Merge "Add a method to create a TAP interface with a given interface name."

framework/src/android/net/ITestNetworkManager.aidl

@@ -29,7 +29,8 @@ import android.os.ParcelFileDescriptor;
  */
 interface ITestNetworkManager
 {
-    TestNetworkInterface createInterface(boolean isTun, boolean bringUp, in LinkAddress[] addrs);
+    TestNetworkInterface createInterface(boolean isTun, boolean bringUp, in LinkAddress[] addrs,
+            in @nullable String iface);
 
     void setupTestNetwork(in String iface, in LinkProperties lp, in boolean isMetered,
             in int[] administratorUids, in IBinder binder);

framework/src/android/net/TestNetworkManager.java

@@ -45,6 +45,12 @@ public class TestNetworkManager {
      */
     public static final String TEST_TAP_PREFIX = "testtap";
 
+    /**
+     * Prefix for clat interfaces.
+     * @hide
+     */
+    public static final String CLAT_INTERFACE_PREFIX = "v4-";
+
     @NonNull private static final String TAG = TestNetworkManager.class.getSimpleName();
 
     @NonNull private final ITestNetworkManager mService;
@@ -160,7 +166,8 @@ public class TestNetworkManager {
     public TestNetworkInterface createTunInterface(@NonNull Collection<LinkAddress> linkAddrs) {
         try {
             final LinkAddress[] arr = new LinkAddress[linkAddrs.size()];
-            return mService.createInterface(TUN, BRING_UP, linkAddrs.toArray(arr));
+            return mService.createInterface(TUN, BRING_UP, linkAddrs.toArray(arr),
+                    null /* iface */);
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }
@@ -178,7 +185,7 @@ public class TestNetworkManager {
     @NonNull
     public TestNetworkInterface createTapInterface() {
         try {
-            return mService.createInterface(TAP, BRING_UP, NO_ADDRS);
+            return mService.createInterface(TAP, BRING_UP, NO_ADDRS, null /* iface */);
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }
@@ -197,7 +204,29 @@ public class TestNetworkManager {
     @NonNull
     public TestNetworkInterface createTapInterface(boolean bringUp) {
         try {
-            return mService.createInterface(TAP, bringUp, NO_ADDRS);
+            return mService.createInterface(TAP, bringUp, NO_ADDRS, null /* iface */);
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
+    /**
+     * Create a tap interface with a given interface name for testing purposes
+     *
+     * @param bringUp whether to bring up the interface before returning it.
+     * @param iface interface name to be assigned, so far only interface name which starts with
+     *              "v4-testtap" or "v4-testtun" is allowed to be created. If it's null, then use
+     *              the default name(e.g. testtap or testtun).
+     *
+     * @return A ParcelFileDescriptor of the underlying TAP interface. Close this to tear down the
+     *     TAP interface.
+     * @hide
+     */
+    @RequiresPermission(Manifest.permission.MANAGE_TEST_NETWORKS)
+    @NonNull
+    public TestNetworkInterface createTapInterface(boolean bringUp, @NonNull String iface) {
+        try {
+            return mService.createInterface(TAP, bringUp, NO_ADDRS, iface);
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }

service/src/com/android/server/TestNetworkService.java

@@ -16,6 +16,7 @@
 
 package com.android.server;
 
+import static android.net.TestNetworkManager.CLAT_INTERFACE_PREFIX;
 import static android.net.TestNetworkManager.TEST_TAP_PREFIX;
 import static android.net.TestNetworkManager.TEST_TUN_PREFIX;
 
@@ -98,6 +99,14 @@ class TestNetworkService extends ITestNetworkManager.Stub {
         }
     }
 
+    // TODO: find a way to allow the caller to pass in non-clat interface names, ensuring that
+    // those names do not conflict with names created by callers that do not pass in an interface
+    // name.
+    private static boolean isValidInterfaceName(@NonNull final String iface) {
+        return iface.startsWith(CLAT_INTERFACE_PREFIX + TEST_TUN_PREFIX)
+                || iface.startsWith(CLAT_INTERFACE_PREFIX + TEST_TAP_PREFIX);
+    }
+
     /**
      * Create a TUN or TAP interface with the specified parameters.
      *
@@ -106,29 +115,35 @@ class TestNetworkService extends ITestNetworkManager.Stub {
      */
     @Override
     public TestNetworkInterface createInterface(boolean isTun, boolean bringUp,
-            LinkAddress[] linkAddrs) {
+            LinkAddress[] linkAddrs, @Nullable String iface) {
         enforceTestNetworkPermissions(mContext);
 
         Objects.requireNonNull(linkAddrs, "missing linkAddrs");
 
-        String ifacePrefix = isTun ? TEST_TUN_PREFIX : TEST_TAP_PREFIX;
+        String interfaceName = iface;
-        String iface = ifacePrefix + sTestTunIndex.getAndIncrement();
+        if (iface == null) {
+            String ifacePrefix = isTun ? TEST_TUN_PREFIX : TEST_TAP_PREFIX;
+            interfaceName = ifacePrefix + sTestTunIndex.getAndIncrement();
+        } else if (!isValidInterfaceName(iface)) {
+            throw new IllegalArgumentException("invalid interface name requested: " + iface);
+        }
+
         final long token = Binder.clearCallingIdentity();
         try {
             ParcelFileDescriptor tunIntf =
-                    ParcelFileDescriptor.adoptFd(jniCreateTunTap(isTun, iface));
+                    ParcelFileDescriptor.adoptFd(jniCreateTunTap(isTun, interfaceName));
             for (LinkAddress addr : linkAddrs) {
                 mNetd.interfaceAddAddress(
-                        iface,
+                        interfaceName,
                         addr.getAddress().getHostAddress(),
                         addr.getPrefixLength());
             }
 
             if (bringUp) {
-                NetdUtils.setInterfaceUp(mNetd, iface);
+                NetdUtils.setInterfaceUp(mNetd, interfaceName);
             }
 
-            return new TestNetworkInterface(tunIntf, iface);
+            return new TestNetworkInterface(tunIntf, interfaceName);
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         } finally {