_ Git - rust-lightning/blob - lightning/src/util/events.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 //! Events are returned from various bits in the library which indicate some action must be taken
  11 //! by the client.
  12 //!
  13 //! Because we don't have a built-in runtime, it's up to the client to call events at a time in the
  14 //! future, as well as generate and broadcast funding transactions handle payment preimages and a
  15 //! few other things.
  16
  17 use crate::chain::keysinterface::SpendableOutputDescriptor;
  18 #[cfg(anchors)]
  19 use crate::ln::chan_utils::HTLCOutputInCommitment;
  20 use crate::ln::channelmanager::PaymentId;
  21 use crate::ln::channel::FUNDING_CONF_DEADLINE_BLOCKS;
  22 use crate::ln::features::ChannelTypeFeatures;
  23 use crate::ln::msgs;
  24 use crate::ln::msgs::DecodeError;
  25 use crate::ln::{PaymentPreimage, PaymentHash, PaymentSecret};
  26 use crate::routing::gossip::NetworkUpdate;
  27 use crate::util::ser::{BigSize, FixedLengthReader, Writeable, Writer, MaybeReadable, Readable, WithoutLength, OptionDeserWrapper};
  28 use crate::routing::router::{RouteHop, RouteParameters};
  29
  30 use bitcoin::{PackedLockTime, Transaction};
  31 #[cfg(anchors)]
  32 use bitcoin::OutPoint;
  33 use bitcoin::blockdata::script::Script;
  34 use bitcoin::hashes::Hash;
  35 use bitcoin::hashes::sha256::Hash as Sha256;
  36 use bitcoin::secp256k1::PublicKey;
  37 use crate::io;
  38 use crate::prelude::*;
  39 use core::time::Duration;
  40 use core::ops::Deref;
  41 use crate::sync::Arc;
  42
  43 /// Some information provided on receipt of payment depends on whether the payment received is a
  44 /// spontaneous payment or a "conventional" lightning payment that's paying an invoice.
  45 #[derive(Clone, Debug)]
  46 pub enum PaymentPurpose {
  47         /// Information for receiving a payment that we generated an invoice for.
  48         InvoicePayment {
  49                 /// The preimage to the payment_hash, if the payment hash (and secret) were fetched via
  50                 /// [`ChannelManager::create_inbound_payment`]. If provided, this can be handed directly to
  51                 /// [`ChannelManager::claim_funds`].
  52                 ///
  53                 /// [`ChannelManager::create_inbound_payment`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment
  54                 /// [`ChannelManager::claim_funds`]: crate::ln::channelmanager::ChannelManager::claim_funds
  55                 payment_preimage: Option<PaymentPreimage>,
  56                 /// The "payment secret". This authenticates the sender to the recipient, preventing a
  57                 /// number of deanonymization attacks during the routing process.
  58                 /// It is provided here for your reference, however its accuracy is enforced directly by
  59                 /// [`ChannelManager`] using the values you previously provided to
  60                 /// [`ChannelManager::create_inbound_payment`] or
  61                 /// [`ChannelManager::create_inbound_payment_for_hash`].
  62                 ///
  63                 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
  64                 /// [`ChannelManager::create_inbound_payment`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment
  65                 /// [`ChannelManager::create_inbound_payment_for_hash`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment_for_hash
  66                 payment_secret: PaymentSecret,
  67         },
  68         /// Because this is a spontaneous payment, the payer generated their own preimage rather than us
  69         /// (the payee) providing a preimage.
  70         SpontaneousPayment(PaymentPreimage),
  71 }
  72
  73 impl_writeable_tlv_based_enum!(PaymentPurpose,
  74         (0, InvoicePayment) => {
  75                 (0, payment_preimage, option),
  76                 (2, payment_secret, required),
  77         };
  78         (2, SpontaneousPayment)
  79 );
  80
  81 #[derive(Clone, Debug, PartialEq, Eq)]
  82 /// The reason the channel was closed. See individual variants more details.
  83 pub enum ClosureReason {
  84         /// Closure generated from receiving a peer error message.
  85         ///
  86         /// Our counterparty may have broadcasted their latest commitment state, and we have
  87         /// as well.
  88         CounterpartyForceClosed {
  89                 /// The error which the peer sent us.
  90                 ///
  91                 /// The string should be sanitized before it is used (e.g emitted to logs
  92                 /// or printed to stdout). Otherwise, a well crafted error message may exploit
  93                 /// a security vulnerability in the terminal emulator or the logging subsystem.
  94                 peer_msg: String,
  95         },
  96         /// Closure generated from [`ChannelManager::force_close_channel`], called by the user.
  97         ///
  98         /// [`ChannelManager::force_close_channel`]: crate::ln::channelmanager::ChannelManager::force_close_channel.
  99         HolderForceClosed,
 100         /// The channel was closed after negotiating a cooperative close and we've now broadcasted
 101         /// the cooperative close transaction. Note the shutdown may have been initiated by us.
 102         //TODO: split between CounterpartyInitiated/LocallyInitiated
 103         CooperativeClosure,
 104         /// A commitment transaction was confirmed on chain, closing the channel. Most likely this
 105         /// commitment transaction came from our counterparty, but it may also have come from
 106         /// a copy of our own `ChannelMonitor`.
 107         CommitmentTxConfirmed,
 108         /// The funding transaction failed to confirm in a timely manner on an inbound channel.
 109         FundingTimedOut,
 110         /// Closure generated from processing an event, likely a HTLC forward/relay/reception.
 111         ProcessingError {
 112                 /// A developer-readable error message which we generated.
 113                 err: String,
 114         },
 115         /// The peer disconnected prior to funding completing. In this case the spec mandates that we
 116         /// forget the channel entirely - we can attempt again if the peer reconnects.
 117         ///
 118         /// This includes cases where we restarted prior to funding completion, including prior to the
 119         /// initial [`ChannelMonitor`] persistence completing.
 120         ///
 121         /// In LDK versions prior to 0.0.107 this could also occur if we were unable to connect to the
 122         /// peer because of mutual incompatibility between us and our channel counterparty.
 123         ///
 124         /// [`ChannelMonitor`]: crate::chain::channelmonitor::ChannelMonitor
 125         DisconnectedPeer,
 126         /// Closure generated from `ChannelManager::read` if the [`ChannelMonitor`] is newer than
 127         /// the [`ChannelManager`] deserialized.
 128         ///
 129         /// [`ChannelMonitor`]: crate::chain::channelmonitor::ChannelMonitor
 130         /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
 131         OutdatedChannelManager
 132 }
 133
 134 impl core::fmt::Display for ClosureReason {
 135         fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
 136                 f.write_str("Channel closed because ")?;
 137                 match self {
 138                         ClosureReason::CounterpartyForceClosed { peer_msg } => {
 139                                 f.write_str("counterparty force-closed with message ")?;
 140                                 f.write_str(&peer_msg)
 141                         },
 142                         ClosureReason::HolderForceClosed => f.write_str("user manually force-closed the channel"),
 143                         ClosureReason::CooperativeClosure => f.write_str("the channel was cooperatively closed"),
 144                         ClosureReason::CommitmentTxConfirmed => f.write_str("commitment or closing transaction was confirmed on chain."),
 145                         ClosureReason::FundingTimedOut => write!(f, "funding transaction failed to confirm within {} blocks", FUNDING_CONF_DEADLINE_BLOCKS),
 146                         ClosureReason::ProcessingError { err } => {
 147                                 f.write_str("of an exception: ")?;
 148                                 f.write_str(&err)
 149                         },
 150                         ClosureReason::DisconnectedPeer => f.write_str("the peer disconnected prior to the channel being funded"),
 151                         ClosureReason::OutdatedChannelManager => f.write_str("the ChannelManager read from disk was stale compared to ChannelMonitor(s)"),
 152                 }
 153         }
 154 }
 155
 156 impl_writeable_tlv_based_enum_upgradable!(ClosureReason,
 157         (0, CounterpartyForceClosed) => { (1, peer_msg, required) },
 158         (1, FundingTimedOut) => {},
 159         (2, HolderForceClosed) => {},
 160         (6, CommitmentTxConfirmed) => {},
 161         (4, CooperativeClosure) => {},
 162         (8, ProcessingError) => { (1, err, required) },
 163         (10, DisconnectedPeer) => {},
 164         (12, OutdatedChannelManager) => {},
 165 );
 166
 167 /// Intended destination of a failed HTLC as indicated in [`Event::HTLCHandlingFailed`].
 168 #[derive(Clone, Debug, PartialEq, Eq)]
 169 pub enum HTLCDestination {
 170         /// We tried forwarding to a channel but failed to do so. An example of such an instance is when
 171         /// there is insufficient capacity in our outbound channel.
 172         NextHopChannel {
 173                 /// The `node_id` of the next node. For backwards compatibility, this field is
 174                 /// marked as optional, versions prior to 0.0.110 may not always be able to provide
 175                 /// counterparty node information.
 176                 node_id: Option<PublicKey>,
 177                 /// The outgoing `channel_id` between us and the next node.
 178                 channel_id: [u8; 32],
 179         },
 180         /// Scenario where we are unsure of the next node to forward the HTLC to.
 181         UnknownNextHop {
 182                 /// Short channel id we are requesting to forward an HTLC to.
 183                 requested_forward_scid: u64,
 184         },
 185         /// Failure scenario where an HTLC may have been forwarded to be intended for us,
 186         /// but is invalid for some reason, so we reject it.
 187         ///
 188         /// Some of the reasons may include:
 189         /// * HTLC Timeouts
 190         /// * Expected MPP amount to claim does not equal HTLC total
 191         /// * Claimable amount does not match expected amount
 192         FailedPayment {
 193                 /// The payment hash of the payment we attempted to process.
