_ 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::TxOut;
  17 use bitcoin::blockdata::constants::ChainHash;
  18
  19 use hex::DisplayHex;
  20
  21 use crate::events::MessageSendEvent;
  22 use crate::ln::chan_utils::make_funding_redeemscript_from_slices;
  23 use crate::ln::msgs::{self, LightningError, ErrorAction};
  24 use crate::routing::gossip::{NetworkGraph, NodeId, P2PGossipSync};
  25 use crate::util::logger::{Level, Logger};
  26
  27 use crate::prelude::*;
  28
  29 use alloc::sync::{Arc, Weak};
  30 use crate::sync::{Mutex, LockTestExt};
  31 use core::ops::Deref;
  32
  33 /// An error when accessing the chain via [`UtxoLookup`].
  34 #[derive(Clone, Debug)]
  35 pub enum UtxoLookupError {
  36         /// The requested chain is unknown.
  37         UnknownChain,
  38
  39         /// The requested transaction doesn't exist or hasn't confirmed.
  40         UnknownTx,
  41 }
  42
  43 /// The result of a [`UtxoLookup::get_utxo`] call. A call may resolve either synchronously,
  44 /// returning the `Sync` variant, or asynchronously, returning an [`UtxoFuture`] in the `Async`
  45 /// variant.
  46 #[derive(Clone)]
  47 pub enum UtxoResult {
  48         /// A result which was resolved synchronously. It either includes a [`TxOut`] for the output
  49         /// requested or a [`UtxoLookupError`].
  50         Sync(Result<TxOut, UtxoLookupError>),
  51         /// A result which will be resolved asynchronously. It includes a [`UtxoFuture`], a `clone` of
  52         /// which you must keep locally and call [`UtxoFuture::resolve`] on once the lookup completes.
  53         ///
  54         /// Note that in order to avoid runaway memory usage, the number of parallel checks is limited,
  55         /// but only fairly loosely. Because a pending checks block all message processing, leaving
  56         /// checks pending for an extended time may cause DoS of other functions. It is recommended you
  57         /// keep a tight timeout on lookups, on the order of a few seconds.
  58         Async(UtxoFuture),
  59 }
  60
  61 /// The `UtxoLookup` trait defines behavior for accessing on-chain UTXOs.
  62 pub trait UtxoLookup {
  63         /// Returns the transaction output of a funding transaction encoded by [`short_channel_id`].
  64         /// Returns an error if `chain_hash` is for a different chain or if such a transaction output is
  65         /// unknown.
  66         ///
  67         /// [`short_channel_id`]: https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#definition-of-short_channel_id
  68         fn get_utxo(&self, chain_hash: &ChainHash, short_channel_id: u64) -> UtxoResult;
  69 }
  70
  71 enum ChannelAnnouncement {
  72         Full(msgs::ChannelAnnouncement),
  73         Unsigned(msgs::UnsignedChannelAnnouncement),
  74 }
  75 impl ChannelAnnouncement {
  76         fn node_id_1(&self) -> &NodeId {
  77                 match self {
  78                         ChannelAnnouncement::Full(msg) => &msg.contents.node_id_1,
  79                         ChannelAnnouncement::Unsigned(msg) => &msg.node_id_1,
  80                 }
  81         }
  82 }
  83
  84 enum NodeAnnouncement {
  85         Full(msgs::NodeAnnouncement),
  86         Unsigned(msgs::UnsignedNodeAnnouncement),
  87 }
  88 impl NodeAnnouncement {
  89         fn timestamp(&self) -> u32 {
  90                 match self {
  91                         NodeAnnouncement::Full(msg) => msg.contents.timestamp,
  92                         NodeAnnouncement::Unsigned(msg) => msg.timestamp,
  93                 }
  94         }
  95 }
  96
  97 enum ChannelUpdate {
  98         Full(msgs::ChannelUpdate),
  99         Unsigned(msgs::UnsignedChannelUpdate),
 100 }
 101 impl ChannelUpdate {
 102         fn timestamp(&self) -> u32 {
 103                 match self {
 104                         ChannelUpdate::Full(msg) => msg.contents.timestamp,
 105                         ChannelUpdate::Unsigned(msg) => msg.timestamp,
 106                 }
 107         }
 108 }
 109
 110 struct UtxoMessages {
 111         complete: Option<Result<TxOut, UtxoLookupError>>,
 112         channel_announce: Option<ChannelAnnouncement>,
 113         latest_node_announce_a: Option<NodeAnnouncement>,
 114         latest_node_announce_b: Option<NodeAnnouncement>,
 115         latest_channel_update_a: Option<ChannelUpdate>,
 116         latest_channel_update_b: Option<ChannelUpdate>,
 117 }
 118
 119 /// Represents a future resolution of a [`UtxoLookup::get_utxo`] query resolving async.
 120 ///
 121 /// See [`UtxoResult::Async`] and [`UtxoFuture::resolve`] for more info.
 122 #[derive(Clone)]
 123 pub struct UtxoFuture {
 124         state: Arc<Mutex<UtxoMessages>>,
 125 }
 126
 127 /// A trivial implementation of [`UtxoLookup`] which is used to call back into the network graph
 128 /// once we have a concrete resolution of a request.
 129 pub(crate) struct UtxoResolver(Result<TxOut, UtxoLookupError>);
 130 impl UtxoLookup for UtxoResolver {
 131         fn get_utxo(&self, _chain_hash: &ChainHash, _short_channel_id: u64) -> UtxoResult {
 132                 UtxoResult::Sync(self.0.clone())
 133         }
 134 }
 135
 136 impl UtxoFuture {
 137         /// Builds a new future for later resolution.
 138         pub fn new() -> Self {
 139                 Self { state: Arc::new(Mutex::new(UtxoMessages {
 140                         complete: None,
 141                         channel_announce: None,
 142                         latest_node_announce_a: None,
 143                         latest_node_announce_b: None,
 144                         latest_channel_update_a: None,
 145                         latest_channel_update_b: None,
 146                 }))}
 147         }
 148
 149         /// Resolves this future against the given `graph` and with the given `result`.
 150         ///
 151         /// This is identical to calling [`UtxoFuture::resolve`] with a dummy `gossip`, disabling
 152         /// forwarding the validated gossip message onwards to peers.
 153         ///
 154         /// Because this may cause the [`NetworkGraph`]'s [`processing_queue_high`] to flip, in order
 155         /// to allow us to interact with peers again, you should call [`PeerManager::process_events`]
 156         /// after this.
 157         ///
 158         /// [`processing_queue_high`]: crate::ln::msgs::RoutingMessageHandler::processing_queue_high
 159         /// [`PeerManager::process_events`]: crate::ln::peer_handler::PeerManager::process_events
 160         pub fn resolve_without_forwarding<L: Deref>(&self,
 161                 graph: &NetworkGraph<L>, result: Result<TxOut, UtxoLookupError>)
 162         where L::Target: Logger {
 163                 self.do_resolve(graph, result);
 164         }
 165
 166         /// Resolves this future against the given `graph` and with the given `result`.
 167         ///
 168         /// The given `gossip` is used to broadcast any validated messages onwards to all peers which
 169         /// have available buffer space.
 170         ///
 171         /// Because this may cause the [`NetworkGraph`]'s [`processing_queue_high`] to flip, in order
 172         /// to allow us to interact with peers again, you should call [`PeerManager::process_events`]
 173         /// after this.
 174         ///
 175         /// [`processing_queue_high`]: crate::ln::msgs::RoutingMessageHandler::processing_queue_high
 176         /// [`PeerManager::process_events`]: crate::ln::peer_handler::PeerManager::process_events
 177         pub fn resolve<L: Deref, G: Deref<Target=NetworkGraph<L>>, U: Deref, GS: Deref<Target = P2PGossipSync<G, U, L>>>(&self,
 178                 graph: &NetworkGraph<L>, gossip: GS, result: Result<TxOut, UtxoLookupError>
 179         ) where L::Target: Logger, U::Target: UtxoLookup {
 180                 let mut res = self.do_resolve(graph, result);
 181                 for msg_opt in res.iter_mut() {
 182                         if let Some(msg) = msg_opt.take() {
 183                                 gossip.forward_gossip_msg(msg);
 184                         }
 185                 }
 186         }
 187
 188         fn do_resolve<L: Deref>(&self, graph: &NetworkGraph<L>, result: Result<TxOut, UtxoLookupError>)
 189         -> [Option<MessageSendEvent>; 5] where L::Target: Logger {
 190                 let (announcement, node_a, node_b, update_a, update_b) = {
 191                         let mut pending_checks = graph.pending_checks.internal.lock().unwrap();
 192                         let mut async_messages = self.state.lock().unwrap();
 193
 194                         if async_messages.channel_announce.is_none() {
 195                                 // We raced returning to `check_channel_announcement` which hasn't updated
 196                                 // `channel_announce` yet. That's okay, we can set the `complete` field which it will
 197                                 // check once it gets control again.
 198                                 async_messages.complete = Some(result);
 199                                 return [None, None, None, None, None];
 200                         }
 201
 202                         let announcement_msg = match async_messages.channel_announce.as_ref().unwrap() {
 203                                 ChannelAnnouncement::Full(signed_msg) => &signed_msg.contents,
 204                                 ChannelAnnouncement::Unsigned(msg) => &msg,
 205                         };
 206
 207                         pending_checks.lookup_completed(announcement_msg, &Arc::downgrade(&self.state));
 208
 209                         (async_messages.channel_announce.take().unwrap(),
 210                                 async_messages.latest_node_announce_a.take(),
 211                                 async_messages.latest_node_announce_b.take(),
 212                                 async_messages.latest_channel_update_a.take(),
 213                                 async_messages.latest_channel_update_b.take())
 214                 };
 215
 216                 let mut res = [None, None, None, None, None];
 217                 let mut res_idx = 0;
 218
 219                 // Now that we've updated our internal state, pass the pending messages back through the
 220                 // network graph with a different `UtxoLookup` which will resolve immediately.
 221                 // Note that we ignore errors as we don't disconnect peers anyway, so there's nothing to do
 222                 // with them.
