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package org.spongycastle.crypto.tls;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
public class UDPTransport
implements DatagramTransport
{
protected final static int MIN_IP_OVERHEAD = 20;
protected final static int MAX_IP_OVERHEAD = MIN_IP_OVERHEAD + 64;
protected final static int UDP_OVERHEAD = 8;
protected final DatagramSocket socket;
protected final int receiveLimit, sendLimit;
public UDPTransport(DatagramSocket socket, int mtu)
throws IOException
{
if (!socket.isBound() || !socket.isConnected())
{
throw new IllegalArgumentException("'socket' must be bound and connected");
}
this.socket = socket;
// NOTE: As of JDK 1.6, can use NetworkInterface.getMTU
this.receiveLimit = mtu - MIN_IP_OVERHEAD - UDP_OVERHEAD;
this.sendLimit = mtu - MAX_IP_OVERHEAD - UDP_OVERHEAD;
}
public int getReceiveLimit()
{
return receiveLimit;
}
public int getSendLimit()
{
// TODO[DTLS] Implement Path-MTU discovery?
return sendLimit;
}
public int receive(byte[] buf, int off, int len, int waitMillis)
throws IOException
{
socket.setSoTimeout(waitMillis);
DatagramPacket packet = new DatagramPacket(buf, off, len);
socket.receive(packet);
return packet.getLength();
}
public void send(byte[] buf, int off, int len)
throws IOException
{
if (len > getSendLimit())
{
/*
* RFC 4347 4.1.1. "If the application attempts to send a record larger than the MTU,
* the DTLS implementation SHOULD generate an error, thus avoiding sending a packet
* which will be fragmented."
*/
throw new TlsFatalAlert(AlertDescription.internal_error);
}
DatagramPacket packet = new DatagramPacket(buf, off, len);
socket.send(packet);
}
public void close()
throws IOException
{
socket.close();
}
}
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