 194                 payment_hash: PaymentHash
 195         },
 196 }
 197
 198 impl_writeable_tlv_based_enum_upgradable!(HTLCDestination,
 199         (0, NextHopChannel) => {
 200                 (0, node_id, required),
 201                 (2, channel_id, required),
 202         },
 203         (2, UnknownNextHop) => {
 204                 (0, requested_forward_scid, required),
 205         },
 206         (4, FailedPayment) => {
 207                 (0, payment_hash, required),
 208         }
 209 );
 210
 211 #[cfg(anchors)]
 212 /// A descriptor used to sign for a commitment transaction's anchor output.
 213 #[derive(Clone, Debug)]
 214 pub struct AnchorDescriptor {
 215         /// A unique identifier used along with `channel_value_satoshis` to re-derive the
 216         /// [`InMemorySigner`] required to sign `input`.
 217         ///
 218         /// [`InMemorySigner`]: crate::chain::keysinterface::InMemorySigner
 219         pub channel_keys_id: [u8; 32],
 220         /// The value in satoshis of the channel we're attempting to spend the anchor output of. This is
 221         /// used along with `channel_keys_id` to re-derive the [`InMemorySigner`] required to sign
 222         /// `input`.
 223         ///
 224         /// [`InMemorySigner`]: crate::chain::keysinterface::InMemorySigner
 225         pub channel_value_satoshis: u64,
 226         /// The transaction input's outpoint corresponding to the commitment transaction's anchor
 227         /// output.
 228         pub outpoint: OutPoint,
 229 }
 230
 231 #[cfg(anchors)]
 232 /// Represents the different types of transactions, originating from LDK, to be bumped.
 233 #[derive(Clone, Debug)]
 234 pub enum BumpTransactionEvent {
 235         /// Indicates that a channel featuring anchor outputs is to be closed by broadcasting the local
 236         /// commitment transaction. Since commitment transactions have a static feerate pre-agreed upon,
 237         /// they may need additional fees to be attached through a child transaction using the popular
 238         /// [Child-Pays-For-Parent](https://bitcoinops.org/en/topics/cpfp) fee bumping technique. This
 239         /// child transaction must include the anchor input described within `anchor_descriptor` along
 240         /// with additional inputs to meet the target feerate. Failure to meet the target feerate
 241         /// decreases the confirmation odds of the transaction package (which includes the commitment
 242         /// and child anchor transactions), possibly resulting in a loss of funds. Once the transaction
 243         /// is constructed, it must be fully signed for and broadcasted by the consumer of the event
 244         /// along with the `commitment_tx` enclosed. Note that the `commitment_tx` must always be
 245         /// broadcast first, as the child anchor transaction depends on it.
 246         ///
 247         /// The consumer should be able to sign for any of the additional inputs included within the
 248         /// child anchor transaction. To sign its anchor input, an [`InMemorySigner`] should be
 249         /// re-derived through [`KeysManager::derive_channel_keys`] with the help of
 250         /// [`AnchorDescriptor::channel_keys_id`] and [`AnchorDescriptor::channel_value_satoshis`].
 251         ///
 252         /// It is possible to receive more than one instance of this event if a valid child anchor
 253         /// transaction is never broadcast or is but not with a sufficient fee to be mined. Care should
 254         /// be taken by the consumer of the event to ensure any future iterations of the child anchor
 255         /// transaction adhere to the [Replace-By-Fee
 256         /// rules](https://github.com/bitcoin/bitcoin/blob/master/doc/policy/mempool-replacements.md)
 257         /// for fee bumps to be accepted into the mempool, and eventually the chain. As the frequency of
 258         /// these events is not user-controlled, users may ignore/drop the event if they are no longer
 259         /// able to commit external confirmed funds to the child anchor transaction.
 260         ///
 261         /// The set of `pending_htlcs` on the commitment transaction to be broadcast can be inspected to
 262         /// determine whether a significant portion of the channel's funds are allocated to HTLCs,
 263         /// enabling users to make their own decisions regarding the importance of the commitment
 264         /// transaction's confirmation. Note that this is not required, but simply exists as an option
 265         /// for users to override LDK's behavior. On commitments with no HTLCs (indicated by those with
 266         /// an empty `pending_htlcs`), confirmation of the commitment transaction can be considered to
 267         /// be not urgent.
 268         ///
 269         /// [`InMemorySigner`]: crate::chain::keysinterface::InMemorySigner
 270         /// [`KeysManager::derive_channel_keys`]: crate::chain::keysinterface::KeysManager::derive_channel_keys
 271         ChannelClose {
 272                 /// The target feerate that the transaction package, which consists of the commitment
 273                 /// transaction and the to-be-crafted child anchor transaction, must meet.
 274                 package_target_feerate_sat_per_1000_weight: u32,
 275                 /// The channel's commitment transaction to bump the fee of. This transaction should be
 276                 /// broadcast along with the anchor transaction constructed as a result of consuming this
 277                 /// event.
 278                 commitment_tx: Transaction,
 279                 /// The absolute fee in satoshis of the commitment transaction. This can be used along the
 280                 /// with weight of the commitment transaction to determine its feerate.
 281                 commitment_tx_fee_satoshis: u64,
 282                 /// The descriptor to sign the anchor input of the anchor transaction constructed as a
 283                 /// result of consuming this event.
 284                 anchor_descriptor: AnchorDescriptor,
 285                 /// The set of pending HTLCs on the commitment transaction that need to be resolved once the
 286                 /// commitment transaction confirms.
 287                 pending_htlcs: Vec<HTLCOutputInCommitment>,
 288         },
 289 }
 290
 291 /// An Event which you should probably take some action in response to.
 292 ///
 293 /// Note that while Writeable and Readable are implemented for Event, you probably shouldn't use
 294 /// them directly as they don't round-trip exactly (for example FundingGenerationReady is never
 295 /// written as it makes no sense to respond to it after reconnecting to peers).
 296 #[derive(Clone, Debug)]
 297 pub enum Event {
 298         /// Used to indicate that the client should generate a funding transaction with the given
 299         /// parameters and then call [`ChannelManager::funding_transaction_generated`].
 300         /// Generated in [`ChannelManager`] message handling.
 301         /// Note that *all inputs* in the funding transaction must spend SegWit outputs or your
 302         /// counterparty can steal your funds!
 303         ///
 304         /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
 305         /// [`ChannelManager::funding_transaction_generated`]: crate::ln::channelmanager::ChannelManager::funding_transaction_generated
 306         FundingGenerationReady {
 307                 /// The random channel_id we picked which you'll need to pass into
 308                 /// [`ChannelManager::funding_transaction_generated`].
 309                 ///
 310                 /// [`ChannelManager::funding_transaction_generated`]: crate::ln::channelmanager::ChannelManager::funding_transaction_generated
 311                 temporary_channel_id: [u8; 32],
 312                 /// The counterparty's node_id, which you'll need to pass back into
 313                 /// [`ChannelManager::funding_transaction_generated`].
 314                 ///
 315                 /// [`ChannelManager::funding_transaction_generated`]: crate::ln::channelmanager::ChannelManager::funding_transaction_generated
 316                 counterparty_node_id: PublicKey,
 317                 /// The value, in satoshis, that the output should have.
 318                 channel_value_satoshis: u64,
 319                 /// The script which should be used in the transaction output.
 320                 output_script: Script,
 321                 /// The `user_channel_id` value passed in to [`ChannelManager::create_channel`], or a
 322                 /// random value for an inbound channel. This may be zero for objects serialized with LDK
 323                 /// versions prior to 0.0.113.
 324                 ///
 325                 /// [`ChannelManager::create_channel`]: crate::ln::channelmanager::ChannelManager::create_channel
 326                 user_channel_id: u128,
 327         },
 328         /// Indicates we've received (an offer of) money! Just gotta dig out that payment preimage and
 329         /// feed it to [`ChannelManager::claim_funds`] to get it....
 330         ///
 331         /// Note that if the preimage is not known, you should call
 332         /// [`ChannelManager::fail_htlc_backwards`] to free up resources for this HTLC and avoid
 333         /// network congestion.
 334         /// If you fail to call either [`ChannelManager::claim_funds`] or
 335         /// [`ChannelManager::fail_htlc_backwards`] within the HTLC's timeout, the HTLC will be
 336         /// automatically failed.
 337         ///
 338         /// # Note
 339         /// LDK will not stop an inbound payment from being paid multiple times, so multiple
 340         /// `PaymentReceived` events may be generated for the same payment.
 341         ///
 342         /// [`ChannelManager::claim_funds`]: crate::ln::channelmanager::ChannelManager::claim_funds
 343         /// [`ChannelManager::fail_htlc_backwards`]: crate::ln::channelmanager::ChannelManager::fail_htlc_backwards
 344         PaymentReceived {
 345                 /// The node that received the payment.
 346                 /// This is useful to identify payments which were received via [phantom node payments].
 347                 /// This field will always be filled in when the event was generated by LDK versions
 348                 /// 0.0.113 and above.
 349                 ///
 350                 /// [phantom node payments]: crate::chain::keysinterface::PhantomKeysManager
 351                 receiver_node_id: Option<PublicKey>,
 352                 /// The hash for which the preimage should be handed to the ChannelManager. Note that LDK will
 353                 /// not stop you from registering duplicate payment hashes for inbound payments.
 354                 payment_hash: PaymentHash,
 355                 /// The value, in thousandths of a satoshi, that this payment is for.
 356                 amount_msat: u64,
 357                 /// Information for claiming this received payment, based on whether the purpose of the
 358                 /// payment is to pay an invoice or to send a spontaneous payment.
 359                 purpose: PaymentPurpose,
 360                 /// The `channel_id` indicating over which channel we received the payment.
 361                 via_channel_id: Option<[u8; 32]>,
 362                 /// The `user_channel_id` indicating over which channel we received the payment.
 363                 via_user_channel_id: Option<u128>,
 364         },
 365         /// Indicates a payment has been claimed and we've received money!
 366         ///
 367         /// This most likely occurs when [`ChannelManager::claim_funds`] has been called in response
 368         /// to an [`Event::PaymentReceived`]. However, if we previously crashed during a
 369         /// [`ChannelManager::claim_funds`] call you may see this event without a corresponding
 370         /// [`Event::PaymentReceived`] event.
 371         ///
 372         /// # Note
 373         /// LDK will not stop an inbound payment from being paid multiple times, so multiple
 374         /// `PaymentReceived` events may be generated for the same payment. If you then call
 375         /// [`ChannelManager::claim_funds`] twice for the same [`Event::PaymentReceived`] you may get
 376         /// multiple `PaymentClaimed` events.
 377         ///
 378         /// [`ChannelManager::claim_funds`]: crate::ln::channelmanager::ChannelManager::claim_funds
 379         PaymentClaimed {
 380                 /// The node that received the payment.
 381                 /// This is useful to identify payments which were received via [phantom node payments].
 382                 /// This field will always be filled in when the event was generated by LDK versions
 383                 /// 0.0.113 and above.
 384                 ///
 385                 /// [phantom node payments]: crate::chain::keysinterface::PhantomKeysManager
 386                 receiver_node_id: Option<PublicKey>,
 387                 /// The payment hash of the claimed payment. Note that LDK will not stop you from
 388                 /// registering duplicate payment hashes for inbound payments.
 389                 payment_hash: PaymentHash,
 390                 /// The value, in thousandths of a satoshi, that this payment is for.
 391                 amount_msat: u64,
 392                 /// The purpose of this claimed payment, i.e. whether the payment was for an invoice or a
 393                 /// spontaneous payment.
 394                 purpose: PaymentPurpose,
 395         },
 396         /// Indicates an outbound payment we made succeeded (i.e. it made it all the way to its target
 397         /// and we got back the payment preimage for it).
 398         ///
 399         /// Note for MPP payments: in rare cases, this event may be preceded by a `PaymentPathFailed`
 400         /// event. In this situation, you SHOULD treat this payment as having succeeded.
 401         PaymentSent {
 402                 /// The id returned by [`ChannelManager::send_payment`] and used with
 403                 /// [`ChannelManager::retry_payment`].
 404                 ///
 405                 /// [`ChannelManager::send_payment`]: crate::ln::channelmanager::ChannelManager::send_payment
 406                 /// [`ChannelManager::retry_payment`]: crate::ln::channelmanager::ChannelManager::retry_payment
 407                 payment_id: Option<PaymentId>,
 408                 /// The preimage to the hash given to ChannelManager::send_payment.
 409                 /// Note that this serves as a payment receipt, if you wish to have such a thing, you must
 410                 /// store it somehow!
 411                 payment_preimage: PaymentPreimage,
 412                 /// The hash that was given to [`ChannelManager::send_payment`].
 413                 ///
 414                 /// [`ChannelManager::send_payment`]: crate::ln::channelmanager::ChannelManager::send_payment
 415                 payment_hash: PaymentHash,
 416                 /// The total fee which was spent at intermediate hops in this payment, across all paths.
 417                 ///
 418                 /// Note that, like [`Route::get_total_fees`] this does *not* include any potential
 419                 /// overpayment to the recipient node.
 420                 ///
 421                 /// If the recipient or an intermediate node misbehaves and gives us free money, this may
 422                 /// overstate the amount paid, though this is unlikely.
 423                 ///
 424                 /// [`Route::get_total_fees`]: crate::routing::router::Route::get_total_fees
 425                 fee_paid_msat: Option<u64>,
 426         },
 427         /// Indicates an outbound payment failed. Individual [`Event::PaymentPathFailed`] events
 428         /// provide failure information for each MPP part in the payment.
 429         ///
 430         /// This event is provided once there are no further pending HTLCs for the payment and the
 431         /// payment is no longer retryable due to [`ChannelManager::abandon_payment`] having been
 432         /// called for the corresponding payment.
 433         ///
 434         /// [`ChannelManager::abandon_payment`]: crate::ln::channelmanager::ChannelManager::abandon_payment
 435         PaymentFailed {
 436                 /// The id returned by [`ChannelManager::send_payment`] and used with
 437                 /// [`ChannelManager::retry_payment`] and [`ChannelManager::abandon_payment`].
 438                 ///
 439                 /// [`ChannelManager::send_payment`]: crate::ln::channelmanager::ChannelManager::send_payment
 440                 /// [`ChannelManager::retry_payment`]: crate::ln::channelmanager::ChannelManager::retry_payment
 441                 /// [`ChannelManager::abandon_payment`]: crate::ln::channelmanager::ChannelManager::abandon_payment
 442                 payment_id: PaymentId,
 443                 /// The hash that was given to [`ChannelManager::send_payment`].
 444                 ///
 445                 /// [`ChannelManager::send_payment`]: crate::ln::channelmanager::ChannelManager::send_payment
 446                 payment_hash: PaymentHash,
 447         },
 448         /// Indicates that a path for an outbound payment was successful.
 449         ///
 450         /// Always generated after [`Event::PaymentSent`] and thus useful for scoring channels. See
 451         /// [`Event::PaymentSent`] for obtaining the payment preimage.
 452         PaymentPathSuccessful {
 453                 /// The id returned by [`ChannelManager::send_payment`] and used with
 454                 /// [`ChannelManager::retry_payment`].
 455                 ///
 456                 /// [`ChannelManager::send_payment`]: crate::ln::channelmanager::ChannelManager::send_payment
 457                 /// [`ChannelManager::retry_payment`]: crate::ln::channelmanager::ChannelManager::retry_payment
 458                 payment_id: PaymentId,
 459                 /// The hash that was given to [`ChannelManager::send_payment`].
 460                 ///
 461                 /// [`ChannelManager::send_payment`]: crate::ln::channelmanager::ChannelManager::send_payment
 462                 payment_hash: Option<PaymentHash>,
 463                 /// The payment path that was successful.
 464                 ///
 465                 /// May contain a closed channel if the HTLC sent along the path was fulfilled on chain.
 466                 path: Vec<RouteHop>,
 467         },
 468         /// Indicates an outbound HTLC we sent failed. Probably some intermediary node dropped
 469         /// something. You may wish to retry with a different route.
 470         ///
 471         /// If you have given up retrying this payment and wish to fail it, you MUST call
 472         /// [`ChannelManager::abandon_payment`] at least once for a given [`PaymentId`] or memory
 473         /// related to payment tracking will leak.
 474         ///
 475         /// Note that this does *not* indicate that all paths for an MPP payment have failed, see
 476         /// [`Event::PaymentFailed`] and [`all_paths_failed`].
 477         ///
 478         /// [`ChannelManager::abandon_payment`]: crate::ln::channelmanager::ChannelManager::abandon_payment
 479         /// [`all_paths_failed`]: Self::PaymentPathFailed::all_paths_failed
 480         PaymentPathFailed {
 481                 /// The id returned by [`ChannelManager::send_payment`] and used with
 482                 /// [`ChannelManager::retry_payment`] and [`ChannelManager::abandon_payment`].
 483                 ///
 484                 /// [`ChannelManager::send_payment`]: crate::ln::channelmanager::ChannelManager::send_payment
 485                 /// [`ChannelManager::retry_payment`]: crate::ln::channelmanager::ChannelManager::retry_payment
 486                 /// [`ChannelManager::abandon_payment`]: crate::ln::channelmanager::ChannelManager::abandon_payment
 487                 payment_id: Option<PaymentId>,
 488                 /// The hash that was given to [`ChannelManager::send_payment`].
 489                 ///
 490                 /// [`ChannelManager::send_payment`]: crate::ln::channelmanager::ChannelManager::send_payment
 491                 payment_hash: PaymentHash,
 492                 /// Indicates the payment was rejected for some reason by the recipient. This implies that
 493                 /// the payment has failed, not just the route in question. If this is not set, you may
 494                 /// retry the payment via a different route.
 495                 payment_failed_permanently: bool,
 496                 /// Any failure information conveyed via the Onion return packet by a node along the failed
 497                 /// payment route.
 498                 ///
 499                 /// Should be applied to the [`NetworkGraph`] so that routing decisions can take into
 500                 /// account the update.
 501                 ///
 502                 /// [`NetworkGraph`]: crate::routing::gossip::NetworkGraph
 503                 network_update: Option<NetworkUpdate>,
 504                 /// For both single-path and multi-path payments, this is set if all paths of the payment have
 505                 /// failed. This will be set to false if (1) this is an MPP payment and (2) other parts of the
 506                 /// larger MPP payment were still in flight when this event was generated.
 507                 ///
 508                 /// Note that if you are retrying individual MPP parts, using this value to determine if a
 509                 /// payment has fully failed is race-y. Because multiple failures can happen prior to events
 510                 /// being processed, you may retry in response to a first failure, with a second failure
 511                 /// (with `all_paths_failed` set) still pending. Then, when the second failure is processed
 512                 /// you will see `all_paths_failed` set even though the retry of the first failure still
 513                 /// has an associated in-flight HTLC. See (1) for an example of such a failure.
