mirror of https://github.com/GeyserMC/Geyser.git
92 lines
3.4 KiB
Java
92 lines
3.4 KiB
Java
/*
|
|
* Copyright (c) 2019-2021 GeyserMC. http://geysermc.org
|
|
*
|
|
* Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
* of this software and associated documentation files (the "Software"), to deal
|
|
* in the Software without restriction, including without limitation the rights
|
|
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
|
* copies of the Software, and to permit persons to whom the Software is
|
|
* furnished to do so, subject to the following conditions:
|
|
*
|
|
* The above copyright notice and this permission notice shall be included in
|
|
* all copies or substantial portions of the Software.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
|
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
|
|
* THE SOFTWARE.
|
|
*
|
|
* @author GeyserMC
|
|
* @link https://github.com/GeyserMC/Geyser
|
|
*/
|
|
|
|
package org.geysermc.floodgate.time;
|
|
|
|
import java.net.DatagramPacket;
|
|
import java.net.DatagramSocket;
|
|
import java.net.InetAddress;
|
|
import java.nio.ByteBuffer;
|
|
|
|
/*
|
|
* Thanks:
|
|
* https://datatracker.ietf.org/doc/html/rfc1769
|
|
* https://github.com/jonsagara/SimpleNtpClient
|
|
* https://stackoverflow.com/a/29138806
|
|
*/
|
|
public final class SntpClientUtils {
|
|
private static final int NTP_PORT = 123;
|
|
|
|
private static final int NTP_PACKET_SIZE = 48;
|
|
private static final int NTP_MODE = 3; // client
|
|
private static final int NTP_VERSION = 3;
|
|
private static final int RECEIVE_TIME_POSITION = 32;
|
|
|
|
private static final long NTP_TIME_OFFSET = ((365L * 70L) + 17L) * 24L * 60L * 60L;
|
|
|
|
public static long requestTimeOffset(String host, int timeout) {
|
|
try (DatagramSocket socket = new DatagramSocket()) {
|
|
socket.setSoTimeout(timeout);
|
|
|
|
InetAddress address = InetAddress.getByName(host);
|
|
|
|
ByteBuffer buff = ByteBuffer.allocate(NTP_PACKET_SIZE);
|
|
|
|
DatagramPacket request = new DatagramPacket(
|
|
buff.array(), NTP_PACKET_SIZE, address, NTP_PORT
|
|
);
|
|
|
|
// mode is in the least signification 3 bits
|
|
// version is in bits 3-5
|
|
buff.put((byte) (NTP_MODE | (NTP_VERSION << 3)));
|
|
|
|
long originateTime = System.currentTimeMillis();
|
|
socket.send(request);
|
|
|
|
DatagramPacket response = new DatagramPacket(buff.array(), NTP_PACKET_SIZE);
|
|
socket.receive(response);
|
|
|
|
long responseTime = System.currentTimeMillis();
|
|
|
|
// everything before isn't important for us
|
|
buff.position(RECEIVE_TIME_POSITION);
|
|
|
|
long receiveTime = readTimestamp(buff);
|
|
long transmitTime = readTimestamp(buff);
|
|
|
|
return ((receiveTime - originateTime) + (transmitTime - responseTime)) / 2;
|
|
} catch (Exception ignored) {
|
|
}
|
|
return Long.MIN_VALUE;
|
|
}
|
|
|
|
private static long readTimestamp(ByteBuffer buffer) {
|
|
//todo look into the ntp 2036 problem
|
|
long seconds = buffer.getInt() & 0xffffffffL;
|
|
long fraction = buffer.getInt() & 0xffffffffL;
|
|
return ((seconds - NTP_TIME_OFFSET) * 1000) + ((fraction * 1000) / 0x100000000L);
|
|
}
|
|
}
|