[udp] update Socket::Open() to include NetifId (openthread#10964)

This commit updates how the `NetifId` is set on a `Udp::Socket`. It is
now specified as a parameter in the `Open()` call instead of `Bind()`.

This change makes the socket more flexible by allowing the `NetifId`
to be known earlier (which can be used for future optimizations). It
also allows the desired `NetifId` to be set even when `Bind()` is not
explicitly called, such as when `Connect()` or `SendTo()` are used on
a socket that is not yet bound. Previously, `kNetifThread` was
assumed by default in these situations.

The public `otUdp` APIs are left unchanged to ensure backward
compatibility.

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), aCallback, aContext);
+    return AsCoreType(aInstance).Get<Ip6::Udp>().Open(AsCoreType(aSocket), Ip6::kNetifThread, aCallback, aContext);
 }
 
 bool otUdpIsOpen(otInstance *aInstance, const otUdpSocket *aSocket)
@@ -59,7 +59,9 @@ otError otUdpClose(otInstance *aInstance, otUdpSocket *aSocket)
 
 otError otUdpBind(otInstance *aInstance, otUdpSocket *aSocket, const otSockAddr *aSockName, otNetifIdentifier aNetif)
 {
-    return AsCoreType(aInstance).Get<Ip6::Udp>().Bind(AsCoreType(aSocket), AsCoreType(aSockName), MapEnum(aNetif));
+    AsCoreType(aSocket).SetNetifId(MapEnum(aNetif));
+
+    return AsCoreType(aInstance).Get<Ip6::Udp>().Bind(AsCoreType(aSocket), AsCoreType(aSockName));
 }
 
 otError otUdpConnect(otInstance *aInstance, otUdpSocket *aSocket, const otSockAddr *aSockName)

src/core/coap/coap.cpp

@@ -1672,10 +1672,10 @@ Error Coap::Start(uint16_t aPort, Ip6::NetifIdentifier aNetifIdentifier)
 
     VerifyOrExit(!mSocket.IsBound());
 
-    SuccessOrExit(error = mSocket.Open());
+    SuccessOrExit(error = mSocket.Open(aNetifIdentifier));
     socketOpened = true;
 
-    SuccessOrExit(error = mSocket.Bind(aPort, aNetifIdentifier));
+    SuccessOrExit(error = mSocket.Bind(aPort));
 
 exit:
     if (error != kErrorNone && socketOpened)

src/core/meshcop/joiner_router.cpp

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

src/core/meshcop/secure_transport.cpp

@@ -131,7 +131,7 @@ Error SecureTransport::Open(ReceiveHandler aReceiveHandler, ConnectedHandler aCo
 
     VerifyOrExit(IsStateClosed(), error = kErrorAlready);
 
-    SuccessOrExit(error = mSocket.Open());
+    SuccessOrExit(error = mSocket.Open(Ip6::kNetifUnspecified));
 
     mConnectedCallback.Set(aConnectedHandler, aContext);
     mReceiveCallback.Set(aReceiveHandler, aContext);
@@ -225,7 +225,7 @@ Error SecureTransport::Bind(uint16_t aPort)
     VerifyOrExit(IsStateOpen(), error = kErrorInvalidState);
     VerifyOrExit(!mTransportCallback.IsSet(), error = kErrorAlready);
 
-    SuccessOrExit(error = mSocket.Bind(aPort, Ip6::kNetifUnspecified));
+    SuccessOrExit(error = mSocket.Bind(aPort));
 
 exit:
     return error;

src/core/net/dhcp6_client.cpp

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

src/core/net/dns_client.cpp

@@ -764,8 +764,8 @@ Error Client::Start(void)
 {
     Error error;
 
-    SuccessOrExit(error = mSocket.Open());
-    SuccessOrExit(error = mSocket.Bind(0, Ip6::kNetifUnspecified));
+    SuccessOrExit(error = mSocket.Open(Ip6::kNetifUnspecified));
+    SuccessOrExit(error = mSocket.Bind(0));
 
 exit:
     return error;

src/core/net/dnssd_server.cpp

@@ -71,8 +71,8 @@ Error Server::Start(void)
 
     VerifyOrExit(!IsRunning());
 
-    SuccessOrExit(error = mSocket.Open());
-    SuccessOrExit(error = mSocket.Bind(kPort, kBindUnspecifiedNetif ? Ip6::kNetifUnspecified : Ip6::kNetifThread));
+    SuccessOrExit(error = mSocket.Open(kBindUnspecifiedNetif ? Ip6::kNetifUnspecified : Ip6::kNetifThread));
+    SuccessOrExit(error = mSocket.Bind(kPort));
 
 #if OPENTHREAD_CONFIG_SRP_SERVER_ENABLE
     Get<Srp::Server>().HandleDnssdServerStateChange();

src/core/net/sntp_client.cpp

@@ -54,8 +54,8 @@ Error Client::Start(void)
 {
     Error error;
 
