Allow loopback traffic in lockdown mode.

Bug: 8245184
Change-Id: If993e3d6f5c7ce5970bfe701074c85b9245aa2aa
diff --git a/services/java/com/android/server/ConnectivityService.java b/services/java/com/android/server/ConnectivityService.java
index 5e4855b..3257d2c 100644
--- a/services/java/com/android/server/ConnectivityService.java
+++ b/services/java/com/android/server/ConnectivityService.java
@@ -3382,6 +3382,7 @@
         try {
             if (tracker != null) {
                 mNetd.setFirewallEnabled(true);
+                mNetd.setFirewallInterfaceRule("lo", true);
                 mLockdownTracker = tracker;
                 mLockdownTracker.init();
             } else {