New firewall chain for default background restrictions

A new firewall chain is needed to configure background network
restrictions for apps.
This change only adds the API stubs and traffic controller constants to
make the chain work. Policy changes using this chain will follow in
the framework code.

Test: atest CtsNetTestCases:ConnectivityManagerTest
Test: atest ConnectivityServiceTest

NO_IFTTT=The Lint rule along with the relevant code in Common.h is
being deleted in aosp/2819759

Bug: 304347838
Change-Id: I33e2db6671431f7c576fc931d9f96e684fc1e78a
diff --git a/framework/src/android/net/BpfNetMapsUtils.java b/framework/src/android/net/BpfNetMapsUtils.java
index e9c9137..11d610c 100644
--- a/framework/src/android/net/BpfNetMapsUtils.java
+++ b/framework/src/android/net/BpfNetMapsUtils.java
@@ -17,6 +17,7 @@
 package android.net;
 
 import static android.net.BpfNetMapsConstants.ALLOW_CHAINS;
+import static android.net.BpfNetMapsConstants.BACKGROUND_MATCH;
 import static android.net.BpfNetMapsConstants.DENY_CHAINS;
 import static android.net.BpfNetMapsConstants.DOZABLE_MATCH;
 import static android.net.BpfNetMapsConstants.LOW_POWER_STANDBY_MATCH;
@@ -28,6 +29,7 @@
 import static android.net.BpfNetMapsConstants.POWERSAVE_MATCH;
 import static android.net.BpfNetMapsConstants.RESTRICTED_MATCH;
 import static android.net.BpfNetMapsConstants.STANDBY_MATCH;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_BACKGROUND;
 import static android.net.ConnectivityManager.FIREWALL_CHAIN_DOZABLE;
 import static android.net.ConnectivityManager.FIREWALL_CHAIN_LOW_POWER_STANDBY;
 import static android.net.ConnectivityManager.FIREWALL_CHAIN_OEM_DENY_1;
@@ -70,6 +72,8 @@
                 return POWERSAVE_MATCH;
             case FIREWALL_CHAIN_RESTRICTED:
                 return RESTRICTED_MATCH;
+            case FIREWALL_CHAIN_BACKGROUND:
+                return BACKGROUND_MATCH;
             case FIREWALL_CHAIN_LOW_POWER_STANDBY:
                 return LOW_POWER_STANDBY_MATCH;
             case FIREWALL_CHAIN_OEM_DENY_1: