] add kNetifThreadInternal which disallows platform UDP use (#10965)

This commit introduces `kNetifThreadInternal` as a network interface
option for UDP sockets. Unlike other options, this disallows the use
of platform UDP for the socket, indicating that the socket should use
the OpenThread internal Thread network interface only.

This model replaces the previous approach where `ShouldUsePlatformUdp()`
would check the socket port against a set of port numbers used by
different modules (such as MLE, TMF, Joiner Router, etc) to determine
whether platform UDP APIs should be used. With the new model, each
module decides whether to associate its socket with the
`kNetifThreadInternal`.

This is a more flexible and extensible model, ensuring that sockets
that should not use the platform do not waste resources (they will
not be created or opened/closed on the platform). This also help
avoid edge cases where platform UDP operations may unintentionally
fail when the platform socket is not actually needed.

include/openthread/instance.h

@@ -52,7 +52,7 @@ extern "C" {
  *
  * @note This number versions both OpenThread platform and user APIs.
  */
-#define OPENTHREAD_API_VERSION (464)
+#define OPENTHREAD_API_VERSION (465)
 
 /**
  * @addtogroup api-instance

include/openthread/udp.h

@@ -115,7 +115,8 @@ typedef void (*otUdpReceive)(void *aContext, otMessage *aMessage, const otMessag
 typedef enum otNetifIdentifier
 {
     OT_NETIF_UNSPECIFIED = 0, ///< Unspecified network interface.
-    OT_NETIF_THREAD,          ///< The Thread interface.
+    OT_NETIF_THREAD_HOST,     ///< The host Thread interface - allow use of platform UDP.
+    OT_NETIF_THREAD_INTERNAL, ///< The internal Thread interface (within OpenThread) - do not use platform UDP.
     OT_NETIF_BACKBONE,        ///< The Backbone interface.
 } otNetifIdentifier;
 

src/cli/cli_udp.cpp

@@ -83,7 +83,7 @@ template <> otError UdpExample::Process<Cmd("bind")>(Arg aArgs[])
 {
     otError           error;
     otSockAddr        sockaddr;
-    otNetifIdentifier netif = OT_NETIF_THREAD;
+    otNetifIdentifier netif = OT_NETIF_THREAD_HOST;
 
     if (aArgs[0] == "-u")
     {

src/core/api/udp_api.cpp

@@ -44,7 +44,7 @@ otMessage *otUdpNewMessage(otInstance *aInstance, const otMessageSettings *aSett
 
 otError otUdpOpen(otInstance *aInstance, otUdpSocket *aSocket, otUdpReceive aCallback, void *aContext)
 {
-    return AsCoreType(aInstance).Get<Ip6::Udp>().Open(AsCoreType(aSocket), Ip6::kNetifThread, aCallback, aContext);
+    return AsCoreType(aInstance).Get<Ip6::Udp>().Open(AsCoreType(aSocket), Ip6::kNetifThreadHost, aCallback, aContext);
 }
 
 bool otUdpIsOpen(otInstance *aInstance, const otUdpSocket *aSocket)

src/core/meshcop/joiner_router.cpp

@@ -69,7 +69,7 @@ void JoinerRouter::Start(void)
 
         VerifyOrExit(!mSocket.IsBound());
 
-        IgnoreError(mSocket.Open(Ip6::kNetifThread));
+        IgnoreError(mSocket.Open(Ip6::kNetifThreadInternal));
         IgnoreError(mSocket.Bind(port));
         IgnoreError(Get<Ip6::Filter>().AddUnsecurePort(port));
         LogInfo("Joiner Router: start");

src/core/net/dhcp6_client.cpp

@@ -162,7 +162,7 @@ void Client::Start(void)
 {
     VerifyOrExit(!mSocket.IsBound());
 
-    IgnoreError(mSocket.Open(Ip6::kNetifThread));
+    IgnoreError(mSocket.Open(Ip6::kNetifThreadInternal));
     IgnoreError(mSocket.Bind(kDhcpClientPort));
 
     ProcessNextIdentityAssociation();

src/core/net/dhcp6_server.cpp

@@ -130,7 +130,7 @@ void Server::Start(void)
 {
     VerifyOrExit(!mSocket.IsOpen());
 
-    IgnoreError(mSocket.Open(Ip6::kNetifThread));
+    IgnoreError(mSocket.Open(Ip6::kNetifThreadInternal));
     IgnoreError(mSocket.Bind(kDhcpServerPort));
 
 exit:

src/core/net/dnssd_server.cpp

@@ -71,7 +71,7 @@ Error Server::Start(void)
 
