Add rate-limiting to reduce CPU loading of IpClient

Bug: b/144826001

Test: Build Pass: OK
Test: Power ON/OFF: OK
Test: Verify CPU loading improvement: OK

Change-Id: I412f3db7071672ebc3213dc128bbfc8f8bd2abcc

1 files changed, 18 insertions, 0 deletions

diff --git a/src/android/net/ip/ConnectivityPacketTracker.java b/src/android/net/ip/ConnectivityPacketTracker.java
index dc793cd..bbaf61e 100644
--- a/src/android/net/ip/ConnectivityPacketTracker.java
+++ b/src/android/net/ip/ConnectivityPacketTracker.java
@@ -28,6 +28,7 @@ import android.net.util.InterfaceParams;
 import android.net.util.NetworkStackUtils;
 import android.net.util.PacketReader;
 import android.os.Handler;
+import android.os.SystemClock;
 import android.system.ErrnoException;
 import android.system.Os;
 import android.text.TextUtils;
@@ -35,6 +36,7 @@ import android.util.LocalLog;
 import android.util.Log;
 
 import com.android.internal.util.HexDump;
+import com.android.internal.util.TokenBucket;
 
 import java.io.FileDescriptor;
 import java.io.IOException;
@@ -63,10 +65,15 @@ public class ConnectivityPacketTracker {
     private static final String MARK_STOP = "--- STOP ---";
     private static final String MARK_NAMED_START = "--- START (%s) ---";
     private static final String MARK_NAMED_STOP = "--- STOP (%s) ---";
+    // Use a TokenBucket to limit CPU usage of logging packets in steady state.
+    private static final int TOKEN_FILL_RATE = 50;   // Maximum one packet every 20ms.
+    private static final int MAX_BURST_LENGTH = 100; // Maximum burst 100 packets.
 
     private final String mTag;
     private final LocalLog mLog;
     private final PacketReader mPacketListener;
+    private final TokenBucket mTokenBucket = new TokenBucket(TOKEN_FILL_RATE, MAX_BURST_LENGTH);
+    private long mLastRateLimitLogTimeMs = 0;
     private boolean mRunning;
     private String mDisplayName;
 
@@ -115,6 +122,17 @@ public class ConnectivityPacketTracker {
 
         @Override
         protected void handlePacket(byte[] recvbuf, int length) {
+            if (!mTokenBucket.get()) {
+                // Rate limited. Log once every second so the user knows packets are missing.
+                final long now = SystemClock.elapsedRealtime();
+                if (now >= mLastRateLimitLogTimeMs + 1000) {
+                    addLogEntry("Warning: too many packets, rate-limiting to one every " +
+                                TOKEN_FILL_RATE + "ms");
+                    mLastRateLimitLogTimeMs = now;
+                }
+                return;
+            }
+
             final String summary = ConnectivityPacketSummary.summarize(
                     mInterface.macAddr, recvbuf, length);
             if (summary == null) return;