_ Git - rust-lightning/blob - lightning/src/onion_message/messenger.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 //! LDK sends, receives, and forwards onion messages via this [`OnionMessenger`], which lives here,
  11 //! as well as various types, traits, and utilities that it uses.
  12
  13 use bitcoin::hashes::{Hash, HashEngine};
  14 use bitcoin::hashes::hmac::{Hmac, HmacEngine};
  15 use bitcoin::hashes::sha256::Hash as Sha256;
  16 use bitcoin::secp256k1::{self, PublicKey, Scalar, Secp256k1, SecretKey};
  17
  18 use crate::blinded_path::{BlindedPath, IntroductionNode, NextMessageHop, NodeIdLookUp};
  19 use crate::blinded_path::message::{advance_path_by_one, ForwardTlvs, ReceiveTlvs};
  20 use crate::blinded_path::utils;
  21 use crate::events::{Event, EventHandler, EventsProvider};
  22 use crate::sign::{EntropySource, NodeSigner, Recipient};
  23 use crate::ln::features::{InitFeatures, NodeFeatures};
  24 use crate::ln::msgs::{self, OnionMessage, OnionMessageHandler, SocketAddress};
  25 use crate::ln::onion_utils;
  26 use crate::routing::gossip::{NetworkGraph, NodeId, ReadOnlyNetworkGraph};
  27 use super::packet::OnionMessageContents;
  28 use super::packet::ParsedOnionMessageContents;
  29 use super::offers::OffersMessageHandler;
  30 use super::packet::{BIG_PACKET_HOP_DATA_LEN, ForwardControlTlvs, Packet, Payload, ReceiveControlTlvs, SMALL_PACKET_HOP_DATA_LEN};
  31 use crate::util::logger::{Logger, WithContext};
  32 use crate::util::ser::Writeable;
  33
  34 use core::fmt;
  35 use core::ops::Deref;
  36 use crate::io;
  37 use crate::sync::Mutex;
  38 use crate::prelude::*;
  39
  40 #[cfg(not(c_bindings))]
  41 use {
  42         crate::sign::KeysManager,
  43         crate::ln::channelmanager::{SimpleArcChannelManager, SimpleRefChannelManager},
  44         crate::ln::peer_handler::IgnoringMessageHandler,
  45         crate::sync::Arc,
  46 };
  47
  48 pub(super) const MAX_TIMER_TICKS: usize = 2;
  49
  50 /// A trivial trait which describes any [`OnionMessenger`].
  51 ///
  52 /// This is not exported to bindings users as general cover traits aren't useful in other
  53 /// languages.
  54 pub trait AOnionMessenger {
  55         /// A type implementing [`EntropySource`]
  56         type EntropySource: EntropySource + ?Sized;
  57         /// A type that may be dereferenced to [`Self::EntropySource`]
  58         type ES: Deref<Target = Self::EntropySource>;
  59         /// A type implementing [`NodeSigner`]
  60         type NodeSigner: NodeSigner + ?Sized;
  61         /// A type that may be dereferenced to [`Self::NodeSigner`]
  62         type NS: Deref<Target = Self::NodeSigner>;
  63         /// A type implementing [`Logger`]
  64         type Logger: Logger + ?Sized;
  65         /// A type that may be dereferenced to [`Self::Logger`]
  66         type L: Deref<Target = Self::Logger>;
  67         /// A type implementing [`NodeIdLookUp`]
  68         type NodeIdLookUp: NodeIdLookUp + ?Sized;
  69         /// A type that may be dereferenced to [`Self::NodeIdLookUp`]
  70         type NL: Deref<Target = Self::NodeIdLookUp>;
  71         /// A type implementing [`MessageRouter`]
  72         type MessageRouter: MessageRouter + ?Sized;
  73         /// A type that may be dereferenced to [`Self::MessageRouter`]
  74         type MR: Deref<Target = Self::MessageRouter>;
  75         /// A type implementing [`OffersMessageHandler`]
  76         type OffersMessageHandler: OffersMessageHandler + ?Sized;
  77         /// A type that may be dereferenced to [`Self::OffersMessageHandler`]
  78         type OMH: Deref<Target = Self::OffersMessageHandler>;
  79         /// A type implementing [`CustomOnionMessageHandler`]
  80         type CustomOnionMessageHandler: CustomOnionMessageHandler + ?Sized;
  81         /// A type that may be dereferenced to [`Self::CustomOnionMessageHandler`]
  82         type CMH: Deref<Target = Self::CustomOnionMessageHandler>;
  83         /// Returns a reference to the actual [`OnionMessenger`] object.
  84         fn get_om(&self) -> &OnionMessenger<Self::ES, Self::NS, Self::L, Self::NL, Self::MR, Self::OMH, Self::CMH>;
  85 }
  86
  87 impl<ES: Deref, NS: Deref, L: Deref, NL: Deref, MR: Deref, OMH: Deref, CMH: Deref> AOnionMessenger
  88 for OnionMessenger<ES, NS, L, NL, MR, OMH, CMH> where
  89         ES::Target: EntropySource,
  90         NS::Target: NodeSigner,
  91         L::Target: Logger,
  92         NL::Target: NodeIdLookUp,
  93         MR::Target: MessageRouter,
  94         OMH::Target: OffersMessageHandler,
  95         CMH::Target: CustomOnionMessageHandler,
  96 {
  97         type EntropySource = ES::Target;
  98         type ES = ES;
  99         type NodeSigner = NS::Target;
 100         type NS = NS;
 101         type Logger = L::Target;
 102         type L = L;
 103         type NodeIdLookUp = NL::Target;
 104         type NL = NL;
 105         type MessageRouter = MR::Target;
 106         type MR = MR;
 107         type OffersMessageHandler = OMH::Target;
 108         type OMH = OMH;
 109         type CustomOnionMessageHandler = CMH::Target;
 110         type CMH = CMH;
 111         fn get_om(&self) -> &OnionMessenger<ES, NS, L, NL, MR, OMH, CMH> { self }
 112 }
 113
 114 /// A sender, receiver and forwarder of [`OnionMessage`]s.
 115 ///
 116 /// # Handling Messages
 117 ///
 118 /// `OnionMessenger` implements [`OnionMessageHandler`], making it responsible for either forwarding
 119 /// messages to peers or delegating to the appropriate handler for the message type. Currently, the
 120 /// available handlers are:
 121 /// * [`OffersMessageHandler`], for responding to [`InvoiceRequest`]s and paying [`Bolt12Invoice`]s
 122 /// * [`CustomOnionMessageHandler`], for handling user-defined message types
 123 ///
 124 /// # Sending Messages
 125 ///
 126 /// [`OnionMessage`]s are sent initially using [`OnionMessenger::send_onion_message`]. When handling
 127 /// a message, the matched handler may return a response message which `OnionMessenger` will send
 128 /// on its behalf.
