Allow mDNS on IFF_POINTOPOINT interfaces

Instead of disallowing mDNS on interfaces that specify IFF_POINTOPOINT,
the code should check for the presence of IFF_MULTICAST instead. It is
perfectly valid to support mDNS on point-to-point links, such as IPv6
over BLE networks, if they support multicast.

Change-Id: I282a039483ad1d677d31e5169d53bbae25a1c9c4
Test: TH
diff --git a/service-t/src/com/android/server/connectivity/mdns/MdnsSocketProvider.java b/service-t/src/com/android/server/connectivity/mdns/MdnsSocketProvider.java
index 1212e29..d91bd11 100644
--- a/service-t/src/com/android/server/connectivity/mdns/MdnsSocketProvider.java
+++ b/service-t/src/com/android/server/connectivity/mdns/MdnsSocketProvider.java
@@ -564,7 +564,6 @@
             // Never try mDNS on cellular, or on interfaces with incompatible flags
             if (CollectionUtils.contains(transports, TRANSPORT_CELLULAR)
                     || iface.isLoopback()
-                    || iface.isPointToPoint()
                     || iface.isVirtual()
                     || !iface.isUp()) {
                 return false;
diff --git a/tests/unit/java/com/android/server/connectivity/mdns/MdnsSocketProviderTest.java b/tests/unit/java/com/android/server/connectivity/mdns/MdnsSocketProviderTest.java
index 1cc9985..f763bae 100644
--- a/tests/unit/java/com/android/server/connectivity/mdns/MdnsSocketProviderTest.java
+++ b/tests/unit/java/com/android/server/connectivity/mdns/MdnsSocketProviderTest.java
@@ -610,6 +610,7 @@
 
     @Test
     public void testSocketCreatedForMulticastInterface() throws Exception {
+        doReturn(true).when(mTestNetworkIfaceWrapper).isPointToPoint();
         doReturn(true).when(mTestNetworkIfaceWrapper).supportsMulticast();
         startMonitoringSockets();
 
@@ -621,18 +622,6 @@
     }
 
     @Test
-    public void testNoSocketCreatedForPTPInterface() throws Exception {
-        doReturn(true).when(mTestNetworkIfaceWrapper).isPointToPoint();
-        startMonitoringSockets();
-
-        final TestSocketCallback testCallback = new TestSocketCallback();
-        runOnHandler(() -> mSocketProvider.requestSocket(TEST_NETWORK, testCallback));
-
-        postNetworkAvailable(TRANSPORT_BLUETOOTH);
-        testCallback.expectedNoCallback();
-    }
-
-    @Test
     public void testNoSocketCreatedForVPNInterface() throws Exception {
         // VPN interfaces generally also have IFF_POINTOPOINT, but even if they don't, they should
         // not be included even with TRANSPORT_WIFI.