 223                 let resolver = UtxoResolver(result);
 224                 match announcement {
 225                         ChannelAnnouncement::Full(signed_msg) => {
 226                                 if graph.update_channel_from_announcement(&signed_msg, &Some(&resolver)).is_ok() {
 227                                         res[res_idx] = Some(MessageSendEvent::BroadcastChannelAnnouncement {
 228                                                 msg: signed_msg, update_msg: None,
 229                                         });
 230                                         res_idx += 1;
 231                                 }
 232                         },
 233                         ChannelAnnouncement::Unsigned(msg) => {
 234                                 let _ = graph.update_channel_from_unsigned_announcement(&msg, &Some(&resolver));
 235                         },
 236                 }
 237
 238                 for announce in core::iter::once(node_a).chain(core::iter::once(node_b)) {
 239                         match announce {
 240                                 Some(NodeAnnouncement::Full(signed_msg)) => {
 241                                         if graph.update_node_from_announcement(&signed_msg).is_ok() {
 242                                                 res[res_idx] = Some(MessageSendEvent::BroadcastNodeAnnouncement {
 243                                                         msg: signed_msg,
 244                                                 });
 245                                                 res_idx += 1;
 246                                         }
 247                                 },
 248                                 Some(NodeAnnouncement::Unsigned(msg)) => {
 249                                         let _ = graph.update_node_from_unsigned_announcement(&msg);
 250                                 },
 251                                 None => {},
 252                         }
 253                 }
 254
 255                 for update in core::iter::once(update_a).chain(core::iter::once(update_b)) {
 256                         match update {
 257                                 Some(ChannelUpdate::Full(signed_msg)) => {
 258                                         if graph.update_channel(&signed_msg).is_ok() {
 259                                                 res[res_idx] = Some(MessageSendEvent::BroadcastChannelUpdate {
 260                                                         msg: signed_msg,
 261                                                 });
 262                                                 res_idx += 1;
 263                                         }
 264                                 },
 265                                 Some(ChannelUpdate::Unsigned(msg)) => {
 266                                         let _ = graph.update_channel_unsigned(&msg);
 267                                 },
 268                                 None => {},
 269                         }
 270                 }
 271
 272                 res
 273         }
 274 }
 275
 276 struct PendingChecksContext {
 277         channels: HashMap<u64, Weak<Mutex<UtxoMessages>>>,
 278         nodes: HashMap<NodeId, Vec<Weak<Mutex<UtxoMessages>>>>,
 279 }
 280
 281 impl PendingChecksContext {
 282         fn lookup_completed(&mut self,
 283                 msg: &msgs::UnsignedChannelAnnouncement, completed_state: &Weak<Mutex<UtxoMessages>>
 284         ) {
 285                 if let hash_map::Entry::Occupied(e) = self.channels.entry(msg.short_channel_id) {
 286                         if Weak::ptr_eq(e.get(), &completed_state) {
 287                                 e.remove();
 288                         }
 289                 }
 290
 291                 if let hash_map::Entry::Occupied(mut e) = self.nodes.entry(msg.node_id_1) {
 292                         e.get_mut().retain(|elem| !Weak::ptr_eq(&elem, &completed_state));
 293                         if e.get().is_empty() { e.remove(); }
 294                 }
 295                 if let hash_map::Entry::Occupied(mut e) = self.nodes.entry(msg.node_id_2) {
 296                         e.get_mut().retain(|elem| !Weak::ptr_eq(&elem, &completed_state));
 297                         if e.get().is_empty() { e.remove(); }
 298                 }
 299         }
 300 }
 301
 302 /// A set of messages which are pending UTXO lookups for processing.
 303 pub(super) struct PendingChecks {
 304         internal: Mutex<PendingChecksContext>,
 305 }
 306
 307 impl PendingChecks {
 308         pub(super) fn new() -> Self {
 309                 PendingChecks { internal: Mutex::new(PendingChecksContext {
 310                         channels: new_hash_map(), nodes: new_hash_map(),
 311                 }) }
 312         }
 313
 314         /// Checks if there is a pending `channel_update` UTXO validation for the given channel,
 315         /// and, if so, stores the channel message for handling later and returns an `Err`.
 316         pub(super) fn check_hold_pending_channel_update(
 317                 &self, msg: &msgs::UnsignedChannelUpdate, full_msg: Option<&msgs::ChannelUpdate>
 318         ) -> Result<(), LightningError> {
 319                 let mut pending_checks = self.internal.lock().unwrap();
 320                 if let hash_map::Entry::Occupied(e) = pending_checks.channels.entry(msg.short_channel_id) {
 321                         let is_from_a = (msg.flags & 1) == 1;
 322                         match Weak::upgrade(e.get()) {
 323                                 Some(msgs_ref) => {
 324                                         let mut messages = msgs_ref.lock().unwrap();
 325                                         let latest_update = if is_from_a {
 326                                                         &mut messages.latest_channel_update_a
 327                                                 } else {
 328                                                         &mut messages.latest_channel_update_b
 329                                                 };
 330                                         if latest_update.is_none() || latest_update.as_ref().unwrap().timestamp() < msg.timestamp {
 331                                                 // If the messages we got has a higher timestamp, just blindly assume the
 332                                                 // signatures on the new message are correct and drop the old message. This
 333                                                 // may cause us to end up dropping valid `channel_update`s if a peer is
 334                                                 // malicious, but we should get the correct ones when the node updates them.
