Track enable/disable of transport components

For fallback / rollback of backup transport selection we need to
handle live enable/disable of legacy or superseded transports.
We now watch for component enable state changes in packages that
host transports, and rebind as needed.

The semantics for selecting the current transport have also been
adjusted.  We no longer require that the selected transport be
live and currently bound in order to be designated as the active
instance.  This prevents nondeterministic races around upgrade
and replacement.

Bug 17136637

Change-Id: Idaf45cf4522a23576444e6b11626ee3f7f47c36c

1 files changed, 60 insertions, 31 deletions

diff --git a/services/backup/java/com/android/server/backup/BackupManagerService.java b/services/backup/java/com/android/server/backup/BackupManagerService.java
index 083aa9b..f6e2e67 100644
--- a/services/backup/java/com/android/server/backup/BackupManagerService.java
+++ b/services/backup/java/com/android/server/backup/BackupManagerService.java
@@ -1234,6 +1234,7 @@ public class BackupManagerService extends IBackupManager.Stub {
         IntentFilter filter = new IntentFilter();
         filter.addAction(Intent.ACTION_PACKAGE_ADDED);
         filter.addAction(Intent.ACTION_PACKAGE_REMOVED);
+        filter.addAction(Intent.ACTION_PACKAGE_CHANGED);
         filter.addDataScheme("package");
         mContext.registerReceiver(mBroadcastReceiver, filter);
         // Register for events related to sdcard installation.
@@ -1688,11 +1689,12 @@ public class BackupManagerService extends IBackupManager.Stub {
             String action = intent.getAction();
             boolean replacing = false;
             boolean added = false;
-            boolean rebind = false;
+            boolean changed = false;
             Bundle extras = intent.getExtras();
             String pkgList[] = null;
             if (Intent.ACTION_PACKAGE_ADDED.equals(action) ||
-                    Intent.ACTION_PACKAGE_REMOVED.equals(action)) {
+                    Intent.ACTION_PACKAGE_REMOVED.equals(action) ||
+                    Intent.ACTION_PACKAGE_CHANGED.equals(action)) {
                 Uri uri = intent.getData();
                 if (uri == null) {
                     return;
@@ -1701,7 +1703,43 @@ public class BackupManagerService extends IBackupManager.Stub {
                 if (pkgName != null) {
                     pkgList = new String[] { pkgName };
                 }
-                rebind = added = Intent.ACTION_PACKAGE_ADDED.equals(action);
+                changed = Intent.ACTION_PACKAGE_CHANGED.equals(action);
+
+                // At package-changed we only care about looking at new transport states
+                if (changed) {
+                    try {
+                        if (MORE_DEBUG) {
+                            Slog.i(TAG, "Package " + pkgName + " changed; rechecking");
+                        }
+                        // unbind existing possibly-stale connections to that package's transports
+                        synchronized (mTransports) {
+                            TransportConnection conn = mTransportConnections.get(pkgName);
+                            if (conn != null) {
+                                final ServiceInfo svc = conn.mTransport;
+                                ComponentName svcName =
+                                        new ComponentName(svc.packageName, svc.name);
+                                String flatName = svcName.flattenToShortString();
+                                Slog.i(TAG, "Unbinding " + svcName);
+
+                                mContext.unbindService(conn);
+                                mTransportConnections.remove(pkgName);
+                                mTransports.remove(mTransportNames.get(flatName));
+                                mTransportNames.remove(flatName);
+                            }
+                        }
+                        // and then (re)bind as appropriate
+                        PackageInfo app = mPackageManager.getPackageInfo(pkgName, 0);
+                        checkForTransportAndBind(app);
+                    } catch (NameNotFoundException e) {
+                        // Nope, can't find it - just ignore
+                        if (MORE_DEBUG) {
+                            Slog.w(TAG, "Can't find changed package " + pkgName);
+                        }
+                    }
+                    return; // nothing more to do in the PACKAGE_CHANGED case
+                }
+
+                added = Intent.ACTION_PACKAGE_ADDED.equals(action);
                 replacing = extras.getBoolean(Intent.EXTRA_REPLACING, false);
             } else if (Intent.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE.equals(action)) {
                 added = true;
@@ -1737,17 +1775,15 @@ public class BackupManagerService extends IBackupManager.Stub {
 
                         // Transport maintenance: rebind to known existing transports that have
                         // just been updated; and bind to any newly-installed transport services.
-                        if (rebind) {
-                            synchronized (mTransportConnections) {
-                                final TransportConnection conn = mTransportConnections.get(packageName);
-                                if (conn != null) {
-                                    if (DEBUG) {
-                                        Slog.i(TAG, "Transport package changed; rebinding");
-                                    }
-                                    bindTransport(conn.mTransport);
-                                } else {
-                                    checkForTransportAndBind(app);
+                        synchronized (mTransports) {
+                            final TransportConnection conn = mTransportConnections.get(packageName);
+                            if (conn != null) {
+                                if (MORE_DEBUG) {
+                                    Slog.i(TAG, "Transport package changed; rebinding");
                                 }
+                                bindTransport(conn.mTransport);
+                            } else {
+                                checkForTransportAndBind(app);
                             }
                         }
 
@@ -1840,7 +1876,7 @@ public class BackupManagerService extends IBackupManager.Stub {
         intent.setComponent(svcName);
 
         TransportConnection connection;
-        synchronized (mTransportConnections) {
+        synchronized (mTransports) {
             connection = mTransportConnections.get(transport.packageName);
             if (null == connection) {
                 connection = new TransportConnection(transport);
@@ -8462,31 +8498,24 @@ if (MORE_DEBUG) Slog.v(TAG, "   + got " + nRead + "; now wanting " + (size - soF
         return list;
     }
 
-    // Select which transport to use for the next backup operation.  If the given
-    // name is not one of the available transports, no action is taken and the method
-    // returns null.
+    // Select which transport to use for the next backup operation.
     public String selectBackupTransport(String transport) {
         mContext.enforceCallingOrSelfPermission(android.Manifest.permission.BACKUP,
                 "selectBackupTransport");
 
         synchronized (mTransports) {
-            String prevTransport = null;
-            if (mTransports.get(transport) != null) {
-                final long oldId = Binder.clearCallingIdentity();
-                try {
-                    prevTransport = mCurrentTransport;
-                    mCurrentTransport = transport;
-                    Settings.Secure.putString(mContext.getContentResolver(),
-                            Settings.Secure.BACKUP_TRANSPORT, transport);
-                } finally {
-                    Binder.restoreCallingIdentity(oldId);
-                }
+            final long oldId = Binder.clearCallingIdentity();
+            try {
+                String prevTransport = mCurrentTransport;
+                mCurrentTransport = transport;
+                Settings.Secure.putString(mContext.getContentResolver(),
+                        Settings.Secure.BACKUP_TRANSPORT, transport);
                 Slog.v(TAG, "selectBackupTransport() set " + mCurrentTransport
                         + " returning " + prevTransport);
-            } else {
-                Slog.w(TAG, "Attempt to select unavailable transport " + transport);
+                return prevTransport;
+            } finally {
+                Binder.restoreCallingIdentity(oldId);
             }
-            return prevTransport;
         }
     }