1 files changed, 39 insertions, 2 deletions
diff --git a/common/moduleutils/src/android/net/shared/NetdUtils.java b/common/moduleutils/src/android/net/shared/NetdUtils.java
index 0137bb77..5fa29c9b 100644
--- a/common/moduleutils/src/android/net/shared/NetdUtils.java
+++ b/common/moduleutils/src/android/net/shared/NetdUtils.java
@@ -17,6 +17,7 @@
 package android.net.shared;
 
 import static android.net.RouteInfo.RTN_UNICAST;
+import static android.system.OsConstants.EBUSY;
 
 import android.net.INetd;
 import android.net.IpPrefix;
@@ -24,6 +25,8 @@ import android.net.RouteInfo;
 import android.net.TetherConfigParcel;
 import android.os.RemoteException;
 import android.os.ServiceSpecificException;
+import android.os.SystemClock;
+import android.util.Log;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -33,6 +36,8 @@ import java.util.List;
  * @hide
  */
 public class NetdUtils {
+    private static final String TAG = NetdUtils.class.getSimpleName();
+
     /** Start tethering. */
     public static void tetherStart(final INetd netd, final boolean usingLegacyDnsProxy,
             final String[] dhcpRange) throws RemoteException, ServiceSpecificException {
@@ -45,14 +50,46 @@ public class NetdUtils {
     /** Setup interface for tethering. */
     public static void tetherInterface(final INetd netd, final String iface, final IpPrefix dest)
             throws RemoteException, ServiceSpecificException {
-        netd.tetherInterfaceAdd(iface);
+        tetherInterface(netd, iface, dest, 20 /* maxAttempts */, 50 /* pollingIntervalMs */);
+    }
 
-        netd.networkAddInterface(INetd.LOCAL_NET_ID, iface);
+    /** Setup interface with configurable retries for tethering. */
+    public static void tetherInterface(final INetd netd, final String iface, final IpPrefix dest,
+            int maxAttempts, int pollingIntervalMs)
+            throws RemoteException, ServiceSpecificException {
+        netd.tetherInterfaceAdd(iface);
+        networkAddInterface(netd, iface, maxAttempts, pollingIntervalMs);
         List<RouteInfo> routes = new ArrayList<>();
         routes.add(new RouteInfo(dest, null, iface, RTN_UNICAST));
         RouteUtils.addRoutesToLocalNetwork(netd, iface, routes);
     }
 
+    /**
+     * Retry Netd#networkAddInterface for EBUSY error code.
+     * If the same interface (e.g., wlan0) is in client mode and then switches to tethered mode.
+     * There can be a race where puts the interface into the local network but interface is still
+     * in use in netd because the ConnectivityService thread hasn't processed the disconnect yet.
+     * See b/158269544 for detail.
+     */
+    private static void networkAddInterface(final INetd netd, final String iface,
+            int maxAttempts, int pollingIntervalMs)
+            throws ServiceSpecificException, RemoteException {
+        for (int i = 1; i <= maxAttempts; i++) {
+            try {
+                netd.networkAddInterface(INetd.LOCAL_NET_ID, iface);
+                return;
+            } catch (ServiceSpecificException e) {
+                if (e.errorCode == EBUSY && i < maxAttempts) {
+                    SystemClock.sleep(pollingIntervalMs);
+                    continue;
+                }
+
+                Log.e(TAG, "Retry Netd#networkAddInterface failure: " + e);
+                throw e;
+            }
+        }
+    }
+
     /** Reset interface for tethering. */
     public static void untetherInterface(final INetd netd, String iface)
             throws RemoteException, ServiceSpecificException {