     VerifyOrExit(!IsRunning());
 
-    SuccessOrExit(error = mSocket.Open(kBindUnspecifiedNetif ? Ip6::kNetifUnspecified : Ip6::kNetifThread));
+    SuccessOrExit(error = mSocket.Open(kBindUnspecifiedNetif ? Ip6::kNetifUnspecified : Ip6::kNetifThreadInternal));
     SuccessOrExit(error = mSocket.Bind(kPort));
 
 #if OPENTHREAD_CONFIG_SRP_SERVER_ENABLE

src/core/net/srp_client.cpp

@@ -400,7 +400,7 @@ Error Client::Start(const Ip6::SockAddr &aServerSockAddr, Requester aRequester)
     VerifyOrExit(GetState() == kStateStopped,
                  error = (aServerSockAddr == GetServerAddress()) ? kErrorNone : kErrorBusy);
 
-    SuccessOrExit(error = mSocket.Open(Ip6::kNetifThread));
+    SuccessOrExit(error = mSocket.Open(Ip6::kNetifThreadInternal));
 
     error = mSocket.Connect(aServerSockAddr);
 

src/core/net/srp_server.cpp

@@ -658,7 +658,7 @@ Error Server::PrepareSocket(void)
 #endif
 
     VerifyOrExit(!mSocket.IsOpen());
-    SuccessOrExit(error = mSocket.Open(Ip6::kNetifThread));
+    SuccessOrExit(error = mSocket.Open(Ip6::kNetifThreadHost));
     error = mSocket.Bind(mPort);
 
 exit:

src/core/net/udp6.cpp

@@ -119,7 +119,7 @@ Error Udp::Socket::JoinNetifMulticastGroup(NetifIdentifier aNetifIdentifier, con
     VerifyOrExit(aAddress.IsMulticast(), error = kErrorInvalidArgs);
 
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-    error = otPlatUdpJoinMulticastGroup(this, MapEnum(aNetifIdentifier), &aAddress);
+    error = Plat::JoinMulticastGroup(*this, aNetifIdentifier, aAddress);
 #endif
 
 exit:
@@ -136,7 +136,7 @@ Error Udp::Socket::LeaveNetifMulticastGroup(NetifIdentifier aNetifIdentifier, co
     VerifyOrExit(aAddress.IsMulticast(), error = kErrorInvalidArgs);
 
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-    error = otPlatUdpLeaveMulticastGroup(this, MapEnum(aNetifIdentifier), &aAddress);
+    error = Plat::LeaveMulticastGroup(*this, aNetifIdentifier, aAddress);
 #endif
 
 exit:
@@ -144,6 +144,57 @@ exit:
 }
 #endif
 
+//---------------------------------------------------------------------------------------------------------------------
+// Udp::Plat
+
+#if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
+
+Error Udp::Plat::Open(SocketHandle &aSocket)
+{
+    return aSocket.ShouldUsePlatformUdp() ? otPlatUdpSocket(&aSocket) : kErrorNone;
+}
+
+Error Udp::Plat::Close(SocketHandle &aSocket)
+{
+    return aSocket.ShouldUsePlatformUdp() ? otPlatUdpClose(&aSocket) : kErrorNone;
+}
+
+Error Udp::Plat::Bind(SocketHandle &aSocket)
+{
+    return aSocket.ShouldUsePlatformUdp() ? otPlatUdpBind(&aSocket) : kErrorNone;
+}
+
+Error Udp::Plat::BindToNetif(SocketHandle &aSocket)
+{
+    return aSocket.ShouldUsePlatformUdp() ? otPlatUdpBindToNetif(&aSocket, MapEnum(aSocket.GetNetifId())) : kErrorNone;
+}
+
+Error Udp::Plat::Connect(SocketHandle &aSocket)
+{
+    return aSocket.ShouldUsePlatformUdp() ? otPlatUdpConnect(&aSocket) : kErrorNone;
+}
+
+Error Udp::Plat::Send(SocketHandle &aSocket, Message &aMessage, const MessageInfo &aMessageInfo)
+{
+    OT_ASSERT(aSocket.ShouldUsePlatformUdp());
+
+    return otPlatUdpSend(&aSocket, &aMessage, &aMessageInfo);
+}
+
+Error Udp::Plat::JoinMulticastGroup(SocketHandle &aSocket, NetifIdentifier aNetifId, const Address &aAddress)
+{
+    return aSocket.ShouldUsePlatformUdp() ? otPlatUdpJoinMulticastGroup(&aSocket, MapEnum(aNetifId), &aAddress)
+                                          : kErrorNone;
+}
+
+Error Udp::Plat::LeaveMulticastGroup(SocketHandle &aSocket, NetifIdentifier aNetifId, const Address &aAddress)
+{
+    return aSocket.ShouldUsePlatformUdp() ? otPlatUdpLeaveMulticastGroup(&aSocket, MapEnum(aNetifId), &aAddress)
+                                          : kErrorNone;
+}
+
+#endif //  OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
+
 //---------------------------------------------------------------------------------------------------------------------
 // Udp
 
