diff --git a/TEST_MAPPING b/TEST_MAPPING
index 85072a7..4eeaf51 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -34,6 +34,18 @@
         }
       ]
     },
+    // CTS tests that target older SDKs.
+    {
+      "name": "CtsNetTestCasesMaxTargetSdk31",
+      "options": [
+        {
+          "exclude-annotation": "com.android.testutils.SkipPresubmit"
+        },
+        {
+          "exclude-annotation": "androidx.test.filters.RequiresDevice"
+        }
+      ]
+    },
     {
       "name": "bpf_existence_test"
     },
@@ -41,6 +53,9 @@
       "name": "connectivity_native_test"
     },
     {
+      "name": "libclat_test"
+    },
+    {
       "name": "netd_updatable_unit_test"
     },
     {
@@ -68,9 +83,6 @@
       "keywords": ["netd-device-kernel-4.9", "netd-device-kernel-4.14"]
     },
     {
-      "name": "libclat_test"
-    },
-    {
       "name": "traffic_controller_unit_test",
       "keywords": ["netd-device-kernel-4.9", "netd-device-kernel-4.14"]
     },
@@ -91,6 +103,17 @@
       ]
     },
     {
+      "name": "CtsNetTestCasesMaxTargetSdk31[CaptivePortalLoginGoogle.apk+NetworkStackGoogle.apk+com.google.android.resolv.apex+com.google.android.tethering.apex]",
+      "options": [
+        {
+          "exclude-annotation": "com.android.testutils.SkipPresubmit"
+        },
+        {
+          "exclude-annotation": "androidx.test.filters.RequiresDevice"
+        }
+      ]
+    },
+    {
       "name": "bpf_existence_test[CaptivePortalLoginGoogle.apk+NetworkStackGoogle.apk+com.google.android.resolv.apex+com.google.android.tethering.apex]"
     },
     {
diff --git a/Tethering/apex/manifest.json b/Tethering/apex/manifest.json
index 88f13b2..3cb03ed 100644
--- a/Tethering/apex/manifest.json
+++ b/Tethering/apex/manifest.json
@@ -1,4 +1,4 @@
 {
   "name": "com.android.tethering",
-  "version": 319999900
+  "version": 339990000
 }
diff --git a/bpf_progs/bpf_shared.h b/bpf_progs/bpf_shared.h
index 14fcdd6..634fbf4 100644
--- a/bpf_progs/bpf_shared.h
+++ b/bpf_progs/bpf_shared.h
@@ -147,9 +147,9 @@
     SELECT_MAP_B,
 };
 
-// TODO: change the configuration object from an 8-bit bitmask to an object with clearer
+// TODO: change the configuration object from a bitmask to an object with clearer
 // semantics, like a struct.
-typedef uint8_t BpfConfig;
+typedef uint32_t BpfConfig;
 static const BpfConfig DEFAULT_CONFIG = 0;
 
 typedef struct {
@@ -160,7 +160,9 @@
 } UidOwnerValue;
 STRUCT_SIZE(UidOwnerValue, 2 * 4);  // 8
 
+// Entry in the configuration map that stores which UID rules are enabled.
 #define UID_RULES_CONFIGURATION_KEY 1
+// Entry in the configuration map that stores which stats map is currently in use.
 #define CURRENT_STATS_MAP_CONFIGURATION_KEY 2
 
 #define BPF_CLATD_PATH "/sys/fs/bpf/net_shared/"
diff --git a/bpf_progs/netd.c b/bpf_progs/netd.c
index ae92686..2a63e81 100644
--- a/bpf_progs/netd.c
+++ b/bpf_progs/netd.c
@@ -62,7 +62,7 @@
 DEFINE_BPF_MAP_GRW(stats_map_B, HASH, StatsKey, StatsValue, STATS_MAP_SIZE, AID_NET_BW_ACCT)
 DEFINE_BPF_MAP_GRW(iface_stats_map, HASH, uint32_t, StatsValue, IFACE_STATS_MAP_SIZE,
                    AID_NET_BW_ACCT)
-DEFINE_BPF_MAP_GRW(configuration_map, HASH, uint32_t, uint8_t, CONFIGURATION_MAP_SIZE,
+DEFINE_BPF_MAP_GRW(configuration_map, HASH, uint32_t, uint32_t, CONFIGURATION_MAP_SIZE,
                    AID_NET_BW_ACCT)
 DEFINE_BPF_MAP_GRW(uid_owner_map, HASH, uint32_t, UidOwnerValue, UID_OWNER_MAP_SIZE,
                    AID_NET_BW_ACCT)
@@ -234,7 +234,7 @@
 }
 
 static __always_inline inline void update_stats_with_config(struct __sk_buff* skb, int direction,
-                                                            StatsKey* key, uint8_t selectedMap) {
+                                                            StatsKey* key, uint32_t selectedMap) {
     if (selectedMap == SELECT_MAP_A) {
         update_stats_map_A(skb, direction, key);
     } else if (selectedMap == SELECT_MAP_B) {
@@ -286,7 +286,7 @@
     if (counterSet) key.counterSet = (uint32_t)*counterSet;
 
     uint32_t mapSettingKey = CURRENT_STATS_MAP_CONFIGURATION_KEY;
-    uint8_t* selectedMap = bpf_configuration_map_lookup_elem(&mapSettingKey);
+    uint32_t* selectedMap = bpf_configuration_map_lookup_elem(&mapSettingKey);
 
     // Use asm("%0 &= 1" : "+r"(match)) before return match,
     // to help kernel's bpf verifier, so that it can be 100% certain
diff --git a/framework-t/src/android/net/NetworkStatsCollection.java b/framework-t/src/android/net/NetworkStatsCollection.java
index 29ea772..6a1d2dd 100644
--- a/framework-t/src/android/net/NetworkStatsCollection.java
+++ b/framework-t/src/android/net/NetworkStatsCollection.java
@@ -865,6 +865,9 @@
          * Add association of the history with the specified key in this map.
          *
          * @param key The object used to identify a network, see {@link Key}.
+         *            If history already exists for this key, then the passed-in history is appended
+         *            to the previously-passed in history. The caller must ensure that the history
+         *            passed-in timestamps are greater than all previously-passed-in timestamps.
          * @param history {@link NetworkStatsHistory} instance associated to the given {@link Key}.
          * @return The builder object.
          */
@@ -874,9 +877,21 @@
             Objects.requireNonNull(key);
             Objects.requireNonNull(history);
             final List<Entry> historyEntries = history.getEntries();
+            final NetworkStatsHistory existing = mEntries.get(key);
 
+            final int size = historyEntries.size() + ((existing != null) ? existing.size() : 0);
             final NetworkStatsHistory.Builder historyBuilder =
-                    new NetworkStatsHistory.Builder(mBucketDurationMillis, historyEntries.size());
+                    new NetworkStatsHistory.Builder(mBucketDurationMillis, size);
+
+            // TODO: this simply appends the entries to any entries that were already present in
+            // the builder, which requires the caller to pass in entries in order. We might be
+            // able to do better with something like recordHistory.
+            if (existing != null) {
+                for (Entry entry : existing.getEntries()) {
+                    historyBuilder.addEntry(entry);
+                }
+            }
+
             for (Entry entry : historyEntries) {
                 historyBuilder.addEntry(entry);
             }
diff --git a/framework-t/src/android/net/NetworkStatsHistory.java b/framework-t/src/android/net/NetworkStatsHistory.java
index b45d44d..0ff9d96 100644
--- a/framework-t/src/android/net/NetworkStatsHistory.java
+++ b/framework-t/src/android/net/NetworkStatsHistory.java
@@ -32,6 +32,7 @@
 import static com.android.net.module.util.NetworkStatsUtils.multiplySafeByRational;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.annotation.SystemApi;
 import android.compat.annotation.UnsupportedAppUsage;
 import android.os.Build;
@@ -949,6 +950,25 @@
         return writer.toString();
     }
 
+    /**
+     * Same as "equals", but not actually called equals as this would affect public API behavior.
+     * @hide
+     */
+    @Nullable
+    public boolean isSameAs(NetworkStatsHistory other) {
+        return bucketCount == other.bucketCount
+                && Arrays.equals(bucketStart, other.bucketStart)
+                // Don't check activeTime since it can change on import due to the importer using
+                // recordHistory. It's also not exposed by the APIs or present in dumpsys or
+                // toString().
+                && Arrays.equals(rxBytes, other.rxBytes)
+                && Arrays.equals(rxPackets, other.rxPackets)
+                && Arrays.equals(txBytes, other.txBytes)
+                && Arrays.equals(txPackets, other.txPackets)
+                && Arrays.equals(operations, other.operations)
+                && totalBytes == other.totalBytes;
+    }
+
     @UnsupportedAppUsage
     public static final @android.annotation.NonNull Creator<NetworkStatsHistory> CREATOR = new Creator<NetworkStatsHistory>() {
         @Override
@@ -1116,14 +1136,44 @@
             mOperations = new ArrayList<>(initialCapacity);
         }
 
+        private void addToElement(List<Long> list, int pos, long value) {
+            list.set(pos, list.get(pos) + value);
+        }
+
         /**
          * Add an {@link Entry} into the {@link NetworkStatsHistory} instance.
          *
-         * @param entry The target {@link Entry} object.
+         * @param entry The target {@link Entry} object. The entry timestamp must be greater than
+         *              that of any previously-added entry.
          * @return The builder object.
          */
         @NonNull
         public Builder addEntry(@NonNull Entry entry) {
+            final int lastBucket = mBucketStart.size() - 1;
+            final long lastBucketStart = (lastBucket != -1) ? mBucketStart.get(lastBucket) : 0;
+
+            // If last bucket has the same timestamp, modify it instead of adding another bucket.
+            // This allows callers to pass in the same bucket twice (e.g., to accumulate
+            // data over time), but still requires that entries must be sorted.
+            // The importer will do this in case a rotated file has the same timestamp as
+            // the previous file.
+            if (lastBucket != -1 && entry.bucketStart == lastBucketStart) {
+                addToElement(mActiveTime, lastBucket, entry.activeTime);
+                addToElement(mRxBytes, lastBucket, entry.rxBytes);
+                addToElement(mRxPackets, lastBucket, entry.rxPackets);
+                addToElement(mTxBytes, lastBucket, entry.txBytes);
+                addToElement(mTxPackets, lastBucket, entry.txPackets);
+                addToElement(mOperations, lastBucket, entry.operations);
+                return this;
+            }
+
+            // Inserting in the middle is prohibited for performance reasons.
+            if (entry.bucketStart <= lastBucketStart) {
+                throw new IllegalArgumentException("new bucket start " + entry.bucketStart
+                        + " must be greater than last bucket start " + lastBucketStart);
+            }
+
+            // Common case: add entries at the end of the list.
             mBucketStart.add(entry.bucketStart);
             mActiveTime.add(entry.activeTime);
             mRxBytes.add(entry.rxBytes);
diff --git a/framework-t/src/android/net/nsd/NsdServiceInfo.java b/framework-t/src/android/net/nsd/NsdServiceInfo.java
index 2621594..200c808 100644
--- a/framework-t/src/android/net/nsd/NsdServiceInfo.java
+++ b/framework-t/src/android/net/nsd/NsdServiceInfo.java
@@ -53,6 +53,8 @@
     @Nullable
     private Network mNetwork;
 
+    private int mInterfaceIndex;
+
     public NsdServiceInfo() {
     }
 
@@ -312,8 +314,11 @@
     /**
      * Get the network where the service can be found.
      *
-     * This is never null if this {@link NsdServiceInfo} was obtained from
-     * {@link NsdManager#discoverServices} or {@link NsdManager#resolveService}.
+     * This is set if this {@link NsdServiceInfo} was obtained from
+     * {@link NsdManager#discoverServices} or {@link NsdManager#resolveService}, unless the service
+     * was found on a network interface that does not have a {@link Network} (such as a tethering
+     * downstream, where services are advertised from devices connected to this device via
+     * tethering).
      */
     @Nullable
     public Network getNetwork() {
@@ -329,6 +334,26 @@
         mNetwork = network;
     }
 
+    /**
+     * Get the index of the network interface where the service was found.
+     *
+     * This is only set when the service was found on an interface that does not have a usable
+     * Network, in which case {@link #getNetwork()} returns null.
+     * @return The interface index as per {@link java.net.NetworkInterface#getIndex}, or 0 if unset.
+     * @hide
+     */
+    public int getInterfaceIndex() {
+        return mInterfaceIndex;
+    }
+
+    /**
+     * Set the index of the network interface where the service was found.
+     * @hide
+     */
+    public void setInterfaceIndex(int interfaceIndex) {
+        mInterfaceIndex = interfaceIndex;
+    }
+
     @Override
     public String toString() {
         StringBuilder sb = new StringBuilder();
@@ -375,6 +400,7 @@
         }
 
         dest.writeParcelable(mNetwork, 0);
+        dest.writeInt(mInterfaceIndex);
     }
 