 335                                                 *latest_update = Some(
 336                                                         if let Some(msg) = full_msg { ChannelUpdate::Full(msg.clone()) }
 337                                                         else { ChannelUpdate::Unsigned(msg.clone()) });
 338                                         }
 339                                         return Err(LightningError {
 340                                                 err: "Awaiting channel_announcement validation to accept channel_update".to_owned(),
 341                                                 action: ErrorAction::IgnoreAndLog(Level::Gossip),
 342                                         });
 343                                 },
 344                                 None => { e.remove(); },
 345                         }
 346                 }
 347                 Ok(())
 348         }
 349
 350         /// Checks if there is a pending `node_announcement` UTXO validation for a channel with the
 351         /// given node and, if so, stores the channel message for handling later and returns an `Err`.
 352         pub(super) fn check_hold_pending_node_announcement(
 353                 &self, msg: &msgs::UnsignedNodeAnnouncement, full_msg: Option<&msgs::NodeAnnouncement>
 354         ) -> Result<(), LightningError> {
 355                 let mut pending_checks = self.internal.lock().unwrap();
 356                 if let hash_map::Entry::Occupied(mut e) = pending_checks.nodes.entry(msg.node_id) {
 357                         let mut found_at_least_one_chan = false;
 358                         e.get_mut().retain(|node_msgs| {
 359                                 match Weak::upgrade(&node_msgs) {
 360                                         Some(chan_mtx) => {
 361                                                 let mut chan_msgs = chan_mtx.lock().unwrap();
 362                                                 if let Some(chan_announce) = &chan_msgs.channel_announce {
 363                                                         let latest_announce =
 364                                                                 if *chan_announce.node_id_1() == msg.node_id {
 365                                                                         &mut chan_msgs.latest_node_announce_a
 366                                                                 } else {
 367                                                                         &mut chan_msgs.latest_node_announce_b
 368                                                                 };
 369                                                         if latest_announce.is_none() ||
 370                                                                 latest_announce.as_ref().unwrap().timestamp() < msg.timestamp
 371                                                         {
 372                                                                 *latest_announce = Some(
 373                                                                         if let Some(msg) = full_msg { NodeAnnouncement::Full(msg.clone()) }
 374                                                                         else { NodeAnnouncement::Unsigned(msg.clone()) });
 375                                                         }
 376                                                         found_at_least_one_chan = true;
 377                                                         true
 378                                                 } else {
 379                                                         debug_assert!(false, "channel_announce is set before struct is added to node map");
 380                                                         false
 381                                                 }
 382                                         },
 383                                         None => false,
 384                                 }
 385                         });
 386                         if e.get().is_empty() { e.remove(); }
 387                         if found_at_least_one_chan {
 388                                 return Err(LightningError {
 389                                         err: "Awaiting channel_announcement validation to accept node_announcement".to_owned(),
 390                                         action: ErrorAction::IgnoreAndLog(Level::Gossip),
 391                                 });
 392                         }
 393                 }
 394                 Ok(())
 395         }
 396
 397         fn check_replace_previous_entry(msg: &msgs::UnsignedChannelAnnouncement,
 398                 full_msg: Option<&msgs::ChannelAnnouncement>, replacement: Option<Weak<Mutex<UtxoMessages>>>,
 399                 pending_channels: &mut HashMap<u64, Weak<Mutex<UtxoMessages>>>
 400         ) -> Result<(), msgs::LightningError> {
 401                 match pending_channels.entry(msg.short_channel_id) {
 402                         hash_map::Entry::Occupied(mut e) => {
 403                                 // There's already a pending lookup for the given SCID. Check if the messages
 404                                 // are the same and, if so, return immediately (don't bother spawning another
 405                                 // lookup if we haven't gotten that far yet).
 406                                 match Weak::upgrade(&e.get()) {
 407                                         Some(pending_msgs) => {
 408                                                 // This may be called with the mutex held on a different UtxoMessages
 409                                                 // struct, however in that case we have a global lockorder of new messages
 410                                                 // -> old messages, which makes this safe.
 411                                                 let pending_matches = match &pending_msgs.unsafe_well_ordered_double_lock_self().channel_announce {
 412                                                         Some(ChannelAnnouncement::Full(pending_msg)) => Some(pending_msg) == full_msg,
 413                                                         Some(ChannelAnnouncement::Unsigned(pending_msg)) => pending_msg == msg,
 414                                                         None => {
 415                                                                 // This shouldn't actually be reachable. We set the
 416                                                                 // `channel_announce` field under the same lock as setting the
 417                                                                 // channel map entry. Still, we can just treat it as
 418                                                                 // non-matching and let the new request fly.
 419                                                                 debug_assert!(false);
 420                                                                 false
 421                                                         },
 422                                                 };
 423                                                 if pending_matches {
 424                                                         return Err(LightningError {
 425                                                                 err: "Channel announcement is already being checked".to_owned(),
 426                                                                 action: ErrorAction::IgnoreDuplicateGossip,
 427                                                         });
 428                                                 } else {
 429                                                         // The earlier lookup is a different message. If we have another
 430                                                         // request in-flight now replace the original.