@@ -178,7 +229,7 @@ Error Udp::Open(SocketHandle &aSocket, NetifIdentifier aNetifId, ReceiveHandler
     aSocket.mContext = aContext;
 
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-    error = otPlatUdpSocket(&aSocket);
+    error = Plat::Open(aSocket);
 #endif
     SuccessOrExit(error);
 
@@ -193,7 +244,7 @@ Error Udp::Bind(SocketHandle &aSocket, const SockAddr &aSockAddr)
     Error error = kErrorNone;
 
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-    SuccessOrExit(error = otPlatUdpBindToNetif(&aSocket, MapEnum(aSocket.GetNetifId())));
+    SuccessOrExit(error = Plat::BindToNetif(aSocket));
 #endif
 
     VerifyOrExit(aSockAddr.GetAddress().IsUnspecified() || Get<ThreadNetif>().HasUnicastAddress(aSockAddr.GetAddress()),
@@ -207,14 +258,14 @@ Error Udp::Bind(SocketHandle &aSocket, const SockAddr &aSockAddr)
         {
             aSocket.mSockName.mPort = GetEphemeralPort();
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-            error = otPlatUdpBind(&aSocket);
+            error = Plat::Bind(aSocket);
 #endif
         } while (error != kErrorNone);
     }
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-    else if (ShouldUsePlatformUdp(aSocket))
+    else
     {
-        error = otPlatUdpBind(&aSocket);
+        error = Plat::Bind(aSocket);
     }
 #endif
 
@@ -234,10 +285,7 @@ Error Udp::Connect(SocketHandle &aSocket, const SockAddr &aSockAddr)
     }
 
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-    if (ShouldUsePlatformUdp(aSocket))
-    {
-        error = otPlatUdpConnect(&aSocket);
-    }
+    error = Plat::Connect(aSocket);
 #endif
 
 exit:
@@ -251,9 +299,8 @@ Error Udp::Close(SocketHandle &aSocket)
     VerifyOrExit(IsOpen(aSocket));
 
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-    error = otPlatUdpClose(&aSocket);
+    SuccessOrExit(error = Plat::Close(aSocket));
 #endif
-    SuccessOrExit(error);
 
     RemoveSocket(aSocket);
     aSocket.GetSockName().Clear();
@@ -299,9 +346,9 @@ Error Udp::SendTo(SocketHandle &aSocket, Message &aMessage, const MessageInfo &a
     messageInfoLocal.SetSockPort(aSocket.GetSockName().mPort);
 
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-    if (ShouldUsePlatformUdp(aSocket))
+    if (aSocket.ShouldUsePlatformUdp())
     {
-        SuccessOrExit(error = otPlatUdpSend(&aSocket, &aMessage, &messageInfoLocal));
+        SuccessOrExit(error = Plat::Send(aSocket, aMessage, messageInfoLocal));
     }
     else
 #endif
@@ -447,45 +494,5 @@ bool Udp::IsPortInUse(uint16_t aPort) const
     return found;
 }
 