 129 ///
 130 /// # Example
 131 ///
 132 /// ```
 133 /// # extern crate bitcoin;
 134 /// # use bitcoin::hashes::_export::_core::time::Duration;
 135 /// # use bitcoin::hashes::hex::FromHex;
 136 /// # use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey, self};
 137 /// # use lightning::blinded_path::{BlindedPath, EmptyNodeIdLookUp};
 138 /// # use lightning::sign::{EntropySource, KeysManager};
 139 /// # use lightning::ln::peer_handler::IgnoringMessageHandler;
 140 /// # use lightning::onion_message::messenger::{Destination, MessageRouter, OnionMessagePath, OnionMessenger};
 141 /// # use lightning::onion_message::packet::OnionMessageContents;
 142 /// # use lightning::util::logger::{Logger, Record};
 143 /// # use lightning::util::ser::{Writeable, Writer};
 144 /// # use lightning::io;
 145 /// # use std::sync::Arc;
 146 /// # struct FakeLogger;
 147 /// # impl Logger for FakeLogger {
 148 /// #     fn log(&self, record: Record) { println!("{:?}" , record); }
 149 /// # }
 150 /// # struct FakeMessageRouter {}
 151 /// # impl MessageRouter for FakeMessageRouter {
 152 /// #     fn find_path(&self, sender: PublicKey, peers: Vec<PublicKey>, destination: Destination) -> Result<OnionMessagePath, ()> {
 153 /// #         let secp_ctx = Secp256k1::new();
 154 /// #         let node_secret = SecretKey::from_slice(&<Vec<u8>>::from_hex("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
 155 /// #         let hop_node_id1 = PublicKey::from_secret_key(&secp_ctx, &node_secret);
 156 /// #         let hop_node_id2 = hop_node_id1;
 157 /// #         Ok(OnionMessagePath {
 158 /// #             intermediate_nodes: vec![hop_node_id1, hop_node_id2],
 159 /// #             destination,
 160 /// #             first_node_addresses: None,
 161 /// #         })
 162 /// #     }
 163 /// #     fn create_blinded_paths<T: secp256k1::Signing + secp256k1::Verification>(
 164 /// #         &self, _recipient: PublicKey, _peers: Vec<PublicKey>, _secp_ctx: &Secp256k1<T>
 165 /// #     ) -> Result<Vec<BlindedPath>, ()> {
 166 /// #         unreachable!()
 167 /// #     }
 168 /// # }
 169 /// # let seed = [42u8; 32];
 170 /// # let time = Duration::from_secs(123456);
 171 /// # let keys_manager = KeysManager::new(&seed, time.as_secs(), time.subsec_nanos());
 172 /// # let logger = Arc::new(FakeLogger {});
 173 /// # let node_secret = SecretKey::from_slice(&<Vec<u8>>::from_hex("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
 174 /// # let secp_ctx = Secp256k1::new();
 175 /// # let hop_node_id1 = PublicKey::from_secret_key(&secp_ctx, &node_secret);
 176 /// # let (hop_node_id3, hop_node_id4) = (hop_node_id1, hop_node_id1);
 177 /// # let destination_node_id = hop_node_id1;
 178 /// # let node_id_lookup = EmptyNodeIdLookUp {};
 179 /// # let message_router = Arc::new(FakeMessageRouter {});
 180 /// # let custom_message_handler = IgnoringMessageHandler {};
 181 /// # let offers_message_handler = IgnoringMessageHandler {};
 182 /// // Create the onion messenger. This must use the same `keys_manager` as is passed to your
 183 /// // ChannelManager.
 184 /// let onion_messenger = OnionMessenger::new(
 185 ///     &keys_manager, &keys_manager, logger, &node_id_lookup, message_router,
 186 ///     &offers_message_handler, &custom_message_handler
 187 /// );
 188
 189 /// # #[derive(Debug)]
 190 /// # struct YourCustomMessage {}
 191 /// impl Writeable for YourCustomMessage {
 192 ///     fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 193 ///             # Ok(())
 194 ///             // Write your custom onion message to `w`
 195 ///     }
 196 /// }
 197 /// impl OnionMessageContents for YourCustomMessage {
 198 ///     fn tlv_type(&self) -> u64 {
 199 ///             # let your_custom_message_type = 42;
 200 ///             your_custom_message_type
 201 ///     }
 202 ///     fn msg_type(&self) -> &'static str { "YourCustomMessageType" }
 203 /// }
 204 /// // Send a custom onion message to a node id.
 205 /// let destination = Destination::Node(destination_node_id);
 206 /// let reply_path = None;
 207 /// # let message = YourCustomMessage {};
 208 /// onion_messenger.send_onion_message(message, destination, reply_path);
 209 ///
 210 /// // Create a blinded path to yourself, for someone to send an onion message to.
 211 /// # let your_node_id = hop_node_id1;
 212 /// let hops = [hop_node_id3, hop_node_id4, your_node_id];
 213 /// let blinded_path = BlindedPath::new_for_message(&hops, &keys_manager, &secp_ctx).unwrap();
 214 ///
 215 /// // Send a custom onion message to a blinded path.
 216 /// let destination = Destination::BlindedPath(blinded_path);
 217 /// let reply_path = None;
 218 /// # let message = YourCustomMessage {};
 219 /// onion_messenger.send_onion_message(message, destination, reply_path);
 220 /// ```
 221 ///
 222 /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 223 /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 224 pub struct OnionMessenger<ES: Deref, NS: Deref, L: Deref, NL: Deref, MR: Deref, OMH: Deref, CMH: Deref>
 225 where
 226         ES::Target: EntropySource,
 227         NS::Target: NodeSigner,
 228         L::Target: Logger,
 229         NL::Target: NodeIdLookUp,
 230         MR::Target: MessageRouter,
 231         OMH::Target: OffersMessageHandler,
 232         CMH::Target: CustomOnionMessageHandler,
 233 {
 234         entropy_source: ES,
 235         node_signer: NS,
 236         logger: L,
 237         message_recipients: Mutex<HashMap<PublicKey, OnionMessageRecipient>>,
 238         secp_ctx: Secp256k1<secp256k1::All>,
 239         node_id_lookup: NL,
 240         message_router: MR,
 241         offers_handler: OMH,
 242         custom_handler: CMH,
 243         intercept_messages_for_offline_peers: bool,
 244         pending_events: Mutex<Vec<Event>>,
 245 }
 246
 247 /// [`OnionMessage`]s buffered to be sent.
 248 enum OnionMessageRecipient {
 249         /// Messages for a node connected as a peer.
 250         ConnectedPeer(VecDeque<OnionMessage>),
 251
 252         /// Messages for a node that is not yet connected, which are dropped after [`MAX_TIMER_TICKS`]
 253         /// and tracked here.
 254         PendingConnection(VecDeque<OnionMessage>, Option<Vec<SocketAddress>>, usize),
 255 }
 256
 257 impl OnionMessageRecipient {
 258         fn pending_connection(addresses: Vec<SocketAddress>) -> Self {
 259                 Self::PendingConnection(VecDeque::new(), Some(addresses), 0)
 260         }
 261
 262         fn pending_messages(&self) -> &VecDeque<OnionMessage> {
 263                 match self {
 264                         OnionMessageRecipient::ConnectedPeer(pending_messages) => pending_messages,
 265                         OnionMessageRecipient::PendingConnection(pending_messages, _, _) => pending_messages,
 266                 }
 267         }
 268
 269         fn enqueue_message(&mut self, message: OnionMessage) {
 270                 let pending_messages = match self {
 271                         OnionMessageRecipient::ConnectedPeer(pending_messages) => pending_messages,
 272                         OnionMessageRecipient::PendingConnection(pending_messages, _, _) => pending_messages,
 273                 };
 274
 275                 pending_messages.push_back(message);
 276         }
 277
 278         fn dequeue_message(&mut self) -> Option<OnionMessage> {
 279                 let pending_messages = match self {
 280                         OnionMessageRecipient::ConnectedPeer(pending_messages) => pending_messages,
 281                         OnionMessageRecipient::PendingConnection(pending_messages, _, _) => {
 282                                 debug_assert!(false);
 283                                 pending_messages
 284                         },
 285                 };
 286
 287                 pending_messages.pop_front()
 288         }
 289
 290         #[cfg(test)]
 291         fn release_pending_messages(&mut self) -> VecDeque<OnionMessage> {
 292                 let pending_messages = match self {
 293                         OnionMessageRecipient::ConnectedPeer(pending_messages) => pending_messages,
 294                         OnionMessageRecipient::PendingConnection(pending_messages, _, _) => pending_messages,
 295                 };
 296
 297                 core::mem::take(pending_messages)
 298         }
 299
 300         fn mark_connected(&mut self) {
 301                 if let OnionMessageRecipient::PendingConnection(pending_messages, _, _) = self {
 302                         let mut new_pending_messages = VecDeque::new();
 303                         core::mem::swap(pending_messages, &mut new_pending_messages);
 304                         *self = OnionMessageRecipient::ConnectedPeer(new_pending_messages);
 305                 }
 306         }
 307
 308         fn is_connected(&self) -> bool {
 309                 match self {
 310                         OnionMessageRecipient::ConnectedPeer(..) => true,
 311                         OnionMessageRecipient::PendingConnection(..) => false,
 312                 }
 313         }
 314 }
 315
 316
 317 /// The `Responder` struct creates an appropriate [`ResponseInstruction`]
 318 /// for responding to a message.
 319 pub struct Responder {
 320         /// The path along which a response can be sent.
 321         reply_path: BlindedPath,
 322         path_id: Option<[u8; 32]>
 323 }
 324
 325 impl Responder {
 326         /// Creates a new [`Responder`] instance with the provided reply path.
 327         fn new(reply_path: BlindedPath, path_id: Option<[u8; 32]>) -> Self {
 328                 Responder {
 329                         reply_path,
 330                         path_id,
 331                 }
 332         }
 333
 334         /// Creates the appropriate [`ResponseInstruction`] for a given response.
 335         pub fn respond<T: OnionMessageContents>(self, response: T) -> ResponseInstruction<T> {
 336                 ResponseInstruction::WithoutReplyPath(OnionMessageResponse {
 337                         message: response,
 338                         reply_path: self.reply_path,
 339                         path_id: self.path_id,
 340                 })
 341         }
 342 }
 343
 344 /// This struct contains the information needed to reply to a received message.
