Use netlink to set interface up/down in EthernetTracker(2/2)

Currently EthernetTracker uses netd to interact with interfaces, such as
retrieving all interfaces, updating interface configurations etc.
However, the usage of netd can bring some unexpected side effects, such
as clearing v4 address when toggling on/off interface.

This change moves forward with one less usage of netd to use netlink
directly to set interface up/down in EthernetTracker.

This patch changes from using netd to netlink in EthernetTracker to set
interface up/down.

Bug: 379021505
Test: atest EthernetManagerTest
Change-Id: I321a442b943a8be92572d20f5fba81dcd0405d0b
diff --git a/service-t/src/com/android/server/ethernet/EthernetTracker.java b/service-t/src/com/android/server/ethernet/EthernetTracker.java
index 5228aab..a1fd779 100644
--- a/service-t/src/com/android/server/ethernet/EthernetTracker.java
+++ b/service-t/src/com/android/server/ethernet/EthernetTracker.java
@@ -21,6 +21,7 @@
 import static android.net.TestNetworkManager.TEST_TAP_PREFIX;
 
 import static com.android.internal.annotations.VisibleForTesting.Visibility.PACKAGE;
+import static com.android.net.module.util.netlink.NetlinkConstants.IFF_UP;
 
 import android.annotation.NonNull;
 import android.annotation.Nullable;
@@ -56,6 +57,7 @@
 import com.android.net.module.util.ip.NetlinkMonitor;
 import com.android.net.module.util.netlink.NetlinkConstants;
 import com.android.net.module.util.netlink.NetlinkMessage;
+import com.android.net.module.util.netlink.NetlinkUtils;
 import com.android.net.module.util.netlink.RtNetlinkLinkMessage;
 import com.android.net.module.util.netlink.StructIfinfoMsg;
 import com.android.server.connectivity.ConnectivityResources;
@@ -593,14 +595,8 @@
             // Read the flags before attempting to bring up the interface. If the interface is
             // already running an UP event is created after adding the interface.
             config = NetdUtils.getInterfaceConfigParcel(mNetd, iface);
-            // Only bring the interface up when ethernet is enabled.
-            if (mIsEthernetEnabled) {
-                // As a side-effect, NetdUtils#setInterfaceUp() also clears the interface's IPv4
-                // address and readds it which *could* lead to unexpected behavior in the future.
-                NetdUtils.setInterfaceUp(mNetd, iface);
-            } else {
-                NetdUtils.setInterfaceDown(mNetd, iface);
-            }
+            // Only bring the interface up when ethernet is enabled, otherwise set interface down.
+            setInterfaceUpState(iface, mIsEthernetEnabled);
         } catch (IllegalStateException e) {
             // Either the system is crashing or the interface has disappeared. Just ignore the
             // error; we haven't modified any state because we only do that if our calls succeed.
@@ -660,15 +656,7 @@
             return;
         }
 
-        if (up) {
-            // WARNING! setInterfaceUp() clears the IPv4 address and readds it. Calling
-            // enableInterface() on an active interface can lead to a provisioning failure which
-            // will cause IpClient to be restarted.
-            // TODO: use netlink directly rather than calling into netd.
-            NetdUtils.setInterfaceUp(mNetd, iface);
-        } else {
-            NetdUtils.setInterfaceDown(mNetd, iface);
-        }
+        setInterfaceUpState(iface, up);
         cb.onResult(iface);
     }
 
@@ -978,11 +966,7 @@
             }
 
             for (String iface : interfaces) {
-                if (enabled) {
-                    NetdUtils.setInterfaceUp(mNetd, iface);
-                } else {
-                    NetdUtils.setInterfaceDown(mNetd, iface);
-                }
+                setInterfaceUpState(iface, enabled);
             }
             broadcastEthernetStateChange(mIsEthernetEnabled);
         });
@@ -1016,6 +1000,12 @@
         mListeners.finishBroadcast();
     }
 
+    private void setInterfaceUpState(@NonNull String interfaceName, boolean up) {
+        if (!NetlinkUtils.setInterfaceFlags(interfaceName, up ? IFF_UP : ~IFF_UP)) {
+            Log.e(TAG, "Failed to set interface " + interfaceName + (up ? " up" : " down"));
+        }
+    }
+
     void dump(FileDescriptor fd, IndentingPrintWriter pw, String[] args) {
         postAndWaitForRunnable(() -> {
             pw.println(getClass().getSimpleName());