     /** Implement the Parcelable interface */
@@ -405,6 +431,7 @@
                     info.mTxtRecord.put(in.readString(), valueArray);
                 }
                 info.mNetwork = in.readParcelable(null, Network.class);
+                info.mInterfaceIndex = in.readInt();
                 return info;
             }
 
diff --git a/netd/BpfHandler.h b/netd/BpfHandler.h
index 2ede1c1..05b9ebc 100644
--- a/netd/BpfHandler.h
+++ b/netd/BpfHandler.h
@@ -62,7 +62,7 @@
     BpfMap<uint64_t, UidTagValue> mCookieTagMap;
     BpfMap<StatsKey, StatsValue> mStatsMapA;
     BpfMap<StatsKey, StatsValue> mStatsMapB;
-    BpfMap<uint32_t, uint8_t> mConfigurationMap;
+    BpfMap<uint32_t, uint32_t> mConfigurationMap;
     BpfMap<uint32_t, uint8_t> mUidPermissionMap;
 
     std::mutex mMutex;
diff --git a/netd/BpfHandlerTest.cpp b/netd/BpfHandlerTest.cpp
index cd6b565..12ae916 100644
--- a/netd/BpfHandlerTest.cpp
+++ b/netd/BpfHandlerTest.cpp
@@ -48,7 +48,7 @@
     BpfHandler mBh;
     BpfMap<uint64_t, UidTagValue> mFakeCookieTagMap;
     BpfMap<StatsKey, StatsValue> mFakeStatsMapA;
-    BpfMap<uint32_t, uint8_t> mFakeConfigurationMap;
+    BpfMap<uint32_t, uint32_t> mFakeConfigurationMap;
     BpfMap<uint32_t, uint8_t> mFakeUidPermissionMap;
 
     void SetUp() {
diff --git a/service-t/native/libs/libnetworkstats/BpfNetworkStats.cpp b/service-t/native/libs/libnetworkstats/BpfNetworkStats.cpp
index 6c7a15e..c67821f 100644
--- a/service-t/native/libs/libnetworkstats/BpfNetworkStats.cpp
+++ b/service-t/native/libs/libnetworkstats/BpfNetworkStats.cpp
@@ -193,7 +193,7 @@
         return ret;
     }
 
-    BpfMapRO<uint32_t, uint8_t> configurationMap(CONFIGURATION_MAP_PATH);
+    BpfMapRO<uint32_t, uint32_t> configurationMap(CONFIGURATION_MAP_PATH);
     if (!configurationMap.isValid()) {
         int ret = -errno;
         ALOGE("get configuration map fd failed: %s", strerror(errno));
diff --git a/service-t/src/com/android/server/NsdService.java b/service-t/src/com/android/server/NsdService.java
index 6def44f..95e6114 100644
--- a/service-t/src/com/android/server/NsdService.java
+++ b/service-t/src/com/android/server/NsdService.java
@@ -23,6 +23,7 @@
 import android.content.Intent;
 import android.content.pm.PackageManager;
 import android.net.ConnectivityManager;
+import android.net.INetd;
 import android.net.LinkProperties;
 import android.net.Network;
 import android.net.mdns.aidl.DiscoveryInfo;
@@ -466,7 +467,7 @@
                             // interfaces that do not have an associated Network.
                             break;
                         }
-                        servInfo.setNetwork(new Network(foundNetId));
+                        setServiceNetworkForCallback(servInfo, info.netId, info.interfaceIdx);
                         clientInfo.onServiceFound(clientId, servInfo);
                         break;
                     }
@@ -476,10 +477,11 @@
                         final String type = info.registrationType;
                         final int lostNetId = info.netId;
                         servInfo = new NsdServiceInfo(name, type);
-                        // The network could be null if it was torn down when the service is lost
-                        // TODO: avoid returning null in that case, possibly by remembering found
-                        // services on the same interface index and their network at the time
-                        servInfo.setNetwork(lostNetId == 0 ? null : new Network(lostNetId));
+                        // The network could be set to null (netId 0) if it was torn down when the
+                        // service is lost
+                        // TODO: avoid returning null in that case, possibly by remembering
+                        // found services on the same interface index and their network at the time
+                        setServiceNetworkForCallback(servInfo, lostNetId, info.interfaceIdx);
                         clientInfo.onServiceLost(clientId, servInfo);
                         break;
                     }
@@ -557,7 +559,6 @@
                         final GetAddressInfo info = (GetAddressInfo) obj;
                         final String address = info.address;
                         final int netId = info.netId;
-                        final Network network = netId == NETID_UNSET ? null : new Network(netId);
                         InetAddress serviceHost = null;
                         try {
                             serviceHost = InetAddress.getByName(address);
@@ -568,9 +569,10 @@
                         // If the resolved service is on an interface without a network, consider it
                         // as a failure: it would not be usable by apps as they would need
                         // privileged permissions.
-                        if (network != null && serviceHost != null) {
+                        if (netId != NETID_UNSET && serviceHost != null) {
                             clientInfo.mResolvedService.setHost(serviceHost);
-                            clientInfo.mResolvedService.setNetwork(network);
+                            setServiceNetworkForCallback(clientInfo.mResolvedService,
+                                    netId, info.interfaceIdx);
                             clientInfo.onResolveServiceSucceeded(
                                     clientId, clientInfo.mResolvedService);
                         } else {
@@ -590,6 +592,26 @@
        }
     }
 
+    private static void setServiceNetworkForCallback(NsdServiceInfo info, int netId, int ifaceIdx) {
+        switch (netId) {
+            case NETID_UNSET:
+                info.setNetwork(null);
+                break;
+            case INetd.LOCAL_NET_ID:
+                // Special case for LOCAL_NET_ID: Networks on netId 99 are not generally
+                // visible / usable for apps, so do not return it. Store the interface
+                // index instead, so at least if the client tries to resolve the service
+                // with that NsdServiceInfo, it will be done on the same interface.
+                // If they recreate the NsdServiceInfo themselves, resolution would be
+                // done on all interfaces as before T, which should also work.
+                info.setNetwork(null);
+                info.setInterfaceIndex(ifaceIdx);
+                break;
+            default:
+                info.setNetwork(new Network(netId));
+        }
+    }
+
     // The full service name is escaped from standard DNS rules on mdnsresponder, making it suitable
     // for passing to standard system DNS APIs such as res_query() . Thus, make the service name
     // unescape for getting right service address. See "Notes on DNS Name Escaping" on
@@ -767,9 +789,8 @@
         String type = service.getServiceType();
         int port = service.getPort();
         byte[] textRecord = service.getTxtRecord();
-        final Network network = service.getNetwork();
-        final int registerInterface = getNetworkInterfaceIndex(network);
-        if (network != null && registerInterface == IFACE_IDX_ANY) {
+        final int registerInterface = getNetworkInterfaceIndex(service);
+        if (service.getNetwork() != null && registerInterface == IFACE_IDX_ANY) {
             Log.e(TAG, "Interface to register service on not found");
             return false;
         }
@@ -781,10 +802,9 @@
     }
 
     private boolean discoverServices(int discoveryId, NsdServiceInfo serviceInfo) {
-        final Network network = serviceInfo.getNetwork();
         final String type = serviceInfo.getServiceType();
-        final int discoverInterface = getNetworkInterfaceIndex(network);
-        if (network != null && discoverInterface == IFACE_IDX_ANY) {
+        final int discoverInterface = getNetworkInterfaceIndex(serviceInfo);
+        if (serviceInfo.getNetwork() != null && discoverInterface == IFACE_IDX_ANY) {
             Log.e(TAG, "Interface to discover service on not found");
             return false;
         }
@@ -798,9 +818,8 @@
     private boolean resolveService(int resolveId, NsdServiceInfo service) {
         final String name = service.getServiceName();
         final String type = service.getServiceType();
-        final Network network = service.getNetwork();
-        final int resolveInterface = getNetworkInterfaceIndex(network);
-        if (network != null && resolveInterface == IFACE_IDX_ANY) {
+        final int resolveInterface = getNetworkInterfaceIndex(service);
+        if (service.getNetwork() != null && resolveInterface == IFACE_IDX_ANY) {
             Log.e(TAG, "Interface to resolve service on not found");
             return false;
         }
@@ -816,8 +835,17 @@
      * this is to support the legacy mdnsresponder implementation, which historically resolved
      * services on an unspecified network.
      */
-    private int getNetworkInterfaceIndex(Network network) {
-        if (network == null) return IFACE_IDX_ANY;
+    private int getNetworkInterfaceIndex(NsdServiceInfo serviceInfo) {
+        final Network network = serviceInfo.getNetwork();
+        if (network == null) {
+            // Fallback to getInterfaceIndex if present (typically if the NsdServiceInfo was
+            // provided by NsdService from discovery results, and the service was found on an
+            // interface that has no app-usable Network).
+            if (serviceInfo.getInterfaceIndex() != 0) {
+                return serviceInfo.getInterfaceIndex();
+            }
+            return IFACE_IDX_ANY;
+        }
 
         final ConnectivityManager cm = mContext.getSystemService(ConnectivityManager.class);
         if (cm == null) {
diff --git a/service-t/src/com/android/server/net/NetworkStatsRecorder.java b/service-t/src/com/android/server/net/NetworkStatsRecorder.java
index 6f070d7..d73e342 100644
--- a/service-t/src/com/android/server/net/NetworkStatsRecorder.java
+++ b/service-t/src/com/android/server/net/NetworkStatsRecorder.java
@@ -21,6 +21,7 @@
 import static android.net.TrafficStats.MB_IN_BYTES;
 import static android.text.format.DateUtils.YEAR_IN_MILLIS;
 
+import android.annotation.NonNull;
 import android.net.NetworkIdentitySet;
 import android.net.NetworkStats;
 import android.net.NetworkStats.NonMonotonicObserver;
@@ -68,7 +69,7 @@
 
     private static final String TAG_NETSTATS_DUMP = "netstats_dump";
 
-    /** Dump before deleting in {@link #recoverFromWtf()}. */
+    /** Dump before deleting in {@link #recoverAndDeleteData()}. */
     private static final boolean DUMP_BEFORE_DELETE = true;
 
     private final FileRotator mRotator;
@@ -156,6 +157,15 @@
         return mSinceBoot;
     }
 
+    public long getBucketDuration() {
+        return mBucketDuration;
+    }
+
+    @NonNull
+    public String getCookie() {
+        return mCookie;
+    }
+
     /**
      * Load complete history represented by {@link FileRotator}. Caches
      * internally as a {@link WeakReference}, and updated with future
@@ -189,10 +199,10 @@
             res.recordCollection(mPending);
         } catch (IOException e) {
             Log.wtf(TAG, "problem completely reading network stats", e);
-            recoverFromWtf();
+            recoverAndDeleteData();
         } catch (OutOfMemoryError e) {
             Log.wtf(TAG, "problem completely reading network stats", e);
-            recoverFromWtf();
+            recoverAndDeleteData();
         }
         return res;
     }
@@ -300,10 +310,10 @@
                 mPending.reset();
             } catch (IOException e) {
                 Log.wtf(TAG, "problem persisting pending stats", e);
-                recoverFromWtf();
+                recoverAndDeleteData();
             } catch (OutOfMemoryError e) {
                 Log.wtf(TAG, "problem persisting pending stats", e);
-                recoverFromWtf();
+                recoverAndDeleteData();
             }
         }
     }
@@ -319,10 +329,10 @@
                 mRotator.rewriteAll(new RemoveUidRewriter(mBucketDuration, uids));
             } catch (IOException e) {
                 Log.wtf(TAG, "problem removing UIDs " + Arrays.toString(uids), e);
-                recoverFromWtf();
+                recoverAndDeleteData();
             } catch (OutOfMemoryError e) {
                 Log.wtf(TAG, "problem removing UIDs " + Arrays.toString(uids), e);
-                recoverFromWtf();
+                recoverAndDeleteData();
             }
         }
 
@@ -347,8 +357,7 @@
 
     /**
      * Rewriter that will combine current {@link NetworkStatsCollection} values
-     * with anything read from disk, and write combined set to disk. Clears the
-     * original {@link NetworkStatsCollection} when finished writing.
+     * with anything read from disk, and write combined set to disk.
      */
     private static class CombiningRewriter implements FileRotator.Rewriter {
         private final NetworkStatsCollection mCollection;
@@ -375,7 +384,6 @@
         @Override
         public void write(OutputStream out) throws IOException {
             mCollection.write(out);
-            mCollection.reset();
         }
     }
 
@@ -456,6 +464,23 @@
     }
 
     /**
+     * Import a specified {@link NetworkStatsCollection} instance into this recorder,
+     * and write it into a standalone file.
+     * @param collection The target {@link NetworkStatsCollection} instance to be imported.
+     */
+    public void importCollectionLocked(@NonNull NetworkStatsCollection collection)
+            throws IOException {
+        if (mRotator != null) {
+            mRotator.rewriteSingle(new CombiningRewriter(collection), collection.getStartMillis(),
+                    collection.getEndMillis());
+        }
+
+        if (mComplete != null) {
+            throw new IllegalStateException("cannot import data when data already loaded");
+        }
+    }
+
+    /**
      * Rewriter that will remove any histories or persisted data points before the
      * specified cutoff time, only writing data back when modified.
      */
@@ -501,10 +526,10 @@
                         mBucketDuration, cutoffMillis));
             } catch (IOException e) {
                 Log.wtf(TAG, "problem importing netstats", e);
-                recoverFromWtf();
+                recoverAndDeleteData();
             } catch (OutOfMemoryError e) {
                 Log.wtf(TAG, "problem importing netstats", e);
-                recoverFromWtf();
+                recoverAndDeleteData();
             }
         }
 