 514                 ///
 515                 /// If you wish to retry individual MPP parts and learn when a payment has failed, you must
 516                 /// call [`ChannelManager::abandon_payment`] and wait for a [`Event::PaymentFailed`] event.
 517                 ///
 518                 /// (1) <https://github.com/lightningdevkit/rust-lightning/issues/1164>
 519                 ///
 520                 /// [`ChannelManager::abandon_payment`]: crate::ln::channelmanager::ChannelManager::abandon_payment
 521                 all_paths_failed: bool,
 522                 /// The payment path that failed.
 523                 path: Vec<RouteHop>,
 524                 /// The channel responsible for the failed payment path.
 525                 ///
 526                 /// Note that for route hints or for the first hop in a path this may be an SCID alias and
 527                 /// may not refer to a channel in the public network graph. These aliases may also collide
 528                 /// with channels in the public network graph.
 529                 ///
 530                 /// If this is `Some`, then the corresponding channel should be avoided when the payment is
 531                 /// retried. May be `None` for older [`Event`] serializations.
 532                 short_channel_id: Option<u64>,
 533                 /// Parameters needed to compute a new [`Route`] when retrying the failed payment path.
 534                 ///
 535                 /// See [`find_route`] for details.
 536                 ///
 537                 /// [`Route`]: crate::routing::router::Route
 538                 /// [`find_route`]: crate::routing::router::find_route
 539                 retry: Option<RouteParameters>,
 540 #[cfg(test)]
 541                 error_code: Option<u16>,
 542 #[cfg(test)]
 543                 error_data: Option<Vec<u8>>,
 544         },
 545         /// Indicates that a probe payment we sent returned successful, i.e., only failed at the destination.
 546         ProbeSuccessful {
 547                 /// The id returned by [`ChannelManager::send_probe`].
 548                 ///
 549                 /// [`ChannelManager::send_probe`]: crate::ln::channelmanager::ChannelManager::send_probe
 550                 payment_id: PaymentId,
 551                 /// The hash generated by [`ChannelManager::send_probe`].
 552                 ///
 553                 /// [`ChannelManager::send_probe`]: crate::ln::channelmanager::ChannelManager::send_probe
 554                 payment_hash: PaymentHash,
 555                 /// The payment path that was successful.
 556                 path: Vec<RouteHop>,
 557         },
 558         /// Indicates that a probe payment we sent failed at an intermediary node on the path.
 559         ProbeFailed {
 560                 /// The id returned by [`ChannelManager::send_probe`].
 561                 ///
 562                 /// [`ChannelManager::send_probe`]: crate::ln::channelmanager::ChannelManager::send_probe
 563                 payment_id: PaymentId,
 564                 /// The hash generated by [`ChannelManager::send_probe`].
 565                 ///
 566                 /// [`ChannelManager::send_probe`]: crate::ln::channelmanager::ChannelManager::send_probe
 567                 payment_hash: PaymentHash,
 568                 /// The payment path that failed.
 569                 path: Vec<RouteHop>,
 570                 /// The channel responsible for the failed probe.
 571                 ///
 572                 /// Note that for route hints or for the first hop in a path this may be an SCID alias and
 573                 /// may not refer to a channel in the public network graph. These aliases may also collide
 574                 /// with channels in the public network graph.
 575                 short_channel_id: Option<u64>,
 576         },
 577         /// Used to indicate that [`ChannelManager::process_pending_htlc_forwards`] should be called at
 578         /// a time in the future.
 579         ///
 580         /// [`ChannelManager::process_pending_htlc_forwards`]: crate::ln::channelmanager::ChannelManager::process_pending_htlc_forwards
 581         PendingHTLCsForwardable {
 582                 /// The minimum amount of time that should be waited prior to calling
 583                 /// process_pending_htlc_forwards. To increase the effort required to correlate payments,
 584                 /// you should wait a random amount of time in roughly the range (now + time_forwardable,
 585                 /// now + 5*time_forwardable).
 586                 time_forwardable: Duration,
 587         },
 588         /// Used to indicate that an output which you should know how to spend was confirmed on chain
 589         /// and is now spendable.
 590         /// Such an output will *not* ever be spent by rust-lightning, and are not at risk of your
 591         /// counterparty spending them due to some kind of timeout. Thus, you need to store them
 592         /// somewhere and spend them when you create on-chain transactions.
 593         SpendableOutputs {
 594                 /// The outputs which you should store as spendable by you.
 595                 outputs: Vec<SpendableOutputDescriptor>,
 596         },
 597         /// This event is generated when a payment has been successfully forwarded through us and a
 598         /// forwarding fee earned.
 599         PaymentForwarded {
 600                 /// The incoming channel between the previous node and us. This is only `None` for events
 601                 /// generated or serialized by versions prior to 0.0.107.
 602                 prev_channel_id: Option<[u8; 32]>,
 603                 /// The outgoing channel between the next node and us. This is only `None` for events
 604                 /// generated or serialized by versions prior to 0.0.107.
 605                 next_channel_id: Option<[u8; 32]>,
 606                 /// The fee, in milli-satoshis, which was earned as a result of the payment.
 607                 ///
 608                 /// Note that if we force-closed the channel over which we forwarded an HTLC while the HTLC
 609                 /// was pending, the amount the next hop claimed will have been rounded down to the nearest
 610                 /// whole satoshi. Thus, the fee calculated here may be higher than expected as we still
 611                 /// claimed the full value in millisatoshis from the source. In this case,
 612                 /// `claim_from_onchain_tx` will be set.
 613                 ///
 614                 /// If the channel which sent us the payment has been force-closed, we will claim the funds
 615                 /// via an on-chain transaction. In that case we do not yet know the on-chain transaction
 616                 /// fees which we will spend and will instead set this to `None`. It is possible duplicate
 617                 /// `PaymentForwarded` events are generated for the same payment iff `fee_earned_msat` is
 618                 /// `None`.
 619                 fee_earned_msat: Option<u64>,
 620                 /// If this is `true`, the forwarded HTLC was claimed by our counterparty via an on-chain
 621                 /// transaction.
 622                 claim_from_onchain_tx: bool,
 623         },
 624         /// Used to indicate that a channel with the given `channel_id` is ready to
 625         /// be used. This event is emitted either when the funding transaction has been confirmed
 626         /// on-chain, or, in case of a 0conf channel, when both parties have confirmed the channel
 627         /// establishment.
 628         ChannelReady {
 629                 /// The channel_id of the channel that is ready.
 630                 channel_id: [u8; 32],
 631                 /// The `user_channel_id` value passed in to [`ChannelManager::create_channel`] for outbound
 632                 /// channels, or to [`ChannelManager::accept_inbound_channel`] for inbound channels if
 633                 /// [`UserConfig::manually_accept_inbound_channels`] config flag is set to true. Otherwise
 634                 /// `user_channel_id` will be randomized for an inbound channel.
 635                 ///
 636                 /// [`ChannelManager::create_channel`]: crate::ln::channelmanager::ChannelManager::create_channel
 637                 /// [`ChannelManager::accept_inbound_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel
 638                 /// [`UserConfig::manually_accept_inbound_channels`]: crate::util::config::UserConfig::manually_accept_inbound_channels
 639                 user_channel_id: u128,
 640                 /// The node_id of the channel counterparty.
 641                 counterparty_node_id: PublicKey,
 642                 /// The features that this channel will operate with.
 643                 channel_type: ChannelTypeFeatures,
 644         },
 645         /// Used to indicate that a previously opened channel with the given `channel_id` is in the
 646         /// process of closure.
 647         ChannelClosed  {
 648                 /// The channel_id of the channel which has been closed. Note that on-chain transactions
 649                 /// resolving the channel are likely still awaiting confirmation.
 650                 channel_id: [u8; 32],
 651                 /// The `user_channel_id` value passed in to [`ChannelManager::create_channel`] for outbound
 652                 /// channels, or to [`ChannelManager::accept_inbound_channel`] for inbound channels if
 653                 /// [`UserConfig::manually_accept_inbound_channels`] config flag is set to true. Otherwise
 654                 /// `user_channel_id` will be randomized for inbound channels.
 655                 /// This may be zero for inbound channels serialized prior to 0.0.113 and will always be
 656                 /// zero for objects serialized with LDK versions prior to 0.0.102.
 657                 ///
 658                 /// [`ChannelManager::create_channel`]: crate::ln::channelmanager::ChannelManager::create_channel
 659                 /// [`ChannelManager::accept_inbound_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel
 660                 /// [`UserConfig::manually_accept_inbound_channels`]: crate::util::config::UserConfig::manually_accept_inbound_channels
 661                 user_channel_id: u128,
 662                 /// The reason the channel was closed.
 663                 reason: ClosureReason
 664         },
 665         /// Used to indicate to the user that they can abandon the funding transaction and recycle the
 666         /// inputs for another purpose.
 667         DiscardFunding {
 668                 /// The channel_id of the channel which has been closed.
 669                 channel_id: [u8; 32],
 670                 /// The full transaction received from the user
 671                 transaction: Transaction
 672         },
 673         /// Indicates a request to open a new channel by a peer.
 674         ///
 675         /// To accept the request, call [`ChannelManager::accept_inbound_channel`]. To reject the
 676         /// request, call [`ChannelManager::force_close_without_broadcasting_txn`].
 677         ///
 678         /// The event is only triggered when a new open channel request is received and the
 679         /// [`UserConfig::manually_accept_inbound_channels`] config flag is set to true.
 680         ///
 681         /// [`ChannelManager::accept_inbound_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel
 682         /// [`ChannelManager::force_close_without_broadcasting_txn`]: crate::ln::channelmanager::ChannelManager::force_close_without_broadcasting_txn
 683         /// [`UserConfig::manually_accept_inbound_channels`]: crate::util::config::UserConfig::manually_accept_inbound_channels
 684         OpenChannelRequest {
 685                 /// The temporary channel ID of the channel requested to be opened.
 686                 ///
 687                 /// When responding to the request, the `temporary_channel_id` should be passed
 688                 /// back to the ChannelManager through [`ChannelManager::accept_inbound_channel`] to accept,
 689                 /// or through [`ChannelManager::force_close_without_broadcasting_txn`] to reject.
 690                 ///
 691                 /// [`ChannelManager::accept_inbound_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel
 692                 /// [`ChannelManager::force_close_without_broadcasting_txn`]: crate::ln::channelmanager::ChannelManager::force_close_without_broadcasting_txn
 693                 temporary_channel_id: [u8; 32],
 694                 /// The node_id of the counterparty requesting to open the channel.
 695                 ///
 696                 /// When responding to the request, the `counterparty_node_id` should be passed
 697                 /// back to the `ChannelManager` through [`ChannelManager::accept_inbound_channel`] to
 698                 /// accept the request, or through [`ChannelManager::force_close_without_broadcasting_txn`] to reject the
 699                 /// request.
 700                 ///
 701                 /// [`ChannelManager::accept_inbound_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel
 702                 /// [`ChannelManager::force_close_without_broadcasting_txn`]: crate::ln::channelmanager::ChannelManager::force_close_without_broadcasting_txn
 703                 counterparty_node_id: PublicKey,
 704                 /// The channel value of the requested channel.
 705                 funding_satoshis: u64,
 706                 /// Our starting balance in the channel if the request is accepted, in milli-satoshi.
 707                 push_msat: u64,
 708                 /// The features that this channel will operate with. If you reject the channel, a
 709                 /// well-behaved counterparty may automatically re-attempt the channel with a new set of
 710                 /// feature flags.
 711                 ///
 712                 /// Note that if [`ChannelTypeFeatures::supports_scid_privacy`] returns true on this type,
 713                 /// the resulting [`ChannelManager`] will not be readable by versions of LDK prior to
 714                 /// 0.0.106.
 715                 ///
 716                 /// Furthermore, note that if [`ChannelTypeFeatures::supports_zero_conf`] returns true on this type,
 717                 /// the resulting [`ChannelManager`] will not be readable by versions of LDK prior to
 718                 /// 0.0.107. Channels setting this type also need to get manually accepted via
 719                 /// [`crate::ln::channelmanager::ChannelManager::accept_inbound_channel_from_trusted_peer_0conf`],
 720                 /// or will be rejected otherwise.
 721                 ///
 722                 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
 723                 channel_type: ChannelTypeFeatures,
 724         },
 725         /// Indicates that the HTLC was accepted, but could not be processed when or after attempting to
 726         /// forward it.
 727         ///
 728         /// Some scenarios where this event may be sent include:
 729         /// * Insufficient capacity in the outbound channel
 730         /// * While waiting to forward the HTLC, the channel it is meant to be forwarded through closes
 731         /// * When an unknown SCID is requested for forwarding a payment.
 732         /// * Claiming an amount for an MPP payment that exceeds the HTLC total
 733         /// * The HTLC has timed out
 734         ///
 735         /// This event, however, does not get generated if an HTLC fails to meet the forwarding
 736         /// requirements (i.e. insufficient fees paid, or a CLTV that is too soon).
 737         HTLCHandlingFailed {
 738                 /// The channel over which the HTLC was received.
 739                 prev_channel_id: [u8; 32],
 740                 /// Destination of the HTLC that failed to be processed.
 741                 failed_next_destination: HTLCDestination,
 742         },
 743         #[cfg(anchors)]
 744         /// Indicates that a transaction originating from LDK needs to have its fee bumped. This event
 745         /// requires confirmed external funds to be readily available to spend.
 746         ///
 747         /// LDK does not currently generate this event. It is limited to the scope of channels with
 748         /// anchor outputs, which will be introduced in a future release.
 749         BumpTransaction(BumpTransactionEvent),
 750 }
 751
 752 impl Writeable for Event {
 753         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 754                 match self {
 755                         &Event::FundingGenerationReady { .. } => {
 756                                 0u8.write(writer)?;
 757                                 // We never write out FundingGenerationReady events as, upon disconnection, peers
 758                                 // drop any channels which have not yet exchanged funding_signed.
 759                         },
 760                         &Event::PaymentReceived { ref payment_hash, ref amount_msat, ref purpose, ref receiver_node_id, ref via_channel_id, ref via_user_channel_id } => {
 761                                 1u8.write(writer)?;
 762                                 let mut payment_secret = None;
 763                                 let payment_preimage;
 764                                 match &purpose {
 765                                         PaymentPurpose::InvoicePayment { payment_preimage: preimage, payment_secret: secret } => {
 766                                                 payment_secret = Some(secret);
 767                                                 payment_preimage = *preimage;
 768                                         },
 769                                         PaymentPurpose::SpontaneousPayment(preimage) => {
 770                                                 payment_preimage = Some(*preimage);
 771                                         }
 772                                 }
 773                                 write_tlv_fields!(writer, {
 774                                         (0, payment_hash, required),
 775                                         (1, receiver_node_id, option),
 776                                         (2, payment_secret, option),
 777                                         (3, via_channel_id, option),
 778                                         (4, amount_msat, required),
 779                                         (5, via_user_channel_id, option),
 780                                         (6, 0u64, required), // user_payment_id required for compatibility with 0.0.103 and earlier
 781                                         (8, payment_preimage, option),
 782                                 });
 783                         },
 784                         &Event::PaymentSent { ref payment_id, ref payment_preimage, ref payment_hash, ref fee_paid_msat } => {
 785                                 2u8.write(writer)?;
 786                                 write_tlv_fields!(writer, {
 787                                         (0, payment_preimage, required),
 788                                         (1, payment_hash, required),
 789                                         (3, payment_id, option),
 790                                         (5, fee_paid_msat, option),
 791                                 });
 792                         },
 793                         &Event::PaymentPathFailed {
 794                                 ref payment_id, ref payment_hash, ref payment_failed_permanently, ref network_update,
 795                                 ref all_paths_failed, ref path, ref short_channel_id, ref retry,
 796                                 #[cfg(test)]
 797                                 ref error_code,
 798                                 #[cfg(test)]
 799                                 ref error_data,
 800                         } => {
 801                                 3u8.write(writer)?;
 802                                 #[cfg(test)]
 803                                 error_code.write(writer)?;
 804                                 #[cfg(test)]
 805                                 error_data.write(writer)?;
 806                                 write_tlv_fields!(writer, {
 807                                         (0, payment_hash, required),
 808                                         (1, network_update, option),
 809                                         (2, payment_failed_permanently, required),
 810                                         (3, all_paths_failed, required),
 811                                         (5, *path, vec_type),
 812                                         (7, short_channel_id, option),
 813                                         (9, retry, option),
 814                                         (11, payment_id, option),
 815                                 });
 816                         },
 817                         &Event::PendingHTLCsForwardable { time_forwardable: _ } => {
 818                                 4u8.write(writer)?;
 819                                 // Note that we now ignore these on the read end as we'll re-generate them in
 820                                 // ChannelManager, we write them here only for backwards compatibility.
 821                         },
 822                         &Event::SpendableOutputs { ref outputs } => {
 823                                 5u8.write(writer)?;
 824                                 write_tlv_fields!(writer, {
 825                                         (0, WithoutLength(outputs), required),
 826                                 });
 827                         },
 828                         &Event::PaymentForwarded { fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id } => {
 829                                 7u8.write(writer)?;
 830                                 write_tlv_fields!(writer, {
 831                                         (0, fee_earned_msat, option),
 832                                         (1, prev_channel_id, option),
 833                                         (2, claim_from_onchain_tx, required),
 834                                         (3, next_channel_id, option),
 835                                 });
 836                         },
 837                         &Event::ChannelClosed { ref channel_id, ref user_channel_id, ref reason } => {
 838                                 9u8.write(writer)?;
 839                                 // `user_channel_id` used to be a single u64 value. In order to remain backwards
 840                                 // compatible with versions prior to 0.0.113, the u128 is serialized as two
 841                                 // separate u64 values.
 842                                 let user_channel_id_low = *user_channel_id as u64;
 843                                 let user_channel_id_high = (*user_channel_id >> 64) as u64;
 844                                 write_tlv_fields!(writer, {
 845                                         (0, channel_id, required),
 846                                         (1, user_channel_id_low, required),
 847                                         (2, reason, required),
 848                                         (3, user_channel_id_high, required),
 849                                 });
 850                         },
 851                         &Event::DiscardFunding { ref channel_id, ref transaction } => {
 852                                 11u8.write(writer)?;
 853                                 write_tlv_fields!(writer, {
 854                                         (0, channel_id, required),
 855                                         (2, transaction, required)
 856                                 })
 857                         },
 858                         &Event::PaymentPathSuccessful { ref payment_id, ref payment_hash, ref path } => {
 859                                 13u8.write(writer)?;
 860                                 write_tlv_fields!(writer, {
 861                                         (0, payment_id, required),
 862                                         (2, payment_hash, option),
 863                                         (4, *path, vec_type)
 864                                 })
 865                         },
 866                         &Event::PaymentFailed { ref payment_id, ref payment_hash } => {
 867                                 15u8.write(writer)?;
 868                                 write_tlv_fields!(writer, {
 869                                         (0, payment_id, required),
 870                                         (2, payment_hash, required),
 871                                 })
 872                         },
 873                         &Event::OpenChannelRequest { .. } => {
 874                                 17u8.write(writer)?;
 875                                 // We never write the OpenChannelRequest events as, upon disconnection, peers
 876                                 // drop any channels which have not yet exchanged funding_signed.
