diff --git a/thread/service/java/com/android/server/thread/ThreadNetworkControllerService.java b/thread/service/java/com/android/server/thread/ThreadNetworkControllerService.java
index 3470f27..f5ebc90 100644
--- a/thread/service/java/com/android/server/thread/ThreadNetworkControllerService.java
+++ b/thread/service/java/com/android/server/thread/ThreadNetworkControllerService.java
@@ -206,6 +206,7 @@
         return mOtDaemon;
     }
 
+    // TODO(b/309792480): restarts the OT daemon service
     private void onOtDaemonDied() {
         Log.w(TAG, "OT daemon became dead, clean up...");
         OperationReceiverWrapper.onOtDaemonDied();
@@ -462,9 +463,15 @@
     private void handleDeviceRoleChanged(@DeviceRole int deviceRole) {
         if (ThreadNetworkController.isAttached(deviceRole)) {
             Log.d(TAG, "Attached to the Thread network");
+
+            // This is an idempotent method which can be called for multiple times when the device
+            // is already attached (e.g. going from Child to Router)
             registerThreadNetwork();
         } else {
             Log.d(TAG, "Detached from the Thread network");
+
+            // This is an idempotent method which can be called for multiple times when the device
+            // is already detached or stopped
             unregisterThreadNetwork();
         }
     }
@@ -521,7 +528,7 @@
         public void registerStateCallback(IStateCallback callback) {
             checkOnHandlerThread();
             if (mStateCallbacks.containsKey(callback)) {
-                return;
+                throw new IllegalStateException("Registering the same IStateCallback twice");
             }
 
             IBinder.DeathRecipient deathRecipient =
@@ -553,7 +560,8 @@
         public void registerDatasetCallback(IOperationalDatasetCallback callback) {
             checkOnHandlerThread();
             if (mOpDatasetCallbacks.containsKey(callback)) {
-                return;
+                throw new IllegalStateException(
+                        "Registering the same IOperationalDatasetCallback twice");
             }
 
             IBinder.DeathRecipient deathRecipient =
@@ -628,7 +636,7 @@
                 mActiveDataset = newActiveDataset;
             } catch (IllegalArgumentException e) {
                 // Is unlikely that OT will generate invalid Operational Dataset
-                Log.w(TAG, "Ignoring invalid Active Operational Dataset changes", e);
+                Log.wtf(TAG, "Invalid Active Operational Dataset from OpenThread", e);
             }
 
             PendingOperationalDataset newPendingDataset;
@@ -642,7 +650,8 @@
                 onPendingOperationalDatasetChanged(newPendingDataset, listenerId);
                 mPendingDataset = newPendingDataset;
             } catch (IllegalArgumentException e) {
-                Log.w(TAG, "Ignoring invalid Pending Operational Dataset changes", e);
+                // Is unlikely that OT will generate invalid Operational Dataset
+                Log.wtf(TAG, "Invalid Pending Operational Dataset from OpenThread", e);
             }
         }
 
diff --git a/thread/service/java/com/android/server/thread/TunInterfaceController.java b/thread/service/java/com/android/server/thread/TunInterfaceController.java
index ac65b11..7223b2a 100644
--- a/thread/service/java/com/android/server/thread/TunInterfaceController.java
+++ b/thread/service/java/com/android/server/thread/TunInterfaceController.java
@@ -16,6 +16,7 @@
 
 package com.android.server.thread;
 
+import android.annotation.Nullable;
 import android.net.LinkAddress;
 import android.net.util.SocketUtils;
 import android.os.ParcelFileDescriptor;
@@ -34,6 +35,7 @@
 /** Controller for virtual/tunnel network interfaces. */
 public class TunInterfaceController {
     private static final String TAG = "TunIfController";
+    private static final long INFINITE_LIFETIME = 0xffffffffL;
     static final int MTU = 1280;
 
     static {
@@ -76,6 +78,7 @@
     }
 
     /** Returns the FD of the tunnel interface. */
+    @Nullable
     public ParcelFileDescriptor getTunFd() {
         return mParcelTunFd;
     }
@@ -98,7 +101,7 @@
 
         if (address.getDeprecationTime() == LinkAddress.LIFETIME_PERMANENT
                 || address.getDeprecationTime() == LinkAddress.LIFETIME_UNKNOWN) {
-            validLifetimeSeconds = 0xffffffffL;
+            validLifetimeSeconds = INFINITE_LIFETIME;
         } else {
             validLifetimeSeconds =
                     Math.max(
@@ -108,7 +111,7 @@
 
         if (address.getExpirationTime() == LinkAddress.LIFETIME_PERMANENT
                 || address.getExpirationTime() == LinkAddress.LIFETIME_UNKNOWN) {
-            preferredLifetimeSeconds = 0xffffffffL;
+            preferredLifetimeSeconds = INFINITE_LIFETIME;
         } else {
             preferredLifetimeSeconds =
                     Math.max(
diff --git a/thread/service/jni/com_android_server_thread_TunInterfaceController.cpp b/thread/service/jni/com_android_server_thread_TunInterfaceController.cpp
index ed39fab..c56bc0b 100644
--- a/thread/service/jni/com_android_server_thread_TunInterfaceController.cpp
+++ b/thread/service/jni/com_android_server_thread_TunInterfaceController.cpp
@@ -53,25 +53,25 @@
     strlcpy(ifr.ifr_name, ifName.c_str(), sizeof(ifr.ifr_name));
 
     if (ioctl(fd, TUNSETIFF, &ifr, sizeof(ifr)) != 0) {
-        close(fd);
         jniThrowExceptionFmt(env, "java/io/IOException", "ioctl(TUNSETIFF) failed (%s)",
                              strerror(errno));
+        close(fd);
         return -1;
     }
 
     int inet6 = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, IPPROTO_IP);
     if (inet6 == -1) {
-        close(fd);
         jniThrowExceptionFmt(env, "java/io/IOException", "create inet6 socket failed (%s)",
                              strerror(errno));
+        close(fd);
         return -1;
     }
     ifr.ifr_mtu = mtu;
     if (ioctl(inet6, SIOCSIFMTU, &ifr) != 0) {
-        close(fd);
-        close(inet6);
         jniThrowExceptionFmt(env, "java/io/IOException", "ioctl(SIOCSIFMTU) failed (%s)",
                              strerror(errno));
+        close(fd);
+        close(inet6);
         return -1;
     }
 
@@ -94,7 +94,6 @@
     }
 
     if (ioctl(inet6, SIOCSIFFLAGS, &ifr) != 0) {
-        close(inet6);
         jniThrowExceptionFmt(env, "java/io/IOException", "ioctl(SIOCSIFFLAGS) failed (%s)",
                              strerror(errno));
     }