Add code to dump OffloadController state.

Bug: 29337859
Bug: 32163131
Test: observed output of "adb shell dumpsys connectivity tethering"
Change-Id: Icc5aa605cd64a4a2bb5993941dcc4010cc0b1d8e

services/core/java/com/android/server/connectivity/Tethering.java

@@ -1759,6 +1759,11 @@ public class Tethering extends BaseNetworkObserver {
             pw.decreaseIndent();
         }
 
+        pw.println("Hardware offload:");
+        pw.increaseIndent();
+        mOffloadController.dump(pw);
+        pw.decreaseIndent();
+
         pw.println("Log:");
         pw.increaseIndent();
         if (argsContain(args, SHORT_ARG)) {

services/core/java/com/android/server/connectivity/tethering/OffloadController.java

@@ -36,6 +36,8 @@ import android.os.SystemClock;
 import android.provider.Settings;
 import android.text.TextUtils;
 
+import com.android.internal.util.IndentingPrintWriter;
+
 import java.net.Inet4Address;
 import java.net.Inet6Address;
 import java.net.InetAddress;
@@ -348,4 +350,16 @@ public class OffloadController {
         for (IpPrefix pfx : prefixSet) localPrefixStrs.add(pfx.toString());
         return localPrefixStrs;
     }
+
+    public void dump(IndentingPrintWriter pw) {
+        if (isOffloadDisabled()) {
+            pw.println("Offload disabled");
+            return;
+        }
+        pw.println("Offload HALs " + (started() ? "started" : "not started"));
+        LinkProperties lp = mUpstreamLinkProperties;
+        String upstream = (lp != null) ? lp.getInterfaceName() : null;
+        pw.println("Current upstream: " + upstream);
+        pw.println("Exempt prefixes: " + mLastLocalPrefixStrs);
+    }
 }