 345 pub struct OnionMessageResponse<T: OnionMessageContents> {
 346         message: T,
 347         reply_path: BlindedPath,
 348         path_id: Option<[u8; 32]>,
 349 }
 350
 351 /// `ResponseInstruction` represents instructions for responding to received messages.
 352 pub enum ResponseInstruction<T: OnionMessageContents> {
 353         /// Indicates that a response should be sent without including a reply path
 354         /// for the recipient to respond back.
 355         WithoutReplyPath(OnionMessageResponse<T>),
 356         /// Indicates that there's no response to send back.
 357         NoResponse,
 358 }
 359
 360 /// An [`OnionMessage`] for [`OnionMessenger`] to send.
 361 ///
 362 /// These are obtained when released from [`OnionMessenger`]'s handlers after which they are
 363 /// enqueued for sending.
 364 #[cfg(not(c_bindings))]
 365 pub struct PendingOnionMessage<T: OnionMessageContents> {
 366         /// The message contents to send in an [`OnionMessage`].
 367         pub contents: T,
 368
 369         /// The destination of the message.
 370         pub destination: Destination,
 371
 372         /// A reply path to include in the [`OnionMessage`] for a response.
 373         pub reply_path: Option<BlindedPath>,
 374 }
 375
 376 #[cfg(c_bindings)]
 377 /// An [`OnionMessage`] for [`OnionMessenger`] to send.
 378 ///
 379 /// These are obtained when released from [`OnionMessenger`]'s handlers after which they are
 380 /// enqueued for sending.
 381 pub type PendingOnionMessage<T> = (T, Destination, Option<BlindedPath>);
 382
 383 pub(crate) fn new_pending_onion_message<T: OnionMessageContents>(
 384         contents: T, destination: Destination, reply_path: Option<BlindedPath>
 385 ) -> PendingOnionMessage<T> {
 386         #[cfg(not(c_bindings))]
 387         return PendingOnionMessage { contents, destination, reply_path };
 388         #[cfg(c_bindings)]
 389         return (contents, destination, reply_path);
 390 }
 391
 392 /// A trait defining behavior for routing an [`OnionMessage`].
 393 pub trait MessageRouter {
 394         /// Returns a route for sending an [`OnionMessage`] to the given [`Destination`].
 395         fn find_path(
 396                 &self, sender: PublicKey, peers: Vec<PublicKey>, destination: Destination
 397         ) -> Result<OnionMessagePath, ()>;
 398
 399         /// Creates [`BlindedPath`]s to the `recipient` node. The nodes in `peers` are assumed to be
 400         /// direct peers with the `recipient`.
 401         fn create_blinded_paths<
 402                 T: secp256k1::Signing + secp256k1::Verification
 403         >(
 404                 &self, recipient: PublicKey, peers: Vec<PublicKey>, secp_ctx: &Secp256k1<T>,
 405         ) -> Result<Vec<BlindedPath>, ()>;
 406 }
 407
 408 /// A [`MessageRouter`] that can only route to a directly connected [`Destination`].
 409 pub struct DefaultMessageRouter<G: Deref<Target=NetworkGraph<L>>, L: Deref, ES: Deref>
 410 where
 411         L::Target: Logger,
 412         ES::Target: EntropySource,
 413 {
 414         network_graph: G,
 415         entropy_source: ES,
 416 }
 417
 418 impl<G: Deref<Target=NetworkGraph<L>>, L: Deref, ES: Deref> DefaultMessageRouter<G, L, ES>
 419 where
 420         L::Target: Logger,
 421         ES::Target: EntropySource,
 422 {
 423         /// Creates a [`DefaultMessageRouter`] using the given [`NetworkGraph`].
 424         pub fn new(network_graph: G, entropy_source: ES) -> Self {
 425                 Self { network_graph, entropy_source }
 426         }
 427 }
 428
 429 impl<G: Deref<Target=NetworkGraph<L>>, L: Deref, ES: Deref> MessageRouter for DefaultMessageRouter<G, L, ES>
 430 where
 431         L::Target: Logger,
 432         ES::Target: EntropySource,
 433 {
 434         fn find_path(
 435                 &self, sender: PublicKey, peers: Vec<PublicKey>, mut destination: Destination
 436         ) -> Result<OnionMessagePath, ()> {
 437                 let network_graph = self.network_graph.deref().read_only();
 438                 destination.resolve(&network_graph);
 439
 440                 let first_node = match destination.first_node() {
 441                         Some(first_node) => first_node,
 442                         None => return Err(()),
 443                 };
 444
 445                 if peers.contains(&first_node) || sender == first_node {
 446                         Ok(OnionMessagePath {
 447                                 intermediate_nodes: vec![], destination, first_node_addresses: None
 448                         })
 449                 } else {
 450                         let node_announcement = network_graph
 451                                 .node(&NodeId::from_pubkey(&first_node))
 452                                 .and_then(|node_info| node_info.announcement_info.as_ref())
 453                                 .and_then(|announcement_info| announcement_info.announcement_message.as_ref())
 454                                 .map(|node_announcement| &node_announcement.contents);
 455
 456                         match node_announcement {
 457                                 Some(node_announcement) if node_announcement.features.supports_onion_messages() => {
 458                                         let first_node_addresses = Some(node_announcement.addresses.clone());
 459                                         Ok(OnionMessagePath {
 460                                                 intermediate_nodes: vec![], destination, first_node_addresses
 461                                         })
 462                                 },
 463                                 _ => Err(()),
 464                         }
 465                 }
 466         }
 467
 468         fn create_blinded_paths<
 469                 T: secp256k1::Signing + secp256k1::Verification
 470         >(
 471                 &self, recipient: PublicKey, peers: Vec<PublicKey>, secp_ctx: &Secp256k1<T>,
 472         ) -> Result<Vec<BlindedPath>, ()> {
 473                 // Limit the number of blinded paths that are computed.
 474                 const MAX_PATHS: usize = 3;
 475
 476                 // Ensure peers have at least three channels so that it is more difficult to infer the
 477                 // recipient's node_id.
 478                 const MIN_PEER_CHANNELS: usize = 3;
 479
 480                 let network_graph = self.network_graph.deref().read_only();
 481                 let is_recipient_announced =
 482                         network_graph.nodes().contains_key(&NodeId::from_pubkey(&recipient));
 483
 484                 let mut peer_info = peers.iter()
 485                         // Limit to peers with announced channels
 486                         .filter_map(|pubkey|
 487                                 network_graph
 488                                         .node(&NodeId::from_pubkey(pubkey))
 489                                         .filter(|info| info.channels.len() >= MIN_PEER_CHANNELS)
 490                                         .map(|info| (*pubkey, info.is_tor_only(), info.channels.len()))
 491                         )
 492                         // Exclude Tor-only nodes when the recipient is announced.
 493                         .filter(|(_, is_tor_only, _)| !(*is_tor_only && is_recipient_announced))
 494                         .collect::<Vec<_>>();
 495
 496                 // Prefer using non-Tor nodes with the most channels as the introduction node.
 497                 peer_info.sort_unstable_by(|(_, a_tor_only, a_channels), (_, b_tor_only, b_channels)| {
 498                         a_tor_only.cmp(b_tor_only).then(a_channels.cmp(b_channels).reverse())
 499                 });
 500
 501                 let paths = peer_info.into_iter()
 502                         .map(|(pubkey, _, _)| vec![pubkey, recipient])
 503                         .map(|node_pks| BlindedPath::new_for_message(&node_pks, &*self.entropy_source, secp_ctx))
 504                         .take(MAX_PATHS)
 505                         .collect::<Result<Vec<_>, _>>();
 506
 507                 match paths {
 508                         Ok(paths) if !paths.is_empty() => Ok(paths),
 509                         _ => {
 510                                 if is_recipient_announced {
 511                                         BlindedPath::one_hop_for_message(recipient, &*self.entropy_source, secp_ctx)
 512                                                 .map(|path| vec![path])
 513                                 } else {
 514                                         Err(())
 515                                 }
 516                         },
 517                 }
 518         }
 519 }
 520
 521 /// A path for sending an [`OnionMessage`].
 522 #[derive(Clone)]
 523 pub struct OnionMessagePath {
 524         /// Nodes on the path between the sender and the destination.
 525         pub intermediate_nodes: Vec<PublicKey>,
 526
 527         /// The recipient of the message.
 528         pub destination: Destination,
 529
 530         /// Addresses that may be used to connect to [`OnionMessagePath::first_node`].
