Allow passing the underlying network to startLegacyVpn.

This will be used by a future change that makes the legacy
lockdown VPN pass the underlying network.

Bug: 173331190
Test: tests in subsequent CLs in stack
Change-Id: I09366a7f872ef3d4538962a75b0114a2ecb536e6
diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index 96c3e57..d6c7dda 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -4838,7 +4838,7 @@
         }
         synchronized (mVpns) {
             throwIfLockdownEnabled();
-            mVpns.get(user).startLegacyVpn(profile, mKeyStore, egress);
+            mVpns.get(user).startLegacyVpn(profile, mKeyStore, null /* underlying */, egress);
         }
     }
 
diff --git a/tests/net/java/com/android/server/connectivity/VpnTest.java b/tests/net/java/com/android/server/connectivity/VpnTest.java
index 68aaaed..f478282 100644
--- a/tests/net/java/com/android/server/connectivity/VpnTest.java
+++ b/tests/net/java/com/android/server/connectivity/VpnTest.java
@@ -148,6 +148,7 @@
         managedProfileA.profileGroupId = primaryUser.id;
     }
 
+    static final Network EGRESS_NETWORK = new Network(101);
     static final String EGRESS_IFACE = "wlan0";
     static final String TEST_VPN_PKG = "com.testvpn.vpn";
     private static final String TEST_VPN_SERVER = "1.2.3.4";
@@ -963,7 +964,7 @@
                         InetAddresses.parseNumericAddress("192.0.2.0"), EGRESS_IFACE);
         lp.addRoute(defaultRoute);
 
-        vpn.startLegacyVpn(vpnProfile, mKeyStore, lp);
+        vpn.startLegacyVpn(vpnProfile, mKeyStore, EGRESS_NETWORK, lp);
         return vpn;
     }