Foreground/background network stats using sets.

Teach NetworkStats about "counter sets" coming from kernel, and use
them to track usage in foreground/background.  Add AID_NET_BW_ACCT to
system_server so it can control counter sets.

Move to composite key of NetworkIdentitySet, UID, set, and tag when
recording historical usage.  Persisting still clusters by identity,
since that is heaviest object.

Request async stats poll during systemReady() to bootstrap later
delta calculations. Reset kernel counters when UID removed. Update
various tests.

Bug: 5105592, 5146067
Change-Id: Idabec9e3ffcaf212879821515602ecde0a03de8c
diff --git a/services/java/com/android/server/NetworkManagementService.java b/services/java/com/android/server/NetworkManagementService.java
index 782e7d7..a854db0 100644
--- a/services/java/com/android/server/NetworkManagementService.java
+++ b/services/java/com/android/server/NetworkManagementService.java
@@ -18,6 +18,7 @@
 
 import static android.Manifest.permission.MANAGE_NETWORK_POLICY;
 import static android.net.NetworkStats.IFACE_ALL;
+import static android.net.NetworkStats.SET_DEFAULT;
 import static android.net.NetworkStats.TAG_NONE;
 import static android.net.NetworkStats.UID_ALL;
 import static android.provider.Settings.Secure.NETSTATS_ENABLED;
@@ -88,8 +89,9 @@
 
     /** {@link #mStatsXtUid} headers. */
     private static final String KEY_IFACE = "iface";
-    private static final String KEY_TAG_HEX = "acct_tag_hex";
     private static final String KEY_UID = "uid_tag_int";
+    private static final String KEY_COUNTER_SET = "cnt_set";
+    private static final String KEY_TAG_HEX = "acct_tag_hex";
     private static final String KEY_RX_BYTES = "rx_bytes";
     private static final String KEY_RX_PACKETS = "rx_packets";
     private static final String KEY_TX_BYTES = "tx_bytes";
@@ -1041,6 +1043,7 @@
                 try {
                     entry.iface = values.get(0);
                     entry.uid = UID_ALL;
+                    entry.set = SET_DEFAULT;
                     entry.tag = TAG_NONE;
                     entry.rxBytes = Long.parseLong(values.get(1));
                     entry.rxPackets = Long.parseLong(values.get(2));
@@ -1071,6 +1074,7 @@
 
                 entry.iface = iface;
                 entry.uid = UID_ALL;
+                entry.set = SET_DEFAULT;
                 entry.tag = TAG_NONE;
                 entry.rxBytes = readSingleLongFromFile(new File(ifacePath, "rx_bytes"));
                 entry.rxPackets = readSingleLongFromFile(new File(ifacePath, "rx_packets"));
@@ -1319,8 +1323,9 @@
 
                 try {
                     entry.iface = parsed.get(KEY_IFACE);
-                    entry.tag = kernelToTag(parsed.get(KEY_TAG_HEX));
                     entry.uid = getParsedInt(parsed, KEY_UID);
+                    entry.set = getParsedInt(parsed, KEY_COUNTER_SET);
+                    entry.tag = kernelToTag(parsed.get(KEY_TAG_HEX));
                     entry.rxBytes = getParsedLong(parsed, KEY_RX_BYTES);
                     entry.rxPackets = getParsedLong(parsed, KEY_RX_PACKETS);
                     entry.txBytes = getParsedLong(parsed, KEY_TX_BYTES);