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Socket plugin that supports exchanging invitations by LAN multicast
(untested).
This commit is contained in:
akwizgran
194
components/net/sf/briar/plugins/socket/LanSocketPlugin.java
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194
components/net/sf/briar/plugins/socket/LanSocketPlugin.java
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package net.sf.briar.plugins.socket;
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import java.io.IOException;
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import java.net.DatagramPacket;
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import java.net.InetAddress;
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import java.net.InetSocketAddress;
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import java.net.MulticastSocket;
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import java.net.NetworkInterface;
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import java.net.ServerSocket;
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import java.net.Socket;
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import java.net.SocketTimeoutException;
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import java.net.UnknownHostException;
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import java.util.Collections;
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import java.util.Enumeration;
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import java.util.Random;
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import java.util.concurrent.Executor;
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import java.util.logging.Level;
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import java.util.logging.Logger;
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import net.sf.briar.api.plugins.StreamPluginCallback;
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import net.sf.briar.api.transport.StreamTransportConnection;
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import net.sf.briar.util.ByteUtils;
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/** A socket plugin that supports exchanging invitations over a LAN. */
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public class LanSocketPlugin extends SimpleSocketPlugin {
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private static final Logger LOG =
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Logger.getLogger(LanSocketPlugin.class.getName());
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LanSocketPlugin(Executor executor, StreamPluginCallback callback,
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long pollingInterval) {
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super(executor, callback, pollingInterval);
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}
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@Override
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public boolean supportsInvitations() {
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return true;
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}
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@Override
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public StreamTransportConnection sendInvitation(int code, long timeout) {
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// Calculate the group address and port from the invitation code
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InetSocketAddress mcast = convertInvitationCodeToMulticastGroup(code);
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// Bind a multicast socket for receiving packets
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MulticastSocket ms;
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try {
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ms = new MulticastSocket(mcast.getPort());
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ms.setInterface(chooseInterface());
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ms.joinGroup(mcast.getAddress());
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} catch(IOException e) {
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if(LOG.isLoggable(Level.WARNING)) LOG.warning(e.getMessage());
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return null;
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}
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// Listen until a valid packet is received or the timeout occurs
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byte[] buffer = new byte[2];
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DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
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long now = System.currentTimeMillis();
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long end = now + timeout;
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try {
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while(now < end) {
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try {
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ms.setSoTimeout((int) (end - now));
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ms.receive(packet);
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byte[] b = packet.getData();
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int off = packet.getOffset();
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int len = packet.getLength();
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int port = parsePacket(b, off, len);
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if(port >= 32768 && port < 65536) {
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try {
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// Connect back on the advertised TCP port
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Socket s = new Socket(packet.getAddress(), port);
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// Close the multicast socket
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ms.leaveGroup(mcast.getAddress());
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ms.close();
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return new SocketTransportConnection(s);
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} catch(IOException e) {
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if(LOG.isLoggable(Level.WARNING))
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LOG.warning(e.getMessage());
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}
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}
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} catch(SocketTimeoutException e) {
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break;
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}
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now = System.currentTimeMillis();
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}
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} catch(IOException e) {
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if(LOG.isLoggable(Level.WARNING)) LOG.warning(e.getMessage());
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}
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return null;
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}
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private InetSocketAddress convertInvitationCodeToMulticastGroup(int code) {
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Random r = new Random(code);
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byte[] b = new byte[5];
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r.nextBytes(b);
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// The group address is 239.random.random.random, excluding 0 and 255
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byte[] group = new byte[4];
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group[0] = (byte) 239;
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group[1] = legalAddressByte(b[0]);
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group[2] = legalAddressByte(b[1]);
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group[3] = legalAddressByte(b[2]);
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// The port is random in the range 32768 - 65535, inclusive
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int port = ByteUtils.readUint16(b, 3);
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if(port < 32768) port += 32768;
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InetAddress address;
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try {
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address = InetAddress.getByAddress(group);
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} catch(UnknownHostException badAddressLength) {
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throw new RuntimeException(badAddressLength);
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}
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return new InetSocketAddress(address, port);
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}
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private byte legalAddressByte(byte b) {
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if(b == 0) return 1;
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if(b == (byte) 255) return (byte) 254;
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return b;
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}
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private InetAddress chooseInterface() throws IOException {
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// Try to find a LAN interface that supports multicast
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Enumeration<NetworkInterface> ifaces =
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NetworkInterface.getNetworkInterfaces();
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for(NetworkInterface iface : Collections.list(ifaces)) {
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if(iface.supportsMulticast()) {
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Enumeration<InetAddress> addrs = iface.getInetAddresses();
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for(InetAddress addr : Collections.list(addrs)) {
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if(addr.isLinkLocalAddress() || addr.isSiteLocalAddress())
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return addr;
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}
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}
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}
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// Bind to 0.0.0.0
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return InetAddress.getByName("0.0.0.0");
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}
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private int parsePacket(byte[] b, int off, int len) {
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if(len != 2) return 0;
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return ByteUtils.readUint16(b, off);
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}
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@Override
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public StreamTransportConnection acceptInvitation(int code, long timeout) {
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// Calculate the group address and port from the invitation code
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InetSocketAddress mcast = convertInvitationCodeToMulticastGroup(code);
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// Bind a TCP socket for receiving connections
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ServerSocket ss;
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try {
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ss = new ServerSocket();
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ss.bind(new InetSocketAddress(chooseInterface(), 0));
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} catch(IOException e) {
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if(LOG.isLoggable(Level.WARNING)) LOG.warning(e.getMessage());
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return null;
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}
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// Bind a multicast socket for sending packets
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MulticastSocket ms;
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try {
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ms = new MulticastSocket();
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ms.setInterface(chooseInterface());
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} catch(IOException e) {
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if(LOG.isLoggable(Level.WARNING)) LOG.warning(e.getMessage());
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return null;
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}
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// Send packets until a connection is received or the timeout expires
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byte[] buffer = new byte[2];
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ByteUtils.writeUint16(ss.getLocalPort(), buffer, 0);
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DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
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packet.setAddress(mcast.getAddress());
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packet.setPort(mcast.getPort());
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long now = System.currentTimeMillis();
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long end = now + timeout;
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long interval = 1000;
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long nextPacket = now + 1;
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try {
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while(now < end) {
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try {
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int wait = (int) (Math.min(end, nextPacket) - now);
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ss.setSoTimeout(wait < 1 ? 1 : wait);
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return new SocketTransportConnection(ss.accept());
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} catch(SocketTimeoutException e) {
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if(System.currentTimeMillis() < end) {
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ms.send(packet);
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now = System.currentTimeMillis();
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nextPacket = now + interval;
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interval += 1000;
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}
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}
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}
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} catch(IOException e) {
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if(LOG.isLoggable(Level.WARNING)) LOG.warning(e.getMessage());
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}
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return null;
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}
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}
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