 431                                                         // Note that in the replace case whether to replace is somewhat
 432                                                         // arbitrary - both results will be handled, we're just updating the
 433                                                         // value that will be compared to future lookups with the same SCID.
 434                                                         if let Some(item) = replacement {
 435                                                                 *e.get_mut() = item;
 436                                                         }
 437                                                 }
 438                                         },
 439                                         None => {
 440                                                 // The earlier lookup already resolved. We can't be sure its the same
 441                                                 // so just remove/replace it and move on.
 442                                                 if let Some(item) = replacement {
 443                                                         *e.get_mut() = item;
 444                                                 } else { e.remove(); }
 445                                         },
 446                                 }
 447                         },
 448                         hash_map::Entry::Vacant(v) => {
 449                                 if let Some(item) = replacement { v.insert(item); }
 450                         },
 451                 }
 452                 Ok(())
 453         }
 454
 455         pub(super) fn check_channel_announcement<U: Deref>(&self,
 456                 utxo_lookup: &Option<U>, msg: &msgs::UnsignedChannelAnnouncement,
 457                 full_msg: Option<&msgs::ChannelAnnouncement>
 458         ) -> Result<Option<u64>, msgs::LightningError> where U::Target: UtxoLookup {
 459                 let handle_result = |res| {
 460                         match res {
 461                                 Ok(TxOut { value, script_pubkey }) => {
 462                                         let expected_script =
 463                                                 make_funding_redeemscript_from_slices(msg.bitcoin_key_1.as_array(), msg.bitcoin_key_2.as_array()).to_v0_p2wsh();
 464                                         if script_pubkey != expected_script {
 465                                                 return Err(LightningError{
 466                                                         err: format!("Channel announcement key ({}) didn't match on-chain script ({})",
 467                                                                 expected_script.to_hex_string(), script_pubkey.to_hex_string()),
 468                                                         action: ErrorAction::IgnoreError
 469                                                 });
 470                                         }
 471                                         Ok(Some(value))
 472                                 },
 473                                 Err(UtxoLookupError::UnknownChain) => {
 474                                         Err(LightningError {
 475                                                 err: format!("Channel announced on an unknown chain ({})",
 476                                                         msg.chain_hash.to_bytes().as_hex()),
 477                                                 action: ErrorAction::IgnoreError
 478                                         })
 479                                 },
 480                                 Err(UtxoLookupError::UnknownTx) => {
 481                                         Err(LightningError {
 482                                                 err: "Channel announced without corresponding UTXO entry".to_owned(),
 483                                                 action: ErrorAction::IgnoreError
 484                                         })
 485                                 },
 486                         }
 487                 };
 488
 489                 Self::check_replace_previous_entry(msg, full_msg, None,
 490                         &mut self.internal.lock().unwrap().channels)?;
 491
 492                 match utxo_lookup {
 493                         &None => {
 494                                 // Tentatively accept, potentially exposing us to DoS attacks
 495                                 Ok(None)
 496                         },
 497                         &Some(ref utxo_lookup) => {
 498                                 match utxo_lookup.get_utxo(&msg.chain_hash, msg.short_channel_id) {
 499                                         UtxoResult::Sync(res) => handle_result(res),
 500                                         UtxoResult::Async(future) => {
 501                                                 let mut pending_checks = self.internal.lock().unwrap();
 502                                                 let mut async_messages = future.state.lock().unwrap();
 503                                                 if let Some(res) = async_messages.complete.take() {
 504                                                         // In the unlikely event the future resolved before we managed to get it,
 505                                                         // handle the result in-line.
 506                                                         handle_result(res)
 507                                                 } else {
 508                                                         Self::check_replace_previous_entry(msg, full_msg,
 509                                                                 Some(Arc::downgrade(&future.state)), &mut pending_checks.channels)?;
 510                                                         async_messages.channel_announce = Some(
 511                                                                 if let Some(msg) = full_msg { ChannelAnnouncement::Full(msg.clone()) }
 512                                                                 else { ChannelAnnouncement::Unsigned(msg.clone()) });
 513                                                         pending_checks.nodes.entry(msg.node_id_1)
 514                                                                 .or_insert(Vec::new()).push(Arc::downgrade(&future.state));
 515                                                         pending_checks.nodes.entry(msg.node_id_2)
 516                                                                 .or_insert(Vec::new()).push(Arc::downgrade(&future.state));
 517                                                         Err(LightningError {
 518                                                                 err: "Channel being checked async".to_owned(),
 519                                                                 action: ErrorAction::IgnoreAndLog(Level::Gossip),
 520                                                         })
 521                                                 }
 522                                         },
 523                                 }
 524                         }
 525                 }
 526         }
 527
 528         /// The maximum number of pending gossip checks before [`Self::too_many_checks_pending`]
 529         /// returns `true`. Note that this isn't a strict upper-bound on the number of checks pending -
 530         /// each peer may, at a minimum, read one more socket buffer worth of `channel_announcement`s
 531         /// which we'll have to process. With a socket buffer of 4KB and a minimum
 532         /// `channel_announcement` size of, roughly, 429 bytes, this may leave us with `10*our peer
 533         /// count` messages to process beyond this limit. Because we'll probably have a few peers,
 534         /// there's no reason for this constant to be materially less than 30 or so, and 32 in-flight
 535         /// checks should be more than enough for decent parallelism.
