fix getIfaceStats and getTotalStats bug

root cause: getIfaceStats and getTotalStats is directly reading
iface_stat_fmt or eBPF, not include tether stats.
solution: add tether stats to getIfaceStats and getTotalStats.

Clean cherry-pick of aosp/848934

Bug: 120039819
Test case1:
1. tether offload is enabled on phone, enable MHS on phone.
2. Use test app to check getMobileRxBytes->getIfaceStats
3. Download 10M file on MHS client
4. Use test app to check getMobileRxBytes->getIfaceStats again
result: getMobileRxBytes increased around 10M

Test case2:
1. tether offload is disabled on phone, enable MHS on phone.
repeat above step 2~4
result: getMobileRxBytes increased around 10M

Following CTS cases passed
run cts -m CtsNetTestCases --test android.net.cts.TrafficStatsTest
run cts -m CtsUsageStatsTestCases --test android.app.usage.cts.NetworkUsageStatsTest

Change-Id: I3d94acb71c142ec38b750e58822881ff383341cc

services/core/java/com/android/server/net/NetworkStatsService.java

@@ -962,12 +962,64 @@ public class NetworkStatsService extends INetworkStatsService.Stub {
 
     @Override
     public long getIfaceStats(String iface, int type) {
-        return nativeGetIfaceStat(iface, type, checkBpfStatsEnable());
+        long nativeIfaceStats = nativeGetIfaceStat(iface, type, checkBpfStatsEnable());
+        if (nativeIfaceStats == -1) {
+            return nativeIfaceStats;
+        } else {
+            // When tethering offload is in use, nativeIfaceStats does not contain usage from
+            // offload, add it back here.
+            // When tethering offload is not in use, nativeIfaceStats contains tethering usage.
+            // this does not cause double-counting of tethering traffic, because
+            // NetdTetheringStatsProvider returns zero NetworkStats
+            // when called with STATS_PER_IFACE.
+            return nativeIfaceStats + getTetherStats(iface, type);
+        }
     }
 
     @Override
     public long getTotalStats(int type) {
-        return nativeGetTotalStat(type, checkBpfStatsEnable());
+        long nativeTotalStats = nativeGetTotalStat(type, checkBpfStatsEnable());
+        if (nativeTotalStats == -1) {
+            return nativeTotalStats;
+        } else {
+            // Refer to comment in getIfaceStats
+            return nativeTotalStats + getTetherStats(IFACE_ALL, type);
+        }
+    }
+
+    private long getTetherStats(String iface, int type) {
+        final NetworkStats tetherSnapshot;
+        final long token = Binder.clearCallingIdentity();
+        try {
+            tetherSnapshot = getNetworkStatsTethering(STATS_PER_IFACE);
+        } catch (RemoteException e) {
+            Slog.w(TAG, "Error get TetherStats: " + e);
+            return 0;
+        } finally {
+            Binder.restoreCallingIdentity(token);
+        }
+        HashSet<String> limitIfaces;
+        if (iface == IFACE_ALL) {
+            limitIfaces = null;
+        } else {
+            limitIfaces = new HashSet<String>();
+            limitIfaces.add(iface);
+        }
+        NetworkStats.Entry entry = tetherSnapshot.getTotal(null, limitIfaces);
+        if (LOGD) Slog.d(TAG, "TetherStats: iface=" + iface + " type=" + type +
+                " entry=" + entry);
+        switch (type) {
+            case 0: // TYPE_RX_BYTES
+                return entry.rxBytes;
+            case 1: // TYPE_RX_PACKETS
+                return entry.rxPackets;
+            case 2: // TYPE_TX_BYTES
+                return entry.txBytes;
+            case 3: // TYPE_TX_PACKETS
+                return entry.txPackets;
+            default:
+                return 0;
+        }
     }
 
     private boolean checkBpfStatsEnable() {