 531         ///
 532         /// Only needs to be set if a connection to the node is required. [`OnionMessenger`] may use
 533         /// this to initiate such a connection.
 534         pub first_node_addresses: Option<Vec<SocketAddress>>,
 535 }
 536
 537 impl OnionMessagePath {
 538         /// Returns the first node in the path.
 539         pub fn first_node(&self) -> Option<PublicKey> {
 540                 self.intermediate_nodes
 541                         .first()
 542                         .copied()
 543                         .or_else(|| self.destination.first_node())
 544         }
 545 }
 546
 547 /// The destination of an onion message.
 548 #[derive(Clone, Hash, Debug, PartialEq, Eq)]
 549 pub enum Destination {
 550         /// We're sending this onion message to a node.
 551         Node(PublicKey),
 552         /// We're sending this onion message to a blinded path.
 553         BlindedPath(BlindedPath),
 554 }
 555
 556 impl Destination {
 557         /// Attempts to resolve the [`IntroductionNode::DirectedShortChannelId`] of a
 558         /// [`Destination::BlindedPath`] to a [`IntroductionNode::NodeId`], if applicable, using the
 559         /// provided [`ReadOnlyNetworkGraph`].
 560         pub fn resolve(&mut self, network_graph: &ReadOnlyNetworkGraph) {
 561                 if let Destination::BlindedPath(path) = self {
 562                         if let IntroductionNode::DirectedShortChannelId(..) = path.introduction_node {
 563                                 if let Some(pubkey) = path
 564                                         .public_introduction_node_id(network_graph)
 565                                         .and_then(|node_id| node_id.as_pubkey().ok())
 566                                 {
 567                                         path.introduction_node = IntroductionNode::NodeId(pubkey);
 568                                 }
 569                         }
 570                 }
 571         }
 572
 573         pub(super) fn num_hops(&self) -> usize {
 574                 match self {
 575                         Destination::Node(_) => 1,
 576                         Destination::BlindedPath(BlindedPath { blinded_hops, .. }) => blinded_hops.len(),
 577                 }
 578         }
 579
 580         fn first_node(&self) -> Option<PublicKey> {
 581                 match self {
 582                         Destination::Node(node_id) => Some(*node_id),
 583                         Destination::BlindedPath(BlindedPath { introduction_node, .. }) => {
 584                                 match introduction_node {
 585                                         IntroductionNode::NodeId(pubkey) => Some(*pubkey),
 586                                         IntroductionNode::DirectedShortChannelId(..) => None,
 587                                 }
 588                         },
 589                 }
 590         }
 591 }
 592
 593 /// Result of successfully [sending an onion message].
 594 ///
 595 /// [sending an onion message]: OnionMessenger::send_onion_message
 596 #[derive(Clone, Hash, Debug, PartialEq, Eq)]
 597 pub enum SendSuccess {
 598         /// The message was buffered and will be sent once it is processed by
 599         /// [`OnionMessageHandler::next_onion_message_for_peer`].
 600         Buffered,
 601         /// The message was buffered and will be sent once the node is connected as a peer and it is
 602         /// processed by [`OnionMessageHandler::next_onion_message_for_peer`].
 603         BufferedAwaitingConnection(PublicKey),
 604 }
 605
 606 /// Errors that may occur when [sending an onion message].
 607 ///
 608 /// [sending an onion message]: OnionMessenger::send_onion_message
 609 #[derive(Clone, Hash, Debug, PartialEq, Eq)]
 610 pub enum SendError {
 611         /// Errored computing onion message packet keys.
 612         Secp256k1(secp256k1::Error),
 613         /// Because implementations such as Eclair will drop onion messages where the message packet
 614         /// exceeds 32834 bytes, we refuse to send messages where the packet exceeds this size.
 615         TooBigPacket,
 616         /// The provided [`Destination`] was an invalid [`BlindedPath`] due to not having any blinded
 617         /// hops.
 618         TooFewBlindedHops,
 619         /// The first hop is not a peer and doesn't have a known [`SocketAddress`].
 620         InvalidFirstHop(PublicKey),
 621         /// A path from the sender to the destination could not be found by the [`MessageRouter`].
 622         PathNotFound,
 623         /// Onion message contents must have a TLV type >= 64.
 624         InvalidMessage,
 625         /// Our next-hop peer's buffer was full or our total outbound buffer was full.
 626         BufferFull,
 627         /// Failed to retrieve our node id from the provided [`NodeSigner`].
 628         ///
 629         /// [`NodeSigner`]: crate::sign::NodeSigner
 630         GetNodeIdFailed,
 631         /// The provided [`Destination`] has a blinded path with an unresolved introduction node. An
 632         /// attempt to resolve it in the [`MessageRouter`] when finding an [`OnionMessagePath`] likely
 633         /// failed.
 634         UnresolvedIntroductionNode,
 635         /// We attempted to send to a blinded path where we are the introduction node, and failed to
 636         /// advance the blinded path to make the second hop the new introduction node. Either
 637         /// [`NodeSigner::ecdh`] failed, we failed to tweak the current blinding point to get the
 638         /// new blinding point, or we were attempting to send to ourselves.
 639         BlindedPathAdvanceFailed,
 640 }
 641
 642 /// Handler for custom onion messages. If you are using [`SimpleArcOnionMessenger`],
 643 /// [`SimpleRefOnionMessenger`], or prefer to ignore inbound custom onion messages,
 644 /// [`IgnoringMessageHandler`] must be provided to [`OnionMessenger::new`]. Otherwise, a custom
 645 /// implementation of this trait must be provided, with [`CustomMessage`] specifying the supported
 646 /// message types.
 647 ///
 648 /// See [`OnionMessenger`] for example usage.
 649 ///
 650 /// [`IgnoringMessageHandler`]: crate::ln::peer_handler::IgnoringMessageHandler
 651 /// [`CustomMessage`]: Self::CustomMessage
 652 pub trait CustomOnionMessageHandler {
 653         /// The message known to the handler. To support multiple message types, you may want to make this
 654         /// an enum with a variant for each supported message.
 655         type CustomMessage: OnionMessageContents;
 656
 657         /// Called with the custom message that was received, returning a response to send, if any.
 658         ///
 659         /// The returned [`Self::CustomMessage`], if any, is enqueued to be sent by [`OnionMessenger`].
 660         fn handle_custom_message(&self, message: Self::CustomMessage, responder: Option<Responder>) -> ResponseInstruction<Self::CustomMessage>;
 661
 662         /// Read a custom message of type `message_type` from `buffer`, returning `Ok(None)` if the
 663         /// message type is unknown.
 664         fn read_custom_message<R: io::Read>(&self, message_type: u64, buffer: &mut R) -> Result<Option<Self::CustomMessage>, msgs::DecodeError>;
 665
 666         /// Releases any [`Self::CustomMessage`]s that need to be sent.
 667         ///
 668         /// Typically, this is used for messages initiating a message flow rather than in response to
 669         /// another message. The latter should use the return value of [`Self::handle_custom_message`].
 670         #[cfg(not(c_bindings))]
 671         fn release_pending_custom_messages(&self) -> Vec<PendingOnionMessage<Self::CustomMessage>>;
 672
 673         /// Releases any [`Self::CustomMessage`]s that need to be sent.
 674         ///
 675         /// Typically, this is used for messages initiating a message flow rather than in response to
 676         /// another message. The latter should use the return value of [`Self::handle_custom_message`].
 677         #[cfg(c_bindings)]
 678         fn release_pending_custom_messages(&self) -> Vec<(Self::CustomMessage, Destination, Option<BlindedPath>)>;
 679 }
 680
 681 /// A processed incoming onion message, containing either a Forward (another onion message)
 682 /// or a Receive payload with decrypted contents.
 683 #[derive(Clone, Debug)]
 684 pub enum PeeledOnion<T: OnionMessageContents> {
 685         /// Forwarded onion, with the next node id and a new onion
 686         Forward(NextMessageHop, OnionMessage),
 687         /// Received onion message, with decrypted contents, path_id, and reply path
 688         Receive(ParsedOnionMessageContents<T>, Option<[u8; 32]>, Option<BlindedPath>)
 689 }
 690
 691
 692 /// Creates an [`OnionMessage`] with the given `contents` for sending to the destination of
 693 /// `path`, first calling [`Destination::resolve`] on `path.destination` with the given
 694 /// [`ReadOnlyNetworkGraph`].
 695 ///
 696 /// Returns the node id of the peer to send the message to, the message itself, and any addresses
 697 /// needed to connect to the first node.
