1 package org.ldk.batteries;
3 import org.ldk.structs.*;
5 import java.io.IOException;
6 import java.net.SocketAddress;
7 import java.net.StandardSocketOptions;
8 import java.nio.Buffer;
9 import java.nio.ByteBuffer;
10 import java.nio.channels.*;
13 * A NioPeerHandler maps LDK's PeerHandler to Java's NIO I/O interface. It spawns a single background thread which
14 * processes socket events and provides the data to LDK for decryption and processing.
16 public class NioPeerHandler {
17 private static class Peer {
18 SocketDescriptor descriptor;
19 // When we are told by LDK to disconnect, we can't return to LDK until we are sure
20 // won't call any more read/write PeerManager functions with the same connection.
21 // This is set to true if we're in such a condition (with disconnect checked
22 // before with the Peer monitor lock held) and false when we can return.
23 boolean block_disconnect_socket = false;
24 // Indicates LDK told us to disconnect this peer, and thus we should not call socket_disconnected.
25 boolean disconnect_requested = false;
29 // Android's java.nio implementation has a big lock inside the selector, preventing any concurrent access to it.
30 // This appears to largely defeat the entire purpose of java.nio, but we work around it here by explicitly checking
31 // for an Android environment and passing any selector access on any thread other than our internal one through
32 // do_selector_action, which wakes up the selector before accessing it.
33 private static boolean IS_ANDROID;
35 IS_ANDROID = System.getProperty("java.vendor").toLowerCase().contains("android");
37 private boolean wakeup_selector = false;
38 private interface SelectorCall {
39 void meth() throws IOException;
41 private void do_selector_action(SelectorCall meth) throws IOException {
43 wakeup_selector = true;
44 this.selector.wakeup();
45 synchronized (this.selector) {
47 wakeup_selector = false;
54 private Peer setup_socket(SocketChannel chan) throws IOException {
55 chan.configureBlocking(false);
56 // Lightning tends to send a number of small messages back and forth between peers quickly, which Nagle is
57 // particularly bad at handling, so we disable it here.
58 chan.setOption(StandardSocketOptions.TCP_NODELAY, true);
61 this.socket_id = this.socket_id + 1;
62 our_id = this.socket_id;
65 final Peer peer = new Peer();
66 SocketDescriptor descriptor = SocketDescriptor.new_impl(new SocketDescriptor.SocketDescriptorInterface() {
68 public long send_data(byte[] data, boolean resume_read) {
71 do_selector_action(() -> peer.key.interestOps(peer.key.interestOps() | SelectionKey.OP_READ));
73 long written = chan.write(ByteBuffer.wrap(data));
74 if (written != data.length) {
75 do_selector_action(() -> peer.key.interestOps(peer.key.interestOps() | SelectionKey.OP_WRITE));
78 } catch (IOException e) {
79 // Most likely the socket is disconnected, let the background thread handle it.
85 public void disconnect_socket() {
87 peer.disconnect_requested = true;
90 do_selector_action(() -> {
92 peer.key.channel().close();
94 } catch (IOException ignored) { }
96 while (peer.block_disconnect_socket) {
99 } catch (InterruptedException ignored) { }
103 @Override public boolean eq(SocketDescriptor other_arg) { return other_arg.hash() == our_id; }
104 @Override public long hash() { return our_id; }
106 peer.descriptor = descriptor;
110 PeerManager peer_manager;
112 final Selector selector;
114 volatile boolean shutdown = false;
117 * Constructs a new peer handler, spawning a thread to monitor for socket events.
118 * The background thread will call the PeerManager's timer_tick_occured() function for you on an appropriate schedule.
120 * @param manager The LDK PeerManager which connection data will be provided to.
121 * @throws IOException If an internal java.nio error occurs.
