Add StructIpv4Header class to parse IPv4 header from a packet
Note that this class doesn't contain options field.
Test: atest NetworkStaticLibTests
Change-Id: If5062d8612e277bb283e253a0c7aa79ea9a3ce60
diff --git a/staticlibs/device/com/android/net/module/util/structs/Ipv4Header.java b/staticlibs/device/com/android/net/module/util/structs/Ipv4Header.java
new file mode 100644
index 0000000..5249454
--- /dev/null
+++ b/staticlibs/device/com/android/net/module/util/structs/Ipv4Header.java
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2021 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 androidx.annotation.VisibleForTesting;
+
+import com.android.net.module.util.Struct;
+import com.android.net.module.util.Struct.Field;
+import com.android.net.module.util.Struct.Type;
+
+import java.net.Inet4Address;
+
+/**
+ * L3 IPv4 header as per https://tools.ietf.org/html/rfc791.
+ * This class doesn't contain options field.
+ *
+ * 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
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |Version| IHL |Type of Service| Total Length |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Identification |Flags| Fragment Offset |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Time to Live | Protocol | Header Checksum |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Source Address |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Destination Address |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ */
+public class Ipv4Header extends Struct {
+ // IP Version=IPv4, IHL is always 5(*4bytes) because options are not supported.
+ @VisibleForTesting
+ public static final byte IPHDR_VERSION_IHL = 0x45;
+
+ @Field(order = 0, type = Type.S8)
+ // version (4 bits), IHL (4 bits)
+ public final byte vi;
+ @Field(order = 1, type = Type.S8)
+ public final byte tos;
+ @Field(order = 2, type = Type.U16)
+ public final int totalLength;
+ @Field(order = 3, type = Type.S16)
+ public final short id;
+ @Field(order = 4, type = Type.S16)
+ // flags (3 bits), fragment offset (13 bits)
+ public final short flagsAndFragmentOffset;
+ @Field(order = 5, type = Type.U8)
+ public final short ttl;
+ @Field(order = 6, type = Type.S8)
+ public final byte protocol;
+ @Field(order = 7, type = Type.S16)
+ public final short checksum;
+ @Field(order = 8, type = Type.Ipv4Address)
+ public final Inet4Address srcIp;
+ @Field(order = 9, type = Type.Ipv4Address)
+ public final Inet4Address dstIp;
+
+ public Ipv4Header(final byte tos, final int totalLength, final short id,
+ final short flagsAndFragmentOffset, final short ttl, final byte protocol,
+ final short checksum, final Inet4Address srcIp, final Inet4Address dstIp) {
+ this(IPHDR_VERSION_IHL, tos, totalLength, id, flagsAndFragmentOffset, ttl,
+ protocol, checksum, srcIp, dstIp);
+ }
+
+ private Ipv4Header(final byte vi, final byte tos, final int totalLength, final short id,
+ final short flagsAndFragmentOffset, final short ttl, final byte protocol,
+ final short checksum, final Inet4Address srcIp, final Inet4Address dstIp) {
+ this.vi = vi;
+ this.tos = tos;
+ this.totalLength = totalLength;
+ this.id = id;
+ this.flagsAndFragmentOffset = flagsAndFragmentOffset;
+ this.ttl = ttl;
+ this.protocol = protocol;
+ this.checksum = checksum;
+ this.srcIp = srcIp;
+ this.dstIp = dstIp;
+ }
+}