Collect historical network stats.
Periodically records delta network traffic into historical buckets to
support other services, such NetworkPolicyManager and Settings UI.
Introduces NetworkStatsHistory structure which contains sparse, uniform
buckets of data usage defined by timestamps. Service periodically
polls NetworkStats and records changes into buckets. It only persists
to disk when substantial changes have occured. Current parameters
create 4 buckets each day, and persist for 90 days, resulting in about
8kB of data per network.
Only records stats for "well known" network interfaces that have been
claimed by Telephony or Wi-Fi subsystems. Historical stats are also
keyed off identity (such as IMSI) to support SIM swapping.
Change-Id: Ia27d1289556a2bf9545fbc4f3b789425a01be53a
diff --git a/core/java/android/net/NetworkStats.java b/core/java/android/net/NetworkStats.java
index 0f207bc..588bf64 100644
--- a/core/java/android/net/NetworkStats.java
+++ b/core/java/android/net/NetworkStats.java
@@ -22,19 +22,22 @@
import java.io.CharArrayWriter;
import java.io.PrintWriter;
+import java.util.HashSet;
/**
- * Collection of network statistics. Can contain summary details across all
- * interfaces, or details with per-UID granularity. Designed to parcel quickly
- * across process boundaries.
+ * Collection of active network statistics. Can contain summary details across
+ * all interfaces, or details with per-UID granularity. Internally stores data
+ * as a large table, closely matching {@code /proc/} data format. This structure
+ * optimizes for rapid in-memory comparison, but consider using
+ * {@link NetworkStatsHistory} when persisting.
*
* @hide
*/
public class NetworkStats implements Parcelable {
- /** {@link #iface} value when entry is summarized over all interfaces. */
+ /** {@link #iface} value when interface details unavailable. */
public static final String IFACE_ALL = null;
- /** {@link #uid} value when entry is summarized over all UIDs. */
- public static final int UID_ALL = 0;
+ /** {@link #uid} value when UID details unavailable. */
+ public static final int UID_ALL = -1;
// NOTE: data should only be accounted for once in this structure; if data
// is broken out, the summarized version should not be included.
@@ -49,7 +52,7 @@
public final long[] rx;
public final long[] tx;
- // TODO: add fg/bg stats and tag granularity
+ // TODO: add fg/bg stats once reported by kernel
private NetworkStats(long elapsedRealtime, String[] iface, int[] uid, long[] rx, long[] tx) {
this.elapsedRealtime = elapsedRealtime;
@@ -120,15 +123,35 @@
}
/**
+ * Return list of unique interfaces known by this data structure.
+ */
+ public String[] getKnownIfaces() {
+ final HashSet<String> ifaces = new HashSet<String>();
+ for (String iface : this.iface) {
+ if (iface != IFACE_ALL) {
+ ifaces.add(iface);
+ }
+ }
+ return ifaces.toArray(new String[ifaces.size()]);
+ }
+
+ /**
* Subtract the given {@link NetworkStats}, effectively leaving the delta
* between two snapshots in time. Assumes that statistics rows collect over
* time, and that none of them have disappeared.
+ *
+ * @param enforceMonotonic Validate that incoming value is strictly
+ * monotonic compared to this object.
*/
- public NetworkStats subtract(NetworkStats value) {
- // result will have our rows, but no meaningful timestamp
- final int length = length();
- final NetworkStats.Builder result = new NetworkStats.Builder(-1, length);
+ public NetworkStats subtract(NetworkStats value, boolean enforceMonotonic) {
+ final long deltaRealtime = this.elapsedRealtime - value.elapsedRealtime;
+ if (enforceMonotonic && deltaRealtime < 0) {
+ throw new IllegalArgumentException("found non-monotonic realtime");
+ }
+ // result will have our rows, and elapsed time between snapshots
+ final int length = length();
+ final NetworkStats.Builder result = new NetworkStats.Builder(deltaRealtime, length);
for (int i = 0; i < length; i++) {
final String iface = this.iface[i];
final int uid = this.uid[i];
@@ -142,6 +165,9 @@
// existing row, subtract remote value
final long rx = this.rx[i] - value.rx[j];
final long tx = this.tx[i] - value.tx[j];
+ if (enforceMonotonic && (rx < 0 || tx < 0)) {
+ throw new IllegalArgumentException("found non-monotonic values");
+ }
result.addEntry(iface, uid, rx, tx);
}
}