 698 pub fn create_onion_message_resolving_destination<
 699         ES: Deref, NS: Deref, NL: Deref, T: OnionMessageContents
 700 >(
 701         entropy_source: &ES, node_signer: &NS, node_id_lookup: &NL,
 702         network_graph: &ReadOnlyNetworkGraph, secp_ctx: &Secp256k1<secp256k1::All>,
 703         mut path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>,
 704 ) -> Result<(PublicKey, OnionMessage, Option<Vec<SocketAddress>>), SendError>
 705 where
 706         ES::Target: EntropySource,
 707         NS::Target: NodeSigner,
 708         NL::Target: NodeIdLookUp,
 709 {
 710         path.destination.resolve(network_graph);
 711         create_onion_message(
 712                 entropy_source, node_signer, node_id_lookup, secp_ctx, path, contents, reply_path,
 713         )
 714 }
 715
 716 /// Creates an [`OnionMessage`] with the given `contents` for sending to the destination of
 717 /// `path`.
 718 ///
 719 /// Returns the node id of the peer to send the message to, the message itself, and any addresses
 720 /// needed to connect to the first node.
 721 ///
 722 /// Returns [`SendError::UnresolvedIntroductionNode`] if:
 723 /// - `destination` contains a blinded path with an [`IntroductionNode::DirectedShortChannelId`],
 724 /// - unless it can be resolved by [`NodeIdLookUp::next_node_id`].
 725 /// Use [`create_onion_message_resolving_destination`] instead to resolve the introduction node
 726 /// first with a [`ReadOnlyNetworkGraph`].
 727 pub fn create_onion_message<ES: Deref, NS: Deref, NL: Deref, T: OnionMessageContents>(
 728         entropy_source: &ES, node_signer: &NS, node_id_lookup: &NL,
 729         secp_ctx: &Secp256k1<secp256k1::All>, path: OnionMessagePath, contents: T,
 730         reply_path: Option<BlindedPath>,
 731 ) -> Result<(PublicKey, OnionMessage, Option<Vec<SocketAddress>>), SendError>
 732 where
 733         ES::Target: EntropySource,
 734         NS::Target: NodeSigner,
 735         NL::Target: NodeIdLookUp,
 736 {
 737         let OnionMessagePath { intermediate_nodes, mut destination, first_node_addresses } = path;
 738         if let Destination::BlindedPath(BlindedPath { ref blinded_hops, .. }) = destination {
 739                 if blinded_hops.is_empty() {
 740                         return Err(SendError::TooFewBlindedHops);
 741                 }
 742         }
 743
 744         if contents.tlv_type() < 64 { return Err(SendError::InvalidMessage) }
 745
 746         // If we are sending straight to a blinded path and we are the introduction node, we need to
 747         // advance the blinded path by 1 hop so the second hop is the new introduction node.
 748         if intermediate_nodes.len() == 0 {
 749                 if let Destination::BlindedPath(ref mut blinded_path) = destination {
 750                         let our_node_id = node_signer.get_node_id(Recipient::Node)
 751                                 .map_err(|()| SendError::GetNodeIdFailed)?;
 752                         let introduction_node_id = match blinded_path.introduction_node {
 753                                 IntroductionNode::NodeId(pubkey) => pubkey,
 754                                 IntroductionNode::DirectedShortChannelId(direction, scid) => {
 755                                         match node_id_lookup.next_node_id(scid) {
 756                                                 Some(next_node_id) => *direction.select_pubkey(&our_node_id, &next_node_id),
 757                                                 None => return Err(SendError::UnresolvedIntroductionNode),
 758                                         }
 759                                 },
 760                         };
 761                         if introduction_node_id == our_node_id {
 762                                 advance_path_by_one(blinded_path, node_signer, node_id_lookup, &secp_ctx)
 763                                         .map_err(|()| SendError::BlindedPathAdvanceFailed)?;
 764                         }
 765                 }
 766         }
 767
 768         let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
 769         let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
 770         let (first_node_id, blinding_point) = if let Some(first_node_id) = intermediate_nodes.first() {
 771                 (*first_node_id, PublicKey::from_secret_key(&secp_ctx, &blinding_secret))
 772         } else {
 773                 match &destination {
 774                         Destination::Node(pk) => (*pk, PublicKey::from_secret_key(&secp_ctx, &blinding_secret)),
 775                         Destination::BlindedPath(BlindedPath { introduction_node, blinding_point, .. }) => {
 776                                 match introduction_node {
 777                                         IntroductionNode::NodeId(pubkey) => (*pubkey, *blinding_point),
 778                                         IntroductionNode::DirectedShortChannelId(..) => {
 779                                                 return Err(SendError::UnresolvedIntroductionNode);
 780                                         },
 781                                 }
 782                         }
 783                 }
 784         };
 785         let (packet_payloads, packet_keys) = packet_payloads_and_keys(
 786                 &secp_ctx, &intermediate_nodes, destination, contents, reply_path, &blinding_secret
 787         )?;
 788
 789         let prng_seed = entropy_source.get_secure_random_bytes();
 790         let onion_routing_packet = construct_onion_message_packet(
 791                 packet_payloads, packet_keys, prng_seed).map_err(|()| SendError::TooBigPacket)?;
 792
 793         let message = OnionMessage { blinding_point, onion_routing_packet };
 794         Ok((first_node_id, message, first_node_addresses))
 795 }
 796
 797 /// Decode one layer of an incoming [`OnionMessage`].
 798 ///
 799 /// Returns either the next layer of the onion for forwarding or the decrypted content for the
 800 /// receiver.
 801 pub fn peel_onion_message<NS: Deref, L: Deref, CMH: Deref>(
 802         msg: &OnionMessage, secp_ctx: &Secp256k1<secp256k1::All>, node_signer: NS, logger: L,
 803         custom_handler: CMH,
 804 ) -> Result<PeeledOnion<<<CMH>::Target as CustomOnionMessageHandler>::CustomMessage>, ()>
 805 where
 806         NS::Target: NodeSigner,
 807         L::Target: Logger,
 808         CMH::Target: CustomOnionMessageHandler,
 809 {
 810         let control_tlvs_ss = match node_signer.ecdh(Recipient::Node, &msg.blinding_point, None) {
 811                 Ok(ss) => ss,
 812                 Err(e) =>  {
 813                         log_error!(logger, "Failed to retrieve node secret: {:?}", e);
 814                         return Err(());
 815                 }
 816         };
 817         let onion_decode_ss = {
 818                 let blinding_factor = {
 819                         let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
 820                         hmac.input(control_tlvs_ss.as_ref());
 821                         Hmac::from_engine(hmac).to_byte_array()
 822                 };
 823                 match node_signer.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
 824                         Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
 825                 {
 826                         Ok(ss) => ss.secret_bytes(),
 827                         Err(()) => {
 828                                 log_trace!(logger, "Failed to compute onion packet shared secret");
 829                                 return Err(());
 830                         }
 831                 }
 832         };
 833         match onion_utils::decode_next_untagged_hop(
 834                 onion_decode_ss, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
 835                 (control_tlvs_ss, custom_handler.deref(), logger.deref())
 836         ) {
 837                 Ok((Payload::Receive::<ParsedOnionMessageContents<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage>> {
 838                         message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
 839                 }, None)) => {
 840                         Ok(PeeledOnion::Receive(message, path_id, reply_path))
 841                 },
 842                 Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
 843                         next_hop, next_blinding_override
 844                 })), Some((next_hop_hmac, new_packet_bytes)))) => {
 845                         // TODO: we need to check whether `next_hop` is our node, in which case this is a dummy
 846                         // blinded hop and this onion message is destined for us. In this situation, we should keep
 847                         // unwrapping the onion layers to get to the final payload. Since we don't have the option
 848                         // of creating blinded paths with dummy hops currently, we should be ok to not handle this
 849                         // for now.
