Add keys for preferred ESP packets type

Add a hidden key for internal usage in VPN to setup preferred
encapsulation type and IP protocol type used in IPSec.

Bug: 269714970
Test: m
Change-Id: Id4cb47c682d8458954792bf7eb374f189c4e27bc

telephony/java/android/telephony/CarrierConfigManager.java

@@ -4322,6 +4322,22 @@ public class CarrierConfigManager {
     public static final String KEY_MIN_UDP_PORT_4500_NAT_TIMEOUT_SEC_INT =
             "min_udp_port_4500_nat_timeout_sec_int";
 
+    /**
+     * The preferred IKE protocol for ESP packets.
+     *
+     * This will be used by Android platform VPNs to select preferred encapsulation type and IP
+     * protocol type. The possible customization values are:
+     *
+     * AUTO IP VERSION and ENCAPSULATION TYPE SELECTION : "0"
+     * IPv4 UDP                                         : "40"
+     * IPv6 ESP                                         : "61"
+     *
+     * See the {@code PREFERRED_IKE_PROTOCOL_} constants in
+     * {@link com.android.server.connectivity.Vpn}.
+     * @hide
+     */
+    public static final String KEY_PREFERRED_IKE_PROTOCOL_INT = "preferred_ike_protocol_int";
+
     /**
      * Specifies whether the system should prefix the EAP method to the anonymous identity.
      * The following prefix will be added if this key is set to TRUE:
@@ -9198,6 +9214,7 @@ public class CarrierConfigManager {
         sDefaults.putInt(KEY_PARAMETERS_USED_FOR_LTE_SIGNAL_BAR_INT,
                 CellSignalStrengthLte.USE_RSRP);
         sDefaults.putInt(KEY_MIN_UDP_PORT_4500_NAT_TIMEOUT_SEC_INT, 300);
+        sDefaults.putInt(KEY_PREFERRED_IKE_PROTOCOL_INT, 0);
         // Default wifi configurations.
         sDefaults.putAll(Wifi.getDefaults());
         sDefaults.putBoolean(ENABLE_EAP_METHOD_PREFIX_BOOL, false);