 536         const MAX_PENDING_LOOKUPS: usize = 32;
 537
 538         /// Returns true if there are a large number of async checks pending and future
 539         /// `channel_announcement` messages should be delayed. Note that this is only a hint and
 540         /// messages already in-flight may still have to be handled for various reasons.
 541         pub(super) fn too_many_checks_pending(&self) -> bool {
 542                 let mut pending_checks = self.internal.lock().unwrap();
 543                 if pending_checks.channels.len() > Self::MAX_PENDING_LOOKUPS {
 544                         // If we have many channel checks pending, ensure we don't have any dangling checks
 545                         // (i.e. checks where the user told us they'd call back but drop'd the `UtxoFuture`
 546                         // instead) before we commit to applying backpressure.
 547                         pending_checks.channels.retain(|_, chan| {
 548                                 Weak::upgrade(&chan).is_some()
 549                         });
 550                         pending_checks.nodes.retain(|_, channels| {
 551                                 channels.retain(|chan| Weak::upgrade(&chan).is_some());
 552                                 !channels.is_empty()
 553                         });
 554                         pending_checks.channels.len() > Self::MAX_PENDING_LOOKUPS
 555                 } else {
 556                         false
 557                 }
 558         }
 559 }
 560
 561 #[cfg(test)]
 562 mod tests {
 563         use super::*;
 564         use crate::routing::gossip::tests::*;
 565         use crate::util::test_utils::{TestChainSource, TestLogger};
 566         use crate::ln::msgs;
 567
 568         use bitcoin::secp256k1::{Secp256k1, SecretKey};
 569
 570         use core::sync::atomic::Ordering;
 571
 572         fn get_network() -> (TestChainSource, NetworkGraph<Box<TestLogger>>) {
 573                 let logger = Box::new(TestLogger::new());
 574                 let chain_source = TestChainSource::new(bitcoin::Network::Testnet);
 575                 let network_graph = NetworkGraph::new(bitcoin::Network::Testnet, logger);
 576
 577                 (chain_source, network_graph)
 578         }
 579
 580         fn get_test_objects() -> (msgs::ChannelAnnouncement, TestChainSource,
 581                 NetworkGraph<Box<TestLogger>>, bitcoin::ScriptBuf, msgs::NodeAnnouncement,
 582                 msgs::NodeAnnouncement, msgs::ChannelUpdate, msgs::ChannelUpdate, msgs::ChannelUpdate)
 583         {
 584                 let secp_ctx = Secp256k1::new();
 585
 586                 let (chain_source, network_graph) = get_network();
 587
 588                 let good_script = get_channel_script(&secp_ctx);
 589                 let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
 590                 let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
 591                 let valid_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
 592
 593                 let node_a_announce = get_signed_node_announcement(|_| {}, node_1_privkey, &secp_ctx);
 594                 let node_b_announce = get_signed_node_announcement(|_| {}, node_2_privkey, &secp_ctx);
 595
 596                 // Note that we have to set the "direction" flag correctly on both messages
 597                 let chan_update_a = get_signed_channel_update(|msg| msg.flags = 0, node_1_privkey, &secp_ctx);
 598                 let chan_update_b = get_signed_channel_update(|msg| msg.flags = 1, node_2_privkey, &secp_ctx);
 599                 let chan_update_c = get_signed_channel_update(|msg| {
 600                         msg.flags = 1; msg.timestamp += 1; }, node_2_privkey, &secp_ctx);
 601
 602                 (valid_announcement, chain_source, network_graph, good_script, node_a_announce,
 603                         node_b_announce, chan_update_a, chan_update_b, chan_update_c)
 604         }
 605
 606         #[test]
 607         fn test_fast_async_lookup() {
 608                 // Check that async lookups which resolve quicker than the future is returned to the
 609                 // `get_utxo` call can read it still resolve properly.
 610                 let (valid_announcement, chain_source, network_graph, good_script, ..) = get_test_objects();
 611
 612                 let future = UtxoFuture::new();
 613                 future.resolve_without_forwarding(&network_graph,
 614                         Ok(TxOut { value: 1_000_000, script_pubkey: good_script }));
 615                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 616
 617                 network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap();
 618                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_some());
 619         }
 620
 621         #[test]
 622         fn test_async_lookup() {
 623                 // Test a simple async lookup
 624                 let (valid_announcement, chain_source, network_graph, good_script,
 625                         node_a_announce, node_b_announce, ..) = get_test_objects();
 626
 627                 let future = UtxoFuture::new();
 628                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 629
 630                 assert_eq!(
 631                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 632                         "Channel being checked async");
 633                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 634
 635                 future.resolve_without_forwarding(&network_graph,
 636                         Ok(TxOut { value: 0, script_pubkey: good_script }));
 637                 network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).unwrap();
 638                 network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).unwrap();
 639
 640                 assert!(network_graph.read_only().nodes().get(&valid_announcement.contents.node_id_1)
 641                         .unwrap().announcement_info.is_none());
 642
 643                 network_graph.update_node_from_announcement(&node_a_announce).unwrap();
 644                 network_graph.update_node_from_announcement(&node_b_announce).unwrap();
 645
 646                 assert!(network_graph.read_only().nodes().get(&valid_announcement.contents.node_id_1)
 647                         .unwrap().announcement_info.is_some());
 648         }
 649
 650         #[test]
 651         fn test_invalid_async_lookup() {
 652                 // Test an async lookup which returns an incorrect script
 653                 let (valid_announcement, chain_source, network_graph, ..) = get_test_objects();
 654
 655                 let future = UtxoFuture::new();
 656                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 657
 658                 assert_eq!(
 659                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 660                         "Channel being checked async");
 661                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 662
 663                 future.resolve_without_forwarding(&network_graph,
 664                         Ok(TxOut { value: 1_000_000, script_pubkey: bitcoin::ScriptBuf::new() }));
 665                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 666         }
 667
 668         #[test]
 669         fn test_failing_async_lookup() {
 670                 // Test an async lookup which returns an error
 671                 let (valid_announcement, chain_source, network_graph, ..) = get_test_objects();
 672
 673                 let future = UtxoFuture::new();
 674                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 675
 676                 assert_eq!(
 677                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 678                         "Channel being checked async");
 679                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 680
 681                 future.resolve_without_forwarding(&network_graph, Err(UtxoLookupError::UnknownTx));
 682                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 683         }
 684
 685         #[test]
 686         fn test_updates_async_lookup() {
 687                 // Test async lookups will process pending channel_update/node_announcements once they
 688                 // complete.
 689                 let (valid_announcement, chain_source, network_graph, good_script, node_a_announce,
 690                         node_b_announce, chan_update_a, chan_update_b, ..) = get_test_objects();
 691
 692                 let future = UtxoFuture::new();
 693                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 694
 695                 assert_eq!(
 696                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 697                         "Channel being checked async");
 698                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 699
 700                 assert_eq!(
 701                         network_graph.update_node_from_announcement(&node_a_announce).unwrap_err().err,
 702                         "Awaiting channel_announcement validation to accept node_announcement");
 703                 assert_eq!(
 704                         network_graph.update_node_from_announcement(&node_b_announce).unwrap_err().err,
 705                         "Awaiting channel_announcement validation to accept node_announcement");
 706
 707                 assert_eq!(network_graph.update_channel(&chan_update_a).unwrap_err().err,
 708                         "Awaiting channel_announcement validation to accept channel_update");
 709                 assert_eq!(network_graph.update_channel(&chan_update_b).unwrap_err().err,
 710                         "Awaiting channel_announcement validation to accept channel_update");
 711
 712                 future.resolve_without_forwarding(&network_graph,
 713                         Ok(TxOut { value: 1_000_000, script_pubkey: good_script }));
 714
 715                 assert!(network_graph.read_only().channels()
 716                         .get(&valid_announcement.contents.short_channel_id).unwrap().one_to_two.is_some());
 717                 assert!(network_graph.read_only().channels()
 718                         .get(&valid_announcement.contents.short_channel_id).unwrap().two_to_one.is_some());
 719
 720                 assert!(network_graph.read_only().nodes().get(&valid_announcement.contents.node_id_1)
 721                         .unwrap().announcement_info.is_some());
 722                 assert!(network_graph.read_only().nodes().get(&valid_announcement.contents.node_id_2)
 723                         .unwrap().announcement_info.is_some());
 724         }
 725
 726         #[test]
 727         fn test_latest_update_async_lookup() {
 728                 // Test async lookups will process the latest channel_update if two are received while
 729                 // awaiting an async UTXO lookup.
 730                 let (valid_announcement, chain_source, network_graph, good_script, _,
 731                         _, chan_update_a, chan_update_b, chan_update_c, ..) = get_test_objects();
 732
 733                 let future = UtxoFuture::new();
 734                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 735
 736                 assert_eq!(
 737                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 738                         "Channel being checked async");
 739                 assert!(network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id).is_none());
 740
 741                 assert_eq!(network_graph.update_channel(&chan_update_a).unwrap_err().err,
 742                         "Awaiting channel_announcement validation to accept channel_update");
 743                 assert_eq!(network_graph.update_channel(&chan_update_b).unwrap_err().err,
 744                         "Awaiting channel_announcement validation to accept channel_update");
 745                 assert_eq!(network_graph.update_channel(&chan_update_c).unwrap_err().err,
 746                         "Awaiting channel_announcement validation to accept channel_update");
 747
 748                 future.resolve_without_forwarding(&network_graph,
 749                         Ok(TxOut { value: 1_000_000, script_pubkey: good_script }));
 750
 751                 assert_eq!(chan_update_a.contents.timestamp, chan_update_b.contents.timestamp);
 752                 let graph_lock = network_graph.read_only();
 753                 assert!(graph_lock.channels()
 754                                 .get(&valid_announcement.contents.short_channel_id).as_ref().unwrap()
 755                                 .one_to_two.as_ref().unwrap().last_update !=
 756                         graph_lock.channels()
 757                                 .get(&valid_announcement.contents.short_channel_id).as_ref().unwrap()
 758                                 .two_to_one.as_ref().unwrap().last_update);
 759         }
 760
 761         #[test]
 762         fn test_no_double_lookups() {
 763                 // Test that a pending async lookup will prevent a second async lookup from flying, but
 764                 // only if the channel_announcement message is identical.
