Treat optimistic addresses as global preferred.

If the kernel sends notification of an optimistic address then
treat is a useable address (isGlobalPreferred()).

Note that addresses flagged as IFA_F_OPTIMISTIC are
simultaneously flagged as IFA_F_TENTATIVE (when the tentative
state has cleared either DAD has succeeded or failed, and both
flags are cleared regardless).

Additionally: do not consider RFC 4193 ULA addresses sufficient
for "global preffered".  They are, by definition, of global scope
but not sufficient for global reachability.

Bug: 17769720
Change-Id: I759623b28fd52758f2d4d76d167f3cafd9319d6a

core/java/android/net/LinkAddress.java

@@ -21,12 +21,14 @@ import android.os.Parcelable;
 import android.util.Pair;
 
 import java.net.Inet4Address;
+import java.net.Inet6Address;
 import java.net.InetAddress;
 import java.net.InterfaceAddress;
 import java.net.UnknownHostException;
 
 import static android.system.OsConstants.IFA_F_DADFAILED;
 import static android.system.OsConstants.IFA_F_DEPRECATED;
+import static android.system.OsConstants.IFA_F_OPTIMISTIC;
 import static android.system.OsConstants.IFA_F_TENTATIVE;
 import static android.system.OsConstants.RT_SCOPE_HOST;
 import static android.system.OsConstants.RT_SCOPE_LINK;
@@ -92,6 +94,20 @@ public class LinkAddress implements Parcelable {
         return RT_SCOPE_UNIVERSE;
     }
 
+    /**
+     * Utility function to check if |address| is a Unique Local IPv6 Unicast Address
+     * (a.k.a. "ULA"; RFC 4193).
+     *
+     * Per RFC 4193 section 8, fc00::/7 identifies these addresses.
+     */
+    private boolean isIPv6ULA() {
+        if (address != null && address instanceof Inet6Address) {
+            byte[] bytes = address.getAddress();
+            return ((bytes[0] & (byte)0xfc) == (byte)0xfc);
+        }
+        return false;
+    }
+
     /**
      * Utility function for the constructors.
      */
@@ -268,8 +284,16 @@ public class LinkAddress implements Parcelable {
      * @hide
      */
     public boolean isGlobalPreferred() {
+        /**
+         * Note that addresses flagged as IFA_F_OPTIMISTIC are
+         * simultaneously flagged as IFA_F_TENTATIVE (when the tentative
+         * state has cleared either DAD has succeeded or failed, and both
+         * flags are cleared regardless).
+         */
         return (scope == RT_SCOPE_UNIVERSE &&
-                (flags & (IFA_F_DADFAILED | IFA_F_DEPRECATED | IFA_F_TENTATIVE)) == 0L);
+                !isIPv6ULA() &&
+                (flags & (IFA_F_DADFAILED | IFA_F_DEPRECATED)) == 0L &&
+                ((flags & IFA_F_TENTATIVE) == 0L || (flags & IFA_F_OPTIMISTIC) != 0L));
     }
 
     /**

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

@@ -33,8 +33,11 @@ import android.test.AndroidTestCase;
 import static android.test.MoreAsserts.assertNotEqual;
 import android.test.suitebuilder.annotation.SmallTest;
 