-    SuccessOrExit(error = mSocket.Open());
-    SuccessOrExit(error = mSocket.Bind(0, Ip6::kNetifUnspecified));
+    SuccessOrExit(error = mSocket.Open(Ip6::kNetifUnspecified));
+    SuccessOrExit(error = mSocket.Bind(0));
 
 exit:
     return error;

src/core/net/srp_client.cpp

@@ -400,9 +400,10 @@ Error Client::Start(const Ip6::SockAddr &aServerSockAddr, Requester aRequester)
     VerifyOrExit(GetState() == kStateStopped,
                  error = (aServerSockAddr == GetServerAddress()) ? kErrorNone : kErrorBusy);
 
-    SuccessOrExit(error = mSocket.Open());
+    SuccessOrExit(error = mSocket.Open(Ip6::kNetifThread));
 
     error = mSocket.Connect(aServerSockAddr);
+
     if (error != kErrorNone)
     {
         LogInfo("Failed to connect to server %s: %s", aServerSockAddr.GetAddress().ToString().AsCString(),

src/core/net/srp_server.cpp

@@ -658,8 +658,8 @@ Error Server::PrepareSocket(void)
 #endif
 
     VerifyOrExit(!mSocket.IsOpen());
-    SuccessOrExit(error = mSocket.Open());
-    error = mSocket.Bind(mPort, Ip6::kNetifThread);
+    SuccessOrExit(error = mSocket.Open(Ip6::kNetifThread));
+    error = mSocket.Bind(mPort);
 
 exit:
     if (error != kErrorNone)

src/core/net/udp6.cpp

@@ -89,19 +89,13 @@ Message *Udp::Socket::NewMessage(uint16_t aReserved, const Message::Settings &aS
     return Get<Udp>().NewMessage(aReserved, aSettings);
 }
 
-Error Udp::Socket::Open(void) { return Get<Udp>().Open(*this, mHandler, mContext); }
+Error Udp::Socket::Open(NetifIdentifier aNetifId) { return Get<Udp>().Open(*this, aNetifId, mHandler, mContext); }
 
 bool Udp::Socket::IsOpen(void) const { return Get<Udp>().IsOpen(*this); }
 
-Error Udp::Socket::Bind(const SockAddr &aSockAddr, NetifIdentifier aNetifIdentifier)
-{
-    return Get<Udp>().Bind(*this, aSockAddr, aNetifIdentifier);
-}
+Error Udp::Socket::Bind(const SockAddr &aSockAddr) { return Get<Udp>().Bind(*this, aSockAddr); }
 
-Error Udp::Socket::Bind(uint16_t aPort, NetifIdentifier aNetifIdentifier)
-{
-    return Bind(SockAddr(aPort), aNetifIdentifier);
-}
+Error Udp::Socket::Bind(uint16_t aPort) { return Bind(SockAddr(aPort)); }
 
 Error Udp::Socket::Connect(const SockAddr &aSockAddr) { return Get<Udp>().Connect(*this, aSockAddr); }
 
@@ -172,13 +166,14 @@ Error Udp::RemoveReceiver(Receiver &aReceiver)
     return error;
 }
 
-Error Udp::Open(SocketHandle &aSocket, ReceiveHandler aHandler, void *aContext)
+Error Udp::Open(SocketHandle &aSocket, NetifIdentifier aNetifId, ReceiveHandler aHandler, void *aContext)
 {
     Error error = kErrorNone;
 
     OT_ASSERT(!IsOpen(aSocket));
 
     aSocket.Clear();
+    aSocket.SetNetifId(aNetifId);
     aSocket.mHandler = aHandler;
     aSocket.mContext = aContext;
 
@@ -193,16 +188,14 @@ Error Udp::Open(SocketHandle &aSocket, ReceiveHandler aHandler, void *aContext)
     return error;
 }
 
-Error Udp::Bind(SocketHandle &aSocket, const SockAddr &aSockAddr, NetifIdentifier aNetifIdentifier)
+Error Udp::Bind(SocketHandle &aSocket, const SockAddr &aSockAddr)
 {
     Error error = kErrorNone;
 
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
-    SuccessOrExit(error = otPlatUdpBindToNetif(&aSocket, MapEnum(aNetifIdentifier)));
+    SuccessOrExit(error = otPlatUdpBindToNetif(&aSocket, MapEnum(aSocket.GetNetifId())));
 #endif
 
-    aSocket.mNetifId = MapEnum(aNetifIdentifier);
-
     VerifyOrExit(aSockAddr.GetAddress().IsUnspecified() || Get<ThreadNetif>().HasUnicastAddress(aSockAddr.GetAddress()),
                  error = kErrorInvalidArgs);
 
@@ -237,7 +230,7 @@ Error Udp::Connect(SocketHandle &aSocket, const SockAddr &aSockAddr)
 
     if (!aSocket.IsBound())
     {
-        SuccessOrExit(error = Bind(aSocket, aSocket.GetSockName(), kNetifThread));
+        SuccessOrExit(error = Bind(aSocket, aSocket.GetSockName()));
     }
 