 765                 let (valid_announcement, chain_source, network_graph, good_script, ..) = get_test_objects();
 766
 767                 let future = UtxoFuture::new();
 768                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 769
 770                 assert_eq!(
 771                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 772                         "Channel being checked async");
 773                 assert_eq!(chain_source.get_utxo_call_count.load(Ordering::Relaxed), 1);
 774
 775                 // If we make a second request with the same message, the call count doesn't increase...
 776                 let future_b = UtxoFuture::new();
 777                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future_b.clone());
 778                 assert_eq!(
 779                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err().err,
 780                         "Channel announcement is already being checked");
 781                 assert_eq!(chain_source.get_utxo_call_count.load(Ordering::Relaxed), 1);
 782
 783                 // But if we make a third request with a tweaked message, we should get a second call
 784                 // against our new future...
 785                 let secp_ctx = Secp256k1::new();
 786                 let replacement_pk_1 = &SecretKey::from_slice(&[99; 32]).unwrap();
 787                 let replacement_pk_2 = &SecretKey::from_slice(&[98; 32]).unwrap();
 788                 let invalid_announcement = get_signed_channel_announcement(|_| {}, replacement_pk_1, replacement_pk_2, &secp_ctx);
 789                 assert_eq!(
 790                         network_graph.update_channel_from_announcement(&invalid_announcement, &Some(&chain_source)).unwrap_err().err,
 791                         "Channel being checked async");
 792                 assert_eq!(chain_source.get_utxo_call_count.load(Ordering::Relaxed), 2);
 793
 794                 // Still, if we resolve the original future, the original channel will be accepted.
 795                 future.resolve_without_forwarding(&network_graph,
 796                         Ok(TxOut { value: 1_000_000, script_pubkey: good_script }));
 797                 assert!(!network_graph.read_only().channels()
 798                         .get(&valid_announcement.contents.short_channel_id).unwrap()
 799                         .announcement_message.as_ref().unwrap()
 800                         .contents.features.supports_unknown_test_feature());
 801         }
 802
 803         #[test]
 804         fn test_checks_backpressure() {
 805                 // Test that too_many_checks_pending returns true when there are many checks pending, and
 806                 // returns false once they complete.
 807                 let secp_ctx = Secp256k1::new();
 808                 let (chain_source, network_graph) = get_network();
 809
 810                 // We cheat and use a single future for all the lookups to complete them all at once.
 811                 let future = UtxoFuture::new();
 812                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(future.clone());
 813
 814                 let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
 815                 let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
 816
 817                 for i in 0..PendingChecks::MAX_PENDING_LOOKUPS {
 818                         let valid_announcement = get_signed_channel_announcement(
 819                                 |msg| msg.short_channel_id += 1 + i as u64, node_1_privkey, node_2_privkey, &secp_ctx);
 820                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err();
 821                         assert!(!network_graph.pending_checks.too_many_checks_pending());
 822                 }
 823
 824                 let valid_announcement = get_signed_channel_announcement(
 825                         |_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
 826                 network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err();
 827                 assert!(network_graph.pending_checks.too_many_checks_pending());
 828
 829                 // Once the future completes the "too many checks" flag should reset.
 830                 future.resolve_without_forwarding(&network_graph, Err(UtxoLookupError::UnknownTx));
 831                 assert!(!network_graph.pending_checks.too_many_checks_pending());
 832         }
 833
 834         #[test]
 835         fn test_checks_backpressure_drop() {
 836                 // Test that too_many_checks_pending returns true when there are many checks pending, and
 837                 // returns false if we drop some of the futures without completion.
 838                 let secp_ctx = Secp256k1::new();
 839                 let (chain_source, network_graph) = get_network();
 840
 841                 // We cheat and use a single future for all the lookups to complete them all at once.
 842                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Async(UtxoFuture::new());
 843
 844                 let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
 845                 let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
 846
 847                 for i in 0..PendingChecks::MAX_PENDING_LOOKUPS {
 848                         let valid_announcement = get_signed_channel_announcement(
 849                                 |msg| msg.short_channel_id += 1 + i as u64, node_1_privkey, node_2_privkey, &secp_ctx);
 850                         network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err();
 851                         assert!(!network_graph.pending_checks.too_many_checks_pending());
 852                 }
 853
 854                 let valid_announcement = get_signed_channel_announcement(
 855                         |_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
 856                 network_graph.update_channel_from_announcement(&valid_announcement, &Some(&chain_source)).unwrap_err();
 857                 assert!(network_graph.pending_checks.too_many_checks_pending());
 858
 859                 // Once the future is drop'd (by resetting the `utxo_ret` value) the "too many checks" flag
 860                 // should reset to false.
 861                 *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Sync(Err(UtxoLookupError::UnknownTx));
 862                 assert!(!network_graph.pending_checks.too_many_checks_pending());
 863         }
 864 }