_ Git - rust-lightning/blob - lightning/src/routing/utxo.rs

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 //! This module contains traits for LDK to access UTXOs to check gossip data is correct.
  11 //!
  12 //! When lightning nodes gossip channel information, they resist DoS attacks by checking that each
  13 //! channel matches a UTXO on-chain, requiring at least some marginal on-chain transacting in
  14 //! order to announce a channel. This module handles that checking.
  15
  16 use bitcoin::{BlockHash, TxOut};
  17 use bitcoin::hashes::hex::ToHex;
  18
  19 use crate::ln::chan_utils::make_funding_redeemscript_from_slices;
  20 use crate::ln::msgs::{self, LightningError, ErrorAction};
  21 use crate::routing::gossip::{NetworkGraph, NodeId, P2PGossipSync};
  22 use crate::util::events::MessageSendEvent;
  23 use crate::util::logger::{Level, Logger};
  24 use crate::util::ser::Writeable;
  25
  26 use crate::prelude::*;
  27
  28 use alloc::sync::{Arc, Weak};
  29 use crate::sync::Mutex;
  30 use core::ops::Deref;
  31
  32 /// An error when accessing the chain via [`UtxoLookup`].
  33 #[derive(Clone, Debug)]
  34 pub enum UtxoLookupError {
  35         /// The requested chain is unknown.
  36         UnknownChain,
  37
  38         /// The requested transaction doesn't exist or hasn't confirmed.
  39         UnknownTx,
  40 }
  41
  42 /// The result of a [`UtxoLookup::get_utxo`] call. A call may resolve either synchronously,
  43 /// returning the `Sync` variant, or asynchronously, returning an [`UtxoFuture`] in the `Async`
  44 /// variant.
  45 #[derive(Clone)]
  46 pub enum UtxoResult {
  47         /// A result which was resolved synchronously. It either includes a [`TxOut`] for the output
  48         /// requested or a [`UtxoLookupError`].
  49         Sync(Result<TxOut, UtxoLookupError>),
  50         /// A result which will be resolved asynchronously. It includes a [`UtxoFuture`], a `clone` of
  51         /// which you must keep locally and call [`UtxoFuture::resolve`] on once the lookup completes.
  52         ///
  53         /// Note that in order to avoid runaway memory usage, the number of parallel checks is limited,
  54         /// but only fairly loosely. Because a pending checks block all message processing, leaving
  55         /// checks pending for an extended time may cause DoS of other functions. It is recommended you
  56         /// keep a tight timeout on lookups, on the order of a few seconds.
  57         Async(UtxoFuture),
  58 }
  59
  60 /// The `UtxoLookup` trait defines behavior for accessing on-chain UTXOs.
  61 pub trait UtxoLookup {
  62         /// Returns the transaction output of a funding transaction encoded by [`short_channel_id`].
  63         /// Returns an error if `genesis_hash` is for a different chain or if such a transaction output
  64         /// is unknown.
  65         ///
  66         /// [`short_channel_id`]: https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#definition-of-short_channel_id
  67         fn get_utxo(&self, genesis_hash: &BlockHash, short_channel_id: u64) -> UtxoResult;
  68 }
  69
  70 enum ChannelAnnouncement {
  71         Full(msgs::ChannelAnnouncement),
  72         Unsigned(msgs::UnsignedChannelAnnouncement),
  73 }
  74 impl ChannelAnnouncement {
  75         fn node_id_1(&self) -> &NodeId {
  76                 match self {
  77                         ChannelAnnouncement::Full(msg) => &msg.contents.node_id_1,
  78                         ChannelAnnouncement::Unsigned(msg) => &msg.node_id_1,
  79                 }
  80         }
  81 }
  82
  83 enum NodeAnnouncement {
  84         Full(msgs::NodeAnnouncement),
  85         Unsigned(msgs::UnsignedNodeAnnouncement),
  86 }
  87 impl NodeAnnouncement {
  88         fn timestamp(&self) -> u32 {
  89                 match self {
  90                         NodeAnnouncement::Full(msg) => msg.contents.timestamp,
  91                         NodeAnnouncement::Unsigned(msg) => msg.timestamp,
  92                 }
  93         }
  94 }
  95
  96 enum ChannelUpdate {
  97         Full(msgs::ChannelUpdate),
  98         Unsigned(msgs::UnsignedChannelUpdate),
  99 }
 100 impl ChannelUpdate {
 101         fn timestamp(&self) -> u32 {
 102                 match self {
 103                         ChannelUpdate::Full(msg) => msg.contents.timestamp,
 104                         ChannelUpdate::Unsigned(msg) => msg.timestamp,
 105                 }
 106         }
 107 }
 108
 109 struct UtxoMessages {
 110         complete: Option<Result<TxOut, UtxoLookupError>>,
 111         channel_announce: Option<ChannelAnnouncement>,
 112         latest_node_announce_a: Option<NodeAnnouncement>,
 113         latest_node_announce_b: Option<NodeAnnouncement>,
 114         latest_channel_update_a: Option<ChannelUpdate>,
 115         latest_channel_update_b: Option<ChannelUpdate>,
 116 }
 117
 118 /// Represents a future resolution of a [`UtxoLookup::get_utxo`] query resolving async.
 119 ///
 120 /// See [`UtxoResult::Async`] and [`UtxoFuture::resolve`] for more info.
 121 #[derive(Clone)]
 122 pub struct UtxoFuture {
 123         state: Arc<Mutex<UtxoMessages>>,
 124 }
 125
 126 /// A trivial implementation of [`UtxoLookup`] which is used to call back into the network graph
 127 /// once we have a concrete resolution of a request.
 128 struct UtxoResolver(Result<TxOut, UtxoLookupError>);
 129 impl UtxoLookup for UtxoResolver {
 130         fn get_utxo(&self, _genesis_hash: &BlockHash, _short_channel_id: u64) -> UtxoResult {
 131                 UtxoResult::Sync(self.0.clone())
 132         }
 133 }
 134
 135 impl UtxoFuture {
 136         /// Builds a new future for later resolution.
 137         pub fn new() -> Self {
 138                 Self { state: Arc::new(Mutex::new(UtxoMessages {
 139                         complete: None,
 140                         channel_announce: None,
 141                         latest_node_announce_a: None,
 142                         latest_node_announce_b: None,
 143                         latest_channel_update_a: None,
 144                         latest_channel_update_b: None,
 145                 }))}
 146         }
 147
 148         /// Resolves this future against the given `graph` and with the given `result`.
 149         ///
 150         /// This is identical to calling [`UtxoFuture::resolve`] with a dummy `gossip`, disabling
 151         /// forwarding the validated gossip message onwards to peers.
 152         ///
 153         /// Because this may cause the [`NetworkGraph`]'s [`processing_queue_high`] to flip, in order
 154         /// to allow us to interact with peers again, you should call [`PeerManager::process_events`]
 155         /// after this.
 156         ///
 157         /// [`processing_queue_high`]: crate::ln::msgs::RoutingMessageHandler::processing_queue_high
 158         /// [`PeerManager::process_events`]: crate::ln::peer_handler::PeerManager::process_events
 159         pub fn resolve_without_forwarding<L: Deref>(&self,
 160                 graph: &NetworkGraph<L>, result: Result<TxOut, UtxoLookupError>)
 161         where L::Target: Logger {
 162                 self.do_resolve(graph, result);
 163         }
 164
 165         /// Resolves this future against the given `graph` and with the given `result`.
 166         ///
 167         /// The given `gossip` is used to broadcast any validated messages onwards to all peers which
 168         /// have available buffer space.
 169         ///
 170         /// Because this may cause the [`NetworkGraph`]'s [`processing_queue_high`] to flip, in order
 171         /// to allow us to interact with peers again, you should call [`PeerManager::process_events`]
 172         /// after this.
 173         ///
 174         /// [`processing_queue_high`]: crate::ln::msgs::RoutingMessageHandler::processing_queue_high
 175         /// [`PeerManager::process_events`]: crate::ln::peer_handler::PeerManager::process_events
 176         pub fn resolve<L: Deref, G: Deref<Target=NetworkGraph<L>>, U: Deref, GS: Deref<Target = P2PGossipSync<G, U, L>>>(&self,
 177                 graph: &NetworkGraph<L>, gossip: GS, result: Result<TxOut, UtxoLookupError>
 178         ) where L::Target: Logger, U::Target: UtxoLookup {
 179                 let mut res = self.do_resolve(graph, result);
 180                 for msg_opt in res.iter_mut() {
 181                         if let Some(msg) = msg_opt.take() {
 182                                 gossip.forward_gossip_msg(msg);
 183                         }
 184                 }
 185         }
 186
 187         fn do_resolve<L: Deref>(&self, graph: &NetworkGraph<L>, result: Result<TxOut, UtxoLookupError>)
 188         -> [Option<MessageSendEvent>; 5] where L::Target: Logger {
 189                 let (announcement, node_a, node_b, update_a, update_b) = {
 190                         let mut pending_checks = graph.pending_checks.internal.lock().unwrap();
 191                         let mut async_messages = self.state.lock().unwrap();
 192
 193                         if async_messages.channel_announce.is_none() {
 194                                 // We raced returning to `check_channel_announcement` which hasn't updated
 195                                 // `channel_announce` yet. That's okay, we can set the `complete` field which it will
 196                                 // check once it gets control again.
 197                                 async_messages.complete = Some(result);
 198                                 return [None, None, None, None, None];
 199                         }
 200
 201                         let announcement_msg = match async_messages.channel_announce.as_ref().unwrap() {
 202                                 ChannelAnnouncement::Full(signed_msg) => &signed_msg.contents,
 203                                 ChannelAnnouncement::Unsigned(msg) => &msg,
 204                         };
 205
 206                         pending_checks.lookup_completed(announcement_msg, &Arc::downgrade(&self.state));
 207
 208                         (async_messages.channel_announce.take().unwrap(),
 209                                 async_messages.latest_node_announce_a.take(),
 210                                 async_messages.latest_node_announce_b.take(),
 211                                 async_messages.latest_channel_update_a.take(),
 212                                 async_messages.latest_channel_update_b.take())
 213                 };
 214
 215                 let mut res = [None, None, None, None, None];
 216                 let mut res_idx = 0;
 217
 218                 // Now that we've updated our internal state, pass the pending messages back through the
 219                 // network graph with a different `UtxoLookup` which will resolve immediately.
 220                 // Note that we ignore errors as we don't disconnect peers anyway, so there's nothing to do
 221                 // with them.
 222                 let resolver = UtxoResolver(result);
 223                 match announcement {
 224                         ChannelAnnouncement::Full(signed_msg) => {
 225                                 if graph.update_channel_from_announcement(&signed_msg, &Some(&resolver)).is_ok() {
 226                                         res[res_idx] = Some(MessageSendEvent::BroadcastChannelAnnouncement {
 227                                                 msg: signed_msg, update_msg: None,
 228                                         });
 229                                         res_idx += 1;
 230                                 }
 231                         },
 232                         ChannelAnnouncement::Unsigned(msg) => {
 233                                 let _ = graph.update_channel_from_unsigned_announcement(&msg, &Some(&resolver));
 234                         },
 235                 }
 236
 237                 for announce in core::iter::once(node_a).chain(core::iter::once(node_b)) {
 238                         match announce {
 239                                 Some(NodeAnnouncement::Full(signed_msg)) => {
 240                                         if graph.update_node_from_announcement(&signed_msg).is_ok() {
 241                                                 res[res_idx] = Some(MessageSendEvent::BroadcastNodeAnnouncement {
 242                                                         msg: signed_msg,
 243                                                 });
 244                                                 res_idx += 1;
 245                                         }
 246                                 },
 247                                 Some(NodeAnnouncement::Unsigned(msg)) => {
 248                                         let _ = graph.update_node_from_unsigned_announcement(&msg);
 249                                 },
 250                                 None => {},
 251                         }
 252                 }
 253
 254                 for update in core::iter::once(update_a).chain(core::iter::once(update_b)) {
 255                         match update {
 256                                 Some(ChannelUpdate::Full(signed_msg)) => {
 257                                         if graph.update_channel(&signed_msg).is_ok() {
 258                                                 res[res_idx] = Some(MessageSendEvent::BroadcastChannelUpdate {
 259                                                         msg: signed_msg,
 260                                                 });
 261                                                 res_idx += 1;
 262                                         }
 263                                 },
 264                                 Some(ChannelUpdate::Unsigned(msg)) => {
 265                                         let _ = graph.update_channel_unsigned(&msg);
 266                                 },
 267                                 None => {},
 268                         }
 269                 }
 270
 271                 res
 272         }
 273 }
 274
 275 struct PendingChecksContext {
 276         channels: HashMap<u64, Weak<Mutex<UtxoMessages>>>,
 277         nodes: HashMap<NodeId, Vec<Weak<Mutex<UtxoMessages>>>>,
 278 }
 279
 280 impl PendingChecksContext {
 281         fn lookup_completed(&mut self,
 282                 msg: &msgs::UnsignedChannelAnnouncement, completed_state: &Weak<Mutex<UtxoMessages>>
 283         ) {
 284                 if let hash_map::Entry::Occupied(e) = self.channels.entry(msg.short_channel_id) {
 285                         if Weak::ptr_eq(e.get(), &completed_state) {
 286                                 e.remove();
 287                         }
 288                 }
 289
 290                 if let hash_map::Entry::Occupied(mut e) = self.nodes.entry(msg.node_id_1) {
 291                         e.get_mut().retain(|elem| !Weak::ptr_eq(&elem, &completed_state));
 292                         if e.get().is_empty() { e.remove(); }
 293                 }
 294                 if let hash_map::Entry::Occupied(mut e) = self.nodes.entry(msg.node_id_2) {
 295                         e.get_mut().retain(|elem| !Weak::ptr_eq(&elem, &completed_state));
 296                         if e.get().is_empty() { e.remove(); }
 297                 }
 298         }
 299 }
 300
 301 /// A set of messages which are pending UTXO lookups for processing.
 302 pub(super) struct PendingChecks {
 303         internal: Mutex<PendingChecksContext>,
 304 }
 305
 306 impl PendingChecks {
 307         pub(super) fn new() -> Self {
 308                 PendingChecks { internal: Mutex::new(PendingChecksContext {
 309                         channels: HashMap::new(), nodes: HashMap::new(),
 310                 }) }
 311         }
 312
 313         /// Checks if there is a pending `channel_update` UTXO validation for the given channel,
 314         /// and, if so, stores the channel message for handling later and returns an `Err`.
 315         pub(super) fn check_hold_pending_channel_update(
 316                 &self, msg: &msgs::UnsignedChannelUpdate, full_msg: Option<&msgs::ChannelUpdate>
 317         ) -> Result<(), LightningError> {
 318                 let mut pending_checks = self.internal.lock().unwrap();
 319                 if let hash_map::Entry::Occupied(e) = pending_checks.channels.entry(msg.short_channel_id) {
 320                         let is_from_a = (msg.flags & 1) == 1;
 321                         match Weak::upgrade(e.get()) {
 322                                 Some(msgs_ref) => {
 323                                         let mut messages = msgs_ref.lock().unwrap();
 324                                         let latest_update = if is_from_a {
 325                                                         &mut messages.latest_channel_update_a
 326                                                 } else {
 327                                                         &mut messages.latest_channel_update_b
 328                                                 };
 329                                         if latest_update.is_none() || latest_update.as_ref().unwrap().timestamp() < msg.timestamp {
 330                                                 // If the messages we got has a higher timestamp, just blindly assume the
 331                                                 // signatures on the new message are correct and drop the old message. This
 332                                                 // may cause us to end up dropping valid `channel_update`s if a peer is
 333                                                 // malicious, but we should get the correct ones when the node updates them.
 334                                                 *latest_update = Some(
 335                                                         if let Some(msg) = full_msg { ChannelUpdate::Full(msg.clone()) }
 336                                                         else { ChannelUpdate::Unsigned(msg.clone()) });
 337                                         }
 338                                         return Err(LightningError {
 339                                                 err: "Awaiting channel_announcement validation to accept channel_update".to_owned(),
 340                                                 action: ErrorAction::IgnoreAndLog(Level::Gossip),
 341                                         });
 342                                 },
 343                                 None => { e.remove(); },
 344                         }
 345                 }
 346                 Ok(())
 347         }
 348
 349         /// Checks if there is a pending `node_announcement` UTXO validation for a channel with the
 350         /// given node and, if so, stores the channel message for handling later and returns an `Err`.
 351         pub(super) fn check_hold_pending_node_announcement(
 352                 &self, msg: &msgs::UnsignedNodeAnnouncement, full_msg: Option<&msgs::NodeAnnouncement>
 353         ) -> Result<(), LightningError> {
 354                 let mut pending_checks = self.internal.lock().unwrap();
 355                 if let hash_map::Entry::Occupied(mut e) = pending_checks.nodes.entry(msg.node_id) {
 356                         let mut found_at_least_one_chan = false;
 357                         e.get_mut().retain(|node_msgs| {
 358                                 match Weak::upgrade(&node_msgs) {
 359                                         Some(chan_mtx) => {
 360                                                 let mut chan_msgs = chan_mtx.lock().unwrap();
 361                                                 if let Some(chan_announce) = &chan_msgs.channel_announce {
 362                                                         let latest_announce =
 363                                                                 if *chan_announce.node_id_1() == msg.node_id {
 364                                                                         &mut chan_msgs.latest_node_announce_a
 365                                                                 } else {
 366                                                                         &mut chan_msgs.latest_node_announce_b
 367                                                                 };
 368                                                         if latest_announce.is_none() ||
 369                                                                 latest_announce.as_ref().unwrap().timestamp() < msg.timestamp
 370                                                         {
 371                                                                 *latest_announce = Some(
 372                                                                         if let Some(msg) = full_msg { NodeAnnouncement::Full(msg.clone()) }
 373                                                                         else { NodeAnnouncement::Unsigned(msg.clone()) });
 374                                                         }
 375                                                         found_at_least_one_chan = true;
 376                                                         true
 377                                                 } else {
 378                                                         debug_assert!(false, "channel_announce is set before struct is added to node map");
 379                                                         false
 380                                                 }
 381                                         },
 382                                         None => false,
 383                                 }
 384                         });
 385                         if e.get().is_empty() { e.remove(); }
 386                         if found_at_least_one_chan {
 387                                 return Err(LightningError {
 388                                         err: "Awaiting channel_announcement validation to accept node_announcement".to_owned(),
 389                                         action: ErrorAction::IgnoreAndLog(Level::Gossip),
 390                                 });
 391                         }
 392                 }
 393                 Ok(())
 394         }
 395
 396         fn check_replace_previous_entry(msg: &msgs::UnsignedChannelAnnouncement,
 397                 full_msg: Option<&msgs::ChannelAnnouncement>, replacement: Option<Weak<Mutex<UtxoMessages>>>,
 398                 pending_channels: &mut HashMap<u64, Weak<Mutex<UtxoMessages>>>
 399         ) -> Result<(), msgs::LightningError> {
 400                 match pending_channels.entry(msg.short_channel_id) {
 401                         hash_map::Entry::Occupied(mut e) => {
 402                                 // There's already a pending lookup for the given SCID. Check if the messages
 403                                 // are the same and, if so, return immediately (don't bother spawning another
 404                                 // lookup if we haven't gotten that far yet).
 405                                 match Weak::upgrade(&e.get()) {
 406                                         Some(pending_msgs) => {
 407                                                 let pending_matches = match &pending_msgs.lock().unwrap().channel_announce {
 408                                                         Some(ChannelAnnouncement::Full(pending_msg)) => Some(pending_msg) == full_msg,
 409                                                         Some(ChannelAnnouncement::Unsigned(pending_msg)) => pending_msg == msg,
 410                                                         None => {
 411                                                                 // This shouldn't actually be reachable. We set the
 412                                                                 // `channel_announce` field under the same lock as setting the
 413                                                                 // channel map entry. Still, we can just treat it as
 414                                                                 // non-matching and let the new request fly.
 415                                                                 debug_assert!(false);
 416                                                                 false
 417                                                         },
 418                                                 };
 419                                                 if pending_matches {
 420                                                         return Err(LightningError {
 421                                                                 err: "Channel announcement is already being checked".to_owned(),
 422                                                                 action: ErrorAction::IgnoreDuplicateGossip,
 423                                                         });
 424                                                 } else {
 425                                                         // The earlier lookup is a different message. If we have another
 426                                                         // request in-flight now replace the original.
 427                                                         // Note that in the replace case whether to replace is somewhat
 428                                                         // arbitrary - both results will be handled, we're just updating the
 429                                                         // value that will be compared to future lookups with the same SCID.
 430                                                         if let Some(item) = replacement {
 431                                                                 *e.get_mut() = item;
 432                                                         }
 433                                                 }
 434                                         },
 435                                         None => {
 436                                                 // The earlier lookup already resolved. We can't be sure its the same
 437                                                 // so just remove/replace it and move on.
 438                                                 if let Some(item) = replacement {
 439                                                         *e.get_mut() = item;
 440                                                 } else { e.remove(); }
 441                                         },
 442                                 }
 443                         },
 444                         hash_map::Entry::Vacant(v) => {
 445                                 if let Some(item) = replacement { v.insert(item); }
 446                         },
 447                 }
 448                 Ok(())
 449         }
 450
 451         pub(super) fn check_channel_announcement<U: Deref>(&self,
 452                 utxo_lookup: &Option<U>, msg: &msgs::UnsignedChannelAnnouncement,
 453                 full_msg: Option<&msgs::ChannelAnnouncement>
 454         ) -> Result<Option<u64>, msgs::LightningError> where U::Target: UtxoLookup {
 455                 let handle_result = |res| {
 456                         match res {
 457                                 Ok(TxOut { value, script_pubkey }) => {
 458                                         let expected_script =
 459                                                 make_funding_redeemscript_from_slices(msg.bitcoin_key_1.as_slice(), msg.bitcoin_key_2.as_slice()).to_v0_p2wsh();
 460                                         if script_pubkey != expected_script {
 461                                                 return Err(LightningError{
 462                                                         err: format!("Channel announcement key ({}) didn't match on-chain script ({})",
 463                                                                 expected_script.to_hex(), script_pubkey.to_hex()),
 464                                                         action: ErrorAction::IgnoreError
 465                                                 });
 466                                         }
 467                                         Ok(Some(value))
 468                                 },
 469                                 Err(UtxoLookupError::UnknownChain) => {
 470                                         Err(LightningError {
 471                                                 err: format!("Channel announced on an unknown chain ({})",
 472                                                         msg.chain_hash.encode().to_hex()),
 473                                                 action: ErrorAction::IgnoreError
 474                                         })
 475                                 },
 476                                 Err(UtxoLookupError::UnknownTx) => {
 477                                         Err(LightningError {
 478                                                 err: "Channel announced without corresponding UTXO entry".to_owned(),
 479                                                 action: ErrorAction::IgnoreError
 480                                         })
 481                                 },
 482                         }
 483                 };
 484
 485                 Self::check_replace_previous_entry(msg, full_msg, None,
 486                         &mut self.internal.lock().unwrap().channels)?;
 487
 488                 match utxo_lookup {
 489                         &None => {
 490                                 // Tentatively accept, potentially exposing us to DoS attacks
 491                                 Ok(None)
 492                         },
 493                         &Some(ref utxo_lookup) => {
 494                                 match utxo_lookup.get_utxo(&msg.chain_hash, msg.short_channel_id) {
 495                                         UtxoResult::Sync(res) => handle_result(res),
 496                                         UtxoResult::Async(future) => {
 497                                                 let mut pending_checks = self.internal.lock().unwrap();
 498                                                 let mut async_messages = future.state.lock().unwrap();
 499                                                 if let Some(res) = async_messages.complete.take() {
 500                                                         // In the unlikely event the future resolved before we managed to get it,
 501                                                         // handle the result in-line.
 502                                                         handle_result(res)
 503                                                 } else {
 504                                                         Self::check_replace_previous_entry(msg, full_msg,
 505                                                                 Some(Arc::downgrade(&future.state)), &mut pending_checks.channels)?;
 506                                                         async_messages.channel_announce = Some(
 507                                                                 if let Some(msg) = full_msg { ChannelAnnouncement::Full(msg.clone()) }
 508                                                                 else { ChannelAnnouncement::Unsigned(msg.clone()) });
 509                                                         pending_checks.nodes.entry(msg.node_id_1)
 510                                                                 .or_insert(Vec::new()).push(Arc::downgrade(&future.state));
 511                                                         pending_checks.nodes.entry(msg.node_id_2)
 512                                                                 .or_insert(Vec::new()).push(Arc::downgrade(&future.state));
 513                                                         Err(LightningError {
 514                                                                 err: "Channel being checked async".to_owned(),
 515                                                                 action: ErrorAction::IgnoreAndLog(Level::Gossip),
 516                                                         })
 517                                                 }
 518                                         },
 519                                 }
 520                         }
 521                 }
 522         }
 523
 524         /// The maximum number of pending gossip checks before [`Self::too_many_checks_pending`]
 525         /// returns `true`. Note that this isn't a strict upper-bound on the number of checks pending -
 526         /// each peer may, at a minimum, read one more socket buffer worth of `channel_announcement`s
 527         /// which we'll have to process. With a socket buffer of 4KB and a minimum
 528         /// `channel_announcement` size of, roughly, 429 bytes, this may leave us with `10*our peer
 529         /// count` messages to process beyond this limit. Because we'll probably have a few peers,
 530         /// there's no reason for this constant to be materially less than 30 or so, and 32 in-flight
 531         /// checks should be more than enough for decent parallelism.
 532         const MAX_PENDING_LOOKUPS: usize = 32;
 533
 534         /// Returns true if there are a large number of async checks pending and future
 535         /// `channel_announcement` messages should be delayed. Note that this is only a hint and
 536         /// messages already in-flight may still have to be handled for various reasons.
 537         pub(super) fn too_many_checks_pending(&self) -> bool {
 538                 let mut pending_checks = self.internal.lock().unwrap();
 539                 if pending_checks.channels.len() > Self::MAX_PENDING_LOOKUPS {
 540                         // If we have many channel checks pending, ensure we don't have any dangling checks
 541                         // (i.e. checks where the user told us they'd call back but drop'd the `UtxoFuture`
 542                         // instead) before we commit to applying backpressure.
 543                         pending_checks.channels.retain(|_, chan| {
 544                                 Weak::upgrade(&chan).is_some()
 545                         });
 546                         pending_checks.nodes.retain(|_, channels| {
 547                                 channels.retain(|chan| Weak::upgrade(&chan).is_some());
 548                                 !channels.is_empty()
 549                         });
 550                         pending_checks.channels.len() > Self::MAX_PENDING_LOOKUPS
 551                 } else {
 552                         false
 553                 }
 554         }
 555 }
 556
 557 #[cfg(test)]
 558 mod tests {
 559         use super::*;
 560         use crate::routing::gossip::tests::*;
 561         use crate::util::test_utils::{TestChainSource, TestLogger};
 562         use crate::ln::msgs;
 563
 564         use bitcoin::blockdata::constants::genesis_block;
 565         use bitcoin::secp256k1::{Secp256k1, SecretKey};
 566
 567         use core::sync::atomic::Ordering;
 568
 569         fn get_network() -> (TestChainSource, NetworkGraph<Box<TestLogger>>) {
 570                 let logger = Box::new(TestLogger::new());
 571                 let genesis_hash = genesis_block(bitcoin::Network::Testnet).header.block_hash();
 572                 let chain_source = TestChainSource::new(bitcoin::Network::Testnet);
 573                 let network_graph = NetworkGraph::new(genesis_hash, logger);
 574
 575                 (chain_source, network_graph)
 576         }
 577
 578         fn get_test_objects() -> (msgs::ChannelAnnouncement, TestChainSource,
 579                 NetworkGraph<Box<TestLogger>>, bitcoin::Script, msgs::NodeAnnouncement,
 580                 msgs::NodeAnnouncement, msgs::ChannelUpdate, msgs::ChannelUpdate, msgs::ChannelUpdate)
 581         {
 582                 let secp_ctx = Secp256k1::new();
 583
 584                 let (chain_source, network_graph) = get_network();
 585
 586                 let good_script = get_channel_script(&secp_ctx);
 587                 let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
 588                 let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
 589                 let valid_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
 590
 591                 let node_a_announce = get_signed_node_announcement(|_| {}, node_1_privkey, &secp_ctx);
 592                 let node_b_announce = get_signed_node_announcement(|_| {}, node_2_privkey, &secp_ctx);
 593
 594                 // Note that we have to set the "direction" flag correctly on both messages
 595                 let chan_update_a = get_signed_channel_update(|msg| msg.flags = 0, node_1_privkey, &secp_ctx);
 596                 let chan_update_b = get_signed_channel_update(|msg| msg.flags = 1, node_2_privkey, &secp_ctx);
 597                 let chan_update_c = get_signed_channel_update(|msg| {
 598                         msg.flags = 1; msg.timestamp += 1; }, node_2_privkey, &secp_ctx);
 599
 600                 (valid_announcement, chain_source, network_graph, good_script, node_a_announce,
 601                         node_b_announce, chan_update_a, chan_update_b, chan_update_c)
 602         }
 603
 604         #[test]
 605         fn test_fast_async_lookup() {
 606                 // Check that async lookups which resolve quicker than the future is returned to the
 607                 // `get_utxo` call can read it still resolve properly.
 608                 let (valid_announcement, chain_source, network_graph, good_script, ..) = get_test_objects();
 609
 610                 let future = UtxoFuture::new();
 611                 future.resolve_without_forwarding(&network_graph,
 612                         Ok(TxOut { value: 1_000_000, script_pubkey: good_script }));
 613                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 614
 615                 network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap();
 616                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_some());
 617         }
 618
 619         #[test]
 620         fn test_async_lookup() {
 621                 // Test a simple async lookup
 622                 let (valid_announcement, chain_source, network_graph, good_script,
 623                         node_a_announce, node_b_announce, ..) = get_test_objects();
 624
 625                 let future = UtxoFuture::new();
 626                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 627
 628                 assert_eq!(
 629                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 630                         "Channel being checked async");
 631                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 632
 633                 future.resolve_without_forwarding(&network_graph,
 634                         Ok(TxOut { value: 0, script_pubkey: good_script }));
 635                 network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).unwrap();
 636                 network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).unwrap();
 637
 638                 assert!(network_graph.read_only().nodes().get(&valid_announcement.contents.node_id_1)
 639                         .unwrap().announcement_info.is_none());
 640
 641                 network_graph.update_node_from_announcement(&node_a_announce).unwrap();
 642                 network_graph.update_node_from_announcement(&node_b_announce).unwrap();
 643
 644                 assert!(network_graph.read_only().nodes().get(&valid_announcement.contents.node_id_1)
 645                         .unwrap().announcement_info.is_some());
 646         }
 647
 648         #[test]
 649         fn test_invalid_async_lookup() {
 650                 // Test an async lookup which returns an incorrect script
 651                 let (valid_announcement, chain_source, network_graph, ..) = get_test_objects();
 652
 653                 let future = UtxoFuture::new();
 654                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 655
 656                 assert_eq!(
 657                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 658                         "Channel being checked async");
 659                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 660
 661                 future.resolve_without_forwarding(&network_graph,
 662                         Ok(TxOut { value: 1_000_000, script_pubkey: bitcoin::Script::new() }));
 663                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 664         }
 665
 666         #[test]
 667         fn test_failing_async_lookup() {
 668                 // Test an async lookup which returns an error
 669                 let (valid_announcement, chain_source, network_graph, ..) = get_test_objects();
 670
 671                 let future = UtxoFuture::new();
 672                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 673
 674                 assert_eq!(
 675                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 676                         "Channel being checked async");
 677                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 678
 679                 future.resolve_without_forwarding(&network_graph, Err(UtxoLookupError::UnknownTx));
 680                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 681         }
 682
 683         #[test]
 684         fn test_updates_async_lookup() {
 685                 // Test async lookups will process pending channel_update/node_announcements once they
 686                 // complete.
 687                 let (valid_announcement, chain_source, network_graph, good_script, node_a_announce,
 688                         node_b_announce, chan_update_a, chan_update_b, ..) = get_test_objects();
 689
 690                 let future = UtxoFuture::new();
 691                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 692
 693                 assert_eq!(
 694                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 695                         "Channel being checked async");
 696                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 697
 698                 assert_eq!(
 699                         network_graph.update_node_from_announcement(&node_a_announce).unwrap_err().err,
 700                         "Awaiting channel_announcement validation to accept node_announcement");
 701                 assert_eq!(
 702                         network_graph.update_node_from_announcement(&node_b_announce).unwrap_err().err,
 703                         "Awaiting channel_announcement validation to accept node_announcement");
 704
 705                 assert_eq!(network_graph.update_channel(&chan_update_a).unwrap_err().err,
 706                         "Awaiting channel_announcement validation to accept channel_update");
 707                 assert_eq!(network_graph.update_channel(&chan_update_b).unwrap_err().err,
 708                         "Awaiting channel_announcement validation to accept channel_update");
 709
 710                 future.resolve_without_forwarding(&network_graph,
 711                         Ok(TxOut { value: 1_000_000, script_pubkey: good_script }));
 712
 713                 assert!(network_graph.read_only().channels()
 714                         .get(&valid_announcement.contents.short_channel_id).unwrap().one_to_two.is_some());
 715                 assert!(network_graph.read_only().channels()
 716                         .get(&valid_announcement.contents.short_channel_id).unwrap().two_to_one.is_some());
 717
 718                 assert!(network_graph.read_only().nodes().get(&valid_announcement.contents.node_id_1)
 719                         .unwrap().announcement_info.is_some());
 720                 assert!(network_graph.read_only().nodes().get(&valid_announcement.contents.node_id_2)
 721                         .unwrap().announcement_info.is_some());
 722         }
 723
 724         #[test]
 725         fn test_latest_update_async_lookup() {
 726                 // Test async lookups will process the latest channel_update if two are received while
 727                 // awaiting an async UTXO lookup.
 728                 let (valid_announcement, chain_source, network_graph, good_script, _,
 729                         _, chan_update_a, chan_update_b, chan_update_c, ..) = get_test_objects();
 730
 731                 let future = UtxoFuture::new();
 732                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 733
 734                 assert_eq!(
 735                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 736                         "Channel being checked async");
 737                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 738
 739                 assert_eq!(network_graph.update_channel(&chan_update_a).unwrap_err().err,
 740                         "Awaiting channel_announcement validation to accept channel_update");
 741                 assert_eq!(network_graph.update_channel(&chan_update_b).unwrap_err().err,
 742                         "Awaiting channel_announcement validation to accept channel_update");
 743                 assert_eq!(network_graph.update_channel(&chan_update_c).unwrap_err().err,
 744                         "Awaiting channel_announcement validation to accept channel_update");
 745
 746                 future.resolve_without_forwarding(&network_graph,
 747                         Ok(TxOut { value: 1_000_000, script_pubkey: good_script }));
 748
 749                 assert_eq!(chan_update_a.contents.timestamp, chan_update_b.contents.timestamp);
 750                 assert!(network_graph.read_only().channels()
 751                                 .get(&valid_announcement.contents.short_channel_id).as_ref().unwrap()
 752                                 .one_to_two.as_ref().unwrap().last_update !=
 753                         network_graph.read_only().channels()
 754                                 .get(&valid_announcement.contents.short_channel_id).as_ref().unwrap()
 755                                 .two_to_one.as_ref().unwrap().last_update);
 756         }
 757
 758         #[test]
 759         fn test_no_double_lookups() {
 760                 // Test that a pending async lookup will prevent a second async lookup from flying, but
 761                 // only if the channel_announcement message is identical.
