Set NLM_F_ACK in our RTM_NEWNEIGH requests

With NLM_F_ACK set in RTM_NEWNEIGH requests we get some response from
the kernel, whether there was an error or not.

Additionally:

    [1] add IpReachabilityMonitor#probeNeighbor() as a public
        static method, since it actually depends very little on the
        class internals and might be of larger use.

    [2] add a unittest for parsing NetlinkErrorMessages.

Bug: 18581716
Change-Id: I5d62e7a9972c7440f0483c38c77677436d3a1a25

2 files changed, 83 insertions, 1 deletions

diff --git a/core/tests/coretests/src/android/net/netlink/NetlinkErrorMessageTest.java b/core/tests/coretests/src/android/net/netlink/NetlinkErrorMessageTest.java
new file mode 100644
index 0000000..e677475
--- /dev/null
+++ b/core/tests/coretests/src/android/net/netlink/NetlinkErrorMessageTest.java
@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.net.netlink;
+
+import static android.net.netlink.StructNlMsgHdr.NLM_F_REQUEST;
+import static android.net.netlink.StructNlMsgHdr.NLM_F_ACK;
+import static android.net.netlink.StructNlMsgHdr.NLM_F_REPLACE;
+
+import android.net.netlink.NetlinkConstants;
+import android.net.netlink.NetlinkErrorMessage;
+import android.net.netlink.NetlinkMessage;
+import android.net.netlink.StructNlMsgErr;
+import android.util.Log;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import junit.framework.TestCase;
+import libcore.util.HexEncoding;
+
+
+public class NetlinkErrorMessageTest extends TestCase {
+    private final String TAG = "NetlinkErrorMessageTest";
+
+    // Hexadecimal representation of packet capture.
+    public static final String NLM_ERROR_OK_HEX =
+            // struct nlmsghdr
+            "24000000" +     // length = 36
+            "0200"     +     // type = 2 (NLMSG_ERROR)
+            "0000"     +     // flags
+            "26350000" +     // seqno
+            "64100000" +     // pid = userspace process
+            // error integer
+            "00000000" +     // "errno" (0 == OK)
+            // struct nlmsghdr
+            "30000000" +     // length (48) of original request
+            "1C00"     +     // type = 28 (RTM_NEWNEIGH)
+            "0501"     +     // flags (NLM_F_REQUEST | NLM_F_ACK | NLM_F_REPLACE)
+            "26350000" +     // seqno
+            "00000000";      // pid = kernel
+    public static final byte[] NLM_ERROR_OK =
+            HexEncoding.decode(NLM_ERROR_OK_HEX.toCharArray(), false);
+
+    public void testParseNlmErrorOk() {
+        final ByteBuffer byteBuffer = ByteBuffer.wrap(NLM_ERROR_OK);
+        byteBuffer.order(ByteOrder.LITTLE_ENDIAN);  // For testing.
+        final NetlinkMessage msg = NetlinkMessage.parse(byteBuffer);
+        assertNotNull(msg);
+        assertTrue(msg instanceof NetlinkErrorMessage);
+        final NetlinkErrorMessage errorMsg = (NetlinkErrorMessage) msg;
+
+        final StructNlMsgHdr hdr = errorMsg.getHeader();
+        assertNotNull(hdr);
+        assertEquals(36, hdr.nlmsg_len);
+        assertEquals(NetlinkConstants.NLMSG_ERROR, hdr.nlmsg_type);
+        assertEquals(0, hdr.nlmsg_flags);
+        assertEquals(13606, hdr.nlmsg_seq);
+        assertEquals(4196, hdr.nlmsg_pid);
+
+        final StructNlMsgErr err = errorMsg.getNlMsgError();
+        assertNotNull(err);
+        assertEquals(0, err.error);
+        assertNotNull(err.msg);
+        assertEquals(48, err.msg.nlmsg_len);
+        assertEquals(NetlinkConstants.RTM_NEWNEIGH, err.msg.nlmsg_type);
+        assertEquals((NLM_F_REQUEST | NLM_F_ACK | NLM_F_REPLACE), err.msg.nlmsg_flags);
+        assertEquals(13606, err.msg.nlmsg_seq);
+        assertEquals(0, err.msg.nlmsg_pid);
+    }
+}
diff --git a/core/tests/coretests/src/android/net/netlink/RtNetlinkNeighborMessageTest.java b/core/tests/coretests/src/android/net/netlink/RtNetlinkNeighborMessageTest.java
index a7bebad..19ee000 100644
--- a/core/tests/coretests/src/android/net/netlink/RtNetlinkNeighborMessageTest.java
+++ b/core/tests/coretests/src/android/net/netlink/RtNetlinkNeighborMessageTest.java
@@ -222,7 +222,7 @@ public class RtNetlinkNeighborMessageTest extends TestCase {
                 // struct nlmsghdr
                 "30000000" +     // length = 48
                 "1c00" +         // type = 28 (RTM_NEWNEIGH)
-                "0101" +         // flags (NLM_F_REQUEST | NLM_F_REPLACE)
+                "0501" +         // flags (NLM_F_REQUEST | NLM_F_ACK | NLM_F_REPLACE)
                 "4b0a0000" +     // seqno
                 "00000000" +     // pid (0 == kernel)
                 // struct ndmsg