From f5e4b90ae2b8c9f9b8cfe089a3c9f1ef49ec81ac Mon Sep 17 00:00:00 2001
From: Mark <markchien@google.com>
Date: Thu, 27 Jul 2023 16:00:47 +0000
Subject: [PATCH] Fix EtherentTetheringTest flaky

The first tethering test case may experience tethering restart
with IP conflict handling. Tethering would cache the last
upstreams so that the next enabled tethering avoids
picking up the address that is in conflict with the upstreams.
To protect subsequent tests, turn tethering on and off before
running them.

Bug: 254183718
Test: atest CtsTetheringTest
      atest MtsTetheringTestLatestSdk
Change-Id: I03729d3212a03bd9fcfe2c09cf327840f13b250c
---
 .../net/EthernetTetheringTestBase.java        | 25 +++++++++++++++++++
 .../net/cts/util/CtsTetheringUtils.java       | 23 +++++++++++------
 2 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/Tethering/tests/integration/base/android/net/EthernetTetheringTestBase.java b/Tethering/tests/integration/base/android/net/EthernetTetheringTestBase.java
index 9dad30188a..83fc3e4ae1 100644
--- a/Tethering/tests/integration/base/android/net/EthernetTetheringTestBase.java
+++ b/Tethering/tests/integration/base/android/net/EthernetTetheringTestBase.java
@@ -58,6 +58,8 @@ import android.net.TetheringManager.TetheringEventCallback;
 import android.net.TetheringManager.TetheringRequest;
 import android.net.TetheringTester.TetheredDevice;
 import android.net.cts.util.CtsNetUtils;
+import android.net.cts.util.CtsTetheringUtils;
+import android.net.cts.util.CtsTetheringUtils.TestTetheringEventCallback;
 import android.os.Handler;
 import android.os.HandlerThread;
 import android.os.SystemClock;
@@ -75,6 +77,7 @@ import com.android.testutils.TestNetworkTracker;
 
 import org.junit.After;
 import org.junit.Before;
+import org.junit.BeforeClass;
 
 import java.io.FileDescriptor;
 import java.net.Inet4Address;
@@ -161,6 +164,28 @@ public abstract class EthernetTetheringTestBase {
     private TapPacketReader mDownstreamReader;
     private MyTetheringEventCallback mTetheringEventCallback;
 
+    @BeforeClass
+    public static void setUpOnce() throws Exception {
+        // The first test case may experience tethering restart with IP conflict handling.
+        // Tethering would cache the last upstreams so that the next enabled tethering avoids
+        // picking up the address that is in conflict with the upstreams. To protect subsequent
+        // tests, turn tethering on and off before running them.
+        final Context ctx = InstrumentationRegistry.getInstrumentation().getContext();
+        final CtsTetheringUtils utils = new CtsTetheringUtils(ctx);
+        final TestTetheringEventCallback callback = utils.registerTetheringEventCallback();
+        try {
+            if (!callback.isWifiTetheringSupported(ctx)) return;
+
+            callback.expectNoTetheringActive();
+
+            utils.startWifiTethering(callback);
+            callback.getCurrentValidUpstream();
+            utils.stopWifiTethering(callback);
+        } finally {
+            utils.unregisterTetheringEventCallback(callback);
+        }
+    }
+
     @Before
     public void setUp() throws Exception {
         mHandlerThread = new HandlerThread(getClass().getSimpleName());
diff --git a/tests/cts/net/util/java/android/net/cts/util/CtsTetheringUtils.java b/tests/cts/net/util/java/android/net/cts/util/CtsTetheringUtils.java
index f506c2366e..dffd9d5bb7 100644
--- a/tests/cts/net/util/java/android/net/cts/util/CtsTetheringUtils.java
+++ b/tests/cts/net/util/java/android/net/cts/util/CtsTetheringUtils.java
@@ -393,21 +393,28 @@ public final class CtsTetheringUtils {
         }
 
         public void assumeTetheringSupported() {
+            assumeTrue(isTetheringSupported());
+        }
+
+        private boolean isTetheringSupported() {
             final ArrayTrackRecord<CallbackValue>.ReadHead history =
                     mHistory.newReadHead();
-            assertNotNull("No onSupported callback", history.poll(TIMEOUT_MS, (cv) -> {
-                if (cv.callbackType != CallbackType.ON_SUPPORTED) return false;
+            final CallbackValue result = history.poll(TIMEOUT_MS, (cv) -> {
+                return cv.callbackType == CallbackType.ON_SUPPORTED;
+            });
 
-                assumeTrue(cv.callbackParam2 == 1 /* supported */);
-                return true;
-            }));
+            assertNotNull("No onSupported callback", result);
+            return result.callbackParam2 == 1 /* supported */;
         }
 
         public void assumeWifiTetheringSupported(final Context ctx) throws Exception {
-            assumeTetheringSupported();
+            assumeTrue(isWifiTetheringSupported(ctx));
+        }
 
-            assumeTrue(!getTetheringInterfaceRegexps().getTetherableWifiRegexs().isEmpty());
-            assumeTrue(isPortableHotspotSupported(ctx));
+        public boolean isWifiTetheringSupported(final Context ctx) throws Exception {
+            return isTetheringSupported()
+                    && !getTetheringInterfaceRegexps().getTetherableWifiRegexs().isEmpty()
+                    && isPortableHotspotSupported(ctx);
         }
 
         public TetheringInterfaceRegexps getTetheringInterfaceRegexps() {