/*
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.net;
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import static android.net.SocketKeepalive.ERROR_INVALID_IP_ADDRESS;
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import static android.net.SocketKeepalive.ERROR_INVALID_PORT;
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import android.net.SocketKeepalive.InvalidPacketException;
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import android.net.util.IpUtils;
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import android.os.Parcel;
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import android.os.Parcelable;
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import android.system.OsConstants;
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import java.net.Inet4Address;
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import java.net.InetAddress;
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import java.nio.ByteBuffer;
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import java.nio.ByteOrder;
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/** @hide */
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public final class NattKeepalivePacketData extends KeepalivePacketData implements Parcelable {
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// This should only be constructed via static factory methods, such as
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// nattKeepalivePacket
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private NattKeepalivePacketData(InetAddress srcAddress, int srcPort,
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InetAddress dstAddress, int dstPort, byte[] data) throws
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InvalidPacketException {
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super(srcAddress, srcPort, dstAddress, dstPort, data);
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}
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/**
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* Factory method to create Nat-T keepalive packet structure.
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*/
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public static NattKeepalivePacketData nattKeepalivePacket(
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InetAddress srcAddress, int srcPort, InetAddress dstAddress, int dstPort)
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throws InvalidPacketException {
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if (!(srcAddress instanceof Inet4Address) || !(dstAddress instanceof Inet4Address)) {
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throw new InvalidPacketException(ERROR_INVALID_IP_ADDRESS);
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}
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if (dstPort != NattSocketKeepalive.NATT_PORT) {
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throw new InvalidPacketException(ERROR_INVALID_PORT);
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}
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int length = IPV4_HEADER_LENGTH + UDP_HEADER_LENGTH + 1;
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ByteBuffer buf = ByteBuffer.allocate(length);
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buf.order(ByteOrder.BIG_ENDIAN);
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buf.putShort((short) 0x4500); // IP version and TOS
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buf.putShort((short) length);
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buf.putInt(0); // ID, flags, offset
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buf.put((byte) 64); // TTL
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buf.put((byte) OsConstants.IPPROTO_UDP);
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int ipChecksumOffset = buf.position();
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buf.putShort((short) 0); // IP checksum
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buf.put(srcAddress.getAddress());
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buf.put(dstAddress.getAddress());
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buf.putShort((short) srcPort);
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buf.putShort((short) dstPort);
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buf.putShort((short) (length - 20)); // UDP length
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int udpChecksumOffset = buf.position();
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buf.putShort((short) 0); // UDP checksum
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buf.put((byte) 0xff); // NAT-T keepalive
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buf.putShort(ipChecksumOffset, IpUtils.ipChecksum(buf, 0));
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buf.putShort(udpChecksumOffset, IpUtils.udpChecksum(buf, 0, IPV4_HEADER_LENGTH));
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return new NattKeepalivePacketData(srcAddress, srcPort, dstAddress, dstPort, buf.array());
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}
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/** Parcelable Implementation */
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public int describeContents() {
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return 0;
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}
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/** Write to parcel */
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public void writeToParcel(Parcel out, int flags) {
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out.writeString(srcAddress.getHostAddress());
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out.writeString(dstAddress.getHostAddress());
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out.writeInt(srcPort);
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out.writeInt(dstPort);
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}
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/** Parcelable Creator */
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public static final Parcelable.Creator<NattKeepalivePacketData> CREATOR =
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new Parcelable.Creator<NattKeepalivePacketData>() {
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public NattKeepalivePacketData createFromParcel(Parcel in) {
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final InetAddress srcAddress =
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InetAddresses.parseNumericAddress(in.readString());
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final InetAddress dstAddress =
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InetAddresses.parseNumericAddress(in.readString());
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final int srcPort = in.readInt();
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final int dstPort = in.readInt();
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try {
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return NattKeepalivePacketData.nattKeepalivePacket(srcAddress, srcPort,
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dstAddress, dstPort);
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} catch (InvalidPacketException e) {
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throw new IllegalArgumentException(
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"Invalid NAT-T keepalive data: " + e.error);
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}
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}
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public NattKeepalivePacketData[] newArray(int size) {
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return new NattKeepalivePacketData[size];
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}
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};
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}
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