[udp] bind to Thread interface by default (#6318)

Bind to Thread network by default so that UDP sockets in CLI can send
multicast packets through Thread network interface.

src/core/coap/coap.cpp

@@ -1666,8 +1666,7 @@ Error Coap::Start(uint16_t aPort, otNetifIdentifier aNetifIdentifier)
     SuccessOrExit(error = mSocket.Open(&Coap::HandleUdpReceive, this));
     socketOpened = true;
 
-    SuccessOrExit(error = mSocket.BindToNetif(aNetifIdentifier));
-    SuccessOrExit(error = mSocket.Bind(aPort));
+    SuccessOrExit(error = mSocket.Bind(aPort, aNetifIdentifier));
 
 exit:
     if (error != kErrorNone && socketOpened)

src/core/meshcop/dtls.cpp

@@ -215,7 +215,7 @@ Error Dtls::Bind(uint16_t aPort)
     VerifyOrExit(mState == kStateOpen, error = kErrorInvalidState);
     VerifyOrExit(mTransportCallback == nullptr, error = kErrorAlready);
 
-    SuccessOrExit(error = mSocket.Bind(aPort));
+    SuccessOrExit(error = mSocket.Bind(aPort, OT_NETIF_UNSPECIFIED));
 
 exit:
     return error;

src/core/net/dnssd_server.cpp

@@ -66,7 +66,7 @@ Error Server::Start(void)
     VerifyOrExit(!IsRunning());
 
     SuccessOrExit(error = mSocket.Open(&Server::HandleUdpReceive, this));
-    SuccessOrExit(error = mSocket.Bind(kPort));
+    SuccessOrExit(error = mSocket.Bind(kPort, OT_NETIF_UNSPECIFIED));
 
 exit:
     otLogInfoDns("[server] started: %s", ErrorToString(error));

src/core/net/srp_server.cpp

@@ -424,7 +424,7 @@ void Server::Start(void)
     VerifyOrExit(!IsRunning());
 
     SuccessOrExit(error = mSocket.Open(HandleUdpReceive, this));
-    SuccessOrExit(error = mSocket.Bind(0));
+    SuccessOrExit(error = mSocket.Bind(0, OT_NETIF_UNSPECIFIED));
 
     SuccessOrExit(error = PublishServerData());
 

src/core/net/udp6.cpp

@@ -87,17 +87,7 @@ Error Udp::Socket::Open(otUdpReceive aHandler, void *aContext)
     return Get<Udp>().Open(*this, aHandler, aContext);
 }
 
-Error Udp::Socket::Bind(const SockAddr &aSockAddr)
-{
-    return Get<Udp>().Bind(*this, aSockAddr);
-}
-
-Error Udp::Socket::Bind(uint16_t aPort)
-{
-    return Bind(SockAddr(aPort));
-}
-
-Error Udp::Socket::BindToNetif(otNetifIdentifier aNetifIdentifier)
+Error Udp::Socket::Bind(const SockAddr &aSockAddr, otNetifIdentifier aNetifIdentifier)
 {
     OT_UNUSED_VARIABLE(aNetifIdentifier);
 
@@ -108,15 +98,23 @@ Error Udp::Socket::BindToNetif(otNetifIdentifier aNetifIdentifier)
 #endif
 
 #if OPENTHREAD_FTD && OPENTHREAD_CONFIG_BACKBONE_ROUTER_ENABLE
-    Get<Udp>().BindToNetif(*this, aNetifIdentifier);
+    if (aNetifIdentifier == OT_NETIF_BACKBONE)
+    {
+        Get<Udp>().SetBackboneSocket(*this);
+    }
 #endif
 
-#if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
+    SuccessOrExit(error = Get<Udp>().Bind(*this, aSockAddr));
+
 exit:
-#endif
     return error;
 }
 
+Error Udp::Socket::Bind(uint16_t aPort, otNetifIdentifier aNetifIdentifier)
+{
+    return Bind(SockAddr(aPort), aNetifIdentifier);
+}
+
 Error Udp::Socket::Connect(const SockAddr &aSockAddr)
 {
     return Get<Udp>().Connect(*this, aSockAddr);
@@ -253,14 +251,6 @@ exit:
 }
 
 #if OPENTHREAD_FTD && OPENTHREAD_CONFIG_BACKBONE_ROUTER_ENABLE
-void Udp::BindToNetif(SocketHandle &aSocket, otNetifIdentifier aNetifIdentifier)
-{
-    if (aNetifIdentifier == OT_NETIF_BACKBONE)
-    {
-        SetBackboneSocket(aSocket);
-    }
-}
-
 void Udp::SetBackboneSocket(SocketHandle &aSocket)
 {
     RemoveSocket(aSocket);

src/core/net/udp6.hpp

@@ -174,36 +174,27 @@ public:
         /**
          * This method binds the UDP socket.
          *
-         * @param[in]  aSockAddr    A reference to the socket address.
+         * @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(const SockAddr &aSockAddr);
-
-        /**
-         * This method binds the UDP socket to a specified network interface.
-         *
-         * @param[in]  aNetifIdentifier     The network interface identifier.
-         *
-         * @retval kErrorNone    Successfully bound to the network interface.
-         * @retval kErrorFailed  Failed to bind to the network interface.
-         *
-         */
-        Error BindToNetif(otNetifIdentifier aNetifIdentifier);
+        Error Bind(const SockAddr &aSockAddr, otNetifIdentifier aNetifIdentifier = OT_NETIF_THREAD);
 
         /**
          * This method binds the UDP socket.
          *
-         * @param[in]  aPort        A port number.
+         * @param[in]  aPort                A port number.
+         * @param[in]  aNetifIdentifier     The network interface identifier.
          *
          * @retval kErrorNone            Successfully bound the socket.
          * @retval kErrorFailed          Failed to bind UDP Socket.
          *
          */
-        Error Bind(uint16_t aPort);
+        Error Bind(uint16_t aPort, otNetifIdentifier aNetifIdentifier = OT_NETIF_THREAD);
 
         /**
          * This method binds the UDP socket.
@@ -468,15 +459,6 @@ public:
      */
     Error Bind(SocketHandle &aSocket, const SockAddr &aSockAddr);
 
-    /**
-     * This method binds a UDP socket to the Network interface.
-     *
-     * @param[in]  aSocket           A reference to the socket.
-     * @param[in]  aNetifIdentifier  The network interface identifier.
-     *
-     */
-    void BindToNetif(SocketHandle &aSocket, otNetifIdentifier aNetifIdentifier);
-
     /**
      * This method connects a UDP socket.
      *