Add struct Icmpv4Header class to parse icmpv4 header from a packet

Bug: 237369591
Test: atest EthernetTetheringTest
Change-Id: I1023fe3bf1cb5504f8e547cfca233dbb8dfaf3c1
diff --git a/staticlibs/device/com/android/net/module/util/structs/Icmpv4Header.java b/staticlibs/device/com/android/net/module/util/structs/Icmpv4Header.java
new file mode 100644
index 0000000..454bb07
--- /dev/null
+++ b/staticlibs/device/com/android/net/module/util/structs/Icmpv4Header.java
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2022 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;
+import com.android.net.module.util.Struct.Field;
+import com.android.net.module.util.Struct.Type;
+
+/**
+ * ICMPv4 header as per https://tools.ietf.org/html/rfc792.
+ *
+ * 0                   1                   2                   3
+ * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |     Type      |     Code      |          Checksum             |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ */
+public class Icmpv4Header extends Struct {
+    @Field(order = 0, type = Type.U8)
+    public short type;
+    @Field(order = 1, type = Type.U8)
+    public short code;
+    @Field(order = 2, type = Type.S16)
+    public short checksum;
+    public Icmpv4Header(final short type, final short code, final short checksum) {
+        this.type = type;
+        this.code = code;
+        this.checksum = checksum;
+    }
+}