123 public NioPeerHandler(PeerManager manager) throws IOException {
124 this.peer_manager = manager;
125 this.selector = Selector.open();
126 io_thread = new Thread(() -> {
127 ByteBuffer buf = ByteBuffer.allocate(8192);
128 long lastTimerTick = System.currentTimeMillis();
133 synchronized (this.selector) {
134 if (!wakeup_selector) {
135 this.selector.select(1000);
141 this.selector.select(1000);
143 } catch (IOException ignored) {
144 System.err.println("java.nio threw an unexpected IOException. Stopping PeerHandler thread!");
147 if (shutdown) return;
148 if (Thread.interrupted()) return;
149 for (SelectionKey key : this.selector.selectedKeys()) {
151 if ((key.interestOps() & SelectionKey.OP_ACCEPT) != 0) {
152 if (key.isAcceptable()) {
155 chan = ((ServerSocketChannel) key.channel()).accept();
156 } catch (IOException ignored) {
160 if (chan == null) continue;
162 Peer peer = setup_socket(chan);
163 Result_NonePeerHandleErrorZ res = this.peer_manager.new_inbound_connection(peer.descriptor);
164 if (res instanceof Result_NonePeerHandleErrorZ.Result_NonePeerHandleErrorZ_OK) {
165 peer.key = chan.register(this.selector, SelectionKey.OP_READ, peer);
167 } catch (IOException ignored) { }
169 continue; // There is no attachment so the rest of the loop is useless
171 Peer peer = (Peer) key.attachment();
172 synchronized (peer) {
173 if (peer.disconnect_requested)
175 peer.block_disconnect_socket = true;
178 if (key.isValid() && (key.interestOps() & SelectionKey.OP_WRITE) != 0 && key.isWritable()) {
179 Result_NonePeerHandleErrorZ res = this.peer_manager.write_buffer_space_avail(peer.descriptor);
180 if (res instanceof Result_NonePeerHandleErrorZ.Result_NonePeerHandleErrorZ_Err) {
181 key.channel().close();
185 if (key.isValid() && (key.interestOps() & SelectionKey.OP_READ) != 0 && key.isReadable()) {
186 ((Buffer)buf).clear();
187 int read = ((SocketChannel) key.channel()).read(buf);
189 this.peer_manager.socket_disconnected(peer.descriptor);
191 } else if (read > 0) {
192 ((Buffer)buf).flip();
193 byte[] read_bytes = new byte[read];
194 buf.get(read_bytes, 0, read);
195 Result_boolPeerHandleErrorZ res = this.peer_manager.read_event(peer.descriptor, read_bytes);
196 if (res instanceof Result_boolPeerHandleErrorZ.Result_boolPeerHandleErrorZ_OK) {
197 if (((Result_boolPeerHandleErrorZ.Result_boolPeerHandleErrorZ_OK) res).res) {
198 key.interestOps(key.interestOps() & (~SelectionKey.OP_READ));
201 key.channel().close();
206 } catch (IOException ignored) {
207 try { key.channel().close(); } catch (IOException ignored2) { }
209 peer_manager.socket_disconnected(peer.descriptor);
211 synchronized (peer) {
212 peer.block_disconnect_socket = false;
215 } catch (CancelledKeyException e) {
216 try { key.channel().close(); } catch (IOException ignored) { }
217 // The key is only cancelled when we have notified the PeerManager that the socket is closed, so
218 // no need to do anything here with the PeerManager.
221 if (lastTimerTick < System.currentTimeMillis() - 30 * 1000) {
222 peer_manager.timer_tick_occurred();
223 lastTimerTick = System.currentTimeMillis();
225 peer_manager.process_events();
227 }, "NioPeerHandler NIO Thread");
232 * Connect to a peer given their node id and socket address. Blocks until a connection is established (or returns
233 * IOException) and then the connection handling runs in the background.
235 * @param their_node_id A valid 33-byte public key representing the peer's Lightning Node ID. If this is invalid,
236 * undefined behavior (read: Segfault, etc) may occur.
237 * @param remote The socket address to connect to.
238 * @param timeout_ms The amount of time, in milliseconds, up to which we will wait for connection to complete.
239 * @throws IOException If connecting to the remote endpoint fails or internal java.nio errors occur.
241 public void connect(byte[] their_node_id, SocketAddress remote, int timeout_ms) throws IOException {
242 SocketChannel chan = SocketChannel.open();
243 chan.configureBlocking(false);
244 Selector open_selector = Selector.open();
245 chan.register(open_selector, SelectionKey.OP_CONNECT);
246 if (!chan.connect(remote)) {
247 open_selector.select(timeout_ms);
249 if (!chan.finishConnect()) { // Note that this may throw its own IOException if we failed for another reason
250 throw new IOException("Timed out");
252 Peer peer = setup_socket(chan);
253 Result_CVec_u8ZPeerHandleErrorZ res = this.peer_manager.new_outbound_connection(their_node_id, peer.descriptor);
254 if (res instanceof Result_CVec_u8ZPeerHandleErrorZ.Result_CVec_u8ZPeerHandleErrorZ_OK) {
255 byte[] initial_bytes = ((Result_CVec_u8ZPeerHandleErrorZ.Result_CVec_u8ZPeerHandleErrorZ_OK) res).res;
256 if (chan.write(ByteBuffer.wrap(initial_bytes)) != initial_bytes.length) {
257 throw new IOException("We assume TCP socket buffer is at least a single packet in length");
259 do_selector_action(() -> peer.key = chan.register(this.selector, SelectionKey.OP_READ, peer));
261 throw new IOException("LDK rejected outbound connection. This likely shouldn't ever happen.");
266 * Binds a listening socket to the given address, accepting incoming connections and handling them on the background
269 * @param socket_address The address to bind the listening socket to.
270 * @throws IOException if binding the listening socket fail.
272 public void bind_listener(SocketAddress socket_address) throws IOException {
273 ServerSocketChannel listen_channel = ServerSocketChannel.open();
274 listen_channel.bind(socket_address);
275 listen_channel.configureBlocking(false);
276 do_selector_action(() -> listen_channel.register(this.selector, SelectionKey.OP_ACCEPT));
280 * Interrupt the background thread, stopping all peer handling. Disconnection events to the PeerHandler are not made,
281 * potentially leaving the PeerHandler in an inconsistent state.
283 public void interrupt() {
288 } catch (InterruptedException ignored) { }
292 * Calls process_events on the PeerManager immediately. Normally process_events is polled regularly to check for new
293 * messages which need to be sent, but you can interrupt the poll and check immediately by calling this function.
295 public void check_events() {