LinkProperties function to compare provisioning and remove DNS servers

Adds:
    - enum ProvisioningChange
    - LinkProperties#compareProvisioning()
          return a ProvisioningChange value describing the delta in
          provisioning between two LinkProperties objects
    - LinkProperties#removeDnsServer()
    - make "@hide public" isIPv4Provisioned() and isIPv6Provisioned()

Bug: 18581716
Change-Id: I3df90b2b89617f693346f2dbe72e77c88ce91ffd

core/java/android/net/LinkProperties.java

@@ -85,6 +85,54 @@ public final class LinkProperties implements Parcelable {
         }
     }
 
+    /**
+     * @hide
+     */
+    public enum ProvisioningChange {
+        STILL_NOT_PROVISIONED,
+        LOST_PROVISIONING,
+        GAINED_PROVISIONING,
+        STILL_PROVISIONED,
+    }
+
+    /**
+     * Compare the provisioning states of two LinkProperties instances.
+     *
+     * @hide
+     */
+    public static ProvisioningChange compareProvisioning(
+            LinkProperties before, LinkProperties after) {
+        if (before.isProvisioned() && after.isProvisioned()) {
+            // On dualstack networks, DHCPv4 renewals can occasionally fail.
+            // When this happens, IPv6-reachable services continue to function
+            // normally but IPv4-only services (naturally) fail.
+            //
+            // When an application using an IPv4-only service reports a bad
+            // network condition to the framework, attempts to re-validate
+            // the network succeed (since we support IPv6-only networks) and
+            // nothing is changed.
+            //
+            // For users, this is confusing and unexpected behaviour, and is
+            // not necessarily easy to diagnose.  Therefore, we treat changing
+            // from a dualstack network to an IPv6-only network equivalent to
+            // a total loss of provisioning.
+            //
+            // For one such example of this, see b/18867306.
+            //
+            // TODO: Remove this special case altogether.
+            if (before.isIPv4Provisioned() && !after.isIPv4Provisioned()) {
+                return ProvisioningChange.LOST_PROVISIONING;
+            }
+            return ProvisioningChange.STILL_PROVISIONED;
+        } else if (before.isProvisioned() && !after.isProvisioned()) {
+            return ProvisioningChange.LOST_PROVISIONING;
+        } else if (!before.isProvisioned() && after.isProvisioned()) {
+            return ProvisioningChange.GAINED_PROVISIONING;
+        } else {  // !before.isProvisioned() && !after.isProvisioned()
+            return ProvisioningChange.STILL_NOT_PROVISIONED;
+        }
+    }
+
     /**
      * @hide
      */
@@ -286,6 +334,20 @@ public final class LinkProperties implements Parcelable {
         return false;
     }
 
+    /**
+     * Removes the given {@link InetAddress} from the list of DNS servers.
+     *
+     * @param dnsServer The {@link InetAddress} to remove from the list of DNS servers.
+     * @return true if the DNS server was removed, false if it did not exist.
+     * @hide
+     */
+    public boolean removeDnsServer(InetAddress dnsServer) {
+        if (dnsServer != null) {
+            return mDnses.remove(dnsServer);
+        }
+        return false;
+    }
+
     /**
      * Replaces the DNS servers in this {@code LinkProperties} with
      * the given {@link Collection} of {@link InetAddress} objects.
@@ -679,8 +741,9 @@ public final class LinkProperties implements Parcelable {
      * This requires an IP address, default route, and DNS server.
      *
      * @return {@code true} if the link is provisioned, {@code false} otherwise.
+     * @hide
      */
-    private boolean hasIPv4() {
+    public boolean isIPv4Provisioned() {
         return (hasIPv4Address() &&
                 hasIPv4DefaultRoute() &&
                 hasIPv4DnsServer());
@@ -691,8 +754,9 @@ public final class LinkProperties implements Parcelable {
      * This requires an IP address, default route, and DNS server.
      *
      * @return {@code true} if the link is provisioned, {@code false} otherwise.
+     * @hide
      */
-    private boolean hasIPv6() {
+    public boolean isIPv6Provisioned() {
         return (hasGlobalIPv6Address() &&
                 hasIPv6DefaultRoute() &&
                 hasIPv6DnsServer());
@@ -706,7 +770,7 @@ public final class LinkProperties implements Parcelable {
      * @hide
      */
     public boolean isProvisioned() {
-        return (hasIPv4() || hasIPv6());
+        return (isIPv4Provisioned() || isIPv6Provisioned());
     }
 
     /**

core/tests/coretests/src/android/net/LinkPropertiesTest.java

@@ -17,6 +17,7 @@
 package android.net;
 
 import android.net.LinkProperties;
+import android.net.LinkProperties.ProvisioningChange;
 import android.net.RouteInfo;
 import android.system.OsConstants;
 import android.test.suitebuilder.annotation.SmallTest;
@@ -34,7 +35,8 @@ public class LinkPropertiesTest extends TestCase {
     private static InetAddress DNS6 = NetworkUtils.numericToInetAddress("2001:4860:4860::8888");
     private static InetAddress GATEWAY1 = NetworkUtils.numericToInetAddress("75.208.8.1");
     private static InetAddress GATEWAY2 = NetworkUtils.numericToInetAddress("69.78.8.1");
-    private static InetAddress GATEWAY6 = NetworkUtils.numericToInetAddress("fe80::6:0000:613");
+    private static InetAddress GATEWAY61 = NetworkUtils.numericToInetAddress("fe80::6:0000:613");
+    private static InetAddress GATEWAY62 = NetworkUtils.numericToInetAddress("fe80::6:2222");
     private static String NAME = "qmi0";
     private static int MTU = 1500;
 
@@ -466,6 +468,8 @@ public class LinkPropertiesTest extends TestCase {
         assertFalse("v4only:addr+dns", lp4.isProvisioned());
         lp4.addRoute(new RouteInfo(GATEWAY1));
         assertTrue("v4only:addr+dns+route", lp4.isProvisioned());
+        assertTrue("v4only:addr+dns+route", lp4.isIPv4Provisioned());
+        assertFalse("v4only:addr+dns+route", lp4.isIPv6Provisioned());
 
         LinkProperties lp6 = new LinkProperties();
         assertFalse("v6only:empty", lp6.isProvisioned());
@@ -473,11 +477,14 @@ public class LinkPropertiesTest extends TestCase {
         assertFalse("v6only:fe80-only", lp6.isProvisioned());
         lp6.addDnsServer(DNS6);
         assertFalse("v6only:fe80+dns", lp6.isProvisioned());
-        lp6.addRoute(new RouteInfo(GATEWAY6));
+        lp6.addRoute(new RouteInfo(GATEWAY61));
         assertFalse("v6only:fe80+dns+route", lp6.isProvisioned());
         lp6.addLinkAddress(LINKADDRV6);
+        assertTrue("v6only:fe80+global+dns+route", lp6.isIPv6Provisioned());
         assertTrue("v6only:fe80+global+dns+route", lp6.isProvisioned());
         lp6.removeLinkAddress(LINKADDRV6LINKLOCAL);
+        assertFalse("v6only:global+dns+route", lp6.isIPv4Provisioned());
+        assertTrue("v6only:global+dns+route", lp6.isIPv6Provisioned());
         assertTrue("v6only:global+dns+route", lp6.isProvisioned());
 
         LinkProperties lp46 = new LinkProperties();
@@ -487,15 +494,77 @@ public class LinkPropertiesTest extends TestCase {
         lp46.addDnsServer(DNS6);
         assertFalse("dualstack:missing-routes", lp46.isProvisioned());
         lp46.addRoute(new RouteInfo(GATEWAY1));
+        assertTrue("dualstack:v4-provisioned", lp46.isIPv4Provisioned());
+        assertFalse("dualstack:v4-provisioned", lp46.isIPv6Provisioned());
         assertTrue("dualstack:v4-provisioned", lp46.isProvisioned());
-        lp6.addRoute(new RouteInfo(GATEWAY6));
+        lp46.addRoute(new RouteInfo(GATEWAY61));
+        assertTrue("dualstack:both-provisioned", lp46.isIPv4Provisioned());
+        assertTrue("dualstack:both-provisioned", lp46.isIPv6Provisioned());
         assertTrue("dualstack:both-provisioned", lp46.isProvisioned());
 
         // A link with an IPv6 address and default route, but IPv4 DNS server.
         LinkProperties mixed = new LinkProperties();
         mixed.addLinkAddress(LINKADDRV6);
         mixed.addDnsServer(DNS1);
-        mixed.addRoute(new RouteInfo(GATEWAY6));
+        mixed.addRoute(new RouteInfo(GATEWAY61));
+        assertFalse("mixed:addr6+route6+dns4", mixed.isIPv4Provisioned());
+        assertFalse("mixed:addr6+route6+dns4", mixed.isIPv6Provisioned());
         assertFalse("mixed:addr6+route6+dns4", mixed.isProvisioned());
     }
+
+    @SmallTest
+    public void testCompareProvisioning() {
+        LinkProperties v4lp = new LinkProperties();
+        v4lp.addLinkAddress(LINKADDRV4);
+        v4lp.addRoute(new RouteInfo(GATEWAY1));
+        v4lp.addDnsServer(DNS1);
+        assertTrue(v4lp.isProvisioned());
+
+        LinkProperties v4r = new LinkProperties(v4lp);
+        v4r.removeDnsServer(DNS1);
+        assertFalse(v4r.isProvisioned());
+
+        assertEquals(ProvisioningChange.STILL_NOT_PROVISIONED,
+                LinkProperties.compareProvisioning(v4r, v4r));
+        assertEquals(ProvisioningChange.LOST_PROVISIONING,
+                LinkProperties.compareProvisioning(v4lp, v4r));
+        assertEquals(ProvisioningChange.GAINED_PROVISIONING,
+                LinkProperties.compareProvisioning(v4r, v4lp));
+        assertEquals(ProvisioningChange.STILL_PROVISIONED,
+                LinkProperties.compareProvisioning(v4lp, v4lp));
+
+        // Check that losing IPv4 provisioning on a dualstack network is
+        // seen as a total loss of provisioning.
+        LinkProperties v6lp = new LinkProperties();
+        v6lp.addLinkAddress(LINKADDRV6);
+        v6lp.addRoute(new RouteInfo(GATEWAY61));
+        v6lp.addDnsServer(DNS6);
+        assertFalse(v6lp.isIPv4Provisioned());
+        assertTrue(v6lp.isIPv6Provisioned());
+        assertTrue(v6lp.isProvisioned());
+
+        LinkProperties v46lp = new LinkProperties(v6lp);
+        v46lp.addLinkAddress(LINKADDRV4);
+        v46lp.addRoute(new RouteInfo(GATEWAY1));
+        v46lp.addDnsServer(DNS1);
+        assertTrue(v46lp.isIPv4Provisioned());
+        assertTrue(v46lp.isIPv6Provisioned());
+        assertTrue(v46lp.isProvisioned());
+
+        assertEquals(ProvisioningChange.STILL_PROVISIONED,
+                LinkProperties.compareProvisioning(v6lp, v46lp));
+        assertEquals(ProvisioningChange.LOST_PROVISIONING,
+                LinkProperties.compareProvisioning(v46lp, v6lp));
+
+        // Check that losing and gaining a secondary router does not change
+        // the provisioning status.
+        LinkProperties v6lp2 = new LinkProperties(v6lp);
+        v6lp2.addRoute(new RouteInfo(GATEWAY62));
+        assertTrue(v6lp2.isProvisioned());
+
+        assertEquals(ProvisioningChange.STILL_PROVISIONED,
+                LinkProperties.compareProvisioning(v6lp2, v6lp));
+        assertEquals(ProvisioningChange.STILL_PROVISIONED,
+                LinkProperties.compareProvisioning(v6lp, v6lp2));
+    }
 }