 850                         let new_pubkey = match onion_utils::next_hop_pubkey(&secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
 851                                 Ok(pk) => pk,
 852                                 Err(e) => {
 853                                         log_trace!(logger, "Failed to compute next hop packet pubkey: {}", e);
 854                                         return Err(())
 855                                 }
 856                         };
 857                         let outgoing_packet = Packet {
 858                                 version: 0,
 859                                 public_key: new_pubkey,
 860                                 hop_data: new_packet_bytes,
 861                                 hmac: next_hop_hmac,
 862                         };
 863                         let onion_message = OnionMessage {
 864                                 blinding_point: match next_blinding_override {
 865                                         Some(blinding_point) => blinding_point,
 866                                         None => {
 867                                                 match onion_utils::next_hop_pubkey(
 868                                                         &secp_ctx, msg.blinding_point, control_tlvs_ss.as_ref()
 869                                                 ) {
 870                                                         Ok(bp) => bp,
 871                                                         Err(e) => {
 872                                                                 log_trace!(logger, "Failed to compute next blinding point: {}", e);
 873                                                                 return Err(())
 874                                                         }
 875                                                 }
 876                                         }
 877                                 },
 878                                 onion_routing_packet: outgoing_packet,
 879                         };
 880
 881                         Ok(PeeledOnion::Forward(next_hop, onion_message))
 882                 },
 883                 Err(e) => {
 884                         log_trace!(logger, "Errored decoding onion message packet: {:?}", e);
 885                         Err(())
 886                 },
 887                 _ => {
 888                         log_trace!(logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
 889                         Err(())
 890                 },
 891         }
 892 }
 893
 894 impl<ES: Deref, NS: Deref, L: Deref, NL: Deref, MR: Deref, OMH: Deref, CMH: Deref>
 895 OnionMessenger<ES, NS, L, NL, MR, OMH, CMH>
 896 where
 897         ES::Target: EntropySource,
 898         NS::Target: NodeSigner,
 899         L::Target: Logger,
 900         NL::Target: NodeIdLookUp,
 901         MR::Target: MessageRouter,
 902         OMH::Target: OffersMessageHandler,
 903         CMH::Target: CustomOnionMessageHandler,
 904 {
 905         /// Constructs a new `OnionMessenger` to send, forward, and delegate received onion messages to
 906         /// their respective handlers.
 907         pub fn new(
 908                 entropy_source: ES, node_signer: NS, logger: L, node_id_lookup: NL, message_router: MR,
 909                 offers_handler: OMH, custom_handler: CMH
 910         ) -> Self {
 911                 Self::new_inner(
 912                         entropy_source, node_signer, logger, node_id_lookup, message_router,
 913                         offers_handler, custom_handler, false
 914                 )
 915         }
 916
 917         /// Similar to [`Self::new`], but rather than dropping onion messages that are
 918         /// intended to be forwarded to offline peers, we will intercept them for
 919         /// later forwarding.
 920         ///
 921         /// Interception flow:
 922         /// 1. If an onion message for an offline peer is received, `OnionMessenger` will
 923         ///    generate an [`Event::OnionMessageIntercepted`]. Event handlers can
 924         ///    then choose to persist this onion message for later forwarding, or drop
 925         ///    it.
 926         /// 2. When the offline peer later comes back online, `OnionMessenger` will
 927         ///    generate an [`Event::OnionMessagePeerConnected`]. Event handlers will
 928         ///    then fetch all previously intercepted onion messages for this peer.
 929         /// 3. Once the stored onion messages are fetched, they can finally be
 930         ///    forwarded to the now-online peer via [`Self::forward_onion_message`].
 931         ///
 932         /// # Note
 933         ///
 934         /// LDK will not rate limit how many [`Event::OnionMessageIntercepted`]s
 935         /// are generated, so it is the caller's responsibility to limit how many
 936         /// onion messages are persisted and only persist onion messages for relevant
 937         /// peers.
 938         pub fn new_with_offline_peer_interception(
 939                 entropy_source: ES, node_signer: NS, logger: L, node_id_lookup: NL,
 940                 message_router: MR, offers_handler: OMH, custom_handler: CMH
 941         ) -> Self {
 942                 Self::new_inner(
 943                         entropy_source, node_signer, logger, node_id_lookup, message_router,
 944                         offers_handler, custom_handler, true
 945                 )
 946         }
 947
 948         fn new_inner(
 949                 entropy_source: ES, node_signer: NS, logger: L, node_id_lookup: NL,
 950                 message_router: MR, offers_handler: OMH, custom_handler: CMH,
 951                 intercept_messages_for_offline_peers: bool
 952         ) -> Self {
 953                 let mut secp_ctx = Secp256k1::new();
 954                 secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());
 955                 OnionMessenger {
 956                         entropy_source,
 957                         node_signer,
 958                         message_recipients: Mutex::new(new_hash_map()),
 959                         secp_ctx,
 960                         logger,
 961                         node_id_lookup,
 962                         message_router,
 963                         offers_handler,
 964                         custom_handler,
 965                         intercept_messages_for_offline_peers,
 966                         pending_events: Mutex::new(Vec::new()),
 967                 }
 968         }
 969
 970         #[cfg(test)]
 971         pub(crate) fn set_offers_handler(&mut self, offers_handler: OMH) {
 972                 self.offers_handler = offers_handler;
 973         }
 974
 975         /// Sends an [`OnionMessage`] with the given `contents` to `destination`.
 976         ///
 977         /// See [`OnionMessenger`] for example usage.
 978         pub fn send_onion_message<T: OnionMessageContents>(
 979                 &self, contents: T, destination: Destination, reply_path: Option<BlindedPath>
 980         ) -> Result<SendSuccess, SendError> {
 981                 self.find_path_and_enqueue_onion_message(
 982                         contents, destination, reply_path, format_args!("")
 983                 )
 984         }
 985
 986         fn find_path_and_enqueue_onion_message<T: OnionMessageContents>(
 987                 &self, contents: T, destination: Destination, reply_path: Option<BlindedPath>,
 988                 log_suffix: fmt::Arguments
 989         ) -> Result<SendSuccess, SendError> {
 990                 let mut logger = WithContext::from(&self.logger, None, None, None);
 991                 let result = self.find_path(destination).and_then(|path| {
 992                         let first_hop = path.intermediate_nodes.get(0).map(|p| *p);
 993                         logger = WithContext::from(&self.logger, first_hop, None, None);
 994                         self.enqueue_onion_message(path, contents, reply_path, log_suffix)
 995                 });
 996
 997                 match result.as_ref() {
 998                         Err(SendError::GetNodeIdFailed) => {
 999                                 log_warn!(logger, "Unable to retrieve node id {}", log_suffix);
1000                         },
1001                         Err(SendError::PathNotFound) => {
1002                                 log_trace!(logger, "Failed to find path {}", log_suffix);
1003                         },
1004                         Err(e) => {
1005                                 log_trace!(logger, "Failed sending onion message {}: {:?}", log_suffix, e);
1006                         },
1007                         Ok(SendSuccess::Buffered) => {
1008                                 log_trace!(logger, "Buffered onion message {}", log_suffix);
1009                         },
1010                         Ok(SendSuccess::BufferedAwaitingConnection(node_id)) => {
1011                                 log_trace!(
1012                                         logger,
1013                                         "Buffered onion message waiting on peer connection {}: {}",
1014                                         log_suffix, node_id
1015                                 );
1016                         },
1017                 }
1018
1019                 result
1020         }
1021
1022         fn find_path(&self, destination: Destination) -> Result<OnionMessagePath, SendError> {
1023                 let sender = self.node_signer
1024                         .get_node_id(Recipient::Node)
1025                         .map_err(|_| SendError::GetNodeIdFailed)?;
1026
1027                 let peers = self.message_recipients.lock().unwrap()
1028                         .iter()
1029                         .filter(|(_, recipient)| matches!(recipient, OnionMessageRecipient::ConnectedPeer(_)))
1030                         .map(|(node_id, _)| *node_id)
1031                         .collect();
1032
1033                 self.message_router
1034                         .find_path(sender, peers, destination)
1035                         .map_err(|_| SendError::PathNotFound)
1036         }
1037
1038         fn enqueue_onion_message<T: OnionMessageContents>(
1039                 &self, path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>,
1040                 log_suffix: fmt::Arguments
1041         ) -> Result<SendSuccess, SendError> {
1042                 log_trace!(self.logger, "Constructing onion message {}: {:?}", log_suffix, contents);
1043
1044                 let (first_node_id, onion_message, addresses) = create_onion_message(
1045                         &self.entropy_source, &self.node_signer, &self.node_id_lookup, &self.secp_ctx, path,
1046                         contents, reply_path,
1047                 )?;
1048
1049                 let mut message_recipients = self.message_recipients.lock().unwrap();
1050                 if outbound_buffer_full(&first_node_id, &message_recipients) {
1051                         return Err(SendError::BufferFull);
1052                 }
1053
1054                 match message_recipients.entry(first_node_id) {
1055                         hash_map::Entry::Vacant(e) => match addresses {
1056                                 None => Err(SendError::InvalidFirstHop(first_node_id)),
1057                                 Some(addresses) => {
1058                                         e.insert(OnionMessageRecipient::pending_connection(addresses))
1059                                                 .enqueue_message(onion_message);
1060                                         Ok(SendSuccess::BufferedAwaitingConnection(first_node_id))
1061                                 },
1062                         },
1063                         hash_map::Entry::Occupied(mut e) => {
1064                                 e.get_mut().enqueue_message(onion_message);
1065                                 if e.get().is_connected() {
1066                                         Ok(SendSuccess::Buffered)
1067                                 } else {
1068                                         Ok(SendSuccess::BufferedAwaitingConnection(first_node_id))
1069                                 }
1070                         },
1071                 }
1072         }
1073
1074         /// Forwards an [`OnionMessage`] to `peer_node_id`. Useful if we initialized
1075         /// the [`OnionMessenger`] with [`Self::new_with_offline_peer_interception`]
1076         /// and want to forward a previously intercepted onion message to a peer that
1077         /// has just come online.
