[meshcop] fix UDP proxy (#6396)

The MeshCoP UDP Proxy packets should not be sent/received with
platform UDP.

src/core/meshcop/border_agent.cpp

@@ -185,6 +185,9 @@ void BorderAgent::HandleCoapResponse(ForwardContext &aForwardContext, const Coap
             IgnoreError(Get<Mle::MleRouter>().GetCommissionerAloc(mCommissionerAloc.GetAddress(), sessionId));
             Get<ThreadNetif>().AddUnicastAddress(mCommissionerAloc);
             IgnoreError(Get<Ip6::Udp>().AddReceiver(mUdpReceiver));
+
+            otLogInfoMeshCoP("commissioner accepted: session ID=%d, ALOC=%s", sessionId,
+                             mCommissionerAloc.GetAddress().ToString().AsCString());
         }
     }
 
@@ -285,6 +288,7 @@ BorderAgent::BorderAgent(Instance &aInstance)
     , mUdpReceiver(BorderAgent::HandleUdpReceive, this)
     , mTimer(aInstance, HandleTimeout)
     , mState(kStateStopped)
+    , mUdpProxyPort(0)
 {
     mCommissionerAloc.InitAsThreadOriginRealmLocalScope();
 }
@@ -325,14 +329,18 @@ void BorderAgent::HandleProxyTransmit(const Coap::Message &aMessage)
     SuccessOrExit(error = message->SetLength(tlv.GetUdpLength()));
     aMessage.CopyTo(offset + sizeof(tlv), 0, tlv.GetUdpLength(), *message);
 
-    messageInfo.SetSockPort(tlv.GetSourcePort() != 0 ? tlv.GetSourcePort() : Get<Ip6::Udp>().GetEphemeralPort());
+    VerifyOrExit(tlv.GetSourcePort() > 0 && tlv.GetDestinationPort() > 0, error = kErrorDrop);
+
+    messageInfo.SetSockPort(tlv.GetSourcePort());
     messageInfo.SetSockAddr(mCommissionerAloc.GetAddress());
     messageInfo.SetPeerPort(tlv.GetDestinationPort());
 
     SuccessOrExit(error = Tlv::Find<Ip6AddressTlv>(aMessage, messageInfo.GetPeerAddr()));
 
     SuccessOrExit(error = Get<Ip6::Udp>().SendDatagram(*message, messageInfo, Ip6::kProtoUdp));
-    otLogInfoMeshCoP("Proxy transmit sent");
+    mUdpProxyPort = tlv.GetSourcePort();
+
+    otLogInfoMeshCoP("Proxy transmit sent to %s", messageInfo.GetPeerAddr().ToString().AsCString());
 
 exit:
     FreeMessageOnError(message, error);
@@ -557,7 +565,8 @@ void BorderAgent::HandleConnected(bool aConnected)
         otLogInfoMeshCoP("Commissioner disconnected");
         IgnoreError(Get<Ip6::Udp>().RemoveReceiver(mUdpReceiver));
         Get<ThreadNetif>().RemoveUnicastAddress(mCommissionerAloc);
-        mState = kStateStarted;
+        mState        = kStateStarted;
+        mUdpProxyPort = 0;
     }
 }
 
@@ -585,7 +594,8 @@ Error BorderAgent::Start(void)
 
     Get<Tmf::TmfAgent>().AddResource(mRelayReceive);
 
-    mState = kStateStarted;
+    mState        = kStateStarted;
+    mUdpProxyPort = 0;
 
 exit:
     return error;
@@ -629,7 +639,8 @@ Error BorderAgent::Stop(void)
 
     coaps.Stop();
 
-    mState = kStateStopped;
+    mState        = kStateStopped;
+    mUdpProxyPort = 0;
 
 exit:
     return error;

src/core/meshcop/border_agent.hpp

@@ -106,6 +106,15 @@ public:
      */
     void ApplyMeshLocalPrefix(void);
 
+    /**
+     * This method returns the UDP Proxy port to which the commissioner is currently
+     * bound.
+     *
+     * @returns  The current UDP Proxy port or 0 if no Proxy Transmit has been received yet.
+     *
+     */
+    uint16_t GetUdpProxyPort(void) const { return mUdpProxyPort; }
+
 private:
     class ForwardContext : public InstanceLocatorInit
     {
@@ -187,6 +196,7 @@ private:
 
     TimerMilli mTimer;
     State      mState;
+    uint16_t   mUdpProxyPort;
 };
 
 } // namespace MeshCoP

src/core/meshcop/dataset_manager.cpp

@@ -448,7 +448,8 @@ void DatasetManager::SendGetResponse(const Coap::Message &   aRequest,
 
     SuccessOrExit(error = Get<Tmf::TmfAgent>().SendMessage(*message, aMessageInfo));
 
-    otLogInfoMeshCoP("sent dataset get response");
+    otLogInfoMeshCoP("sent %s dataset get response to %s", (GetType() == Dataset::kActive ? "active" : "pending"),
+                     aMessageInfo.GetPeerAddr().ToString().AsCString());
 
 exit:
     FreeMessageOnError(message, error);

src/core/net/ip6_address.hpp

@@ -421,7 +421,7 @@ public:
     bool IsAnycastLocator(void) const;
 
     /**
-     * This method indicates whether or not the Interface Identifier (IID) matches a Service Anycast  Locator (ALOC).
+     * This method indicates whether or not the Interface Identifier (IID) matches a Service Anycast Locator (ALOC).
      *
      * In addition to checking that the IID matches the locator pattern (`0000:00ff:fe00:xxxx`), this method also
      * checks that the locator value is a valid Service ALOC16 (0xfc10 – 0xfc2f).

src/core/net/udp6.cpp

@@ -527,6 +527,9 @@ exit:
 bool Udp::ShouldUsePlatformUdp(uint16_t aPort) const
 {
     return (aPort != Mle::kUdpPort && aPort != Tmf::kUdpPort
+#if OPENTHREAD_CONFIG_BORDER_AGENT_ENABLE
+            && aPort != Get<MeshCoP::BorderAgent>().GetUdpProxyPort()
+#endif
 #if OPENTHREAD_FTD
             && aPort != Get<MeshCoP::JoinerRouter>().GetJoinerUdpPort()
 #endif