-#if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-
-bool Udp::ShouldUsePlatformUdp(uint16_t aPort) const
-{
-    bool shouldUse = false;
-
-    VerifyOrExit(aPort != Mle::kUdpPort);
-    VerifyOrExit(aPort != Tmf::kUdpPort);
-#if OPENTHREAD_CONFIG_DNSSD_SERVER_ENABLE && !OPENTHREAD_CONFIG_DNSSD_SERVER_BIND_UNSPECIFIED_NETIF
-    VerifyOrExit(aPort != Dns::ServiceDiscovery::Server::kPort);
-#endif
-#if OPENTHREAD_CONFIG_BORDER_AGENT_ENABLE
-    VerifyOrExit(aPort != Get<MeshCoP::BorderAgent>().GetUdpProxyPort());
-#endif
-#if OPENTHREAD_FTD
-    VerifyOrExit(aPort != Get<MeshCoP::JoinerRouter>().GetJoinerUdpPort());
-#endif
-#if OPENTHREAD_CONFIG_DHCP6_SERVER_ENABLE
-    VerifyOrExit(aPort != Dhcp6::kDhcpServerPort);
-#endif
-#if OPENTHREAD_CONFIG_DHCP6_CLIENT_ENABLE
-    VerifyOrExit(aPort != Dhcp6::kDhcpClientPort);
-#endif
-
-    shouldUse = true;
-
-exit:
-    return shouldUse;
-}
-
-bool Udp::ShouldUsePlatformUdp(const Udp::SocketHandle &aSocket) const
-{
-    return (ShouldUsePlatformUdp(aSocket.mSockName.mPort)
-#if OPENTHREAD_FTD && OPENTHREAD_CONFIG_BACKBONE_ROUTER_ENABLE
-            || aSocket.IsBackbone()
-#endif
-    );
-}
-#endif // OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-
 } // namespace Ip6
 } // namespace ot

src/core/net/udp6.hpp

@@ -70,9 +70,10 @@ class Udp;
  */
 enum NetifIdentifier : uint8_t
 {
-    kNetifUnspecified = OT_NETIF_UNSPECIFIED, ///< Unspecified network interface.
-    kNetifThread      = OT_NETIF_THREAD,      ///< The Thread interface.
-    kNetifBackbone    = OT_NETIF_BACKBONE,    ///< The Backbone interface.
+    kNetifUnspecified    = OT_NETIF_UNSPECIFIED,     ///< Unspecified network interface.
+    kNetifThreadHost     = OT_NETIF_THREAD_HOST,     ///< The host Thread interface - allow use of platform UDP.
+    kNetifThreadInternal = OT_NETIF_THREAD_INTERNAL, ///< The internal Thread interface - do not use platform UDP.
+    kNetifBackbone       = OT_NETIF_BACKBONE,        ///< The Backbone interface.
 };
 
 /**
@@ -142,6 +143,14 @@ public:
          */
         void SetNetifId(NetifIdentifier aNetifId) { mNetifId = static_cast<otNetifIdentifier>(aNetifId); }
 
+        /**
+         * Indicates whether or not the socket can use platform UDP.
+         *
+         * @retval TRUE    This socket should use platform UDP.
+         * @retval FALSE   This socket is associated with the internal Thread interface and should not use platform UDP.
+         */
+        bool ShouldUsePlatformUdp(void) const { return GetNetifId() != kNetifThreadInternal; }
+
 #if OPENTHREAD_FTD && OPENTHREAD_CONFIG_BACKBONE_ROUTER_ENABLE
         /**
          * Indicate whether or not the socket is bound to the backbone network interface.
@@ -649,14 +658,24 @@ private:
     static constexpr uint16_t kSrpServerPortMin = OPENTHREAD_CONFIG_SRP_SERVER_UDP_PORT_MIN;
     static constexpr uint16_t kSrpServerPortMax = OPENTHREAD_CONFIG_SRP_SERVER_UDP_PORT_MAX;
 
+#if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
+    struct Plat
+    {
+        static Error Open(SocketHandle &aSocket);
+        static Error Close(SocketHandle &aSocket);
+        static Error Bind(SocketHandle &aSocket);
+        static Error BindToNetif(SocketHandle &aSocket);
+        static Error Connect(SocketHandle &aSocket);
+        static Error Send(SocketHandle &aSocket, Message &aMessage, const MessageInfo &aMessageInfo);
+        static Error JoinMulticastGroup(SocketHandle &aSocket, NetifIdentifier aNetifId, const Address &aAddress);
+        static Error LeaveMulticastGroup(SocketHandle &aSocket, NetifIdentifier aNetifId, const Address &aAddress);
+    };
+#endif
+
     static bool IsPortReserved(uint16_t aPort);
 
     void AddSocket(SocketHandle &aSocket);
     void RemoveSocket(SocketHandle &aSocket);
-#if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-    bool ShouldUsePlatformUdp(uint16_t aPort) const;
-    bool ShouldUsePlatformUdp(const SocketHandle &aSocket) const;
-#endif
 
     uint16_t                 mEphemeralPort;
     LinkedList<Receiver>     mReceivers;

src/core/thread/mle.cpp

@@ -127,7 +127,7 @@ Error Mle::Enable(void)
     Error error = kErrorNone;
 
