| /* |
| * Copyright (C) 2019 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; |
| |
| import static android.net.SocketKeepalive.ERROR_INVALID_IP_ADDRESS; |
| import static android.net.SocketKeepalive.ERROR_INVALID_PORT; |
| |
| import android.net.SocketKeepalive.InvalidPacketException; |
| import android.net.util.IpUtils; |
| import android.system.OsConstants; |
| |
| import java.net.Inet4Address; |
| import java.net.InetAddress; |
| import java.nio.ByteBuffer; |
| import java.nio.ByteOrder; |
| |
| /** @hide */ |
| public final class NattKeepalivePacketData extends KeepalivePacketData { |
| |
| // This should only be constructed via static factory methods, such as |
| // nattKeepalivePacket |
| private NattKeepalivePacketData(InetAddress srcAddress, int srcPort, |
| InetAddress dstAddress, int dstPort, byte[] data) throws |
| InvalidPacketException { |
| super(srcAddress, srcPort, dstAddress, dstPort, data); |
| } |
| |
| /** |
| * Factory method to create Nat-T keepalive packet structure. |
| */ |
| public static NattKeepalivePacketData nattKeepalivePacket( |
| InetAddress srcAddress, int srcPort, InetAddress dstAddress, int dstPort) |
| throws InvalidPacketException { |
| |
| if (!(srcAddress instanceof Inet4Address) || !(dstAddress instanceof Inet4Address)) { |
| throw new InvalidPacketException(ERROR_INVALID_IP_ADDRESS); |
| } |
| |
| if (dstPort != NattSocketKeepalive.NATT_PORT) { |
| throw new InvalidPacketException(ERROR_INVALID_PORT); |
| } |
| |
| int length = IPV4_HEADER_LENGTH + UDP_HEADER_LENGTH + 1; |
| ByteBuffer buf = ByteBuffer.allocate(length); |
| buf.order(ByteOrder.BIG_ENDIAN); |
| buf.putShort((short) 0x4500); // IP version and TOS |
| buf.putShort((short) length); |
| buf.putInt(0); // ID, flags, offset |
| buf.put((byte) 64); // TTL |
| buf.put((byte) OsConstants.IPPROTO_UDP); |
| int ipChecksumOffset = buf.position(); |
| buf.putShort((short) 0); // IP checksum |
| buf.put(srcAddress.getAddress()); |
| buf.put(dstAddress.getAddress()); |
| buf.putShort((short) srcPort); |
| buf.putShort((short) dstPort); |
| buf.putShort((short) (length - 20)); // UDP length |
| int udpChecksumOffset = buf.position(); |
| buf.putShort((short) 0); // UDP checksum |
| buf.put((byte) 0xff); // NAT-T keepalive |
| buf.putShort(ipChecksumOffset, IpUtils.ipChecksum(buf, 0)); |
| buf.putShort(udpChecksumOffset, IpUtils.udpChecksum(buf, 0, IPV4_HEADER_LENGTH)); |
| |
| return new NattKeepalivePacketData(srcAddress, srcPort, dstAddress, dstPort, buf.array()); |
| } |
| } |