diff --git a/core/java/android/net/ConnectivityManager.java b/core/java/android/net/ConnectivityManager.java
index 8333b81..1fbfa40 100644
--- a/core/java/android/net/ConnectivityManager.java
+++ b/core/java/android/net/ConnectivityManager.java
@@ -83,6 +83,7 @@
 @SystemService(Context.CONNECTIVITY_SERVICE)
 public class ConnectivityManager {
     private static final String TAG = "ConnectivityManager";
+    private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
 
     /**
      * A change in network connectivity has occurred. A default connection has either
@@ -2493,6 +2494,7 @@
      * {@hide}
      */
     public void reportInetCondition(int networkType, int percentage) {
+        printStackTrace();
         try {
             mService.reportInetCondition(networkType, percentage);
         } catch (RemoteException e) {
@@ -2513,6 +2515,7 @@
      */
     @Deprecated
     public void reportBadNetwork(Network network) {
+        printStackTrace();
         try {
             // One of these will be ignored because it matches system's current state.
             // The other will trigger the necessary reevaluation.
@@ -2535,6 +2538,7 @@
      *                        Internet using {@code network} or {@code false} if not.
      */
     public void reportNetworkConnectivity(Network network, boolean hasConnectivity) {
+        printStackTrace();
         try {
             mService.reportNetworkConnectivity(network, hasConnectivity);
         } catch (RemoteException e) {
@@ -2727,8 +2731,11 @@
      *
      * @hide
      */
-    @RequiresPermission(android.Manifest.permission.CONNECTIVITY_INTERNAL)
-    @UnsupportedAppUsage
+    @RequiresPermission(anyOf = {
+            android.Manifest.permission.NETWORK_SETTINGS,
+            android.Manifest.permission.NETWORK_SETUP_WIZARD,
+            android.Manifest.permission.NETWORK_STACK})
+    @SystemApi
     public void setAirplaneMode(boolean enable) {
         try {
             mService.setAirplaneMode(enable);
@@ -3073,6 +3080,7 @@
 
     private NetworkRequest sendRequestForNetwork(NetworkCapabilities need, NetworkCallback callback,
             int timeoutMs, int action, int legacyType, CallbackHandler handler) {
+        printStackTrace();
         checkCallbackNotNull(callback);
         Preconditions.checkArgument(action == REQUEST || need != null, "null NetworkCapabilities");
         final NetworkRequest request;
@@ -3332,6 +3340,7 @@
      *         {@link NetworkCapabilities#NET_CAPABILITY_CAPTIVE_PORTAL}.
      */
     public void requestNetwork(NetworkRequest request, PendingIntent operation) {
+        printStackTrace();
         checkPendingIntentNotNull(operation);
         try {
             mService.pendingRequestForNetwork(request.networkCapabilities, operation);
@@ -3355,6 +3364,7 @@
      *                  corresponding NetworkRequest you'd like to remove. Cannot be null.
      */
     public void releaseNetworkRequest(PendingIntent operation) {
+        printStackTrace();
         checkPendingIntentNotNull(operation);
         try {
             mService.releasePendingNetworkRequest(operation);
@@ -3439,6 +3449,7 @@
      */
     @RequiresPermission(android.Manifest.permission.ACCESS_NETWORK_STATE)
     public void registerNetworkCallback(NetworkRequest request, PendingIntent operation) {
+        printStackTrace();
         checkPendingIntentNotNull(operation);
         try {
             mService.pendingListenForNetwork(request.networkCapabilities, operation);
@@ -3520,6 +3531,7 @@
      * @param networkCallback The {@link NetworkCallback} used when making the request.
      */
     public void unregisterNetworkCallback(NetworkCallback networkCallback) {
+        printStackTrace();
         checkCallbackNotNull(networkCallback);
         final List<NetworkRequest> reqs = new ArrayList<>();
         // Find all requests associated to this callback and stop callback triggers immediately.
@@ -3948,4 +3960,19 @@
             throw e.rethrowFromSystemServer();
         }
     }
+
+    private void printStackTrace() {
+        if (DEBUG) {
+            final StackTraceElement[] callStack = Thread.currentThread().getStackTrace();
+            final StringBuffer sb = new StringBuffer();
+            for (int i = 3; i < callStack.length; i++) {
+                final String stackTrace = callStack[i].toString();
+                if (stackTrace == null || stackTrace.contains("android.os")) {
+                    break;
+                }
+                sb.append(" [").append(stackTrace).append("]");
+            }
+            Log.d(TAG, "StackLog:" + sb.toString());
+        }
+    }
 }
diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index b820a2b..686e80b 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -1679,6 +1679,16 @@
                 "ConnectivityService");
     }
 