     UpdateLinkLocalAddress();
-    SuccessOrExit(error = mSocket.Open(Ip6::kNetifThread));
+    SuccessOrExit(error = mSocket.Open(Ip6::kNetifThreadInternal));
     SuccessOrExit(error = mSocket.Bind(kUdpPort));
 
 #if OPENTHREAD_CONFIG_PARENT_SEARCH_ENABLE

src/core/thread/tmf.cpp

@@ -83,7 +83,7 @@ Agent::Agent(Instance &aInstance)
     SetResourceHandler(&HandleResource);
 }
 
-Error Agent::Start(void) { return Coap::Start(kUdpPort, Ip6::kNetifThread); }
+Error Agent::Start(void) { return Coap::Start(kUdpPort, Ip6::kNetifThreadInternal); }
 
 template <> void Agent::HandleTmf<kUriRelayRx>(Message &aMessage, const Ip6::MessageInfo &aMessageInfo)
 {

src/posix/platform/udp.cpp

@@ -305,7 +305,7 @@ otError otPlatUdpBindToNetif(otUdpSocket *aUdpSocket, otNetifIdentifier aNetifId
 #endif // __linux__
         break;
     }
-    case OT_NETIF_THREAD:
+    case OT_NETIF_THREAD_HOST:
     {
 #ifdef __linux__
         VerifyOrExit(setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, &gNetifName, strlen(gNetifName)) == 0,
@@ -341,6 +341,9 @@ otError otPlatUdpBindToNetif(otUdpSocket *aUdpSocket, otNetifIdentifier aNetifId
 
         break;
     }
+
+    case OT_NETIF_THREAD_INTERNAL:
+        assert(false);
     }
 
     VerifyOrExit(setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &zero, sizeof(zero)) == 0, error = OT_ERROR_FAILED);
@@ -471,7 +474,7 @@ otError otPlatUdpJoinMulticastGroup(otUdpSocket        *aUdpSocket,
     {
     case OT_NETIF_UNSPECIFIED:
         break;
-    case OT_NETIF_THREAD:
+    case OT_NETIF_THREAD_HOST:
         mreq.ipv6mr_interface = gNetifIndex;
         break;
     case OT_NETIF_BACKBONE:
@@ -481,6 +484,8 @@ otError otPlatUdpJoinMulticastGroup(otUdpSocket        *aUdpSocket,
         ExitNow(error = OT_ERROR_NOT_IMPLEMENTED);
 #endif
         break;
+    case OT_NETIF_THREAD_INTERNAL:
+        assert(false);
     }
 
     VerifyOrExit(setsockopt(fd, IPPROTO_IPV6, IPV6_JOIN_GROUP, &mreq, sizeof(mreq)) == 0 || errno == EADDRINUSE,
@@ -512,7 +517,7 @@ otError otPlatUdpLeaveMulticastGroup(otUdpSocket        *aUdpSocket,
     {
     case OT_NETIF_UNSPECIFIED:
         break;
-    case OT_NETIF_THREAD:
+    case OT_NETIF_THREAD_HOST:
         mreq.ipv6mr_interface = gNetifIndex;
         break;
     case OT_NETIF_BACKBONE:
@@ -522,6 +527,9 @@ otError otPlatUdpLeaveMulticastGroup(otUdpSocket        *aUdpSocket,
         ExitNow(error = OT_ERROR_NOT_IMPLEMENTED);
 #endif
         break;
+
+    case OT_NETIF_THREAD_INTERNAL:
+        assert(false);
     }
 
     VerifyOrExit(setsockopt(fd, IPPROTO_IPV6, IPV6_LEAVE_GROUP, &mreq, sizeof(mreq)) == 0 || errno == EADDRINUSE,

tests/unit/test_srp_server.cpp

@@ -1076,7 +1076,7 @@ void TestSrpClientDelayedResponse(void)
 
         sServerRxCount = 0;
 
-        SuccessOrQuit(udpSocket.Open(Ip6::kNetifThread));
+        SuccessOrQuit(udpSocket.Open(Ip6::kNetifThreadHost));
         SuccessOrQuit(udpSocket.Bind(kServerPort));
 
         //- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -