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.ByteBuffer;
9 import java.nio.channels.*;
12 * A NioPeerHandler maps LDK's PeerHandler to Java's NIO I/O interface. It spawns a single background thread which
13 * processes socket events and provides the data to LDK for decryption and processing.
15 public class NioPeerHandler {
16 private static class Peer {
17 SocketDescriptor descriptor;
18 // When we are told by LDK to disconnect, we can't return to LDK until we are sure
19 // won't call any more read/write PeerManager functions with the same connection.
20 // This is set to true if we're in such a condition (with disconnect checked
21 // before with the Peer monitor lock held) and false when we can return.
22 boolean block_disconnect_socket = false;
23 // Indicates LDK told us to disconnect this peer, and thus we should not call socket_disconnected.
24 boolean disconnect_requested = false;
28 // Android's java.nio implementation has a big lock inside the selector, preventing any concurrent access to it.
29 // This appears to largely defeat the entire purpose of java.nio, but we work around it here by explicitly checking
30 // for an Android environment and passing any selector access on any thread other than our internal one through
31 // do_selector_action, which wakes up the selector before accessing it.
32 private static boolean IS_ANDROID;
34 IS_ANDROID = System.getProperty("java.vendor").toLowerCase().contains("android");
36 private boolean wakeup_selector = false;
37 private interface SelectorCall {
38 void meth() throws IOException;
40 private void do_selector_action(SelectorCall meth) throws IOException {
42 wakeup_selector = true;
43 this.selector.wakeup();
44 synchronized (this.selector) {
46 wakeup_selector = false;
53 private Peer setup_socket(SocketChannel chan) throws IOException {
54 chan.configureBlocking(false);
55 // Lightning tends to send a number of small messages back and forth between peers quickly, which Nagle is
56 // particularly bad at handling, so we disable it here.
57 chan.setOption(StandardSocketOptions.TCP_NODELAY, true);
60 this.socket_id = this.socket_id + 1;
61 our_id = this.socket_id;
64 final Peer peer = new Peer();
65 SocketDescriptor descriptor = SocketDescriptor.new_impl(new SocketDescriptor.SocketDescriptorInterface() {
67 public long send_data(byte[] data, boolean resume_read) {
70 do_selector_action(() -> peer.key.interestOps(peer.key.interestOps() | SelectionKey.OP_READ));
72 long written = chan.write(ByteBuffer.wrap(data));
73 if (written != data.length) {
74 do_selector_action(() -> peer.key.interestOps(peer.key.interestOps() | SelectionKey.OP_WRITE));
77 } catch (IOException e) {
78 // Most likely the socket is disconnected, let the background thread handle it.
84 public void disconnect_socket() {
86 peer.disconnect_requested = true;
89 do_selector_action(() -> {
91 peer.key.channel().close();
93 } catch (IOException ignored) { }
95 while (peer.block_disconnect_socket) {
98 } catch (InterruptedException ignored) { }
102 @Override public boolean eq(SocketDescriptor other_arg) { return other_arg.hash() == our_id; }
103 @Override public long hash() { return our_id; }
105 peer.descriptor = descriptor;
109 PeerManager peer_manager;
111 final Selector selector;
113 volatile boolean shutdown = false;
116 * Constructs a new peer handler, spawning a thread to monitor for socket events.
117 * The background thread will call the PeerManager's timer_tick_occured() function for you on an appropriate schedule.
119 * @param manager The LDK PeerManager which connection data will be provided to.
120 * @throws IOException If an internal java.nio error occurs.
122 public NioPeerHandler(PeerManager manager) throws IOException {
123 this.peer_manager = manager;
124 this.selector = Selector.open();
125 io_thread = new Thread(() -> {
126 ByteBuffer buf = ByteBuffer.allocate(8192);
127 long lastTimerTick = System.currentTimeMillis();
132 synchronized (this.selector) {
133 if (!wakeup_selector) {
134 this.selector.select(1000);
140 this.selector.select(1000);
142 } catch (IOException ignored) {
143 System.err.println("java.nio threw an unexpected IOException. Stopping PeerHandler thread!");
146 if (shutdown) return;
147 if (Thread.interrupted()) return;
148 for (SelectionKey key : this.selector.selectedKeys()) {
150 if ((key.interestOps() & SelectionKey.OP_ACCEPT) != 0) {
151 if (key.isAcceptable()) {
154 chan = ((ServerSocketChannel) key.channel()).accept();
155 } catch (IOException ignored) {
159 if (chan == null) continue;
161 Peer peer = setup_socket(chan);
162 Result_NonePeerHandleErrorZ res = this.peer_manager.new_inbound_connection(peer.descriptor);
163 if (res instanceof Result_NonePeerHandleErrorZ.Result_NonePeerHandleErrorZ_OK) {
164 peer.key = chan.register(this.selector, SelectionKey.OP_READ, peer);
166 } catch (IOException ignored) { }
