IpConn metrics: add dhcp transition times

This patch adds lifetime durations of DhcpClient states to
DhcpClientEvents.

To record the duration of a state, the event is now recorded when the
DhcpClient state machine exits that state.

In addition this patch removes event logging of StoppedState,
DhcpState and DhcpHaveLeaseState.

Change-Id: Ibd37b5e3070f35113b6b45942b1e1ff19c27a90b
diff --git a/api/system-current.txt b/api/system-current.txt
index 9d07e84..b0fb9f3 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -26063,6 +26063,7 @@
     method public static void logStateEvent(java.lang.String, java.lang.String);
     method public void writeToParcel(android.os.Parcel, int);
     field public static final android.os.Parcelable.Creator<android.net.metrics.DhcpClientEvent> CREATOR;
+    field public final int durationMs;
     field public final java.lang.String ifName;
     field public final java.lang.String msg;
   }
diff --git a/core/java/android/net/metrics/DhcpClientEvent.java b/core/java/android/net/metrics/DhcpClientEvent.java
index 3fe68b4..169f571 100644
--- a/core/java/android/net/metrics/DhcpClientEvent.java
+++ b/core/java/android/net/metrics/DhcpClientEvent.java
@@ -21,36 +21,43 @@
 import android.os.Parcelable;
 
 /**
+ *  An event recorded when a DhcpClient state machine transitions to a new state.
  * {@hide}
  */
 @SystemApi
 public final class DhcpClientEvent implements Parcelable {
     public final String ifName;
     public final String msg;
+    public final int durationMs;
 
     /** {@hide} */
-    public DhcpClientEvent(String ifName, String msg) {
+    public DhcpClientEvent(String ifName, String msg, int durationMs) {
         this.ifName = ifName;
         this.msg = msg;
+        this.durationMs = durationMs;
     }
 
     private DhcpClientEvent(Parcel in) {
         this.ifName = in.readString();
         this.msg = in.readString();
+        this.durationMs = in.readInt();
     }
 
+    @Override
     public void writeToParcel(Parcel out, int flags) {
         out.writeString(ifName);
         out.writeString(msg);
+        out.writeInt(durationMs);
     }
 
+    @Override
     public int describeContents() {
         return 0;
     }
 
     @Override
     public String toString() {
-        return String.format("DhcpClientEvent(%s, %s)", ifName, msg);
+        return String.format("DhcpClientEvent(%s, %s, %dms)", ifName, msg, durationMs);
     }
 
     public static final Parcelable.Creator<DhcpClientEvent> CREATOR
diff --git a/services/net/java/android/net/dhcp/DhcpClient.java b/services/net/java/android/net/dhcp/DhcpClient.java
index 5852626..83cfc010 100644
--- a/services/net/java/android/net/dhcp/DhcpClient.java
+++ b/services/net/java/android/net/dhcp/DhcpClient.java
@@ -492,10 +492,19 @@
     }
 
     abstract class LoggingState extends State {
+        private long mEnterTimeMs;
+
         @Override
         public void enter() {
             if (STATE_DBG) Log.d(TAG, "Entering state " + getName());
-            mMetricsLog.log(new DhcpClientEvent(mIfaceName, getName()));
+            mEnterTimeMs = SystemClock.elapsedRealtime();
+            // TODO: record time for Init -> Bound and Bound -> Renewing -> Bound
+        }
+
+        @Override
+        public void exit() {
+            long durationMs = SystemClock.elapsedRealtime() - mEnterTimeMs;
+            mMetricsLog.log(new DhcpClientEvent(mIfaceName, getName(), (int) durationMs));
         }
 
         private String messageName(int what) {
@@ -520,6 +529,13 @@
             }
             return NOT_HANDLED;
         }
+
+        @Override
+        public String getName() {
+            // All DhcpClient's states are inner classes with a well defined name.
+            // Use getSimpleName() and avoid super's getName() creating new String instances.
+            return getClass().getSimpleName();
+        }
     }
 
     // Sends CMD_PRE_DHCP_ACTION to the controller, waits for the controller to respond with
@@ -546,10 +562,9 @@
         }
     }
 
-    class StoppedState extends LoggingState {
+    class StoppedState extends State {
         @Override
         public boolean processMessage(Message message) {
-            super.processMessage(message);
             switch (message.what) {
                 case CMD_START_DHCP:
                     if (mRegisteredForPreDhcpNotification) {
@@ -578,10 +593,9 @@
         }
     }
 
-    class DhcpState extends LoggingState {
+    class DhcpState extends State {
         @Override
         public void enter() {
-            super.enter();
             clearDhcpState();
             if (initInterface() && initSockets()) {
                 mReceiveThread = new ReceiveThread();
@@ -679,7 +693,9 @@
             }
         }
 
+        @Override
         public void exit() {
+            super.exit();
             mKickAlarm.cancel();
             mTimeoutAlarm.cancel();
         }
@@ -784,15 +800,9 @@
         }
     }
 
-    class DhcpHaveLeaseState extends LoggingState {
-        @Override
-        public void enter() {
-            super.enter();
-        }
-
+    class DhcpHaveLeaseState extends State {
         @Override
         public boolean processMessage(Message message) {
-            super.processMessage(message);
             switch (message.what) {
                 case CMD_EXPIRE_DHCP:
                     Log.d(TAG, "Lease expired!");