@@ -555,7 +580,7 @@
      * Recover from {@link FileRotator} failure by dumping state to
      * {@link DropBoxManager} and deleting contents.
      */
-    private void recoverFromWtf() {
+    void recoverAndDeleteData() {
         if (DUMP_BEFORE_DELETE) {
             final ByteArrayOutputStream os = new ByteArrayOutputStream();
             try {
diff --git a/service-t/src/com/android/server/net/NetworkStatsService.java b/service-t/src/com/android/server/net/NetworkStatsService.java
index a015177..63e6501 100644
--- a/service-t/src/com/android/server/net/NetworkStatsService.java
+++ b/service-t/src/com/android/server/net/NetworkStatsService.java
@@ -67,6 +67,7 @@
 import android.app.AlarmManager;
 import android.app.PendingIntent;
 import android.app.usage.NetworkStatsManager;
+import android.content.ApexEnvironment;
 import android.content.BroadcastReceiver;
 import android.content.ContentResolver;
 import android.content.Context;
@@ -75,6 +76,7 @@
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
 import android.database.ContentObserver;
+import android.net.ConnectivityManager;
 import android.net.DataUsageRequest;
 import android.net.INetd;
 import android.net.INetworkStatsService;
@@ -100,6 +102,7 @@
 import android.net.UnderlyingNetworkInfo;
 import android.net.Uri;
 import android.net.netstats.IUsageCallback;
+import android.net.netstats.NetworkStatsDataMigrationUtils;
 import android.net.netstats.provider.INetworkStatsProvider;
 import android.net.netstats.provider.INetworkStatsProviderCallback;
 import android.net.netstats.provider.NetworkStatsProvider;
@@ -118,6 +121,7 @@
 import android.os.SystemClock;
 import android.os.Trace;
 import android.os.UserHandle;
+import android.provider.DeviceConfig;
 import android.provider.Settings;
 import android.provider.Settings.Global;
 import android.service.NetworkInterfaceProto;
@@ -143,6 +147,7 @@
 import com.android.net.module.util.BinderUtils;
 import com.android.net.module.util.BpfMap;
 import com.android.net.module.util.CollectionUtils;
+import com.android.net.module.util.DeviceConfigUtils;
 import com.android.net.module.util.IBpfMap;
 import com.android.net.module.util.LocationPermissionChecker;
 import com.android.net.module.util.NetworkStatsUtils;
@@ -155,7 +160,9 @@
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.PrintWriter;
+import java.nio.file.Path;
 import java.time.Clock;
+import java.time.Instant;
 import java.time.ZoneOffset;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -232,6 +239,22 @@
     private static final String STATS_MAP_B_PATH =
             "/sys/fs/bpf/netd_shared/map_netd_stats_map_B";
 
+    /**
+     * DeviceConfig flag used to indicate whether the files should be stored in the apex data
+     * directory.
+     */
+    static final String NETSTATS_STORE_FILES_IN_APEXDATA = "netstats_store_files_in_apexdata";
+    /**
+     * DeviceConfig flag is used to indicate whether the legacy files need to be imported, and
+     * retry count before giving up. Only valid when {@link #NETSTATS_STORE_FILES_IN_APEXDATA}
+     * set to true. Note that the value gets rollback when the mainline module gets rollback.
+     */
+    static final String NETSTATS_IMPORT_LEGACY_TARGET_ATTEMPTS =
+            "netstats_import_legacy_target_attempts";
+    static final int DEFAULT_NETSTATS_IMPORT_LEGACY_TARGET_ATTEMPTS = 1;
+    static final String NETSTATS_IMPORT_ATTEMPTS_COUNTER_NAME = "import.attempts";
+    static final String NETSTATS_IMPORT_SUCCESS_COUNTER_NAME = "import.successes";
+
     private final Context mContext;
     private final NetworkStatsFactory mStatsFactory;
     private final AlarmManager mAlarmManager;
@@ -239,8 +262,7 @@
     private final NetworkStatsSettings mSettings;
     private final NetworkStatsObservers mStatsObservers;
 
-    private final File mSystemDir;
-    private final File mBaseDir;
+    private final File mStatsDir;
 
     private final PowerManager.WakeLock mWakeLock;
 
@@ -250,6 +272,12 @@
     protected INetd mNetd;
     private final AlertObserver mAlertObserver = new AlertObserver();
 
+    // Persistent counters that backed by AtomicFile which stored in the data directory as a file,
+    // to track attempts/successes count across reboot. Note that these counter values will be
+    // rollback as the module rollbacks.
+    private PersistentInt mImportLegacyAttemptsCounter = null;
+    private PersistentInt mImportLegacySuccessesCounter = null;
+
     @VisibleForTesting
     public static final String ACTION_NETWORK_STATS_POLL =
             "com.android.server.action.NETWORK_STATS_POLL";
@@ -405,16 +433,6 @@
     @NonNull
     private final BpfInterfaceMapUpdater mInterfaceMapUpdater;
 
-    private static @NonNull File getDefaultSystemDir() {
-        return new File(Environment.getDataDirectory(), "system");
-    }
-
-    private static @NonNull File getDefaultBaseDir() {
-        File baseDir = new File(getDefaultSystemDir(), "netstats");
-        baseDir.mkdirs();
-        return baseDir;
-    }
-
     private static @NonNull Clock getDefaultClock() {
         return new BestClock(ZoneOffset.UTC, SystemClock.currentNetworkTimeClock(),
                 Clock.systemUTC());
@@ -506,8 +524,7 @@
                 INetd.Stub.asInterface((IBinder) context.getSystemService(Context.NETD_SERVICE)),
                 alarmManager, wakeLock, getDefaultClock(),
                 new DefaultNetworkStatsSettings(), new NetworkStatsFactory(context),
-                new NetworkStatsObservers(), getDefaultSystemDir(), getDefaultBaseDir(),
-                new Dependencies());
+                new NetworkStatsObservers(), new Dependencies());
 
         return service;
     }
@@ -517,8 +534,8 @@
     @VisibleForTesting
     NetworkStatsService(Context context, INetd netd, AlarmManager alarmManager,
             PowerManager.WakeLock wakeLock, Clock clock, NetworkStatsSettings settings,
-            NetworkStatsFactory factory, NetworkStatsObservers statsObservers, File systemDir,
-            File baseDir, @NonNull Dependencies deps) {
+            NetworkStatsFactory factory, NetworkStatsObservers statsObservers,
+            @NonNull Dependencies deps) {
         mContext = Objects.requireNonNull(context, "missing Context");
         mNetd = Objects.requireNonNull(netd, "missing Netd");
         mAlarmManager = Objects.requireNonNull(alarmManager, "missing AlarmManager");
@@ -527,9 +544,11 @@
         mWakeLock = Objects.requireNonNull(wakeLock, "missing WakeLock");
         mStatsFactory = Objects.requireNonNull(factory, "missing factory");
         mStatsObservers = Objects.requireNonNull(statsObservers, "missing NetworkStatsObservers");
-        mSystemDir = Objects.requireNonNull(systemDir, "missing systemDir");
-        mBaseDir = Objects.requireNonNull(baseDir, "missing baseDir");
         mDeps = Objects.requireNonNull(deps, "missing Dependencies");
+        mStatsDir = mDeps.getOrCreateStatsDir();
+        if (!mStatsDir.exists()) {
+            throw new IllegalStateException("Persist data directory does not exist: " + mStatsDir);
+        }
 
         final HandlerThread handlerThread = mDeps.makeHandlerThread();
         handlerThread.start();
@@ -556,6 +575,87 @@
     @VisibleForTesting
     public static class Dependencies {
         /**
+         * Get legacy platform stats directory.
+         */
+        @NonNull
+        public File getLegacyStatsDir() {
+            final File systemDataDir = new File(Environment.getDataDirectory(), "system");
+            return new File(systemDataDir, "netstats");
+        }
+
+        /**
+         * Get or create the directory that stores the persisted data usage.
+         */
+        @NonNull
+        public File getOrCreateStatsDir() {
+            final boolean storeInApexDataDir = getStoreFilesInApexData();
+
+            final File statsDataDir;
+            if (storeInApexDataDir) {
+                final File apexDataDir = ApexEnvironment
+                        .getApexEnvironment(DeviceConfigUtils.TETHERING_MODULE_NAME)
+                        .getDeviceProtectedDataDir();
+                statsDataDir = new File(apexDataDir, "netstats");
+
+            } else {
+                statsDataDir = getLegacyStatsDir();
+            }
+
+            if (statsDataDir.exists() || statsDataDir.mkdirs()) {
+                return statsDataDir;
+            }
+            throw new IllegalStateException("Cannot write into stats data directory: "
+                    + statsDataDir);
+        }
+
+        /**
+         * Get the count of import legacy target attempts.
+         */
+        public int getImportLegacyTargetAttempts() {
+            return DeviceConfigUtils.getDeviceConfigPropertyInt(
+                    DeviceConfig.NAMESPACE_TETHERING,
+                    NETSTATS_IMPORT_LEGACY_TARGET_ATTEMPTS,
+                    DEFAULT_NETSTATS_IMPORT_LEGACY_TARGET_ATTEMPTS);
+        }
+
+        /**
+         * Create the persistent counter that counts total import legacy stats attempts.
+         */
+        public PersistentInt createImportLegacyAttemptsCounter(@NonNull Path path)
+                throws IOException {
+            // TODO: Modify PersistentInt to call setStartTime every time a write is made.
+            //  Create and pass a real logger here.
+            return new PersistentInt(path.toString(), null /* logger */);
+        }
+
+        /**
+         * Create the persistent counter that counts total import legacy stats successes.
+         */
+        public PersistentInt createImportLegacySuccessesCounter(@NonNull Path path)
+                throws IOException {
+            return new PersistentInt(path.toString(), null /* logger */);
+        }
+
+        /**
+         * Get the flag of storing files in the apex data directory.
+         * @return whether to store files in the apex data directory.
+         */
+        public boolean getStoreFilesInApexData() {
+            return DeviceConfigUtils.getDeviceConfigPropertyBoolean(
+                    DeviceConfig.NAMESPACE_TETHERING,
+                    NETSTATS_STORE_FILES_IN_APEXDATA, true);
+        }
+
+        /**
+         * Read legacy persisted network stats from disk.
+         */
+        @NonNull
+        public NetworkStatsCollection readPlatformCollection(
+                @NonNull String prefix, long bucketDuration) throws IOException {
+            return NetworkStatsDataMigrationUtils.readPlatformCollection(prefix, bucketDuration);
+        }
+
+        /**
          * Create a HandlerThread to use in NetworkStatsService.
          */
         @NonNull
@@ -690,14 +790,15 @@
             mSystemReady = true;
 
             // create data recorders along with historical rotators
-            mDevRecorder = buildRecorder(PREFIX_DEV, mSettings.getDevConfig(), false);
-            mXtRecorder = buildRecorder(PREFIX_XT, mSettings.getXtConfig(), false);
-            mUidRecorder = buildRecorder(PREFIX_UID, mSettings.getUidConfig(), false);
-            mUidTagRecorder = buildRecorder(PREFIX_UID_TAG, mSettings.getUidTagConfig(), true);
+            mDevRecorder = buildRecorder(PREFIX_DEV, mSettings.getDevConfig(), false, mStatsDir);
+            mXtRecorder = buildRecorder(PREFIX_XT, mSettings.getXtConfig(), false, mStatsDir);
+            mUidRecorder = buildRecorder(PREFIX_UID, mSettings.getUidConfig(), false, mStatsDir);
+            mUidTagRecorder = buildRecorder(PREFIX_UID_TAG, mSettings.getUidTagConfig(), true,
+                    mStatsDir);
 
             updatePersistThresholdsLocked();
 
-            // upgrade any legacy stats, migrating them to rotated files
+            // upgrade any legacy stats
             maybeUpgradeLegacyStatsLocked();
 
             // read historical network stats from disk, since policy service
@@ -757,11 +858,12 @@
     }
 
     private NetworkStatsRecorder buildRecorder(
-            String prefix, NetworkStatsSettings.Config config, boolean includeTags) {
+            String prefix, NetworkStatsSettings.Config config, boolean includeTags,
+            File baseDir) {
         final DropBoxManager dropBox = (DropBoxManager) mContext.getSystemService(
                 Context.DROPBOX_SERVICE);
         return new NetworkStatsRecorder(new FileRotator(
-                mBaseDir, prefix, config.rotateAgeMillis, config.deleteAgeMillis),
+                baseDir, prefix, config.rotateAgeMillis, config.deleteAgeMillis),
                 mNonMonotonicObserver, dropBox, prefix, config.bucketDuration, includeTags);
     }
 
@@ -791,32 +893,285 @@
         mSystemReady = false;
     }
 
+    private static class MigrationInfo {
+        public final NetworkStatsRecorder recorder;
+        public NetworkStatsCollection collection;
+        public boolean imported;
+        MigrationInfo(@NonNull final NetworkStatsRecorder recorder) {
+            this.recorder = recorder;
+            collection = null;
+            imported = false;
+        }
+    }
+
     @GuardedBy("mStatsLock")
     private void maybeUpgradeLegacyStatsLocked() {
-        File file;
-        try {
-            file = new File(mSystemDir, "netstats.bin");
-            if (file.exists()) {
-                mDevRecorder.importLegacyNetworkLocked(file);
-                file.delete();
-            }
-
-            file = new File(mSystemDir, "netstats_xt.bin");
-            if (file.exists()) {
-                file.delete();
-            }
-
-            file = new File(mSystemDir, "netstats_uid.bin");
-            if (file.exists()) {
-                mUidRecorder.importLegacyUidLocked(file);
-                mUidTagRecorder.importLegacyUidLocked(file);
-                file.delete();
-            }
-        } catch (IOException e) {
-            Log.wtf(TAG, "problem during legacy upgrade", e);
-        } catch (OutOfMemoryError e) {
-            Log.wtf(TAG, "problem during legacy upgrade", e);
+        final boolean storeFilesInApexData = mDeps.getStoreFilesInApexData();
+        if (!storeFilesInApexData) {
+            return;
         }
+        try {
+            mImportLegacyAttemptsCounter = mDeps.createImportLegacyAttemptsCounter(
+                    mStatsDir.toPath().resolve(NETSTATS_IMPORT_ATTEMPTS_COUNTER_NAME));
+            mImportLegacySuccessesCounter = mDeps.createImportLegacySuccessesCounter(
+                    mStatsDir.toPath().resolve(NETSTATS_IMPORT_SUCCESS_COUNTER_NAME));
+        } catch (IOException e) {
+            Log.wtf(TAG, "Failed to create persistent counters, skip.", e);
+            return;
+        }
+
+        final int targetAttempts = mDeps.getImportLegacyTargetAttempts();
+        final int attempts;
+        try {
+            attempts = mImportLegacyAttemptsCounter.get();
+        } catch (IOException e) {
+            Log.wtf(TAG, "Failed to read attempts counter, skip.", e);
+            return;
+        }
+        if (attempts >= targetAttempts) return;
+
+        Log.i(TAG, "Starting import : attempts " + attempts + "/" + targetAttempts);
+
+        final MigrationInfo[] migrations = new MigrationInfo[]{
+                new MigrationInfo(mDevRecorder), new MigrationInfo(mXtRecorder),
+                new MigrationInfo(mUidRecorder), new MigrationInfo(mUidTagRecorder)
+        };
+
+        // Legacy directories will be created by recorders if they do not exist
+        final File legacyBaseDir = mDeps.getLegacyStatsDir();
+        final NetworkStatsRecorder[] legacyRecorders = new NetworkStatsRecorder[]{
+                buildRecorder(PREFIX_DEV, mSettings.getDevConfig(), false, legacyBaseDir),
+                buildRecorder(PREFIX_XT, mSettings.getXtConfig(), false, legacyBaseDir),
+                buildRecorder(PREFIX_UID, mSettings.getUidConfig(), false, legacyBaseDir),
+                buildRecorder(PREFIX_UID_TAG, mSettings.getUidTagConfig(), true, legacyBaseDir)
+        };
+
+        long migrationEndTime = Long.MIN_VALUE;
+        boolean endedWithFallback = false;
+        try {
+            // First, read all legacy collections. This is OEM code and it can throw. Don't
+            // commit any data to disk until all are read.
+            for (int i = 0; i < migrations.length; i++) {
+                final MigrationInfo migration = migrations[i];
+                migration.collection = readPlatformCollectionForRecorder(migration.recorder);
+
+                // Also read the collection with legacy method
+                final NetworkStatsRecorder legacyRecorder = legacyRecorders[i];
+
+                final NetworkStatsCollection legacyStats;
+                try {
+                    legacyStats = legacyRecorder.getOrLoadCompleteLocked();
+                } catch (Throwable e) {
+                    Log.wtf(TAG, "Failed to read stats with legacy method", e);
+                    // Newer stats will be used here; that's the only thing that is usable
+                    continue;
+                }
+
+                String errMsg;
+                Throwable exception = null;
+                try {
+                    errMsg = compareStats(migration.collection, legacyStats);
+                } catch (Throwable e) {
+                    errMsg = "Failed to compare migrated stats with all stats";
+                    exception = e;
+                }
+
+                if (errMsg != null) {
+                    Log.wtf(TAG, "NetworkStats import for migration " + i
+                            + " returned invalid data: " + errMsg, exception);
+                    // Fall back to legacy stats for this boot. The stats for old data will be
+                    // re-imported again on next boot until they succeed the import. This is fine
+                    // since every import clears the previous stats for the imported timespan.
+                    migration.collection = legacyStats;
+                    endedWithFallback = true;
+                }
+            }
+
+            // Find the latest end time.
+            for (final MigrationInfo migration : migrations) {
+                final long migrationEnd = migration.collection.getEndMillis();
+                if (migrationEnd > migrationEndTime) migrationEndTime = migrationEnd;
+            }
+
+            // Reading all collections from legacy data has succeeded. At this point it is
+            // safe to start overwriting the files on disk. The next step is to remove all
+            // data in the new location that overlaps with imported data. This ensures that
+            // any data in the new location that was created by a previous failed import is
+            // ignored. After that, write the imported data into the recorder. The code
+            // below can still possibly throw (disk error or OutOfMemory for example), but
+            // does not depend on code from non-mainline code.
+            Log.i(TAG, "Rewriting data with imported collections with cutoff "
+                    + Instant.ofEpochMilli(migrationEndTime));
+            for (final MigrationInfo migration : migrations) {
+                migration.imported = true;
+                migration.recorder.removeDataBefore(migrationEndTime);
+                if (migration.collection.isEmpty()) continue;
+                migration.recorder.importCollectionLocked(migration.collection);
+            }
+
+            if (endedWithFallback) {
+                Log.wtf(TAG, "Imported platform collections with legacy fallback");
+            } else {
+                Log.i(TAG, "Successfully imported platform collections");
+            }
+        } catch (Throwable e) {
+            // The code above calls OEM code that may behave differently across devices.
+            // It can throw any exception including RuntimeExceptions and
+            // OutOfMemoryErrors. Try to recover anyway.
+            Log.wtf(TAG, "Platform data import failed. Remaining tries "
+                    + (targetAttempts - attempts), e);
+
+            // Failed this time around : try again next time unless we're out of tries.
+            try {
+                mImportLegacyAttemptsCounter.set(attempts + 1);
+            } catch (IOException ex) {
+                Log.wtf(TAG, "Failed to update attempts counter.", ex);
+            }
+
+            // Try to remove any data from the failed import.
+            if (migrationEndTime > Long.MIN_VALUE) {
+                try {
+                    for (final MigrationInfo migration : migrations) {
+                        if (migration.imported) {
+                            migration.recorder.removeDataBefore(migrationEndTime);
+                        }
+                    }
+                } catch (Throwable f) {
+                    // If rollback still throws, there isn't much left to do. Try nuking
+                    // all data, since that's the last stop. If nuking still throws, the
+                    // framework will reboot, and if there are remaining tries, the migration
+                    // process will retry, which is fine because it's idempotent.
+                    for (final MigrationInfo migration : migrations) {
+                        migration.recorder.recoverAndDeleteData();
+                    }
+                }
+            }
+
+            return;
+        }
+
+        // Success ! No need to import again next time.
+        try {
+            mImportLegacyAttemptsCounter.set(targetAttempts);
+            // The successes counter is only for debugging. Hence, the synchronization
+            // between these two counters are not very critical.
+            final int successCount = mImportLegacySuccessesCounter.get();
+            mImportLegacySuccessesCounter.set(successCount + 1);
+        } catch (IOException e) {
+            Log.wtf(TAG, "Succeed but failed to update counters.", e);
+        }
+    }
+
+    private static String str(NetworkStatsCollection.Key key) {
+        StringBuilder sb = new StringBuilder()
+                .append(key.ident.toString())
+                .append(" uid=").append(key.uid);
+        if (key.set != SET_FOREGROUND) {
+            sb.append(" set=").append(key.set);
+        }
+        if (key.tag != 0) {
+            sb.append(" tag=").append(key.tag);
+        }
+        return sb.toString();
+    }
+
+    // The importer will modify some keys when importing them.
+    // In order to keep the comparison code simple, add such special cases here and simply
+    // ignore them. This should not impact fidelity much because the start/end checks and the total
+    // bytes check still need to pass.
+    private static boolean couldKeyChangeOnImport(NetworkStatsCollection.Key key) {
+        if (key.ident.isEmpty()) return false;
+        final NetworkIdentity firstIdent = key.ident.iterator().next();
+
+        // Non-mobile network with non-empty RAT type.
+        // This combination is invalid and the NetworkIdentity.Builder will throw if it is passed
+        // in, but it looks like it was previously possible to persist it to disk. The importer sets
+        // the RAT type to NETWORK_TYPE_ALL.
+        if (firstIdent.getType() != ConnectivityManager.TYPE_MOBILE
+                && firstIdent.getRatType() != NetworkTemplate.NETWORK_TYPE_ALL) {
+            return true;
+        }
+
+        return false;
+    }
+
+    @Nullable
+    private static String compareStats(
+            NetworkStatsCollection migrated, NetworkStatsCollection legacy) {
+        final Map<NetworkStatsCollection.Key, NetworkStatsHistory> migEntries =
+                migrated.getEntries();
+        final Map<NetworkStatsCollection.Key, NetworkStatsHistory> legEntries = legacy.getEntries();
+
+        final ArraySet<NetworkStatsCollection.Key> unmatchedLegKeys =
+                new ArraySet<>(legEntries.keySet());
+
+        for (NetworkStatsCollection.Key legKey : legEntries.keySet()) {
+            final NetworkStatsHistory legHistory = legEntries.get(legKey);
+            final NetworkStatsHistory migHistory = migEntries.get(legKey);
+
+            if (migHistory == null && couldKeyChangeOnImport(legKey)) {
+                unmatchedLegKeys.remove(legKey);
+                continue;
+            }
+
+            if (migHistory == null) {
+                return "Missing migrated history for legacy key " + str(legKey)
+                        + ", legacy history was " + legHistory;
+            }
+            if (!migHistory.isSameAs(legHistory)) {
+                return "Difference in history for key " + legKey + "; legacy history " + legHistory
+                        + ", migrated history " + migHistory;
+            }
+            unmatchedLegKeys.remove(legKey);
+        }
+
+        if (!unmatchedLegKeys.isEmpty()) {
+            final NetworkStatsHistory first = legEntries.get(unmatchedLegKeys.valueAt(0));
+            return "Found unmatched legacy keys: count=" + unmatchedLegKeys.size()
+                    + ", first unmatched collection " + first;
+        }
+
+        if (migrated.getStartMillis() != legacy.getStartMillis()
+                || migrated.getEndMillis() != legacy.getEndMillis()) {
+            return "Start / end of the collections "
+                    + migrated.getStartMillis() + "/" + legacy.getStartMillis() + " and "
+                    + migrated.getEndMillis() + "/" + legacy.getEndMillis()
+                    + " don't match";
+        }
+
+        if (migrated.getTotalBytes() != legacy.getTotalBytes()) {
+            return "Total bytes " + migrated.getTotalBytes() + " and " + legacy.getTotalBytes()
+                    + " don't match for collections with start/end "
+                    + migrated.getStartMillis()
+                    + "/" + legacy.getStartMillis();
+        }
+
+        return null;
+    }
+
+    @GuardedBy("mStatsLock")
+    @NonNull
+    private NetworkStatsCollection readPlatformCollectionForRecorder(
+            @NonNull final NetworkStatsRecorder rec) throws IOException {
+        final String prefix = rec.getCookie();
+        Log.i(TAG, "Importing platform collection for prefix " + prefix);
+        final NetworkStatsCollection collection = Objects.requireNonNull(
+                mDeps.readPlatformCollection(prefix, rec.getBucketDuration()),
+                "Imported platform collection for prefix " + prefix + " must not be null");
+
+        final long bootTimestamp = System.currentTimeMillis() - SystemClock.elapsedRealtime();
+        if (!collection.isEmpty() && bootTimestamp < collection.getStartMillis()) {
+            throw new IllegalArgumentException("Platform collection for prefix " + prefix
+                    + " contains data that could not possibly come from the previous boot "
+                    + "(start timestamp = " + Instant.ofEpochMilli(collection.getStartMillis())
+                    + ", last booted at " + Instant.ofEpochMilli(bootTimestamp));
+        }
+
+        Log.i(TAG, "Successfully read platform collection spanning from "
+                // Instant uses ISO-8601 for toString()
+                + Instant.ofEpochMilli(collection.getStartMillis()).toString() + " to "
+                + Instant.ofEpochMilli(collection.getEndMillis()).toString());
+        return collection;
     }
 
     /**
@@ -2102,10 +2457,32 @@
                 return;
             }
 
+            pw.println("Directory:");
+            pw.increaseIndent();
+            pw.println(mStatsDir);
+            pw.decreaseIndent();
+
             pw.println("Configs:");
             pw.increaseIndent();
             pw.print(NETSTATS_COMBINE_SUBTYPE_ENABLED, mSettings.getCombineSubtypeEnabled());
             pw.println();
+            pw.print(NETSTATS_STORE_FILES_IN_APEXDATA, mDeps.getStoreFilesInApexData());
+            pw.println();
+            pw.print(NETSTATS_IMPORT_LEGACY_TARGET_ATTEMPTS, mDeps.getImportLegacyTargetAttempts());
+            pw.println();
+            if (mDeps.getStoreFilesInApexData()) {
+                try {
+                    pw.print("platform legacy stats import attempts count",
+                            mImportLegacyAttemptsCounter.get());
+                    pw.println();
+                    pw.print("platform legacy stats import successes count",
+                            mImportLegacySuccessesCounter.get());
+                    pw.println();
+                } catch (IOException e) {
+                    pw.println("(failed to dump platform legacy stats import counters)");
+                }
+            }
+
             pw.decreaseIndent();
 
             pw.println("Active interfaces:");
diff --git a/service-t/src/com/android/server/net/PersistentInt.java b/service-t/src/com/android/server/net/PersistentInt.java
new file mode 100644
index 0000000..c212b77
--- /dev/null
+++ b/service-t/src/com/android/server/net/PersistentInt.java
@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.net;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.util.AtomicFile;
+import android.util.SystemConfigFileCommitEventLogger;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+/**
+ * A simple integer backed by an on-disk {@link AtomicFile}. Not thread-safe.
+ */
+public class PersistentInt {
+    private final String mPath;
+    private final AtomicFile mFile;
+
+    /**
+     * Constructs a new {@code PersistentInt}. The counter is set to 0 if the file does not exist.
+     * Before returning, the constructor checks that the file is readable and writable. This
+     * indicates that in the future {@link #get} and {@link #set} are likely to succeed,
+     * though other events (data corruption, other code deleting the file, etc.) may cause these
+     * calls to fail in the future.
+     *
+     * @param path the path of the file to use.
+     * @param logger the logger
+     * @throws IOException the counter could not be read or written
+     */
+    public PersistentInt(@NonNull String path, @Nullable SystemConfigFileCommitEventLogger logger)
+            throws IOException {
+        mPath = path;
+        mFile = new AtomicFile(new File(path), logger);
+        checkReadWrite();
+    }
+
+    private void checkReadWrite() throws IOException {
+        int value;
+        try {
+            value = get();
+        } catch (FileNotFoundException e) {
+            // Counter does not exist. Attempt to initialize to 0.
+            // Note that we cannot tell here if the file does not exist or if opening it failed,
+            // because in Java both of those throw FileNotFoundException.
+            value = 0;
+        }
+        set(value);
+        get();
+        // No exceptions? Good.
+    }
+
+    /**
+      * Gets the current value.
+      *
+      * @return the current value of the counter.
+      * @throws IOException if reading the value failed.
+      */
+    public int get() throws IOException {
+        try (FileInputStream fin = mFile.openRead();
+             DataInputStream din = new DataInputStream(fin)) {
+            return din.readInt();
+        }
+    }
+
+    /**
+     * Sets the current value.
+     * @param value the value to set
+     * @throws IOException if writing the value failed.
+     */
+    public void set(int value) throws IOException {
+        FileOutputStream fout = null;
+        try {
+            fout = mFile.startWrite();
+            DataOutputStream dout = new DataOutputStream(fout);
+            dout.writeInt(value);
+            mFile.finishWrite(fout);
+        } catch (IOException e) {
+            if (fout != null) {
+                mFile.failWrite(fout);
+            }
+            throw e;
+        }
+    }
+
+    public String getPath() {
+        return mPath;
+    }
+}
diff --git a/service/native/TrafficController.cpp b/service/native/TrafficController.cpp
index a9ede6a..55db393 100644
--- a/service/native/TrafficController.cpp
+++ b/service/native/TrafficController.cpp
@@ -455,15 +455,15 @@
 int TrafficController::toggleUidOwnerMap(ChildChain chain, bool enable) {
     std::lock_guard guard(mMutex);
     uint32_t key = UID_RULES_CONFIGURATION_KEY;
-    auto oldConfiguration = mConfigurationMap.readValue(key);
-    if (!oldConfiguration.ok()) {
+    auto oldConfigure = mConfigurationMap.readValue(key);
+    if (!oldConfigure.ok()) {
         ALOGE("Cannot read the old configuration from map: %s",
-              oldConfiguration.error().message().c_str());
-        return -oldConfiguration.error().code();
+              oldConfigure.error().message().c_str());
+        return -oldConfigure.error().code();
     }
     Status res;
     BpfConfig newConfiguration;
-    uint8_t match;
+    uint32_t match;
     switch (chain) {
         case DOZABLE:
             match = DOZABLE_MATCH;
@@ -484,7 +484,7 @@
             return -EINVAL;
     }
     newConfiguration =
-            enable ? (oldConfiguration.value() | match) : (oldConfiguration.value() & (~match));
+            enable ? (oldConfigure.value() | match) : (oldConfigure.value() & (~match));
     res = mConfigurationMap.writeValue(key, newConfiguration, BPF_EXIST);
     if (!isOk(res)) {
         ALOGE("Failed to toggleUidOwnerMap(%d): %s", chain, res.msg().c_str());
@@ -496,17 +496,17 @@
     std::lock_guard guard(mMutex);
 
     uint32_t key = CURRENT_STATS_MAP_CONFIGURATION_KEY;
-    auto oldConfiguration = mConfigurationMap.readValue(key);
-    if (!oldConfiguration.ok()) {
+    auto oldConfigure = mConfigurationMap.readValue(key);
+    if (!oldConfigure.ok()) {
         ALOGE("Cannot read the old configuration from map: %s",
-              oldConfiguration.error().message().c_str());
-        return Status(oldConfiguration.error().code(), oldConfiguration.error().message());
+              oldConfigure.error().message().c_str());
+        return Status(oldConfigure.error().code(), oldConfigure.error().message());
     }
 
     // Write to the configuration map to inform the kernel eBPF program to switch
     // from using one map to the other. Use flag BPF_EXIST here since the map should
     // be already populated in initMaps.
-    uint8_t newConfigure = (oldConfiguration.value() == SELECT_MAP_A) ? SELECT_MAP_B : SELECT_MAP_A;
+    uint32_t newConfigure = (oldConfigure.value() == SELECT_MAP_A) ? SELECT_MAP_B : SELECT_MAP_A;
     auto res = mConfigurationMap.writeValue(CURRENT_STATS_MAP_CONFIGURATION_KEY, newConfigure,
                                             BPF_EXIST);
     if (!res.ok()) {
diff --git a/service/native/TrafficControllerTest.cpp b/service/native/TrafficControllerTest.cpp
index 3f13532..96bd57c 100644
--- a/service/native/TrafficControllerTest.cpp
+++ b/service/native/TrafficControllerTest.cpp
@@ -65,7 +65,7 @@
     BpfMap<uint64_t, UidTagValue> mFakeCookieTagMap;
     BpfMap<uint32_t, StatsValue> mFakeAppUidStatsMap;
     BpfMap<StatsKey, StatsValue> mFakeStatsMapA;
-    BpfMap<uint32_t, uint8_t> mFakeConfigurationMap;
+    BpfMap<uint32_t, uint32_t> mFakeConfigurationMap;
     BpfMap<uint32_t, UidOwnerValue> mFakeUidOwnerMap;
     BpfMap<uint32_t, uint8_t> mFakeUidPermissionMap;
 
diff --git a/service/native/include/TrafficController.h b/service/native/include/TrafficController.h
index 79e75ac..d3d52e2 100644
--- a/service/native/include/TrafficController.h
+++ b/service/native/include/TrafficController.h
@@ -155,7 +155,7 @@
      *    Userspace can do scraping and cleaning job on the other one depending on the
      *    current configs.
      */
-    bpf::BpfMap<uint32_t, uint8_t> mConfigurationMap GUARDED_BY(mMutex);
+    bpf::BpfMap<uint32_t, uint32_t> mConfigurationMap GUARDED_BY(mMutex);
 
     /*
      * mUidOwnerMap: Store uids that are used for bandwidth control uid match.
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index f760d3b..e55678c 100644
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -3872,7 +3872,6 @@
             }
 
             final boolean wasValidated = nai.lastValidated;
-            final boolean wasDefault = isDefaultNetwork(nai);
             final boolean wasPartial = nai.partialConnectivity;
             nai.partialConnectivity = ((testResult & NETWORK_VALIDATION_RESULT_PARTIAL) != 0);
             final boolean partialConnectivityChanged =
@@ -9252,7 +9251,18 @@
             params.networkCapabilities = networkAgent.networkCapabilities;
             params.linkProperties = new LinkProperties(networkAgent.linkProperties,
                     true /* parcelSensitiveFields */);
-            networkAgent.networkMonitor().notifyNetworkConnected(params);
+            // isAtLeastT() is conservative here, as recent versions of NetworkStack support the
+            // newer callback even before T. However getInterfaceVersion is a synchronized binder
+            // call that would cause a Log.wtf to be emitted from the system_server process, and
+            // in the absence of a satisfactory, scalable solution which follows an easy/standard
+            // process to check the interface version, just use an SDK check. NetworkStack will
+            // always be new enough when running on T+.
+            if (SdkLevel.isAtLeastT()) {
+                networkAgent.networkMonitor().notifyNetworkConnected(params);
+            } else {
+                networkAgent.networkMonitor().notifyNetworkConnected(params.linkProperties,
+                        params.networkCapabilities);
+            }
             scheduleUnvalidatedPrompt(networkAgent);
 
             // Whether a particular NetworkRequest listen should cause signal strength thresholds to
diff --git a/service/src/com/android/server/net/DelayedDiskWrite.java b/service/src/com/android/server/net/DelayedDiskWrite.java
index 35dc455..41cb419 100644
--- a/service/src/com/android/server/net/DelayedDiskWrite.java
+++ b/service/src/com/android/server/net/DelayedDiskWrite.java
@@ -21,6 +21,8 @@
 import android.text.TextUtils;
 import android.util.Log;
 
+import com.android.internal.annotations.VisibleForTesting;
+
 import java.io.BufferedOutputStream;
 import java.io.DataOutputStream;
 import java.io.FileOutputStream;
@@ -32,11 +34,42 @@
 public class DelayedDiskWrite {
     private static final String TAG = "DelayedDiskWrite";
 
+    private final Dependencies mDeps;
+
     private HandlerThread mDiskWriteHandlerThread;
     private Handler mDiskWriteHandler;
     /* Tracks multiple writes on the same thread */
     private int mWriteSequence = 0;
 
+    public DelayedDiskWrite() {
+        this(new Dependencies());
+    }
+
+    @VisibleForTesting
+    DelayedDiskWrite(Dependencies deps) {
+        mDeps = deps;
+    }
+
+    /**
+     * Dependencies class of DelayedDiskWrite, used for injection in tests.
+     */
+    @VisibleForTesting
+    static class Dependencies {
+        /**
+         * Create a HandlerThread to use in DelayedDiskWrite.
+         */
+        public HandlerThread makeHandlerThread() {
+            return new HandlerThread("DelayedDiskWriteThread");
+        }
+
+        /**
+         * Quit the HandlerThread looper.
+         */
+        public void quitHandlerThread(HandlerThread handlerThread) {
+            handlerThread.getLooper().quit();
+        }
+    }
+
     /**
      * Used to do a delayed data write to a given {@link OutputStream}.
      */
@@ -65,7 +98,7 @@
         /* Do a delayed write to disk on a separate handler thread */
         synchronized (this) {
             if (++mWriteSequence == 1) {
-                mDiskWriteHandlerThread = new HandlerThread("DelayedDiskWriteThread");
+                mDiskWriteHandlerThread = mDeps.makeHandlerThread();
                 mDiskWriteHandlerThread.start();
                 mDiskWriteHandler = new Handler(mDiskWriteHandlerThread.getLooper());
             }
@@ -99,9 +132,9 @@
             // Quit if no more writes sent
             synchronized (this) {
                 if (--mWriteSequence == 0) {
-                    mDiskWriteHandler.getLooper().quit();
-                    mDiskWriteHandler = null;
+                    mDeps.quitHandlerThread(mDiskWriteHandlerThread);
                     mDiskWriteHandlerThread = null;
+                    mDiskWriteHandler = null;
                 }
             }
         }
diff --git a/tests/common/Android.bp b/tests/common/Android.bp
index 509e881..58731e0 100644
--- a/tests/common/Android.bp
+++ b/tests/common/Android.bp
@@ -140,6 +140,30 @@
     ],
 }
 
+// defaults for tests that need to build against framework-connectivity's @hide APIs, but also
+// using fully @hide classes that are jarjared (because they have no API member). Similar to
+// framework-connectivity-test-defaults above but uses pre-jarjar class names.
+// Only usable from targets that have visibility on framework-connectivity-pre-jarjar, and apply
+// connectivity jarjar rules so that references to jarjared classes still match: this is limited to
+// connectivity internal tests only.
+java_defaults {
+    name: "framework-connectivity-internal-test-defaults",
+    sdk_version: "core_platform", // tests can use @CorePlatformApi's
+    libs: [
+        // order matters: classes in framework-connectivity are resolved before framework,
+        // meaning @hide APIs in framework-connectivity are resolved before @SystemApi
+        // stubs in framework
+        "framework-connectivity-pre-jarjar",
+        "framework-connectivity-t-pre-jarjar",
+        "framework-tethering.impl",
+        "framework",
+
+        // if sdk_version="" this gets automatically included, but here we need to add manually.
+        "framework-res",
+    ],
+    defaults_visibility: ["//packages/modules/Connectivity/tests:__subpackages__"],
+}
+
 // Defaults for tests that want to run in mainline-presubmit.
 // Not widely used because many of our tests have AndroidTest.xml files and
 // use the mainline-param config-descriptor metadata in AndroidTest.xml.
diff --git a/tests/common/java/android/net/LinkPropertiesTest.java b/tests/common/java/android/net/LinkPropertiesTest.java
index b66a979..581ee22 100644
--- a/tests/common/java/android/net/LinkPropertiesTest.java
+++ b/tests/common/java/android/net/LinkPropertiesTest.java
@@ -46,6 +46,7 @@
 import com.android.testutils.DevSdkIgnoreRule;
 import com.android.testutils.DevSdkIgnoreRule.IgnoreAfter;
 import com.android.testutils.DevSdkIgnoreRule.IgnoreUpTo;
+import com.android.testutils.filters.CtsNetTestCasesMaxTargetSdk31;
 
 import libcore.junit.util.compat.CoreCompatChangeRule.DisableCompatChanges;
 import libcore.junit.util.compat.CoreCompatChangeRule.EnableCompatChanges;
@@ -1307,6 +1308,7 @@
     }
 
     @Test @IgnoreUpTo(SC_V2)
+    @CtsNetTestCasesMaxTargetSdk31(reason = "Compat change cannot be overridden on T or above")
     @DisableCompatChanges({LinkProperties.EXCLUDED_ROUTES})
     public void testExcludedRoutesDisabled() {
         final LinkProperties lp = new LinkProperties();
diff --git a/tests/common/java/android/net/netstats/NetworkStatsHistoryTest.kt b/tests/common/java/android/net/netstats/NetworkStatsHistoryTest.kt
index c2654c5..f8e041a 100644
--- a/tests/common/java/android/net/netstats/NetworkStatsHistoryTest.kt
+++ b/tests/common/java/android/net/netstats/NetworkStatsHistoryTest.kt
@@ -27,6 +27,7 @@
 import org.junit.runner.RunWith
 import org.junit.runners.JUnit4
 import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
 
 @ConnectivityModuleTest
 @RunWith(JUnit4::class)
@@ -51,12 +52,22 @@
                 .build()
         statsSingle.assertEntriesEqual(entry1)
         assertEquals(DateUtils.HOUR_IN_MILLIS, statsSingle.bucketDuration)
+
+        // Verify the builder throws if the timestamp of added entry is not greater than
+        // that of any previously-added entry.
+        assertFailsWith(IllegalArgumentException::class) {
+            NetworkStatsHistory
+                    .Builder(DateUtils.SECOND_IN_MILLIS, /* initialCapacity */ 0)
+                    .addEntry(entry1).addEntry(entry2).addEntry(entry3)
+                    .build()
+        }
+
         val statsMultiple = NetworkStatsHistory
                 .Builder(DateUtils.SECOND_IN_MILLIS, /* initialCapacity */ 0)
-                .addEntry(entry1).addEntry(entry2).addEntry(entry3)
+                .addEntry(entry3).addEntry(entry1).addEntry(entry2)
                 .build()
         assertEquals(DateUtils.SECOND_IN_MILLIS, statsMultiple.bucketDuration)
-        statsMultiple.assertEntriesEqual(entry1, entry2, entry3)
+        statsMultiple.assertEntriesEqual(entry3, entry1, entry2)
     }
 
     fun NetworkStatsHistory.assertEntriesEqual(vararg entries: NetworkStatsHistory.Entry) {
diff --git a/tests/cts/net/Android.bp b/tests/cts/net/Android.bp
index 4d85d72..a6ed762 100644
--- a/tests/cts/net/Android.bp
+++ b/tests/cts/net/Android.bp
@@ -62,6 +62,7 @@
     // sdk_version: "current",
     platform_apis: true,
     required: ["ConnectivityChecker"],
+    test_config_template: "AndroidTestTemplate.xml",
 }
 
 // Networking CTS tests for development and release. These tests always target the platform SDK
@@ -79,7 +80,16 @@
         "cts",
         "general-tests",
     ],
-    test_config_template: "AndroidTestTemplate.xml",
+}
+
+java_defaults {
+    name: "CtsNetTestCasesApiStableDefaults",
+    // TODO: CTS should not depend on the entirety of the networkstack code.
+    static_libs: [
+        "NetworkStackApiStableLib",
+    ],
+    jni_uses_sdk_apis: true,
+    min_sdk_version: "29",
 }
 
 // Networking CTS tests that target the latest released SDK. These tests can be installed on release
@@ -87,13 +97,10 @@
 // on release devices.
 android_test {
     name: "CtsNetTestCasesLatestSdk",
-    defaults: ["CtsNetTestCasesDefaults"],
-    // TODO: CTS should not depend on the entirety of the networkstack code.
-    static_libs: [
-        "NetworkStackApiStableLib",
+    defaults: [
+        "CtsNetTestCasesDefaults",
+        "CtsNetTestCasesApiStableDefaults",
     ],
-    jni_uses_sdk_apis: true,
-    min_sdk_version: "29",
     target_sdk_version: "33",
     test_suites: [
         "general-tests",
@@ -102,5 +109,21 @@
         "mts-tethering",
         "mts-wifi",
     ],
-    test_config_template: "AndroidTestTemplate.xml",
 }
+
+android_test {
+    name: "CtsNetTestCasesMaxTargetSdk31",  // Must match CtsNetTestCasesMaxTargetSdk31 annotation.
+    defaults: [
+        "CtsNetTestCasesDefaults",
+        "CtsNetTestCasesApiStableDefaults",
+    ],
+    target_sdk_version: "31",
+    package_name: "android.net.cts.maxtargetsdk31",  // CTS package names must be unique.
+    instrumentation_target_package: "android.net.cts.maxtargetsdk31",
+    test_suites: [
+        "cts",
+        "general-tests",
+        "mts-networking",
+    ],
+}
+
diff --git a/tests/cts/net/AndroidTestTemplate.xml b/tests/cts/net/AndroidTestTemplate.xml
index 33f3af5..d2fb04a 100644
--- a/tests/cts/net/AndroidTestTemplate.xml
+++ b/tests/cts/net/AndroidTestTemplate.xml
@@ -33,10 +33,21 @@
     <target_preparer class="com.android.testutils.DisableConfigSyncTargetPreparer">
     </target_preparer>
     <test class="com.android.tradefed.testtype.AndroidJUnitTest" >
-        <option name="package" value="android.net.cts" />
+        <option name="package" value="{PACKAGE}" />
         <option name="runtime-hint" value="9m4s" />
         <option name="hidden-api-checks" value="false" />
         <option name="isolated-storage" value="false" />
+        <!-- Test filter that allows test APKs to select which tests they want to run by annotating
+             those tests with an annotation matching the name of the APK.
+
+             This allows us to maintain one AndroidTestTemplate.xml for all CtsNetTestCases*.apk,
+             and have CtsNetTestCases and CtsNetTestCasesLatestSdk run all tests, but have
+             CtsNetTestCasesMaxTargetSdk31 run only tests that require target SDK 31.
+
+             This relies on the fact that if the class specified in include-annotation exists, then
+             the runner will only run the tests annotated with that annotation, but if it does not,
+             the runner will run all the tests. -->
+        <option name="include-annotation" value="com.android.testutils.filters.{MODULE}" />
     </test>
     <!-- When this test is run in a Mainline context (e.g. with `mts-tradefed`), only enable it if
         one of the Mainline modules below is present on the device used for testing. -->
diff --git a/tests/unit/Android.bp b/tests/unit/Android.bp
index e6cf22a..3ea27f7 100644
--- a/tests/unit/Android.bp
+++ b/tests/unit/Android.bp
@@ -87,7 +87,7 @@
     name: "FrameworksNetTestsDefaults",
     min_sdk_version: "30",
     defaults: [
-        "framework-connectivity-test-defaults",
+        "framework-connectivity-internal-test-defaults",
     ],
     srcs: [
         "java/**/*.java",
diff --git a/tests/unit/java/android/net/netstats/NetworkStatsDataMigrationUtilsTest.kt b/tests/unit/java/android/net/netstats/NetworkStatsDataMigrationUtilsTest.kt
index 743d39e..aa5a246 100644
--- a/tests/unit/java/android/net/netstats/NetworkStatsDataMigrationUtilsTest.kt
+++ b/tests/unit/java/android/net/netstats/NetworkStatsDataMigrationUtilsTest.kt
@@ -61,14 +61,6 @@
         assertValues(builder.build(), 55, 1814302L, 21050L, 31001636L, 26152L)
     }
 
-    @Test
-    fun testMaybeReadLegacyUid() {
-        val builder = NetworkStatsCollection.Builder(BUCKET_DURATION_MS)
-        NetworkStatsDataMigrationUtils.readLegacyUid(builder,
-                getInputStreamForResource(R.raw.netstats_uid_v4), false /* taggedData */)
-        assertValues(builder.build(), 223, 106245210L, 710722L, 1130647496L, 1103989L)
-    }
-
     private fun assertValues(
         collection: NetworkStatsCollection,
         expectedSize: Int,
diff --git a/tests/unit/java/android/net/nsd/NsdServiceInfoTest.java b/tests/unit/java/android/net/nsd/NsdServiceInfoTest.java
index 0354377..64355ed 100644
--- a/tests/unit/java/android/net/nsd/NsdServiceInfoTest.java
+++ b/tests/unit/java/android/net/nsd/NsdServiceInfoTest.java
@@ -125,6 +125,7 @@
         fullInfo.setPort(4242);
         fullInfo.setHost(LOCALHOST);
         fullInfo.setNetwork(new Network(123));
+        fullInfo.setInterfaceIndex(456);
         checkParcelable(fullInfo);
 
         NsdServiceInfo noHostInfo = new NsdServiceInfo();
@@ -175,6 +176,7 @@
         assertEquals(original.getHost(), result.getHost());
         assertTrue(original.getPort() == result.getPort());
         assertEquals(original.getNetwork(), result.getNetwork());
+        assertEquals(original.getInterfaceIndex(), result.getInterfaceIndex());
 
         // Assert equality of attribute map.
         Map<String, byte[]> originalMap = original.getAttributes();
diff --git a/tests/unit/java/com/android/server/ConnectivityServiceTest.java b/tests/unit/java/com/android/server/ConnectivityServiceTest.java
index ef97168..1ea8d75 100644
--- a/tests/unit/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/unit/java/com/android/server/ConnectivityServiceTest.java
@@ -11704,6 +11704,12 @@
         mCm.unregisterNetworkCallback(networkCallback);
     }
 
+    private void verifyDump(String[] args) {
+        final StringWriter stringWriter = new StringWriter();
+        mService.dump(new FileDescriptor(), new PrintWriter(stringWriter), args);
+        assertFalse(stringWriter.toString().isEmpty());
+    }
+
     @Test
     public void testDumpDoesNotCrash() {
         mServiceContext.setPermission(DUMP, PERMISSION_GRANTED);
@@ -11716,11 +11722,26 @@
                 .addTransportType(TRANSPORT_WIFI).build();
         mCm.registerNetworkCallback(genericRequest, genericNetworkCallback);
         mCm.registerNetworkCallback(wifiRequest, wifiNetworkCallback);
-        final StringWriter stringWriter = new StringWriter();
 
-        mService.dump(new FileDescriptor(), new PrintWriter(stringWriter), new String[0]);
+        verifyDump(new String[0]);
 
-        assertFalse(stringWriter.toString().isEmpty());
+        // Verify dump with arguments.
+        final String dumpPrio = "--dump-priority";
+        final String[] dumpArgs = {dumpPrio};
+        verifyDump(dumpArgs);
+
+        final String[] highDumpArgs = {dumpPrio, "HIGH"};
+        verifyDump(highDumpArgs);
+
+        final String[] normalDumpArgs = {dumpPrio, "NORMAL"};
+        verifyDump(normalDumpArgs);
+
+        // Invalid args should do dumpNormal w/o exception
+        final String[] unknownDumpArgs = {dumpPrio, "UNKNOWN"};
+        verifyDump(unknownDumpArgs);
+
+        final String[] invalidDumpArgs = {"UNKNOWN"};
+        verifyDump(invalidDumpArgs);
     }
 
     @Test
diff --git a/tests/unit/java/com/android/server/NsdServiceTest.java b/tests/unit/java/com/android/server/NsdServiceTest.java
index 7ecf1f3..9365bee 100644
--- a/tests/unit/java/com/android/server/NsdServiceTest.java
+++ b/tests/unit/java/com/android/server/NsdServiceTest.java
@@ -19,7 +19,9 @@
 import static libcore.junit.util.compat.CoreCompatChangeRule.DisableCompatChanges;
 import static libcore.junit.util.compat.CoreCompatChangeRule.EnableCompatChanges;
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.Mockito.any;
@@ -37,6 +39,12 @@
 import android.compat.testing.PlatformCompatChangeRule;
 import android.content.ContentResolver;
 import android.content.Context;
+import android.net.INetd;
+import android.net.InetAddresses;
+import android.net.mdns.aidl.DiscoveryInfo;
+import android.net.mdns.aidl.GetAddressInfo;
+import android.net.mdns.aidl.IMDnsEventListener;
+import android.net.mdns.aidl.ResolutionInfo;
 import android.net.nsd.INsdManagerCallback;
 import android.net.nsd.INsdServiceConnector;
 import android.net.nsd.MDnsManager;
@@ -64,6 +72,7 @@
 import org.junit.rules.TestRule;
 import org.junit.runner.RunWith;
 import org.mockito.AdditionalAnswers;
+import org.mockito.ArgumentCaptor;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
@@ -280,6 +289,105 @@
         verify(mMockMDnsM, never()).stopDaemon();
     }
 
+    @Test
+    public void testDiscoverOnTetheringDownstream() throws Exception {
+        NsdService service = makeService();
+        NsdManager client = connectClient(service);
+
+        final String serviceType = "a_type";
+        final String serviceName = "a_name";
+        final String domainName = "mytestdevice.local";
+        final int interfaceIdx = 123;
+        final NsdManager.DiscoveryListener discListener = mock(NsdManager.DiscoveryListener.class);
+        client.discoverServices(serviceType, NsdManager.PROTOCOL_DNS_SD, discListener);
+        waitForIdle();
+
+        final ArgumentCaptor<IMDnsEventListener> listenerCaptor =
+                ArgumentCaptor.forClass(IMDnsEventListener.class);
+        verify(mMockMDnsM).registerEventListener(listenerCaptor.capture());
+        final ArgumentCaptor<Integer> discIdCaptor = ArgumentCaptor.forClass(Integer.class);
+        verify(mMockMDnsM).discover(discIdCaptor.capture(), eq(serviceType),
+                eq(0) /* interfaceIdx */);
+        // NsdManager uses a separate HandlerThread to dispatch callbacks (on ServiceHandler), so
+        // this needs to use a timeout
+        verify(discListener, timeout(TIMEOUT_MS)).onDiscoveryStarted(serviceType);
+
+        final DiscoveryInfo discoveryInfo = new DiscoveryInfo(
+                discIdCaptor.getValue(),
+                IMDnsEventListener.SERVICE_FOUND,
+                serviceName,
+                serviceType,
+                domainName,
+                interfaceIdx,
+                INetd.LOCAL_NET_ID); // LOCAL_NET_ID (99) used on tethering downstreams
+        final IMDnsEventListener eventListener = listenerCaptor.getValue();
+        eventListener.onServiceDiscoveryStatus(discoveryInfo);
+        waitForIdle();
+
+        final ArgumentCaptor<NsdServiceInfo> discoveredInfoCaptor =
+                ArgumentCaptor.forClass(NsdServiceInfo.class);
+        verify(discListener, timeout(TIMEOUT_MS)).onServiceFound(discoveredInfoCaptor.capture());
+        final NsdServiceInfo foundInfo = discoveredInfoCaptor.getValue();
+        assertEquals(serviceName, foundInfo.getServiceName());
+        assertEquals(serviceType, foundInfo.getServiceType());
+        assertNull(foundInfo.getHost());
+        assertNull(foundInfo.getNetwork());
+        assertEquals(interfaceIdx, foundInfo.getInterfaceIndex());
+
+        // After discovering the service, verify resolving it
+        final NsdManager.ResolveListener resolveListener = mock(NsdManager.ResolveListener.class);
+        client.resolveService(foundInfo, resolveListener);
+        waitForIdle();
+
+        final ArgumentCaptor<Integer> resolvIdCaptor = ArgumentCaptor.forClass(Integer.class);
+        verify(mMockMDnsM).resolve(resolvIdCaptor.capture(), eq(serviceName), eq(serviceType),
+                eq("local.") /* domain */, eq(interfaceIdx));
+
+        final int servicePort = 10123;
+        final String serviceFullName = serviceName + "." + serviceType;
+        final ResolutionInfo resolutionInfo = new ResolutionInfo(
+                resolvIdCaptor.getValue(),
+                IMDnsEventListener.SERVICE_RESOLVED,
+                null /* serviceName */,
+                null /* serviceType */,
+                null /* domain */,
+                serviceFullName,
+                domainName,
+                servicePort,
+                new byte[0] /* txtRecord */,
+                interfaceIdx);
+
+        doReturn(true).when(mMockMDnsM).getServiceAddress(anyInt(), any(), anyInt());
+        eventListener.onServiceResolutionStatus(resolutionInfo);
+        waitForIdle();
+
+        final ArgumentCaptor<Integer> getAddrIdCaptor = ArgumentCaptor.forClass(Integer.class);
+        verify(mMockMDnsM).getServiceAddress(getAddrIdCaptor.capture(), eq(domainName),
+                eq(interfaceIdx));
+
+        final String serviceAddress = "192.0.2.123";
+        final GetAddressInfo addressInfo = new GetAddressInfo(
+                getAddrIdCaptor.getValue(),
+                IMDnsEventListener.SERVICE_GET_ADDR_SUCCESS,
+                serviceFullName,
+                serviceAddress,
+                interfaceIdx,
+                INetd.LOCAL_NET_ID);
+        eventListener.onGettingServiceAddressStatus(addressInfo);
+        waitForIdle();
+
+        final ArgumentCaptor<NsdServiceInfo> resInfoCaptor =
+                ArgumentCaptor.forClass(NsdServiceInfo.class);
+        verify(resolveListener, timeout(TIMEOUT_MS)).onServiceResolved(resInfoCaptor.capture());
+        final NsdServiceInfo resolvedService = resInfoCaptor.getValue();
+        assertEquals(serviceName, resolvedService.getServiceName());
+        assertEquals("." + serviceType, resolvedService.getServiceType());
+        assertEquals(InetAddresses.parseNumericAddress(serviceAddress), resolvedService.getHost());
+        assertEquals(servicePort, resolvedService.getPort());
+        assertNull(resolvedService.getNetwork());
+        assertEquals(interfaceIdx, resolvedService.getInterfaceIndex());
+    }
+
     private void waitForIdle() {
         HandlerUtils.waitForIdle(mHandler, TIMEOUT_MS);
     }
diff --git a/tests/unit/java/com/android/server/net/IpConfigStoreTest.java b/tests/unit/java/com/android/server/net/IpConfigStoreTest.java
index 1801c45..4adc999 100644
--- a/tests/unit/java/com/android/server/net/IpConfigStoreTest.java
+++ b/tests/unit/java/com/android/server/net/IpConfigStoreTest.java
@@ -20,6 +20,7 @@
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.fail;
 
+import android.content.Context;
 import android.net.InetAddresses;
 import android.net.IpConfiguration;
 import android.net.IpConfiguration.IpAssignment;
@@ -28,10 +29,14 @@
 import android.net.ProxyInfo;
 import android.net.StaticIpConfiguration;
 import android.os.Build;
+import android.os.HandlerThread;
 import android.util.ArrayMap;
 
+import androidx.test.InstrumentationRegistry;
+
 import com.android.testutils.DevSdkIgnoreRule;
 import com.android.testutils.DevSdkIgnoreRunner;
+import com.android.testutils.HandlerUtils;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -39,11 +44,13 @@
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.DataOutputStream;
+import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.InetAddress;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.List;
 
 /**
  * Unit tests for {@link IpConfigStore}
@@ -51,6 +58,7 @@
 @RunWith(DevSdkIgnoreRunner.class)
 @DevSdkIgnoreRule.IgnoreUpTo(Build.VERSION_CODES.S_V2)
 public class IpConfigStoreTest {
+    private static final int TIMEOUT_MS = 2_000;
     private static final int KEY_CONFIG = 17;
     private static final String IFACE_1 = "eth0";
     private static final String IFACE_2 = "eth1";
@@ -59,6 +67,22 @@
     private static final String DNS_IP_ADDR_1 = "1.2.3.4";
     private static final String DNS_IP_ADDR_2 = "5.6.7.8";
 
+    private static final ArrayList<InetAddress> DNS_SERVERS = new ArrayList<>(List.of(
+            InetAddresses.parseNumericAddress(DNS_IP_ADDR_1),
+            InetAddresses.parseNumericAddress(DNS_IP_ADDR_2)));
+    private static final StaticIpConfiguration STATIC_IP_CONFIG_1 =
+            new StaticIpConfiguration.Builder()
+                    .setIpAddress(new LinkAddress(IP_ADDR_1))
+                    .setDnsServers(DNS_SERVERS)
+                    .build();
+    private static final StaticIpConfiguration STATIC_IP_CONFIG_2 =
+            new StaticIpConfiguration.Builder()
+                    .setIpAddress(new LinkAddress(IP_ADDR_2))
+                    .setDnsServers(DNS_SERVERS)
+                    .build();
+    private static final ProxyInfo PROXY_INFO =
+            ProxyInfo.buildDirectProxy("10.10.10.10", 88, Arrays.asList("host1", "host2"));
+
     @Test
     public void backwardCompatibility2to3() throws IOException {
         ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
@@ -82,40 +106,73 @@
 
     @Test
     public void staticIpMultiNetworks() throws Exception {
-        final ArrayList<InetAddress> dnsServers = new ArrayList<>();
-        dnsServers.add(InetAddresses.parseNumericAddress(DNS_IP_ADDR_1));
-        dnsServers.add(InetAddresses.parseNumericAddress(DNS_IP_ADDR_2));
-        final StaticIpConfiguration staticIpConfiguration1 = new StaticIpConfiguration.Builder()
-                .setIpAddress(new LinkAddress(IP_ADDR_1))
-                .setDnsServers(dnsServers).build();
-        final StaticIpConfiguration staticIpConfiguration2 = new StaticIpConfiguration.Builder()
-                .setIpAddress(new LinkAddress(IP_ADDR_2))
-                .setDnsServers(dnsServers).build();
+        final IpConfiguration expectedConfig1 = newIpConfiguration(IpAssignment.STATIC,
+                ProxySettings.STATIC, STATIC_IP_CONFIG_1, PROXY_INFO);
+        final IpConfiguration expectedConfig2 = newIpConfiguration(IpAssignment.STATIC,
+                ProxySettings.STATIC, STATIC_IP_CONFIG_2, PROXY_INFO);
 
-        ProxyInfo proxyInfo =
-                ProxyInfo.buildDirectProxy("10.10.10.10", 88, Arrays.asList("host1", "host2"));
-
-        IpConfiguration expectedConfig1 = newIpConfiguration(IpAssignment.STATIC,
-                ProxySettings.STATIC, staticIpConfiguration1, proxyInfo);
-        IpConfiguration expectedConfig2 = newIpConfiguration(IpAssignment.STATIC,
-                ProxySettings.STATIC, staticIpConfiguration2, proxyInfo);
-
-        ArrayMap<String, IpConfiguration> expectedNetworks = new ArrayMap<>();
+        final ArrayMap<String, IpConfiguration> expectedNetworks = new ArrayMap<>();
         expectedNetworks.put(IFACE_1, expectedConfig1);
         expectedNetworks.put(IFACE_2, expectedConfig2);
 
-        MockedDelayedDiskWrite writer = new MockedDelayedDiskWrite();
-        IpConfigStore store = new IpConfigStore(writer);
+        final MockedDelayedDiskWrite writer = new MockedDelayedDiskWrite();
+        final IpConfigStore store = new IpConfigStore(writer);
         store.writeIpConfigurations("file/path/not/used/", expectedNetworks);
 
-        InputStream in = new ByteArrayInputStream(writer.mByteStream.toByteArray());
-        ArrayMap<String, IpConfiguration> actualNetworks = IpConfigStore.readIpConfigurations(in);
+        final InputStream in = new ByteArrayInputStream(writer.mByteStream.toByteArray());
+        final ArrayMap<String, IpConfiguration> actualNetworks =
+                IpConfigStore.readIpConfigurations(in);
         assertNotNull(actualNetworks);
         assertEquals(2, actualNetworks.size());
         assertEquals(expectedNetworks.get(IFACE_1), actualNetworks.get(IFACE_1));
         assertEquals(expectedNetworks.get(IFACE_2), actualNetworks.get(IFACE_2));
     }
 
+    @Test
+    public void readIpConfigurationFromFilePath() throws Exception {
+        final HandlerThread testHandlerThread = new HandlerThread("IpConfigStoreTest");
+        final DelayedDiskWrite.Dependencies dependencies =
+                new DelayedDiskWrite.Dependencies() {
+                    @Override
+                    public HandlerThread makeHandlerThread() {
+                        return testHandlerThread;
+                    }
+                    @Override
+                    public void quitHandlerThread(HandlerThread handlerThread) {
+                        testHandlerThread.quitSafely();
+                    }
+        };
+
+        final IpConfiguration ipConfig = newIpConfiguration(IpAssignment.STATIC,
+                ProxySettings.STATIC, STATIC_IP_CONFIG_1, PROXY_INFO);
+        final ArrayMap<String, IpConfiguration> expectedNetworks = new ArrayMap<>();
+        expectedNetworks.put(IFACE_1, ipConfig);
+
+        // Write IP config to specific file path and read it later.
+        final Context context = InstrumentationRegistry.getContext();
+        final File configFile = new File(context.getFilesDir().getPath(),
+                "IpConfigStoreTest-ipconfig.txt");
+        final DelayedDiskWrite writer = new DelayedDiskWrite(dependencies);
+        final IpConfigStore store = new IpConfigStore(writer);
+        store.writeIpConfigurations(configFile.getPath(), expectedNetworks);
+        HandlerUtils.waitForIdle(testHandlerThread, TIMEOUT_MS);
+
+        // Read IP config from the file path.
+        final ArrayMap<String, IpConfiguration> actualNetworks =
+                IpConfigStore.readIpConfigurations(configFile.getPath());
+        assertNotNull(actualNetworks);
+        assertEquals(1, actualNetworks.size());
+        assertEquals(expectedNetworks.get(IFACE_1), actualNetworks.get(IFACE_1));
+
+        // Return an empty array when reading IP configuration from an non-exist config file.
+        final ArrayMap<String, IpConfiguration> emptyNetworks =
+                IpConfigStore.readIpConfigurations("/dev/null");
+        assertNotNull(emptyNetworks);
+        assertEquals(0, emptyNetworks.size());
+
+        configFile.delete();
+    }
+
     private IpConfiguration newIpConfiguration(IpAssignment ipAssignment,
             ProxySettings proxySettings, StaticIpConfiguration staticIpConfig, ProxyInfo info) {
         final IpConfiguration config = new IpConfiguration();
diff --git a/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java b/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java
index ceeb997..f1820b3 100644
--- a/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java
+++ b/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java
@@ -18,6 +18,7 @@
 
 import static android.Manifest.permission.READ_NETWORK_USAGE_HISTORY;
 import static android.Manifest.permission.UPDATE_DEVICE_STATS;
+import static android.app.usage.NetworkStatsManager.PREFIX_DEV;
 import static android.content.Intent.ACTION_UID_REMOVED;
 import static android.content.Intent.EXTRA_UID;
 import static android.content.pm.PackageManager.PERMISSION_DENIED;
@@ -56,6 +57,9 @@
 import static android.net.TrafficStats.MB_IN_BYTES;
 import static android.net.TrafficStats.UID_REMOVED;
 import static android.net.TrafficStats.UID_TETHERING;
+import static android.net.netstats.NetworkStatsDataMigrationUtils.PREFIX_UID;
+import static android.net.netstats.NetworkStatsDataMigrationUtils.PREFIX_UID_TAG;
+import static android.net.netstats.NetworkStatsDataMigrationUtils.PREFIX_XT;
 import static android.text.format.DateUtils.DAY_IN_MILLIS;
 import static android.text.format.DateUtils.HOUR_IN_MILLIS;
 import static android.text.format.DateUtils.MINUTE_IN_MILLIS;
@@ -77,6 +81,7 @@
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.spy;
@@ -96,6 +101,7 @@
 import android.net.NetworkCapabilities;
 import android.net.NetworkStateSnapshot;
 import android.net.NetworkStats;
+import android.net.NetworkStatsCollection;
 import android.net.NetworkStatsHistory;
 import android.net.NetworkTemplate;
 import android.net.TelephonyNetworkSpecifier;
@@ -104,6 +110,7 @@
 import android.net.UnderlyingNetworkInfo;
 import android.net.netstats.provider.INetworkStatsProviderCallback;
 import android.net.wifi.WifiInfo;
+import android.os.DropBoxManager;
 import android.os.Handler;
 import android.os.HandlerThread;
 import android.os.IBinder;
@@ -112,11 +119,13 @@
 import android.provider.Settings;
 import android.system.ErrnoException;
 import android.telephony.TelephonyManager;
+import android.util.ArrayMap;
 
 import androidx.annotation.Nullable;
 import androidx.test.InstrumentationRegistry;
 import androidx.test.filters.SmallTest;
 
+import com.android.internal.util.FileRotator;
 import com.android.internal.util.test.BroadcastInterceptingContext;
 import com.android.net.module.util.IBpfMap;
 import com.android.net.module.util.LocationPermissionChecker;
@@ -131,6 +140,16 @@
 import com.android.testutils.TestBpfMap;
 import com.android.testutils.TestableNetworkStatsProviderBinder;
 