+    private void enforceAnyPermissionOf(String... permissions) {
+        for (String permission : permissions) {
+            if (mContext.checkCallingOrSelfPermission(permission) == PERMISSION_GRANTED) {
+                return;
+            }
+        }
+        throw new SecurityException(
+            "Requires one of the following permissions: " + String.join(", ", permissions) + ".");
+    }
+
     private void enforceInternetPermission() {
         mContext.enforceCallingOrSelfPermission(
                 android.Manifest.permission.INTERNET,
@@ -1723,6 +1733,13 @@
                 "ConnectivityService");
     }
 
+    private void enforceNetworkStackSettingsOrSetup() {
+        enforceAnyPermissionOf(
+            android.Manifest.permission.NETWORK_SETTINGS,
+            android.Manifest.permission.NETWORK_SETUP_WIZARD,
+            android.Manifest.permission.NETWORK_STACK);
+    }
+
     private boolean checkNetworkStackPermission() {
         return PERMISSION_GRANTED == mContext.checkCallingOrSelfPermission(
                 android.Manifest.permission.NETWORK_STACK);
@@ -1798,7 +1815,8 @@
 
     private void sendStickyBroadcast(Intent intent) {
         synchronized (this) {
-            if (!mSystemReady) {
+            if (!mSystemReady
+                    && intent.getAction().equals(ConnectivityManager.CONNECTIVITY_ACTION)) {
                 mInitialBroadcast = new Intent(intent);
             }
             intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT);
@@ -1847,8 +1865,6 @@
                 mInitialBroadcast = null;
             }
         }
-        // load the global proxy at startup
-        mHandler.sendMessage(mHandler.obtainMessage(EVENT_APPLY_GLOBAL_HTTP_PROXY));
 
         // Try bringing up tracker, but KeyStore won't be ready yet for secondary users so wait
         // for user to unlock device too.
@@ -3089,7 +3105,7 @@
                     break;
                 }
                 case EVENT_APPLY_GLOBAL_HTTP_PROXY: {
-                    handleDeprecatedGlobalHttpProxy();
+                    mProxyTracker.loadDeprecatedGlobalHttpProxy();
                     break;
                 }
                 case EVENT_PROXY_HAS_CHANGED: {
@@ -3483,29 +3499,6 @@
         }
     }
 
-    private void handleDeprecatedGlobalHttpProxy() {
-        final String proxy = Settings.Global.getString(mContext.getContentResolver(),
-                Settings.Global.HTTP_PROXY);
-        if (!TextUtils.isEmpty(proxy)) {
-            String data[] = proxy.split(":");
-            if (data.length == 0) {
-                return;
-            }
-
-            final String proxyHost = data[0];
-            int proxyPort = 8080;
-            if (data.length > 1) {
-                try {
-                    proxyPort = Integer.parseInt(data[1]);
-                } catch (NumberFormatException e) {
-                    return;
-                }
-            }
-            final ProxyInfo p = new ProxyInfo(proxyHost, proxyPort, "");
-            setGlobalProxy(p);
-        }
-    }
-
     private static class SettingsObserver extends ContentObserver {
         final private HashMap<Uri, Integer> mUriEventMap;
         final private Context mContext;
@@ -4008,7 +4001,7 @@
 
     @Override
     public void setAirplaneMode(boolean enable) {
-        enforceConnectivityInternalPermission();
+        enforceNetworkStackSettingsOrSetup();
         final long ident = Binder.clearCallingIdentity();
         try {
             final ContentResolver cr = mContext.getContentResolver();
@@ -5536,15 +5529,7 @@
 
             if (networkAgent.isVPN()) {
                 // Temporarily disable the default proxy (not global).
-                synchronized (mProxyTracker.mProxyLock) {
-                    if (!mProxyTracker.mDefaultProxyDisabled) {
-                        mProxyTracker.mDefaultProxyDisabled = true;
-                        if (mProxyTracker.mGlobalProxy == null
-                                && mProxyTracker.mDefaultProxy != null) {
-                            mProxyTracker.sendProxyBroadcast(null);
-                        }
-                    }
-                }
+                mProxyTracker.setDefaultProxyEnabled(false);
                 // TODO: support proxy per network.
             }
 
@@ -5566,15 +5551,7 @@
         } else if (state == NetworkInfo.State.DISCONNECTED) {
             networkAgent.asyncChannel.disconnect();
             if (networkAgent.isVPN()) {
-                synchronized (mProxyTracker.mProxyLock) {
-                    if (mProxyTracker.mDefaultProxyDisabled) {
-                        mProxyTracker.mDefaultProxyDisabled = false;
-                        if (mProxyTracker.mGlobalProxy == null
-                                && mProxyTracker.mDefaultProxy != null) {
-                            mProxyTracker.sendProxyBroadcast(mProxyTracker.mDefaultProxy);
-                        }
-                    }
-                }
+                mProxyTracker.setDefaultProxyEnabled(true);
                 updateUids(networkAgent, networkAgent.networkCapabilities, null);
             }
             disconnectAndDestroyNetwork(networkAgent);
diff --git a/services/core/java/com/android/server/connectivity/ProxyTracker.java b/services/core/java/com/android/server/connectivity/ProxyTracker.java
index b7bbd42..47e85b5 100644
--- a/services/core/java/com/android/server/connectivity/ProxyTracker.java
+++ b/services/core/java/com/android/server/connectivity/ProxyTracker.java
@@ -16,6 +16,12 @@
 
 package com.android.server.connectivity;
 
+import static android.provider.Settings.Global.GLOBAL_HTTP_PROXY_EXCLUSION_LIST;
+import static android.provider.Settings.Global.GLOBAL_HTTP_PROXY_HOST;
+import static android.provider.Settings.Global.GLOBAL_HTTP_PROXY_PAC;
+import static android.provider.Settings.Global.GLOBAL_HTTP_PROXY_PORT;
+import static android.provider.Settings.Global.HTTP_PROXY;
+
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.content.ContentResolver;
@@ -47,16 +53,14 @@
     @NonNull
     private final Context mContext;
 
-    // TODO : make this private and import as much managing logic from ConnectivityService as
-    // possible
     @NonNull
-    public final Object mProxyLock = new Object();
+    private final Object mProxyLock = new Object();
     // The global proxy is the proxy that is set device-wide, overriding any network-specific
     // proxy. Note however that proxies are hints ; the system does not enforce their use. Hence
     // this value is only for querying.
     @Nullable
     @GuardedBy("mProxyLock")
-    public ProxyInfo mGlobalProxy = null;
+    private ProxyInfo mGlobalProxy = null;
     // The default proxy is the proxy that applies to no particular network if the global proxy
     // is not set. Individual networks have their own settings that override this. This member
     // is set through setDefaultProxy, which is called when the default network changes proxies
@@ -64,10 +68,10 @@
     // when PacManager resolves the proxy.
     @Nullable
     @GuardedBy("mProxyLock")
-    public volatile ProxyInfo mDefaultProxy = null;
-    // Whether the default proxy is disabled. TODO : make this mDefaultProxyEnabled
+    private volatile ProxyInfo mDefaultProxy = null;
+    // Whether the default proxy is enabled.
     @GuardedBy("mProxyLock")
-    public boolean mDefaultProxyDisabled = false;
+    private boolean mDefaultProxyEnabled = true;
 
     // The object responsible for Proxy Auto Configuration (PAC).
     @NonNull
@@ -85,7 +89,7 @@
     @Nullable
     private static ProxyInfo canonicalizeProxyInfo(@Nullable final ProxyInfo proxy) {
         if (proxy != null && TextUtils.isEmpty(proxy.getHost())
-                && (proxy.getPacFileUrl() == null || Uri.EMPTY.equals(proxy.getPacFileUrl()))) {
+                && Uri.EMPTY.equals(proxy.getPacFileUrl())) {
             return null;
         }
         return proxy;
@@ -123,7 +127,7 @@
         // This information is already available as a world read/writable jvm property.
         synchronized (mProxyLock) {
             final ProxyInfo ret = mGlobalProxy;
-            if ((ret == null) && !mDefaultProxyDisabled) return mDefaultProxy;
+            if ((ret == null) && mDefaultProxyEnabled) return mDefaultProxy;
             return ret;
         }
     }
@@ -146,11 +150,10 @@
      */
     public void loadGlobalProxy() {
         ContentResolver res = mContext.getContentResolver();
-        String host = Settings.Global.getString(res, Settings.Global.GLOBAL_HTTP_PROXY_HOST);
-        int port = Settings.Global.getInt(res, Settings.Global.GLOBAL_HTTP_PROXY_PORT, 0);
-        String exclList = Settings.Global.getString(res,
-                Settings.Global.GLOBAL_HTTP_PROXY_EXCLUSION_LIST);
-        String pacFileUrl = Settings.Global.getString(res, Settings.Global.GLOBAL_HTTP_PROXY_PAC);
+        String host = Settings.Global.getString(res, GLOBAL_HTTP_PROXY_HOST);
+        int port = Settings.Global.getInt(res, GLOBAL_HTTP_PROXY_PORT, 0);
+        String exclList = Settings.Global.getString(res, GLOBAL_HTTP_PROXY_EXCLUSION_LIST);
+        String pacFileUrl = Settings.Global.getString(res, GLOBAL_HTTP_PROXY_PAC);
         if (!TextUtils.isEmpty(host) || !TextUtils.isEmpty(pacFileUrl)) {
             ProxyInfo proxyProperties;
             if (!TextUtils.isEmpty(pacFileUrl)) {
@@ -167,10 +170,36 @@
                 mGlobalProxy = proxyProperties;
             }
         }
+        loadDeprecatedGlobalHttpProxy();
         // TODO : shouldn't this function call mPacManager.setCurrentProxyScriptUrl ?
     }
 
