Add mif6ctl struct definition.

This is used to configure interfaces for multicast routing.

Test: atest NetworkStaticLibTests:com.android.net.moduletests.util.structs.StructMif6ctlTest
Change-Id: Ic26cddab2d5a9f90f63b0828c3e133d830aa0db4

staticlibs/device/com/android/net/module/util/structs/StructMif6ctl.java

+/*
+ * Copyright (C) 2023 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 com.android.net.module.util.structs;
+
+import com.android.net.module.util.Struct;
+
+/*
+ * Implements the mif6ctl structure which is used to add a multicast routing
+ * interface, see /usr/include/linux/mroute6.h
+ */
+public class StructMif6ctl extends Struct {
+    @Field(order = 0, type = Type.U16)
+    public final int mif6cMifi; // Index of MIF
+    @Field(order = 1, type = Type.U8)
+    public final short mif6cFlags; // MIFF_ flags
+    @Field(order = 2, type = Type.U8)
+    public final short vifcThreshold; // ttl limit
+    @Field(order = 3, type = Type.U16)
+    public final int mif6cPifi; //the index of the physical IF
+    @Field(order = 4, type = Type.U32, padding = 2)
+    public final long vifcRateLimit; // Rate limiter values (NI)
+
+    public StructMif6ctl(final int mif6cMifi, final short mif6cFlags, final short vifcThreshold,
+            final int mif6cPifi, final long vifcRateLimit) {
+        this.mif6cMifi = mif6cMifi;
+        this.mif6cFlags = mif6cFlags;
+        this.vifcThreshold = vifcThreshold;
+        this.mif6cPifi = mif6cPifi;
+        this.vifcRateLimit = vifcRateLimit;
+    }
+}
+

staticlibs/tests/unit/src/com/android/net/module/util/structs/StructMif6ctlTest.java

+package com.android.net.module.util.structs;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import android.util.ArraySet;
+import androidx.test.runner.AndroidJUnit4;
+import java.net.Inet6Address;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.Arrays;
+import java.util.Set;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@RunWith(AndroidJUnit4.class)
+public class StructMif6ctlTest {
+    private static final byte[] MSG_BYTES = new byte[] {
+        1, 0,  /* mif6cMifi */
+        0, /* mif6cFlags */
+        1, /* vifcThreshold*/
+        20, 0, /* mif6cPifi */
+        0, 0, 0, 0, /* vifcRateLimit */
+        0, 0 /* padding */
+    };
+
+    @Test
+    public void testConstructor() {
+        StructMif6ctl mif6ctl = new StructMif6ctl(10 /* mif6cMifi */,
+                (short) 11 /* mif6cFlags */,
+                (short) 12 /* vifcThreshold */,
+                13 /* mif6cPifi */,
+                14L /* vifcRateLimit */);
+
+        assertEquals(10, mif6ctl.mif6cMifi);
+        assertEquals(11, mif6ctl.mif6cFlags);
+        assertEquals(12, mif6ctl.vifcThreshold);
+        assertEquals(13, mif6ctl.mif6cPifi);
+        assertEquals(14, mif6ctl.vifcRateLimit);
+    }
+
+    @Test
+    public void testParseMif6ctl() {
+        final ByteBuffer buf = ByteBuffer.wrap(MSG_BYTES);
+        buf.order(ByteOrder.nativeOrder());
+        StructMif6ctl mif6ctl = StructMif6ctl.parse(StructMif6ctl.class, buf);
+
+        assertEquals(1, mif6ctl.mif6cMifi);
+        assertEquals(0, mif6ctl.mif6cFlags);
+        assertEquals(1, mif6ctl.vifcThreshold);
+        assertEquals(20, mif6ctl.mif6cPifi);
+        assertEquals(0, mif6ctl.vifcRateLimit);
+    }
+
+    @Test
+    public void testWriteToBytes() {
+        StructMif6ctl mif6ctl = new StructMif6ctl(1 /* mif6cMifi */,
+                (short) 0 /* mif6cFlags */,
+                (short) 1 /* vifcThreshold */,
+                20 /* mif6cPifi */,
+                (long) 0 /* vifcRateLimit */);
+
+        byte[] bytes = mif6ctl.writeToBytes();
+
+        assertArrayEquals("bytes = " + Arrays.toString(bytes), MSG_BYTES, bytes);
+    }
+}