1078         pub fn forward_onion_message(
1079                 &self, message: OnionMessage, peer_node_id: &PublicKey
1080         ) -> Result<(), SendError> {
1081                 let mut message_recipients = self.message_recipients.lock().unwrap();
1082                 if outbound_buffer_full(&peer_node_id, &message_recipients) {
1083                         return Err(SendError::BufferFull);
1084                 }
1085
1086                 match message_recipients.entry(*peer_node_id) {
1087                         hash_map::Entry::Occupied(mut e) if e.get().is_connected() => {
1088                                 e.get_mut().enqueue_message(message);
1089                                 Ok(())
1090                         },
1091                         _ => Err(SendError::InvalidFirstHop(*peer_node_id))
1092                 }
1093         }
1094
1095         #[cfg(any(test, feature = "_test_utils"))]
1096         pub fn send_onion_message_using_path<T: OnionMessageContents>(
1097                 &self, path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>
1098         ) -> Result<SendSuccess, SendError> {
1099                 self.enqueue_onion_message(path, contents, reply_path, format_args!(""))
1100         }
1101
1102         pub(crate) fn peel_onion_message(
1103                 &self, msg: &OnionMessage
1104         ) -> Result<PeeledOnion<<<CMH>::Target as CustomOnionMessageHandler>::CustomMessage>, ()> {
1105                 peel_onion_message(
1106                         msg, &self.secp_ctx, &*self.node_signer, &*self.logger, &*self.custom_handler
1107                 )
1108         }
1109
1110         fn handle_onion_message_response<T: OnionMessageContents>(
1111                 &self, response: ResponseInstruction<T>
1112         ) {
1113                 if let ResponseInstruction::WithoutReplyPath(response) = response {
1114                         let message_type = response.message.msg_type();
1115                         let _ = self.find_path_and_enqueue_onion_message(
1116                                 response.message, Destination::BlindedPath(response.reply_path), None,
1117                                 format_args!(
1118                                         "when responding with {} to an onion message with path_id {:02x?}",
1119                                         message_type,
1120                                         response.path_id
1121                                 )
1122                         );
1123                 }
1124         }
1125
1126         #[cfg(test)]
1127         pub(super) fn release_pending_msgs(&self) -> HashMap<PublicKey, VecDeque<OnionMessage>> {
1128                 let mut message_recipients = self.message_recipients.lock().unwrap();
1129                 let mut msgs = new_hash_map();
1130                 // We don't want to disconnect the peers by removing them entirely from the original map, so we
1131                 // release the pending message buffers individually.
1132                 for (node_id, recipient) in &mut *message_recipients {
1133                         msgs.insert(*node_id, recipient.release_pending_messages());
1134                 }
1135                 msgs
1136         }
1137
1138         fn enqueue_event(&self, event: Event) {
1139                 const MAX_EVENTS_BUFFER_SIZE: usize = (1 << 10) * 256;
1140                 let mut pending_events = self.pending_events.lock().unwrap();
1141                 let total_buffered_bytes: usize = pending_events
1142                         .iter()
1143                         .map(|ev| ev.serialized_length())
1144                         .sum();
1145                 if total_buffered_bytes >= MAX_EVENTS_BUFFER_SIZE {
1146                         log_trace!(self.logger, "Dropping event {:?}: buffer full", event);
1147                         return
1148                 }
1149                 pending_events.push(event);
1150         }
1151 }
1152
1153 fn outbound_buffer_full(peer_node_id: &PublicKey, buffer: &HashMap<PublicKey, OnionMessageRecipient>) -> bool {
1154         const MAX_TOTAL_BUFFER_SIZE: usize = (1 << 20) * 128;
1155         const MAX_PER_PEER_BUFFER_SIZE: usize = (1 << 10) * 256;
1156         let mut total_buffered_bytes = 0;
1157         let mut peer_buffered_bytes = 0;
1158         for (pk, peer_buf) in buffer {
1159                 for om in peer_buf.pending_messages() {
1160                         let om_len = om.serialized_length();
1161                         if pk == peer_node_id {
1162                                 peer_buffered_bytes += om_len;
1163                         }
1164                         total_buffered_bytes += om_len;
1165
1166                         if total_buffered_bytes >= MAX_TOTAL_BUFFER_SIZE ||
1167                                 peer_buffered_bytes >= MAX_PER_PEER_BUFFER_SIZE
1168                         {
1169                                 return true
1170                         }
1171                 }
1172         }
1173         false
1174 }
1175
1176 impl<ES: Deref, NS: Deref, L: Deref, NL: Deref, MR: Deref, OMH: Deref, CMH: Deref> EventsProvider
1177 for OnionMessenger<ES, NS, L, NL, MR, OMH, CMH>
1178 where
1179         ES::Target: EntropySource,
1180         NS::Target: NodeSigner,
1181         L::Target: Logger,
1182         NL::Target: NodeIdLookUp,
1183         MR::Target: MessageRouter,
1184         OMH::Target: OffersMessageHandler,
1185         CMH::Target: CustomOnionMessageHandler,
1186 {
1187         fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {
1188                 for (node_id, recipient) in self.message_recipients.lock().unwrap().iter_mut() {
1189                         if let OnionMessageRecipient::PendingConnection(_, addresses, _) = recipient {
1190                                 if let Some(addresses) = addresses.take() {
1191                                         handler.handle_event(Event::ConnectionNeeded { node_id: *node_id, addresses });
1192                                 }
1193                         }
1194                 }
1195                 let mut events = Vec::new();
1196                 core::mem::swap(&mut *self.pending_events.lock().unwrap(), &mut events);
1197                 for ev in events {
1198                         handler.handle_event(ev);
1199                 }
1200         }
1201 }
1202
1203 impl<ES: Deref, NS: Deref, L: Deref, NL: Deref, MR: Deref, OMH: Deref, CMH: Deref> OnionMessageHandler
1204 for OnionMessenger<ES, NS, L, NL, MR, OMH, CMH>
1205 where
1206         ES::Target: EntropySource,
1207         NS::Target: NodeSigner,
1208         L::Target: Logger,
1209         NL::Target: NodeIdLookUp,
1210         MR::Target: MessageRouter,
1211         OMH::Target: OffersMessageHandler,
1212         CMH::Target: CustomOnionMessageHandler,
1213 {
1214         fn handle_onion_message(&self, peer_node_id: &PublicKey, msg: &OnionMessage) {
1215                 let logger = WithContext::from(&self.logger, Some(*peer_node_id), None, None);
1216                 match self.peel_onion_message(msg) {
1217                         Ok(PeeledOnion::Receive(message, path_id, reply_path)) => {
1218                                 log_trace!(
1219                                         logger,
1220                                         "Received an onion message with path_id {:02x?} and {} reply_path: {:?}",
1221                                         path_id, if reply_path.is_some() { "a" } else { "no" }, message);
1222
1223                                 match message {
1224                                         ParsedOnionMessageContents::Offers(msg) => {
1225                                                 let responder = reply_path.map(
1226                                                         |reply_path| Responder::new(reply_path, path_id)
1227                                                 );
1228                                                 let response_instructions = self.offers_handler.handle_message(msg, responder);
1229                                                 self.handle_onion_message_response(response_instructions);
1230                                         },
1231                                         ParsedOnionMessageContents::Custom(msg) => {
1232                                                 let responder = reply_path.map(
1233                                                         |reply_path| Responder::new(reply_path, path_id)
1234                                                 );
1235                                                 let response_instructions = self.custom_handler.handle_custom_message(msg, responder);
1236                                                 self.handle_onion_message_response(response_instructions);
1237                                         },
1238                                 }
1239                         },
1240                         Ok(PeeledOnion::Forward(next_hop, onion_message)) => {
1241                                 let next_node_id = match next_hop {
1242                                         NextMessageHop::NodeId(pubkey) => pubkey,
1243                                         NextMessageHop::ShortChannelId(scid) => match self.node_id_lookup.next_node_id(scid) {
1244                                                 Some(pubkey) => pubkey,
1245                                                 None => {
1246                                                         log_trace!(self.logger, "Dropping forwarded onion messager: unable to resolve next hop using SCID {}", scid);
1247                                                         return
1248                                                 },
1249                                         },
1250                                 };
1251
1252                                 let mut message_recipients = self.message_recipients.lock().unwrap();
1253                                 if outbound_buffer_full(&next_node_id, &message_recipients) {
1254                                         log_trace!(
1255                                                 logger,
1256                                                 "Dropping forwarded onion message to peer {}: outbound buffer full",
1257                                                 next_node_id);
1258                                         return
1259                                 }
1260
1261                                 #[cfg(fuzzing)]
1262                                 message_recipients
1263                                         .entry(next_node_id)
1264                                         .or_insert_with(|| OnionMessageRecipient::ConnectedPeer(VecDeque::new()));
1265
1266                                 match message_recipients.entry(next_node_id) {
1267                                         hash_map::Entry::Occupied(mut e) if matches!(
1268                                                 e.get(), OnionMessageRecipient::ConnectedPeer(..)
