From a9382c9793116d4f419a1f198e04003a30168ecb Mon Sep 17 00:00:00 2001
From: Chenbo Feng <fengc@google.com>
Date: Thu, 10 Jan 2019 14:48:54 -0800
Subject: [PATCH] Use delta reads for per uid traffic stats

For the detailed network stats of each uid and tag, the native
implementation provides delta read instead of consistent stats
data since boot. Every time the readNetworkStatsDetail function gets
called, the data pulled will be cleared. We will keep a persistent data
since boot in NetworkStatsService instead.

Fixed some checkstyle complains in related files as well.

Bug: 79171384
Test: android.app.usage.cts.NetworkUsageStatsTest
      NetworkStatsServiceTest
Change-Id: I50bcf278739135081d522e50b0e88d76fd9ab131
---
 .../internal/net/NetworkStatsFactory.java     | 35 ++++++++++++++-----
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/core/java/com/android/internal/net/NetworkStatsFactory.java b/core/java/com/android/internal/net/NetworkStatsFactory.java
index 9bacf9b6c2..f8483461c2 100644
--- a/core/java/com/android/internal/net/NetworkStatsFactory.java
+++ b/core/java/com/android/internal/net/NetworkStatsFactory.java
@@ -64,6 +64,9 @@ public class NetworkStatsFactory {
 
     private boolean mUseBpfStats;
 
+    // A persistent Snapshot since device start for eBPF stats
+    private final NetworkStats mPersistSnapshot;
+
     // TODO: only do adjustments in NetworkStatsService and remove this.
     /**
      * (Stacked interface) -> (base interface) association for all connected ifaces since boot.
@@ -135,6 +138,7 @@ public class NetworkStatsFactory {
         mStatsXtIfaceFmt = new File(procRoot, "net/xt_qtaguid/iface_stat_fmt");
         mStatsXtUid = new File(procRoot, "net/xt_qtaguid/stats");
         mUseBpfStats = useBpfStats;
+        mPersistSnapshot = new NetworkStats(SystemClock.elapsedRealtime(), -1);
     }
 
     public NetworkStats readBpfNetworkStatsDev() throws IOException {
@@ -268,6 +272,7 @@ public class NetworkStatsFactory {
         return stats;
     }
 
+    // TODO: delete the lastStats parameter
     private NetworkStats readNetworkStatsDetailInternal(int limitUid, String[] limitIfaces,
             int limitTag, NetworkStats lastStats) throws IOException {
         if (USE_NATIVE_PARSING) {
@@ -278,16 +283,28 @@ public class NetworkStatsFactory {
             } else {
                 stats = new NetworkStats(SystemClock.elapsedRealtime(), -1);
             }
-            if (nativeReadNetworkStatsDetail(stats, mStatsXtUid.getAbsolutePath(), limitUid,
-                    limitIfaces, limitTag, mUseBpfStats) != 0) {
-                throw new IOException("Failed to parse network stats");
+            if (mUseBpfStats) {
+                if (nativeReadNetworkStatsDetail(stats, mStatsXtUid.getAbsolutePath(), UID_ALL,
+                        null, TAG_ALL, mUseBpfStats) != 0) {
+                    throw new IOException("Failed to parse network stats");
+                }
+                mPersistSnapshot.setElapsedRealtime(stats.getElapsedRealtime());
+                mPersistSnapshot.combineAllValues(stats);
+                NetworkStats result = mPersistSnapshot.clone();
+                result.filter(limitUid, limitIfaces, limitTag);
+                return result;
+            } else {
+                if (nativeReadNetworkStatsDetail(stats, mStatsXtUid.getAbsolutePath(), limitUid,
+                        limitIfaces, limitTag, mUseBpfStats) != 0) {
+                    throw new IOException("Failed to parse network stats");
+                }
+                if (SANITY_CHECK_NATIVE) {
+                    final NetworkStats javaStats = javaReadNetworkStatsDetail(mStatsXtUid, limitUid,
+                            limitIfaces, limitTag);
+                    assertEquals(javaStats, stats);
+                }
+                return stats;
             }
-            if (SANITY_CHECK_NATIVE) {
-                final NetworkStats javaStats = javaReadNetworkStatsDetail(mStatsXtUid, limitUid,
-                        limitIfaces, limitTag);
-                assertEquals(javaStats, stats);
-            }
-            return stats;
         } else {
             return javaReadNetworkStatsDetail(mStatsXtUid, limitUid, limitIfaces, limitTag);
         }