 762                 let (valid_announcement, chain_source, network_graph, good_script, ..) = get_test_objects();
 763
 764                 let future = UtxoFuture::new();
 765                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 766
 767                 assert_eq!(
 768                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 769                         "Channel being checked async");
 770                 assert_eq!(chain_source.get_utxo_call_count.load(Ordering::Relaxed), 1);
 771
 772                 // If we make a second request with the same message, the call count doesn't increase...
 773                 let future_b = UtxoFuture::new();
 774                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future_b.clone());
 775                 assert_eq!(
 776                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 777                         "Channel announcement is already being checked");
 778                 assert_eq!(chain_source.get_utxo_call_count.load(Ordering::Relaxed), 1);
 779
 780                 // But if we make a third request with a tweaked message, we should get a second call
 781                 // against our new future...
 782                 let secp_ctx = Secp256k1::new();
 783                 let replacement_pk_1 = &SecretKey::from_slice(&[99; 32]).unwrap();
 784                 let replacement_pk_2 = &SecretKey::from_slice(&[98; 32]).unwrap();
 785                 let invalid_announcement = get_signed_channel_announcement(|_| {}, replacement_pk_1, replacement_pk_2, &secp_ctx);
 786                 assert_eq!(
 787                         network_graph.update_channel_from_announcement(&invalid_announcement, &Some(&chain_source)).unwrap_err().err,
 788                         "Channel being checked async");
 789                 assert_eq!(chain_source.get_utxo_call_count.load(Ordering::Relaxed), 2);
 790
 791                 // Still, if we resolve the original future, the original channel will be accepted.
 792                 future.resolve_without_forwarding(&network_graph,
 793                         Ok(TxOut { value: 1_000_000, script_pubkey: good_script }));
 794                 assert!(!network_graph.read_only().channels()
 795                         .get(&valid_announcement.contents.short_channel_id).unwrap()
 796                         .announcement_message.as_ref().unwrap()
 797                         .contents.features.supports_unknown_test_feature());
 798         }
 799
 800         #[test]
 801         fn test_checks_backpressure() {
 802                 // Test that too_many_checks_pending returns true when there are many checks pending, and
 803                 // returns false once they complete.
 804                 let secp_ctx = Secp256k1::new();
 805                 let (chain_source, network_graph) = get_network();
 806
 807                 // We cheat and use a single future for all the lookups to complete them all at once.
 808                 let future = UtxoFuture::new();
 809                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 810
 811                 let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
 812                 let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
 813
 814                 for i in 0..PendingChecks::MAX_PENDING_LOOKUPS {
 815                         let valid_announcement = get_signed_channel_announcement(
 816                                 |msg| msg.short_channel_id += 1 + i as u64, node_1_privkey, node_2_privkey, &secp_ctx);
 817                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err();
 818                         assert!(!network_graph.pending_checks.too_many_checks_pending());
 819                 }
 820
 821                 let valid_announcement = get_signed_channel_announcement(
 822                         |_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
 823                 network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err();
 824                 assert!(network_graph.pending_checks.too_many_checks_pending());
 825
 826                 // Once the future completes the "too many checks" flag should reset.
 827                 future.resolve_without_forwarding(&network_graph, Err(UtxoLookupError::UnknownTx));
 828                 assert!(!network_graph.pending_checks.too_many_checks_pending());
 829         }
 830
 831         #[test]
 832         fn test_checks_backpressure_drop() {
 833                 // Test that too_many_checks_pending returns true when there are many checks pending, and
 834                 // returns false if we drop some of the futures without completion.
 835                 let secp_ctx = Secp256k1::new();
 836                 let (chain_source, network_graph) = get_network();
 837
 838                 // We cheat and use a single future for all the lookups to complete them all at once.
 839                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(UtxoFuture::new());
 840
 841                 let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
 842                 let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
 843
 844                 for i in 0..PendingChecks::MAX_PENDING_LOOKUPS {
 845                         let valid_announcement = get_signed_channel_announcement(
 846                                 |msg| msg.short_channel_id += 1 + i as u64, node_1_privkey, node_2_privkey, &secp_ctx);
 847                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err();
 848                         assert!(!network_graph.pending_checks.too_many_checks_pending());
 849                 }
 850
 851                 let valid_announcement = get_signed_channel_announcement(
 852                         |_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
 853                 network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err();
 854                 assert!(network_graph.pending_checks.too_many_checks_pending());
 855
 856                 // Once the future is drop'd (by resetting the `utxo_ret` value) the "too many checks" flag
 857                 // should reset to false.
 858                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Sync(Err(UtxoLookupError::UnknownTx));
 859                 assert!(!network_graph.pending_checks.too_many_checks_pending());
 860         }
 861 }