168 continue; // There is no attachment so the rest of the loop is useless
170 Peer peer = (Peer) key.attachment();
171 synchronized (peer) {
172 if (peer.disconnect_requested)
174 peer.block_disconnect_socket = true;
177 if (key.isValid() && (key.interestOps() & SelectionKey.OP_WRITE) != 0 && key.isWritable()) {
178 Result_NonePeerHandleErrorZ res = this.peer_manager.write_buffer_space_avail(peer.descriptor);
179 if (res instanceof Result_NonePeerHandleErrorZ.Result_NonePeerHandleErrorZ_Err) {
180 key.channel().close();
184 if (key.isValid() && (key.interestOps() & SelectionKey.OP_READ) != 0 && key.isReadable()) {
186 int read = ((SocketChannel) key.channel()).read(buf);
188 this.peer_manager.socket_disconnected(peer.descriptor);
190 } else if (read > 0) {
192 byte[] read_bytes = new byte[read];
193 buf.get(read_bytes, 0, read);
194 Result_boolPeerHandleErrorZ res = this.peer_manager.read_event(peer.descriptor, read_bytes);
195 if (res instanceof Result_boolPeerHandleErrorZ.Result_boolPeerHandleErrorZ_OK) {
196 if (((Result_boolPeerHandleErrorZ.Result_boolPeerHandleErrorZ_OK) res).res) {
197 key.interestOps(key.interestOps() & (~SelectionKey.OP_READ));
200 key.channel().close();
205 } catch (IOException ignored) {
206 try { key.channel().close(); } catch (IOException ignored2) { }
208 peer_manager.socket_disconnected(peer.descriptor);
210 synchronized (peer) {
211 peer.block_disconnect_socket = false;
214 } catch (CancelledKeyException e) {
215 try { key.channel().close(); } catch (IOException ignored) { }
216 // The key is only cancelled when we have notified the PeerManager that the socket is closed, so
217 // no need to do anything here with the PeerManager.
220 if (lastTimerTick < System.currentTimeMillis() - 30 * 1000) {
221 peer_manager.timer_tick_occurred();
222 lastTimerTick = System.currentTimeMillis();
224 peer_manager.process_events();
226 }, "NioPeerHandler NIO Thread");
231 * Connect to a peer given their node id and socket address. Blocks until a connection is established (or returns
232 * IOException) and then the connection handling runs in the background.
234 * @param their_node_id A valid 33-byte public key representing the peer's Lightning Node ID. If this is invalid,
235 * undefined behavior (read: Segfault, etc) may occur.
236 * @param remote The socket address to connect to.
237 * @param timeout_ms The amount of time, in milliseconds, up to which we will wait for connection to complete.
238 * @throws IOException If connecting to the remote endpoint fails or internal java.nio errors occur.
240 public void connect(byte[] their_node_id, SocketAddress remote, int timeout_ms) throws IOException {
241 SocketChannel chan = SocketChannel.open();
242 chan.configureBlocking(false);
243 Selector open_selector = Selector.open();
244 chan.register(open_selector, SelectionKey.OP_CONNECT);
245 if (!chan.connect(remote)) {
246 open_selector.select(timeout_ms);
248 if (!chan.finishConnect()) { // Note that this may throw its own IOException if we failed for another reason
249 throw new IOException("Timed out");
251 Peer peer = setup_socket(chan);
252 Result_CVec_u8ZPeerHandleErrorZ res = this.peer_manager.new_outbound_connection(their_node_id, peer.descriptor);
253 if (res instanceof Result_CVec_u8ZPeerHandleErrorZ.Result_CVec_u8ZPeerHandleErrorZ_OK) {
254 byte[] initial_bytes = ((Result_CVec_u8ZPeerHandleErrorZ.Result_CVec_u8ZPeerHandleErrorZ_OK) res).res;
255 if (chan.write(ByteBuffer.wrap(initial_bytes)) != initial_bytes.length) {
256 throw new IOException("We assume TCP socket buffer is at least a single packet in length");
258 do_selector_action(() -> peer.key = chan.register(this.selector, SelectionKey.OP_READ, peer));
260 throw new IOException("LDK rejected outbound connection. This likely shouldn't ever happen.");
265 * Binds a listening socket to the given address, accepting incoming connections and handling them on the background
268 * @param socket_address The address to bind the listening socket to.
269 * @throws IOException if binding the listening socket fail.
271 public void bind_listener(SocketAddress socket_address) throws IOException {
272 ServerSocketChannel listen_channel = ServerSocketChannel.open();
273 listen_channel.bind(socket_address);
274 listen_channel.configureBlocking(false);
275 do_selector_action(() -> listen_channel.register(this.selector, SelectionKey.OP_ACCEPT));
279 * Interrupt the background thread, stopping all peer handling. Disconnection events to the PeerHandler are not made,
280 * potentially leaving the PeerHandler in an inconsistent state.
282 public void interrupt() {
287 } catch (InterruptedException ignored) { }
291 * Calls process_events on the PeerManager immediately. Normally process_events is polled regularly to check for new
292 * messages which need to be sent, but you can interrupt the poll and check immediately by calling this function.
294 public void check_events() {