     /**
+     * Read the global proxy from the deprecated Settings.Global.HTTP_PROXY setting and apply it.
+     */
+    public void loadDeprecatedGlobalHttpProxy() {
+        final String proxy = Settings.Global.getString(mContext.getContentResolver(), HTTP_PROXY);
+        if (!TextUtils.isEmpty(proxy)) {
+            String data[] = proxy.split(":");
+            if (data.length == 0) {
+                return;
+            }
+
+            final String proxyHost = data[0];
+            int proxyPort = 8080;
+            if (data.length > 1) {
+                try {
+                    proxyPort = Integer.parseInt(data[1]);
+                } catch (NumberFormatException e) {
+                    return;
+                }
+            }
+            final ProxyInfo p = new ProxyInfo(proxyHost, proxyPort, "");
+            setGlobalProxy(p);
+        }
+    }
+
+    /**
      * Sends the system broadcast informing apps about a new proxy configuration.
      *
      * Confusingly this method also sets the PAC file URL. TODO : separate this, it has nothing
@@ -232,11 +261,10 @@
             final ContentResolver res = mContext.getContentResolver();
             final long token = Binder.clearCallingIdentity();
             try {
-                Settings.Global.putString(res, Settings.Global.GLOBAL_HTTP_PROXY_HOST, host);
-                Settings.Global.putInt(res, Settings.Global.GLOBAL_HTTP_PROXY_PORT, port);
-                Settings.Global.putString(res, Settings.Global.GLOBAL_HTTP_PROXY_EXCLUSION_LIST,
-                        exclList);
-                Settings.Global.putString(res, Settings.Global.GLOBAL_HTTP_PROXY_PAC, pacFileUrl);
+                Settings.Global.putString(res, GLOBAL_HTTP_PROXY_HOST, host);
+                Settings.Global.putInt(res, GLOBAL_HTTP_PROXY_PORT, port);
+                Settings.Global.putString(res, GLOBAL_HTTP_PROXY_EXCLUSION_LIST, exclList);
+                Settings.Global.putString(res, GLOBAL_HTTP_PROXY_PAC, pacFileUrl);
             } finally {
                 Binder.restoreCallingIdentity(token);
             }
@@ -253,10 +281,7 @@
      */
     public void setDefaultProxy(@Nullable ProxyInfo proxyInfo) {
         synchronized (mProxyLock) {
-            if (mDefaultProxy != null && mDefaultProxy.equals(proxyInfo)) {
-                return;
-            }
-            if (mDefaultProxy == proxyInfo) return; // catches repeated nulls
+            if (Objects.equals(mDefaultProxy, proxyInfo)) return;
             if (proxyInfo != null &&  !proxyInfo.isValid()) {
                 if (DBG) Slog.d(TAG, "Invalid proxy properties, ignoring: " + proxyInfo);
                 return;
@@ -277,9 +302,27 @@
             mDefaultProxy = proxyInfo;
 
             if (mGlobalProxy != null) return;
-            if (!mDefaultProxyDisabled) {
+            if (mDefaultProxyEnabled) {
                 sendProxyBroadcast(proxyInfo);
             }
         }
     }
+
+    /**
+     * Enable or disable the default proxy.
+     *
+     * This sets the flag for enabling/disabling the default proxy and sends the broadcast
+     * if applicable.
+     * @param enabled whether the default proxy should be enabled.
+     */
+    public void setDefaultProxyEnabled(final boolean enabled) {
+        synchronized (mProxyLock) {
+            if (mDefaultProxyEnabled != enabled) {
+                mDefaultProxyEnabled = enabled;
+                if (mGlobalProxy == null && mDefaultProxy != null) {
+                    sendProxyBroadcast(enabled ? mDefaultProxy : null);
+                }
+            }
+        }
+    }
 }