+import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.Clock;
+import java.time.ZoneOffset;
+import java.util.Map;
+import java.util.Objects;
+import java.util.concurrent.Executor;
+import java.util.concurrent.atomic.AtomicBoolean;
+
 import libcore.testing.io.TestIoUtils;
 
 import org.junit.After;
@@ -142,13 +161,6 @@
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
-import java.io.File;
-import java.time.Clock;
-import java.time.ZoneOffset;
-import java.util.Objects;
-import java.util.concurrent.Executor;
-import java.util.concurrent.atomic.AtomicBoolean;
-
 /**
  * Tests for {@link NetworkStatsService}.
  *
@@ -187,6 +199,7 @@
     private long mElapsedRealtime;
 
     private File mStatsDir;
+    private File mLegacyStatsDir;
     private MockContext mServiceContext;
     private @Mock TelephonyManager mTelephonyManager;
     private static @Mock WifiInfo sWifiInfo;
@@ -220,6 +233,12 @@
     private ContentObserver mContentObserver;
     private Handler mHandler;
     private TetheringManager.TetheringEventCallback mTetheringEventCallback;
+    private Map<String, NetworkStatsCollection> mPlatformNetworkStatsCollection =
+            new ArrayMap<String, NetworkStatsCollection>();
+    private boolean mStoreFilesInApexData = false;
+    private int mImportLegacyTargetAttempts = 0;
+    private @Mock PersistentInt mImportLegacyAttemptsCounter;
+    private @Mock PersistentInt mImportLegacySuccessesCounter;
 
     private class MockContext extends BroadcastInterceptingContext {
         private final Context mBaseContext;
@@ -286,6 +305,8 @@
                 any(), any(), anyInt(), anyBoolean(), any())).thenReturn(true);
         when(sWifiInfo.getNetworkKey()).thenReturn(TEST_WIFI_NETWORK_KEY);
         mStatsDir = TestIoUtils.createTemporaryDirectory(getClass().getSimpleName());
+        mLegacyStatsDir = TestIoUtils.createTemporaryDirectory(
+                getClass().getSimpleName() + "-legacy");
 
         PowerManager powerManager = (PowerManager) mServiceContext.getSystemService(
                 Context.POWER_SERVICE);
@@ -295,8 +316,7 @@
         mHandlerThread = new HandlerThread("HandlerThread");
         final NetworkStatsService.Dependencies deps = makeDependencies();
         mService = new NetworkStatsService(mServiceContext, mNetd, mAlarmManager, wakeLock,
-                mClock, mSettings, mStatsFactory, new NetworkStatsObservers(), mStatsDir,
-                getBaseDir(mStatsDir), deps);
+                mClock, mSettings, mStatsFactory, new NetworkStatsObservers(), deps);
 
         mElapsedRealtime = 0L;
 
@@ -339,6 +359,44 @@
     private NetworkStatsService.Dependencies makeDependencies() {
         return new NetworkStatsService.Dependencies() {
             @Override
+            public File getLegacyStatsDir() {
+                return mLegacyStatsDir;
+            }
+
+            @Override
+            public File getOrCreateStatsDir() {
+                return mStatsDir;
+            }
+
+            @Override
+            public boolean getStoreFilesInApexData() {
+                return mStoreFilesInApexData;
+            }
+
+            @Override
+            public int getImportLegacyTargetAttempts() {
+                return mImportLegacyTargetAttempts;
+            }
+
+            @Override
+            public PersistentInt createImportLegacyAttemptsCounter(
+                    @androidx.annotation.NonNull Path path) {
+                return mImportLegacyAttemptsCounter;
+            }
+
+            @Override
+            public PersistentInt createImportLegacySuccessesCounter(
+                    @androidx.annotation.NonNull Path path) {
+                return mImportLegacySuccessesCounter;
+            }
+
+            @Override
+            public NetworkStatsCollection readPlatformCollection(
+                    @NonNull String prefix, long bucketDuration) {
+                return mPlatformNetworkStatsCollection.get(prefix);
+            }
+
+            @Override
             public HandlerThread makeHandlerThread() {
                 return mHandlerThread;
             }
@@ -1704,10 +1762,108 @@
         assertNetworkTotal(sTemplateImsi1, 0L, 0L, 0L, 0L, 0);
     }
 
-    private static File getBaseDir(File statsDir) {
-        File baseDir = new File(statsDir, "netstats");
-        baseDir.mkdirs();
-        return baseDir;
+    /**
+     * Verify the service will perform data migration process can be controlled by the device flag.
+     */
+    @Test
+    public void testDataMigration() throws Exception {
+        assertStatsFilesExist(false);
+        expectDefaultSettings();
+
+        NetworkStateSnapshot[] states = new NetworkStateSnapshot[] {buildWifiState()};
+
+        mService.notifyNetworkStatus(NETWORKS_WIFI, states, getActiveIface(states),
+                new UnderlyingNetworkInfo[0]);
+
+        // modify some number on wifi, and trigger poll event
+        incrementCurrentTime(HOUR_IN_MILLIS);
+        // expectDefaultSettings();
+        expectNetworkStatsSummary(new NetworkStats(getElapsedRealtime(), 1)
+                .insertEntry(TEST_IFACE, 1024L, 8L, 2048L, 16L));
+        expectNetworkStatsUidDetail(new NetworkStats(getElapsedRealtime(), 2)
+                .insertEntry(TEST_IFACE, UID_RED, SET_DEFAULT, TAG_NONE, 512L, 4L, 256L, 2L, 0L)
+                .insertEntry(TEST_IFACE, UID_RED, SET_DEFAULT, 0xFAAD, 256L, 2L, 128L, 1L, 0L)
+                .insertEntry(TEST_IFACE, UID_RED, SET_FOREGROUND, TAG_NONE, 512L, 4L, 256L, 2L, 0L)
+                .insertEntry(TEST_IFACE, UID_RED, SET_FOREGROUND, 0xFAAD, 256L, 2L, 128L, 1L, 0L)
+                .insertEntry(TEST_IFACE, UID_BLUE, SET_DEFAULT, TAG_NONE, 128L, 1L, 128L, 1L, 0L));
+
+        mService.noteUidForeground(UID_RED, false);
+        verify(mUidCounterSetMap, never()).deleteEntry(any());
+        mService.incrementOperationCount(UID_RED, 0xFAAD, 4);
+        mService.noteUidForeground(UID_RED, true);
+        verify(mUidCounterSetMap).updateEntry(
+                eq(new U32(UID_RED)), eq(new U8((short) SET_FOREGROUND)));
+        mService.incrementOperationCount(UID_RED, 0xFAAD, 6);
+
+        forcePollAndWaitForIdle();
+        // Simulate shutdown to force persisting data
+        mServiceContext.sendBroadcast(new Intent(Intent.ACTION_SHUTDOWN));
+        assertStatsFilesExist(true);
+
+        // Move the files to the legacy directory to simulate an import from old data
+        for (File f : mStatsDir.listFiles()) {
+            Files.move(f.toPath(), mLegacyStatsDir.toPath().resolve(f.getName()));
+        }
+        assertStatsFilesExist(false);
+
+        // Fetch the stats from the legacy files and set platform stats collection to be identical
+        mPlatformNetworkStatsCollection.put(PREFIX_DEV,
+                getLegacyCollection(PREFIX_DEV, false /* includeTags */));
+        mPlatformNetworkStatsCollection.put(PREFIX_XT,
+                getLegacyCollection(PREFIX_XT, false /* includeTags */));
+        mPlatformNetworkStatsCollection.put(PREFIX_UID,
+                getLegacyCollection(PREFIX_UID, false /* includeTags */));
+        mPlatformNetworkStatsCollection.put(PREFIX_UID_TAG,
+                getLegacyCollection(PREFIX_UID_TAG, true /* includeTags */));
+
+        // Mock zero usage and boot through serviceReady(), verify there is no imported data.
+        expectDefaultSettings();
+        expectNetworkStatsUidDetail(buildEmptyStats());
+        expectSystemReady();
+        mService.systemReady();
+        assertStatsFilesExist(false);
+
+        // Set the flag and reboot, verify the imported data is not there until next boot.
+        mStoreFilesInApexData = true;
+        mImportLegacyTargetAttempts = 3;
+        mServiceContext.sendBroadcast(new Intent(Intent.ACTION_SHUTDOWN));
+        assertStatsFilesExist(false);
+
+        // Boot through systemReady() again.
+        expectDefaultSettings();
+        expectNetworkStatsUidDetail(buildEmptyStats());
+        expectSystemReady();
+        mService.systemReady();
+
+        // After systemReady(), the service should have historical stats loaded again.
+        // Thus, verify
+        //  1. The stats are absorbed by the recorder.
+        //  2. The imported data are persisted.
+        //  3. The attempts count is set to target attempts count to indicate a successful
+        //     migration.
+        assertNetworkTotal(sTemplateWifi, 1024L, 8L, 2048L, 16L, 0);
+        assertStatsFilesExist(true);
+        verify(mImportLegacyAttemptsCounter).set(3);
+        verify(mImportLegacySuccessesCounter).set(1);
+
+        // TODO: Verify upgrading with Exception won't damege original data and
+        //  will decrease the retry counter by 1.
+    }
+
+    private NetworkStatsRecorder makeTestRecorder(File directory, String prefix, Config config,
+            boolean includeTags) {
+        final NetworkStats.NonMonotonicObserver observer =
+                mock(NetworkStats.NonMonotonicObserver.class);
+        final DropBoxManager dropBox = mock(DropBoxManager.class);
+        return new NetworkStatsRecorder(new FileRotator(
+                directory, prefix, config.rotateAgeMillis, config.deleteAgeMillis),
+                observer, dropBox, prefix, config.bucketDuration, includeTags);
+    }
+
+    private NetworkStatsCollection getLegacyCollection(String prefix, boolean includeTags) {
+        final NetworkStatsRecorder recorder = makeTestRecorder(mLegacyStatsDir, PREFIX_DEV,
+                mSettings.getDevConfig(), includeTags);
+        return recorder.getOrLoadCompleteLocked();
     }
 
     private void assertNetworkTotal(NetworkTemplate template, long rxBytes, long rxPackets,
@@ -1816,11 +1972,10 @@
     }
 
     private void assertStatsFilesExist(boolean exist) {
-        final File basePath = new File(mStatsDir, "netstats");
         if (exist) {
-            assertTrue(basePath.list().length > 0);
+            assertTrue(mStatsDir.list().length > 0);
         } else {
-            assertTrue(basePath.list().length == 0);
+            assertTrue(mStatsDir.list().length == 0);
         }
     }
 
diff --git a/tests/unit/java/com/android/server/net/PersistentIntTest.kt b/tests/unit/java/com/android/server/net/PersistentIntTest.kt
new file mode 100644
index 0000000..9268352
--- /dev/null
+++ b/tests/unit/java/com/android/server/net/PersistentIntTest.kt
@@ -0,0 +1,133 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.net
+
+import android.util.SystemConfigFileCommitEventLogger
+import com.android.testutils.DevSdkIgnoreRule.IgnoreUpTo
+import com.android.testutils.DevSdkIgnoreRunner
+import com.android.testutils.SC_V2
+import com.android.testutils.assertThrows
+import org.junit.After
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import java.io.File
+import java.io.IOException
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.attribute.PosixFilePermission
+import java.nio.file.attribute.PosixFilePermission.OWNER_EXECUTE
+import java.nio.file.attribute.PosixFilePermission.OWNER_READ
+import java.nio.file.attribute.PosixFilePermission.OWNER_WRITE
+import java.util.Random
+import kotlin.test.assertEquals
+
+@RunWith(DevSdkIgnoreRunner::class)
+@IgnoreUpTo(SC_V2)
+class PersistentIntTest {
+    val tempFilesCreated = mutableSetOf<Path>()
+    lateinit var tempDir: Path
+
+    @Before
+    fun setUp() {
+        tempDir = Files.createTempDirectory("tmp.PersistentIntTest.")
+    }
+
+    @After
+    fun tearDown() {
+        var permissions = setOf(OWNER_READ, OWNER_WRITE, OWNER_EXECUTE)
+        Files.setPosixFilePermissions(tempDir, permissions)
+
+        for (file in tempFilesCreated) {
+            Files.deleteIfExists(file)
+        }
+        Files.delete(tempDir)
+    }
+
+    @Test
+    fun testNormalReadWrite() {
+        // New, initialized to 0.
+        val pi = createPersistentInt()
+        assertEquals(0, pi.get())
+        pi.set(12345)
+        assertEquals(12345, pi.get())
+
+        // Existing.
+        val pi2 = createPersistentInt(pathOf(pi))
+        assertEquals(12345, pi2.get())
+    }
+
+    @Test
+    fun testReadOrWriteFailsInCreate() {
+        setWritable(tempDir, false)
+        assertThrows(IOException::class.java) {
+            createPersistentInt()
+        }
+    }
+
+    @Test
+    fun testReadOrWriteFailsAfterCreate() {
+        val pi = createPersistentInt()
+        pi.set(42)
+        assertEquals(42, pi.get())
+
+        val path = pathOf(pi)
+        setReadable(path, false)
+        assertThrows(IOException::class.java) { pi.get() }
+        pi.set(77)
+
+        setReadable(path, true)
+        setWritable(path, false)
+        setWritable(tempDir, false) // Writing creates a new file+renames, make this fail.
+        assertThrows(IOException::class.java) { pi.set(99) }
+        assertEquals(77, pi.get())
+    }
+
+    fun addOrRemovePermission(p: Path, permission: PosixFilePermission, add: Boolean) {
+        val permissions = Files.getPosixFilePermissions(p)
+        if (add) {
+            permissions.add(permission)
+        } else {
+            permissions.remove(permission)
+        }
+        Files.setPosixFilePermissions(p, permissions)
+    }
+
+    fun setReadable(p: Path, readable: Boolean) {
+        addOrRemovePermission(p, OWNER_READ, readable)
+    }
+
+    fun setWritable(p: Path, writable: Boolean) {
+        addOrRemovePermission(p, OWNER_WRITE, writable)
+    }
+
+    fun pathOf(pi: PersistentInt): Path {
+        return File(pi.path).toPath()
+    }
+
+    fun createPersistentInt(path: Path = randomTempPath()): PersistentInt {
+        tempFilesCreated.add(path)
+        return PersistentInt(path.toString(),
+                SystemConfigFileCommitEventLogger("PersistentIntTest"))
+    }
+
+    fun randomTempPath(): Path {
+        return tempDir.resolve(Integer.toHexString(Random().nextInt())).also {
+            tempFilesCreated.add(it)
+        }
+    }
+}