 877                         },
 878                         &Event::PaymentClaimed { ref payment_hash, ref amount_msat, ref purpose, ref receiver_node_id } => {
 879                                 19u8.write(writer)?;
 880                                 write_tlv_fields!(writer, {
 881                                         (0, payment_hash, required),
 882                                         (1, receiver_node_id, option),
 883                                         (2, purpose, required),
 884                                         (4, amount_msat, required),
 885                                 });
 886                         },
 887                         &Event::ProbeSuccessful { ref payment_id, ref payment_hash, ref path } => {
 888                                 21u8.write(writer)?;
 889                                 write_tlv_fields!(writer, {
 890                                         (0, payment_id, required),
 891                                         (2, payment_hash, required),
 892                                         (4, *path, vec_type)
 893                                 })
 894                         },
 895                         &Event::ProbeFailed { ref payment_id, ref payment_hash, ref path, ref short_channel_id } => {
 896                                 23u8.write(writer)?;
 897                                 write_tlv_fields!(writer, {
 898                                         (0, payment_id, required),
 899                                         (2, payment_hash, required),
 900                                         (4, *path, vec_type),
 901                                         (6, short_channel_id, option),
 902                                 })
 903                         },
 904                         &Event::HTLCHandlingFailed { ref prev_channel_id, ref failed_next_destination } => {
 905                                 25u8.write(writer)?;
 906                                 write_tlv_fields!(writer, {
 907                                         (0, prev_channel_id, required),
 908                                         (2, failed_next_destination, required),
 909                                 })
 910                         },
 911                         #[cfg(anchors)]
 912                         &Event::BumpTransaction(ref event)=> {
 913                                 27u8.write(writer)?;
 914                                 match event {
 915                                         // We never write the ChannelClose events as they'll be replayed upon restarting
 916                                         // anyway if the commitment transaction remains unconfirmed.
 917                                         BumpTransactionEvent::ChannelClose { .. } => {}
 918                                 }
 919                         }
 920                         &Event::ChannelReady { ref channel_id, ref user_channel_id, ref counterparty_node_id, ref channel_type } => {
 921                                 29u8.write(writer)?;
 922                                 write_tlv_fields!(writer, {
 923                                         (0, channel_id, required),
 924                                         (2, user_channel_id, required),
 925                                         (4, counterparty_node_id, required),
 926                                         (6, channel_type, required),
 927                                 });
 928                         },
 929                         // Note that, going forward, all new events must only write data inside of
 930                         // `write_tlv_fields`. Versions 0.0.101+ will ignore odd-numbered events that write
 931                         // data via `write_tlv_fields`.
 932                 }
 933                 Ok(())
 934         }
 935 }
 936 impl MaybeReadable for Event {
 937         fn read<R: io::Read>(reader: &mut R) -> Result<Option<Self>, msgs::DecodeError> {
 938                 match Readable::read(reader)? {
 939                         // Note that we do not write a length-prefixed TLV for FundingGenerationReady events,
 940                         // unlike all other events, thus we return immediately here.
 941                         0u8 => Ok(None),
 942                         1u8 => {
 943                                 let f = || {
 944                                         let mut payment_hash = PaymentHash([0; 32]);
 945                                         let mut payment_preimage = None;
 946                                         let mut payment_secret = None;
 947                                         let mut amount_msat = 0;
 948                                         let mut receiver_node_id = None;
 949                                         let mut _user_payment_id = None::<u64>; // For compatibility with 0.0.103 and earlier
 950                                         let mut via_channel_id = None;
 951                                         let mut via_user_channel_id = None;
 952                                         read_tlv_fields!(reader, {
 953                                                 (0, payment_hash, required),
 954                                                 (1, receiver_node_id, option),
 955                                                 (2, payment_secret, option),
 956                                                 (3, via_channel_id, option),
 957                                                 (4, amount_msat, required),
 958                                                 (5, via_user_channel_id, option),
 959                                                 (6, _user_payment_id, option),
 960                                                 (8, payment_preimage, option),
 961                                         });
 962                                         let purpose = match payment_secret {
 963                                                 Some(secret) => PaymentPurpose::InvoicePayment {
 964                                                         payment_preimage,
 965                                                         payment_secret: secret
 966                                                 },
 967                                                 None if payment_preimage.is_some() => PaymentPurpose::SpontaneousPayment(payment_preimage.unwrap()),
 968                                                 None => return Err(msgs::DecodeError::InvalidValue),
 969                                         };
 970                                         Ok(Some(Event::PaymentReceived {
 971                                                 receiver_node_id,
 972                                                 payment_hash,
 973                                                 amount_msat,
 974                                                 purpose,
 975                                                 via_channel_id,
 976                                                 via_user_channel_id,
 977                                         }))
 978                                 };
 979                                 f()
 980                         },
 981                         2u8 => {
 982                                 let f = || {
 983                                         let mut payment_preimage = PaymentPreimage([0; 32]);
 984                                         let mut payment_hash = None;
 985                                         let mut payment_id = None;
 986                                         let mut fee_paid_msat = None;
 987                                         read_tlv_fields!(reader, {
 988                                                 (0, payment_preimage, required),
 989                                                 (1, payment_hash, option),
 990                                                 (3, payment_id, option),
 991                                                 (5, fee_paid_msat, option),
 992                                         });
 993                                         if payment_hash.is_none() {
 994                                                 payment_hash = Some(PaymentHash(Sha256::hash(&payment_preimage.0[..]).into_inner()));
 995                                         }
 996                                         Ok(Some(Event::PaymentSent {
 997                                                 payment_id,
 998                                                 payment_preimage,
 999                                                 payment_hash: payment_hash.unwrap(),
1000                                                 fee_paid_msat,
1001                                         }))
1002                                 };
1003                                 f()
1004                         },
1005                         3u8 => {
1006                                 let f = || {
1007                                         #[cfg(test)]
1008                                         let error_code = Readable::read(reader)?;
1009                                         #[cfg(test)]
1010                                         let error_data = Readable::read(reader)?;
1011                                         let mut payment_hash = PaymentHash([0; 32]);
1012                                         let mut payment_failed_permanently = false;
1013                                         let mut network_update = None;
1014                                         let mut all_paths_failed = Some(true);
1015                                         let mut path: Option<Vec<RouteHop>> = Some(vec![]);
1016                                         let mut short_channel_id = None;
1017                                         let mut retry = None;
1018                                         let mut payment_id = None;
1019                                         read_tlv_fields!(reader, {
1020                                                 (0, payment_hash, required),
1021                                                 (1, network_update, ignorable),
1022                                                 (2, payment_failed_permanently, required),
1023                                                 (3, all_paths_failed, option),
1024                                                 (5, path, vec_type),
1025                                                 (7, short_channel_id, option),
1026                                                 (9, retry, option),
1027                                                 (11, payment_id, option),
1028                                         });
1029                                         Ok(Some(Event::PaymentPathFailed {
1030                                                 payment_id,
1031                                                 payment_hash,
1032                                                 payment_failed_permanently,
1033                                                 network_update,
1034                                                 all_paths_failed: all_paths_failed.unwrap(),
1035                                                 path: path.unwrap(),
1036                                                 short_channel_id,
1037                                                 retry,
1038                                                 #[cfg(test)]
1039                                                 error_code,
1040                                                 #[cfg(test)]
1041                                                 error_data,
1042                                         }))
1043                                 };
1044                                 f()
1045                         },
1046                         4u8 => Ok(None),
1047                         5u8 => {
1048                                 let f = || {
1049                                         let mut outputs = WithoutLength(Vec::new());
1050                                         read_tlv_fields!(reader, {
1051                                                 (0, outputs, required),
1052                                         });
1053                                         Ok(Some(Event::SpendableOutputs { outputs: outputs.0 }))
1054                                 };
1055                                 f()
1056                         },
1057                         7u8 => {
1058                                 let f = || {
1059                                         let mut fee_earned_msat = None;
1060                                         let mut prev_channel_id = None;
1061                                         let mut claim_from_onchain_tx = false;
1062                                         let mut next_channel_id = None;
1063                                         read_tlv_fields!(reader, {
1064                                                 (0, fee_earned_msat, option),
1065                                                 (1, prev_channel_id, option),
1066                                                 (2, claim_from_onchain_tx, required),
1067                                                 (3, next_channel_id, option),
1068                                         });
1069                                         Ok(Some(Event::PaymentForwarded { fee_earned_msat, prev_channel_id, claim_from_onchain_tx, next_channel_id }))
1070                                 };
1071                                 f()
1072                         },
1073                         9u8 => {
1074                                 let f = || {
1075                                         let mut channel_id = [0; 32];
1076                                         let mut reason = None;
1077                                         let mut user_channel_id_low_opt: Option<u64> = None;
1078                                         let mut user_channel_id_high_opt: Option<u64> = None;
1079                                         read_tlv_fields!(reader, {
1080                                                 (0, channel_id, required),
1081                                                 (1, user_channel_id_low_opt, option),
1082                                                 (2, reason, ignorable),
1083                                                 (3, user_channel_id_high_opt, option),
1084                                         });
1085                                         if reason.is_none() { return Ok(None); }
1086
1087                                         // `user_channel_id` used to be a single u64 value. In order to remain
1088                                         // backwards compatible with versions prior to 0.0.113, the u128 is serialized
1089                                         // as two separate u64 values.