+import static android.system.OsConstants.IFA_F_DADFAILED;
 import static android.system.OsConstants.IFA_F_DEPRECATED;
+import static android.system.OsConstants.IFA_F_OPTIMISTIC;
 import static android.system.OsConstants.IFA_F_PERMANENT;
+import static android.system.OsConstants.IFA_F_TEMPORARY;
 import static android.system.OsConstants.IFA_F_TENTATIVE;
 import static android.system.OsConstants.RT_SCOPE_HOST;
 import static android.system.OsConstants.RT_SCOPE_LINK;
@@ -340,4 +343,73 @@ public class LinkAddressTest extends AndroidTestCase {
         l = new LinkAddress(V4 + "/28", IFA_F_PERMANENT, RT_SCOPE_LINK);
         assertParcelingIsLossless(l);
     }
+
+    private void assertGlobalPreferred(LinkAddress l, String msg) {
+        assertTrue(msg, l.isGlobalPreferred());
+    }
+
+    private void assertNotGlobalPreferred(LinkAddress l, String msg) {
+        assertFalse(msg, l.isGlobalPreferred());
+    }
+
+    public void testIsGlobalPreferred() {
+        LinkAddress l;
+
+        l = new LinkAddress(V4_ADDRESS, 32, 0, RT_SCOPE_UNIVERSE);
+        assertGlobalPreferred(l, "v4,global,noflags");
+
+        l = new LinkAddress("10.10.1.7/23", 0, RT_SCOPE_UNIVERSE);
+        assertGlobalPreferred(l, "v4-rfc1918,global,noflags");
+
+        l = new LinkAddress("10.10.1.7/23", 0, RT_SCOPE_SITE);
+        assertNotGlobalPreferred(l, "v4-rfc1918,site-local,noflags");
+
+        l = new LinkAddress("127.0.0.7/8", 0, RT_SCOPE_HOST);
+        assertNotGlobalPreferred(l, "v4-localhost,node-local,noflags");
+
+        l = new LinkAddress(V6_ADDRESS, 64, 0, RT_SCOPE_UNIVERSE);
+        assertGlobalPreferred(l, "v6,global,noflags");
+
+        l = new LinkAddress(V6_ADDRESS, 64, IFA_F_PERMANENT, RT_SCOPE_UNIVERSE);
+        assertGlobalPreferred(l, "v6,global,permanent");
+
+        // IPv6 ULAs are not acceptable "global preferred" addresses.
+        l = new LinkAddress("fc12::1/64", 0, RT_SCOPE_UNIVERSE);
+        assertNotGlobalPreferred(l, "v6,ula1,noflags");
+
+        l = new LinkAddress("fd34::1/64", 0, RT_SCOPE_UNIVERSE);
+        assertNotGlobalPreferred(l, "v6,ula2,noflags");
+
+        l = new LinkAddress(V6_ADDRESS, 64, IFA_F_TEMPORARY, RT_SCOPE_UNIVERSE);
+        assertGlobalPreferred(l, "v6,global,tempaddr");
+
+        l = new LinkAddress(V6_ADDRESS, 64, (IFA_F_TEMPORARY|IFA_F_DADFAILED),
+                            RT_SCOPE_UNIVERSE);
+        assertNotGlobalPreferred(l, "v6,global,tempaddr+dadfailed");
+
+        l = new LinkAddress(V6_ADDRESS, 64, (IFA_F_TEMPORARY|IFA_F_DEPRECATED),
+                            RT_SCOPE_UNIVERSE);
+        assertNotGlobalPreferred(l, "v6,global,tempaddr+deprecated");
+
+        l = new LinkAddress(V6_ADDRESS, 64, IFA_F_TEMPORARY, RT_SCOPE_SITE);
+        assertNotGlobalPreferred(l, "v6,site-local,tempaddr");
+
+        l = new LinkAddress(V6_ADDRESS, 64, IFA_F_TEMPORARY, RT_SCOPE_LINK);
+        assertNotGlobalPreferred(l, "v6,link-local,tempaddr");
+
+        l = new LinkAddress(V6_ADDRESS, 64, IFA_F_TEMPORARY, RT_SCOPE_HOST);
+        assertNotGlobalPreferred(l, "v6,node-local,tempaddr");
+
+        l = new LinkAddress("::1/128", IFA_F_PERMANENT, RT_SCOPE_HOST);
+        assertNotGlobalPreferred(l, "v6-localhost,node-local,permanent");
+
+        l = new LinkAddress(V6_ADDRESS, 64, (IFA_F_TEMPORARY|IFA_F_TENTATIVE),
+                            RT_SCOPE_UNIVERSE);
+        assertNotGlobalPreferred(l, "v6,global,tempaddr+tentative");
+
+        l = new LinkAddress(V6_ADDRESS, 64,
+                            (IFA_F_TEMPORARY|IFA_F_TENTATIVE|IFA_F_OPTIMISTIC),
+                            RT_SCOPE_UNIVERSE);
+        assertGlobalPreferred(l, "v6,global,tempaddr+optimistic");
+    }
 }