TestNetworkService: add support for creating iface without carrier

Disabling the carrier of a tun/tap interface before the interface is
brought up is useful in testing.

Test: atest EthernetManagerTest
Change-Id: Ic189b2c0eda76e3f58c3f664e5f5d18c2d7e6e96
diff --git a/framework/src/android/net/ITestNetworkManager.aidl b/framework/src/android/net/ITestNetworkManager.aidl
index b5aadc6..d18b931 100644
--- a/framework/src/android/net/ITestNetworkManager.aidl
+++ b/framework/src/android/net/ITestNetworkManager.aidl
@@ -29,8 +29,8 @@
  */
 interface ITestNetworkManager
 {
-    TestNetworkInterface createInterface(boolean isTun, boolean bringUp, in LinkAddress[] addrs,
-            in @nullable String iface);
+    TestNetworkInterface createInterface(boolean isTun, boolean hasCarrier, boolean bringUp,
+            in LinkAddress[] addrs, in @nullable String iface);
 
     void setCarrierEnabled(in TestNetworkInterface iface, boolean enabled);
 
diff --git a/framework/src/android/net/TestNetworkManager.java b/framework/src/android/net/TestNetworkManager.java
index 8c6bf92..7b18765 100644
--- a/framework/src/android/net/TestNetworkManager.java
+++ b/framework/src/android/net/TestNetworkManager.java
@@ -58,6 +58,7 @@
     private static final boolean TAP = false;
     private static final boolean TUN = true;
     private static final boolean BRING_UP = true;
+    private static final boolean CARRIER_UP = true;
     private static final LinkAddress[] NO_ADDRS = new LinkAddress[0];
 
     /** @hide */
@@ -166,7 +167,7 @@
     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, CARRIER_UP, BRING_UP, linkAddrs.toArray(arr),
                     null /* iface */);
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
@@ -185,7 +186,7 @@
     @NonNull
     public TestNetworkInterface createTapInterface() {
         try {
-            return mService.createInterface(TAP, BRING_UP, NO_ADDRS, null /* iface */);
+            return mService.createInterface(TAP, CARRIER_UP, BRING_UP, NO_ADDRS, null /* iface */);
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }
@@ -204,7 +205,7 @@
     @NonNull
     public TestNetworkInterface createTapInterface(boolean bringUp) {
         try {
-            return mService.createInterface(TAP, bringUp, NO_ADDRS, null /* iface */);
+            return mService.createInterface(TAP, CARRIER_UP, bringUp, NO_ADDRS, null /* iface */);
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }
@@ -226,7 +227,24 @@
     @NonNull
     public TestNetworkInterface createTapInterface(boolean bringUp, @NonNull String iface) {
         try {
-            return mService.createInterface(TAP, bringUp, NO_ADDRS, iface);
+            return mService.createInterface(TAP, CARRIER_UP, bringUp, NO_ADDRS, iface);
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
+    /**
+     * Create a tap interface with or without carrier for testing purposes.
+     *
+     * @param carrierUp whether the created interface has a carrier or not.
+     * @param bringUp whether to bring up the interface before returning it.
+     * @hide
+     */
+    @RequiresPermission(Manifest.permission.MANAGE_TEST_NETWORKS)
+    @NonNull
+    public TestNetworkInterface createTapInterface(boolean carrierUp, boolean bringUp) {
+        try {
+            return mService.createInterface(TAP, carrierUp, bringUp, NO_ADDRS, null /* iface */);
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }
diff --git a/service/jni/com_android_server_TestNetworkService.cpp b/service/jni/com_android_server_TestNetworkService.cpp
index 0a9a3a2..9c7a761 100644
--- a/service/jni/com_android_server_TestNetworkService.cpp
+++ b/service/jni/com_android_server_TestNetworkService.cpp
@@ -59,7 +59,7 @@
     }
 }
 
-static int createTunTapImpl(JNIEnv* env, bool isTun, const char* iface) {
+static int createTunTapImpl(JNIEnv* env, bool isTun, bool hasCarrier, const char* iface) {
     base::unique_fd tun(open("/dev/tun", O_RDWR | O_NONBLOCK));
     ifreq ifr{};
 
@@ -71,6 +71,11 @@
         return -1;
     }
 
+    if (!hasCarrier) {
+        // disable carrier before setting IFF_UP
+        setTunTapCarrierEnabledImpl(env, iface, tun.get(), hasCarrier);
+    }
+
     // Activate interface using an unconnected datagram socket.
     base::unique_fd inet6CtrlSock(socket(AF_INET6, SOCK_DGRAM, 0));
     ifr.ifr_flags = IFF_UP;
@@ -96,21 +101,22 @@
     setTunTapCarrierEnabledImpl(env, iface.c_str(), tunFd, enabled);
 }
 
-static jint createTunTap(JNIEnv* env, jclass /* clazz */, jboolean isTun, jstring jIface) {
+static jint createTunTap(JNIEnv* env, jclass /* clazz */, jboolean isTun,
+                             jboolean hasCarrier, jstring jIface) {
     ScopedUtfChars iface(env, jIface);
     if (!iface.c_str()) {
         jniThrowNullPointerException(env, "iface");
         return -1;
     }
 
-    return createTunTapImpl(env, isTun, iface.c_str());
+    return createTunTapImpl(env, isTun, hasCarrier, iface.c_str());
 }
 
 //------------------------------------------------------------------------------
 
 static const JNINativeMethod gMethods[] = {
     {"nativeSetTunTapCarrierEnabled", "(Ljava/lang/String;IZ)V", (void*)setTunTapCarrierEnabled},
-    {"nativeCreateTunTap", "(ZLjava/lang/String;)I", (void*)createTunTap},
+    {"nativeCreateTunTap", "(ZZLjava/lang/String;)I", (void*)createTunTap},
 };
 
 int register_com_android_server_TestNetworkService(JNIEnv* env) {
diff --git a/service/src/com/android/server/TestNetworkService.java b/service/src/com/android/server/TestNetworkService.java
index 0d50b32..1209579 100644
--- a/service/src/com/android/server/TestNetworkService.java
+++ b/service/src/com/android/server/TestNetworkService.java
@@ -77,7 +77,8 @@
     @NonNull private final NetworkProvider mNetworkProvider;
 
     // Native method stubs
-    private static native int nativeCreateTunTap(boolean isTun, @NonNull String iface);
+    private static native int nativeCreateTunTap(boolean isTun, boolean hasCarrier,
+            @NonNull String iface);
 
     private static native void nativeSetTunTapCarrierEnabled(@NonNull String iface, int tunFd,
             boolean enabled);
@@ -118,7 +119,7 @@
      * interface.
      */
     @Override
-    public TestNetworkInterface createInterface(boolean isTun, boolean bringUp,
+    public TestNetworkInterface createInterface(boolean isTun, boolean hasCarrier, boolean bringUp,
             LinkAddress[] linkAddrs, @Nullable String iface) {
         enforceTestNetworkPermissions(mContext);
 
@@ -134,8 +135,8 @@
 
         final long token = Binder.clearCallingIdentity();
         try {
-            ParcelFileDescriptor tunIntf =
-                    ParcelFileDescriptor.adoptFd(nativeCreateTunTap(isTun, interfaceName));
+            ParcelFileDescriptor tunIntf = ParcelFileDescriptor.adoptFd(
+                    nativeCreateTunTap(isTun, hasCarrier, interfaceName));
             for (LinkAddress addr : linkAddrs) {
                 mNetd.interfaceAddAddress(
                         interfaceName,