1090                                         let user_channel_id = (user_channel_id_low_opt.unwrap_or(0) as u128) +
1091                                                 ((user_channel_id_high_opt.unwrap_or(0) as u128) << 64);
1092
1093                                         Ok(Some(Event::ChannelClosed { channel_id, user_channel_id, reason: reason.unwrap() }))
1094                                 };
1095                                 f()
1096                         },
1097                         11u8 => {
1098                                 let f = || {
1099                                         let mut channel_id = [0; 32];
1100                                         let mut transaction = Transaction{ version: 2, lock_time: PackedLockTime::ZERO, input: Vec::new(), output: Vec::new() };
1101                                         read_tlv_fields!(reader, {
1102                                                 (0, channel_id, required),
1103                                                 (2, transaction, required),
1104                                         });
1105                                         Ok(Some(Event::DiscardFunding { channel_id, transaction } ))
1106                                 };
1107                                 f()
1108                         },
1109                         13u8 => {
1110                                 let f = || {
1111                                         let mut payment_id = PaymentId([0; 32]);
1112                                         let mut payment_hash = None;
1113                                         let mut path: Option<Vec<RouteHop>> = Some(vec![]);
1114                                         read_tlv_fields!(reader, {
1115                                                 (0, payment_id, required),
1116                                                 (2, payment_hash, option),
1117                                                 (4, path, vec_type),
1118                                         });
1119                                         Ok(Some(Event::PaymentPathSuccessful {
1120                                                 payment_id,
1121                                                 payment_hash,
1122                                                 path: path.unwrap(),
1123                                         }))
1124                                 };
1125                                 f()
1126                         },
1127                         15u8 => {
1128                                 let f = || {
1129                                         let mut payment_hash = PaymentHash([0; 32]);
1130                                         let mut payment_id = PaymentId([0; 32]);
1131                                         read_tlv_fields!(reader, {
1132                                                 (0, payment_id, required),
1133                                                 (2, payment_hash, required),
1134                                         });
1135                                         Ok(Some(Event::PaymentFailed {
1136                                                 payment_id,
1137                                                 payment_hash,
1138                                         }))
1139                                 };
1140                                 f()
1141                         },
1142                         17u8 => {
1143                                 // Value 17 is used for `Event::OpenChannelRequest`.
1144                                 Ok(None)
1145                         },
1146                         19u8 => {
1147                                 let f = || {
1148                                         let mut payment_hash = PaymentHash([0; 32]);
1149                                         let mut purpose = None;
1150                                         let mut amount_msat = 0;
1151                                         let mut receiver_node_id = None;
1152                                         read_tlv_fields!(reader, {
1153                                                 (0, payment_hash, required),
1154                                                 (1, receiver_node_id, option),
1155                                                 (2, purpose, ignorable),
1156                                                 (4, amount_msat, required),
1157                                         });
1158                                         if purpose.is_none() { return Ok(None); }
1159                                         Ok(Some(Event::PaymentClaimed {
1160                                                 receiver_node_id,
1161                                                 payment_hash,
1162                                                 purpose: purpose.unwrap(),
1163                                                 amount_msat,
1164                                         }))
1165                                 };
1166                                 f()
1167                         },
1168                         21u8 => {
1169                                 let f = || {
1170                                         let mut payment_id = PaymentId([0; 32]);
1171                                         let mut payment_hash = PaymentHash([0; 32]);
1172                                         let mut path: Option<Vec<RouteHop>> = Some(vec![]);
1173                                         read_tlv_fields!(reader, {
1174                                                 (0, payment_id, required),
1175                                                 (2, payment_hash, required),
1176                                                 (4, path, vec_type),
1177                                         });
1178                                         Ok(Some(Event::ProbeSuccessful {
1179                                                 payment_id,
1180                                                 payment_hash,
1181                                                 path: path.unwrap(),
1182                                         }))
1183                                 };
1184                                 f()
1185                         },
1186                         23u8 => {
1187                                 let f = || {
1188                                         let mut payment_id = PaymentId([0; 32]);
1189                                         let mut payment_hash = PaymentHash([0; 32]);
1190                                         let mut path: Option<Vec<RouteHop>> = Some(vec![]);
1191                                         let mut short_channel_id = None;
1192                                         read_tlv_fields!(reader, {
1193                                                 (0, payment_id, required),
1194                                                 (2, payment_hash, required),
1195                                                 (4, path, vec_type),
1196                                                 (6, short_channel_id, option),
1197                                         });
1198                                         Ok(Some(Event::ProbeFailed {
1199                                                 payment_id,
1200                                                 payment_hash,
1201                                                 path: path.unwrap(),
1202                                                 short_channel_id,
1203                                         }))
1204                                 };
1205                                 f()
1206                         },
1207                         25u8 => {
1208                                 let f = || {
1209                                         let mut prev_channel_id = [0; 32];
1210                                         let mut failed_next_destination_opt = None;
1211                                         read_tlv_fields!(reader, {
1212                                                 (0, prev_channel_id, required),
1213                                                 (2, failed_next_destination_opt, ignorable),
1214                                         });
1215                                         if let Some(failed_next_destination) = failed_next_destination_opt {
1216                                                 Ok(Some(Event::HTLCHandlingFailed {
1217                                                         prev_channel_id,
1218                                                         failed_next_destination,
1219                                                 }))
1220                                         } else {
1221                                                 // If we fail to read a `failed_next_destination` assume it's because
1222                                                 // `MaybeReadable::read` returned `Ok(None)`, though it's also possible we
1223                                                 // were simply missing the field.
1224                                                 Ok(None)
1225                                         }
1226                                 };
1227                                 f()
1228                         },
1229                         27u8 => Ok(None),
1230                         29u8 => {
1231                                 let f = || {
1232                                         let mut channel_id = [0; 32];
1233                                         let mut user_channel_id: u128 = 0;
1234                                         let mut counterparty_node_id = OptionDeserWrapper(None);
1235                                         let mut channel_type = OptionDeserWrapper(None);
1236                                         read_tlv_fields!(reader, {
1237                                                 (0, channel_id, required),
1238                                                 (2, user_channel_id, required),
1239                                                 (4, counterparty_node_id, required),
1240                                                 (6, channel_type, required),
1241                                         });
1242
1243                                         Ok(Some(Event::ChannelReady {
1244                                                 channel_id,
1245                                                 user_channel_id,
1246                                                 counterparty_node_id: counterparty_node_id.0.unwrap(),
1247                                                 channel_type: channel_type.0.unwrap()
1248                                         }))
1249                                 };
1250                                 f()
1251                         },
1252                         // Versions prior to 0.0.100 did not ignore odd types, instead returning InvalidValue.
1253                         // Version 0.0.100 failed to properly ignore odd types, possibly resulting in corrupt
1254                         // reads.
1255                         x if x % 2 == 1 => {
1256                                 // If the event is of unknown type, assume it was written with `write_tlv_fields`,
1257                                 // which prefixes the whole thing with a length BigSize. Because the event is
1258                                 // odd-type unknown, we should treat it as `Ok(None)` even if it has some TLV
1259                                 // fields that are even. Thus, we avoid using `read_tlv_fields` and simply read
1260                                 // exactly the number of bytes specified, ignoring them entirely.
1261                                 let tlv_len: BigSize = Readable::read(reader)?;
1262                                 FixedLengthReader::new(reader, tlv_len.0)
1263                                         .eat_remaining().map_err(|_| msgs::DecodeError::ShortRead)?;
1264                                 Ok(None)
1265                         },
1266                         _ => Err(msgs::DecodeError::InvalidValue)
1267                 }
1268         }
1269 }
1270
1271 /// An event generated by ChannelManager which indicates a message should be sent to a peer (or
1272 /// broadcast to most peers).
1273 /// These events are handled by PeerManager::process_events if you are using a PeerManager.
1274 #[derive(Clone, Debug)]
1275 pub enum MessageSendEvent {
1276         /// Used to indicate that we've accepted a channel open and should send the accept_channel
1277         /// message provided to the given peer.
1278         SendAcceptChannel {
1279                 /// The node_id of the node which should receive this message
1280                 node_id: PublicKey,
1281                 /// The message which should be sent.
1282                 msg: msgs::AcceptChannel,
1283         },
1284         /// Used to indicate that we've initiated a channel open and should send the open_channel
1285         /// message provided to the given peer.
1286         SendOpenChannel {
1287                 /// The node_id of the node which should receive this message
1288                 node_id: PublicKey,
1289                 /// The message which should be sent.
1290                 msg: msgs::OpenChannel,
1291         },
1292         /// Used to indicate that a funding_created message should be sent to the peer with the given node_id.
1293         SendFundingCreated {
1294                 /// The node_id of the node which should receive this message
1295                 node_id: PublicKey,
1296                 /// The message which should be sent.
1297                 msg: msgs::FundingCreated,
1298         },
1299         /// Used to indicate that a funding_signed message should be sent to the peer with the given node_id.
1300         SendFundingSigned {
1301                 /// The node_id of the node which should receive this message
1302                 node_id: PublicKey,
1303                 /// The message which should be sent.
1304                 msg: msgs::FundingSigned,
1305         },
1306         /// Used to indicate that a channel_ready message should be sent to the peer with the given node_id.
1307         SendChannelReady {
1308                 /// The node_id of the node which should receive these message(s)
1309                 node_id: PublicKey,
1310                 /// The channel_ready message which should be sent.
1311                 msg: msgs::ChannelReady,
1312         },
1313         /// Used to indicate that an announcement_signatures message should be sent to the peer with the given node_id.
1314         SendAnnouncementSignatures {
1315                 /// The node_id of the node which should receive these message(s)
1316                 node_id: PublicKey,
1317                 /// The announcement_signatures message which should be sent.