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
@@ -300,7 +293,7 @@ Error Udp::SendTo(SocketHandle &aSocket, Message &aMessage, const MessageInfo &a
 
     if (!aSocket.IsBound())
     {
-        SuccessOrExit(error = Bind(aSocket, aSocket.GetSockName(), kNetifThread));
+        SuccessOrExit(error = Bind(aSocket, aSocket.GetSockName()));
     }
 
     messageInfoLocal.SetSockPort(aSocket.GetSockName().mPort);

src/core/net/udp6.hpp

@@ -135,6 +135,13 @@ class Udp : public InstanceLocator, private NonCopyable
          */
         NetifIdentifier GetNetifId(void) const { return static_cast<NetifIdentifier>(mNetifId); }
 
+        /**
+         * Sets the network interface identifier.
+         *
+         * @param[in] aNetifId   The network interface identifier.
+         */
+        void SetNetifId(NetifIdentifier aNetifId) { mNetifId = static_cast<otNetifIdentifier>(aNetifId); }
+
 #if OPENTHREAD_FTD && OPENTHREAD_CONFIG_BACKBONE_ROUTER_ENABLE
         /**
          * Indicate whether or not the socket is bound to the backbone network interface.
@@ -200,10 +207,12 @@ class Udp : public InstanceLocator, private NonCopyable
         /**
          * Opens the UDP socket.
          *
+         * @param[in]  aNetifId   The network interface identifier.
+         *
          * @retval kErrorNone     Successfully opened the socket.
          * @retval kErrorFailed   Failed to open the socket.
          */
-        Error Open(void);
+        Error Open(NetifIdentifier aNetifId);
 
         /**
          * Returns if the UDP socket is open.
@@ -215,25 +224,23 @@ class Udp : public InstanceLocator, private NonCopyable
         /**
          * Binds the UDP socket.
          *
-         * @param[in]  aSockAddr            A reference to the socket address.
-         * @param[in]  aNetifIdentifier     The network interface identifier.
+         * @param[in]  aSockAddr         A reference to the socket address.
          *
          * @retval kErrorNone            Successfully bound the socket.
          * @retval kErrorInvalidArgs     Unable to bind to Thread network interface with the given address.
          * @retval kErrorFailed          Failed to bind UDP Socket.
          */
-        Error Bind(const SockAddr &aSockAddr, NetifIdentifier aNetifIdentifier = kNetifThread);
+        Error Bind(const SockAddr &aSockAddr);
 
         /**
          * Binds the UDP socket.
          *
-         * @param[in]  aPort                A port number.
-         * @param[in]  aNetifIdentifier     The network interface identifier.
+         * @param[in]  aPort             A port number.
          *
          * @retval kErrorNone            Successfully bound the socket.
          * @retval kErrorFailed          Failed to bind UDP Socket.
          */
-        Error Bind(uint16_t aPort, NetifIdentifier aNetifIdentifier = kNetifThread);
+        Error Bind(uint16_t aPort);
 
         /**
          * Binds the UDP socket.
@@ -479,13 +486,14 @@ class Udp : public InstanceLocator, private NonCopyable
      * Opens a UDP socket.
      *
      * @param[in]  aSocket   A reference to the socket.
+     * @param[in]  aNetifId  A network interface identifier.
      * @param[in]  aHandler  A pointer to a function that is called when receiving UDP messages.
      * @param[in]  aContext  A pointer to arbitrary context information.
      *
      * @retval kErrorNone     Successfully opened the socket.
      * @retval kErrorFailed   Failed to open the socket.
      */
-    Error Open(SocketHandle &aSocket, ReceiveHandler aHandler, void *aContext);
+    Error Open(SocketHandle &aSocket, NetifIdentifier aNetifId, ReceiveHandler aHandler, void *aContext);
 
     /**
      * Returns if a UDP socket is open.
@@ -501,13 +509,12 @@ class Udp : public InstanceLocator, private NonCopyable
      *
      * @param[in]  aSocket          A reference to the socket.
      * @param[in]  aSockAddr        A reference to the socket address.
-     * @param[in]  aNetifIdentifier The network interface identifier.
      *
      * @retval kErrorNone            Successfully bound the socket.
      * @retval kErrorInvalidArgs     Unable to bind to Thread network interface with the given address.
      * @retval kErrorFailed          Failed to bind UDP Socket.
      */
-    Error Bind(SocketHandle &aSocket, const SockAddr &aSockAddr, NetifIdentifier aNetifIdentifier);
+    Error Bind(SocketHandle &aSocket, const SockAddr &aSockAddr);
 
     /**
      * Connects a UDP socket.

src/core/thread/mle.cpp

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

tests/unit/test_srp_server.cpp

@@ -1076,8 +1076,8 @@ void TestSrpClientDelayedResponse(void)
 
         sServerRxCount = 0;
 
-        SuccessOrQuit(udpSocket.Open());
-        SuccessOrQuit(udpSocket.Bind(kServerPort, Ip6::kNetifThread));
+        SuccessOrQuit(udpSocket.Open(Ip6::kNetifThread));
+        SuccessOrQuit(udpSocket.Bind(kServerPort));
 
         //- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
         // Manually start the client with a message ID based on `testIter`