1318                 msg: msgs::AnnouncementSignatures,
1319         },
1320         /// Used to indicate that a series of HTLC update messages, as well as a commitment_signed
1321         /// message should be sent to the peer with the given node_id.
1322         UpdateHTLCs {
1323                 /// The node_id of the node which should receive these message(s)
1324                 node_id: PublicKey,
1325                 /// The update messages which should be sent. ALL messages in the struct should be sent!
1326                 updates: msgs::CommitmentUpdate,
1327         },
1328         /// Used to indicate that a revoke_and_ack message should be sent to the peer with the given node_id.
1329         SendRevokeAndACK {
1330                 /// The node_id of the node which should receive this message
1331                 node_id: PublicKey,
1332                 /// The message which should be sent.
1333                 msg: msgs::RevokeAndACK,
1334         },
1335         /// Used to indicate that a closing_signed message should be sent to the peer with the given node_id.
1336         SendClosingSigned {
1337                 /// The node_id of the node which should receive this message
1338                 node_id: PublicKey,
1339                 /// The message which should be sent.
1340                 msg: msgs::ClosingSigned,
1341         },
1342         /// Used to indicate that a shutdown message should be sent to the peer with the given node_id.
1343         SendShutdown {
1344                 /// The node_id of the node which should receive this message
1345                 node_id: PublicKey,
1346                 /// The message which should be sent.
1347                 msg: msgs::Shutdown,
1348         },
1349         /// Used to indicate that a channel_reestablish message should be sent to the peer with the given node_id.
1350         SendChannelReestablish {
1351                 /// The node_id of the node which should receive this message
1352                 node_id: PublicKey,
1353                 /// The message which should be sent.
1354                 msg: msgs::ChannelReestablish,
1355         },
1356         /// Used to send a channel_announcement and channel_update to a specific peer, likely on
1357         /// initial connection to ensure our peers know about our channels.
1358         SendChannelAnnouncement {
1359                 /// The node_id of the node which should receive this message
1360                 node_id: PublicKey,
1361                 /// The channel_announcement which should be sent.
1362                 msg: msgs::ChannelAnnouncement,
1363                 /// The followup channel_update which should be sent.
1364                 update_msg: msgs::ChannelUpdate,
1365         },
1366         /// Used to indicate that a channel_announcement and channel_update should be broadcast to all
1367         /// peers (except the peer with node_id either msg.contents.node_id_1 or msg.contents.node_id_2).
1368         ///
1369         /// Note that after doing so, you very likely (unless you did so very recently) want to
1370         /// broadcast a node_announcement (e.g. via [`PeerManager::broadcast_node_announcement`]). This
1371         /// ensures that any nodes which see our channel_announcement also have a relevant
1372         /// node_announcement, including relevant feature flags which may be important for routing
1373         /// through or to us.
1374         ///
1375         /// [`PeerManager::broadcast_node_announcement`]: crate::ln::peer_handler::PeerManager::broadcast_node_announcement
1376         BroadcastChannelAnnouncement {
1377                 /// The channel_announcement which should be sent.
1378                 msg: msgs::ChannelAnnouncement,
1379                 /// The followup channel_update which should be sent.
1380                 update_msg: msgs::ChannelUpdate,
1381         },
1382         /// Used to indicate that a channel_update should be broadcast to all peers.
1383         BroadcastChannelUpdate {
1384                 /// The channel_update which should be sent.
1385                 msg: msgs::ChannelUpdate,
1386         },
1387         /// Used to indicate that a channel_update should be sent to a single peer.
1388         /// In contrast to [`Self::BroadcastChannelUpdate`], this is used when the channel is a
1389         /// private channel and we shouldn't be informing all of our peers of channel parameters.
1390         SendChannelUpdate {
1391                 /// The node_id of the node which should receive this message
1392                 node_id: PublicKey,
1393                 /// The channel_update which should be sent.
1394                 msg: msgs::ChannelUpdate,
1395         },
1396         /// Broadcast an error downstream to be handled
1397         HandleError {
1398                 /// The node_id of the node which should receive this message
1399                 node_id: PublicKey,
1400                 /// The action which should be taken.
1401                 action: msgs::ErrorAction
1402         },
1403         /// Query a peer for channels with funding transaction UTXOs in a block range.
1404         SendChannelRangeQuery {
1405                 /// The node_id of this message recipient
1406                 node_id: PublicKey,
1407                 /// The query_channel_range which should be sent.
1408                 msg: msgs::QueryChannelRange,
1409         },
1410         /// Request routing gossip messages from a peer for a list of channels identified by
1411         /// their short_channel_ids.
1412         SendShortIdsQuery {
1413                 /// The node_id of this message recipient
1414                 node_id: PublicKey,
1415                 /// The query_short_channel_ids which should be sent.
1416                 msg: msgs::QueryShortChannelIds,
1417         },
1418         /// Sends a reply to a channel range query. This may be one of several SendReplyChannelRange events
1419         /// emitted during processing of the query.
1420         SendReplyChannelRange {
1421                 /// The node_id of this message recipient
1422                 node_id: PublicKey,
1423                 /// The reply_channel_range which should be sent.
1424                 msg: msgs::ReplyChannelRange,
1425         },
1426         /// Sends a timestamp filter for inbound gossip. This should be sent on each new connection to
1427         /// enable receiving gossip messages from the peer.
1428         SendGossipTimestampFilter {
1429                 /// The node_id of this message recipient
1430                 node_id: PublicKey,
1431                 /// The gossip_timestamp_filter which should be sent.
1432                 msg: msgs::GossipTimestampFilter,
1433         },
1434 }
1435
1436 /// A trait indicating an object may generate message send events
1437 pub trait MessageSendEventsProvider {
1438         /// Gets the list of pending events which were generated by previous actions, clearing the list
1439         /// in the process.
1440         fn get_and_clear_pending_msg_events(&self) -> Vec<MessageSendEvent>;
1441 }
1442
1443 /// A trait indicating an object may generate onion messages to send
1444 pub trait OnionMessageProvider {
1445         /// Gets the next pending onion message for the peer with the given node id.
1446         fn next_onion_message_for_peer(&self, peer_node_id: PublicKey) -> Option<msgs::OnionMessage>;
1447 }
1448
1449 /// A trait indicating an object may generate events.
1450 ///
1451 /// Events are processed by passing an [`EventHandler`] to [`process_pending_events`].
1452 ///
1453 /// Implementations of this trait may also feature an async version of event handling, as shown with
1454 /// [`ChannelManager::process_pending_events_async`] and
1455 /// [`ChainMonitor::process_pending_events_async`].
1456 ///
1457 /// # Requirements
1458 ///
1459 /// When using this trait, [`process_pending_events`] will call [`handle_event`] for each pending
1460 /// event since the last invocation.
1461 ///
1462 /// In order to ensure no [`Event`]s are lost, implementors of this trait will persist [`Event`]s
1463 /// and replay any unhandled events on startup. An [`Event`] is considered handled when
1464 /// [`process_pending_events`] returns, thus handlers MUST fully handle [`Event`]s and persist any
1465 /// relevant changes to disk *before* returning.
1466 ///
1467 /// Further, because an application may crash between an [`Event`] being handled and the
1468 /// implementor of this trait being re-serialized, [`Event`] handling must be idempotent - in
1469 /// effect, [`Event`]s may be replayed.
1470 ///
1471 /// Note, handlers may call back into the provider and thus deadlocking must be avoided. Be sure to
1472 /// consult the provider's documentation on the implication of processing events and how a handler
1473 /// may safely use the provider (e.g., see [`ChannelManager::process_pending_events`] and
1474 /// [`ChainMonitor::process_pending_events`]).
1475 ///
1476 /// (C-not implementable) As there is likely no reason for a user to implement this trait on their
1477 /// own type(s).
1478 ///
1479 /// [`process_pending_events`]: Self::process_pending_events
1480 /// [`handle_event`]: EventHandler::handle_event
1481 /// [`ChannelManager::process_pending_events`]: crate::ln::channelmanager::ChannelManager#method.process_pending_events
1482 /// [`ChainMonitor::process_pending_events`]: crate::chain::chainmonitor::ChainMonitor#method.process_pending_events
1483 /// [`ChannelManager::process_pending_events_async`]: crate::ln::channelmanager::ChannelManager::process_pending_events_async
1484 /// [`ChainMonitor::process_pending_events_async`]: crate::chain::chainmonitor::ChainMonitor::process_pending_events_async
1485 pub trait EventsProvider {
1486         /// Processes any events generated since the last call using the given event handler.
1487         ///
1488         /// See the trait-level documentation for requirements.
1489         fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler;
1490 }
1491
1492 /// A trait implemented for objects handling events from [`EventsProvider`].
1493 ///
1494 /// An async variation also exists for implementations of [`EventsProvider`] that support async
1495 /// event handling. The async event handler should satisfy the generic bounds: `F:
1496 /// core::future::Future, H: Fn(Event) -> F`.
1497 pub trait EventHandler {
1498         /// Handles the given [`Event`].
1499         ///
1500         /// See [`EventsProvider`] for details that must be considered when implementing this method.
1501         fn handle_event(&self, event: Event);
1502 }
1503
1504 impl<F> EventHandler for F where F: Fn(Event) {
1505         fn handle_event(&self, event: Event) {
1506                 self(event)
1507         }
1508 }
1509
1510 impl<T: EventHandler> EventHandler for Arc<T> {
1511         fn handle_event(&self, event: Event) {
1512                 self.deref().handle_event(event)
1513         }
1514 }