1269                                         ) => {
1270                                                 e.get_mut().enqueue_message(onion_message);
1271                                                 log_trace!(logger, "Forwarding an onion message to peer {}", next_node_id);
1272                                         },
1273                                         _ if self.intercept_messages_for_offline_peers => {
1274                                                 self.enqueue_event(
1275                                                         Event::OnionMessageIntercepted {
1276                                                                 peer_node_id: next_node_id, message: onion_message
1277                                                         }
1278                                                 );
1279                                         },
1280                                         _ => {
1281                                                 log_trace!(
1282                                                         logger,
1283                                                         "Dropping forwarded onion message to disconnected peer {}",
1284                                                         next_node_id);
1285                                                 return
1286                                         },
1287                                 }
1288                         },
1289                         Err(e) => {
1290                                 log_error!(logger, "Failed to process onion message {:?}", e);
1291                         }
1292                 }
1293         }
1294
1295         fn peer_connected(&self, their_node_id: &PublicKey, init: &msgs::Init, _inbound: bool) -> Result<(), ()> {
1296                 if init.features.supports_onion_messages() {
1297                         self.message_recipients.lock().unwrap()
1298                                 .entry(*their_node_id)
1299                                 .or_insert_with(|| OnionMessageRecipient::ConnectedPeer(VecDeque::new()))
1300                                 .mark_connected();
1301                         if self.intercept_messages_for_offline_peers {
1302                                 self.enqueue_event(
1303                                         Event::OnionMessagePeerConnected { peer_node_id: *their_node_id }
1304                                 );
1305                         }
1306                 } else {
1307                         self.message_recipients.lock().unwrap().remove(their_node_id);
1308                 }
1309
1310                 Ok(())
1311         }
1312
1313         fn peer_disconnected(&self, their_node_id: &PublicKey) {
1314                 match self.message_recipients.lock().unwrap().remove(their_node_id) {
1315                         Some(OnionMessageRecipient::ConnectedPeer(..)) => {},
1316                         Some(_) => debug_assert!(false),
1317                         None => {},
1318                 }
1319         }
1320
1321         fn timer_tick_occurred(&self) {
1322                 let mut message_recipients = self.message_recipients.lock().unwrap();
1323
1324                 // Drop any pending recipients since the last call to avoid retaining buffered messages for
1325                 // too long.
1326                 message_recipients.retain(|_, recipient| match recipient {
1327                         OnionMessageRecipient::PendingConnection(_, None, ticks) => *ticks < MAX_TIMER_TICKS,
1328                         OnionMessageRecipient::PendingConnection(_, Some(_), _) => true,
1329                         _ => true,
1330                 });
1331
1332                 // Increment a timer tick for pending recipients so that their buffered messages are dropped
1333                 // at MAX_TIMER_TICKS.
1334                 for recipient in message_recipients.values_mut() {
1335                         if let OnionMessageRecipient::PendingConnection(_, None, ticks) = recipient {
1336                                 *ticks += 1;
1337                         }
1338                 }
1339         }
1340
1341         fn provided_node_features(&self) -> NodeFeatures {
1342                 let mut features = NodeFeatures::empty();
1343                 features.set_onion_messages_optional();
1344                 features
1345         }
1346
1347         fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
1348                 let mut features = InitFeatures::empty();
1349                 features.set_onion_messages_optional();
1350                 features
1351         }
1352
1353         // Before returning any messages to send for the peer, this method will see if any messages were
1354         // enqueued in the handler by users, find a path to the corresponding blinded path's introduction
1355         // node, and then enqueue the message for sending to the first peer in the full path.
1356         fn next_onion_message_for_peer(&self, peer_node_id: PublicKey) -> Option<OnionMessage> {
1357                 // Enqueue any initiating `OffersMessage`s to send.
1358                 for message in self.offers_handler.release_pending_messages() {
1359                         #[cfg(not(c_bindings))]
1360                         let PendingOnionMessage { contents, destination, reply_path } = message;
1361                         #[cfg(c_bindings)]
1362                         let (contents, destination, reply_path) = message;
1363                         let _ = self.find_path_and_enqueue_onion_message(
1364                                 contents, destination, reply_path, format_args!("when sending OffersMessage")
1365                         );
1366                 }
1367
1368                 // Enqueue any initiating `CustomMessage`s to send.
1369                 for message in self.custom_handler.release_pending_custom_messages() {
1370                         #[cfg(not(c_bindings))]
1371                         let PendingOnionMessage { contents, destination, reply_path } = message;
1372                         #[cfg(c_bindings)]
1373                         let (contents, destination, reply_path) = message;
1374                         let _ = self.find_path_and_enqueue_onion_message(
1375                                 contents, destination, reply_path, format_args!("when sending CustomMessage")
1376                         );
1377                 }
1378
1379                 self.message_recipients.lock().unwrap()
1380                         .get_mut(&peer_node_id)
1381                         .and_then(|buffer| buffer.dequeue_message())
1382         }
1383 }
1384
1385 // TODO: parameterize the below Simple* types with OnionMessenger and handle the messages it
1386 // produces
1387 /// Useful for simplifying the parameters of [`SimpleArcChannelManager`] and
1388 /// [`SimpleArcPeerManager`]. See their docs for more details.
1389 ///
1390 /// This is not exported to bindings users as type aliases aren't supported in most languages.
1391 ///
1392 /// [`SimpleArcChannelManager`]: crate::ln::channelmanager::SimpleArcChannelManager
1393 /// [`SimpleArcPeerManager`]: crate::ln::peer_handler::SimpleArcPeerManager
1394 #[cfg(not(c_bindings))]
1395 pub type SimpleArcOnionMessenger<M, T, F, L> = OnionMessenger<
1396         Arc<KeysManager>,
1397         Arc<KeysManager>,
1398         Arc<L>,
1399         Arc<SimpleArcChannelManager<M, T, F, L>>,
1400         Arc<DefaultMessageRouter<Arc<NetworkGraph<Arc<L>>>, Arc<L>, Arc<KeysManager>>>,
1401         Arc<SimpleArcChannelManager<M, T, F, L>>,
1402         IgnoringMessageHandler
1403 >;
1404
1405 /// Useful for simplifying the parameters of [`SimpleRefChannelManager`] and
1406 /// [`SimpleRefPeerManager`]. See their docs for more details.
1407 ///
1408 /// This is not exported to bindings users as type aliases aren't supported in most languages.
1409 ///
1410 /// [`SimpleRefChannelManager`]: crate::ln::channelmanager::SimpleRefChannelManager
1411 /// [`SimpleRefPeerManager`]: crate::ln::peer_handler::SimpleRefPeerManager
1412 #[cfg(not(c_bindings))]
1413 pub type SimpleRefOnionMessenger<
1414         'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, M, T, F, L
1415 > = OnionMessenger<
1416         &'a KeysManager,
1417         &'a KeysManager,
1418         &'b L,
1419         &'i SimpleRefChannelManager<'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, M, T, F, L>,
1420         &'j DefaultMessageRouter<&'g NetworkGraph<&'b L>, &'b L, &'a KeysManager>,
1421         &'i SimpleRefChannelManager<'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, M, T, F, L>,
1422         IgnoringMessageHandler
1423 >;
1424
1425 /// Construct onion packet payloads and keys for sending an onion message along the given
1426 /// `unblinded_path` to the given `destination`.
1427 fn packet_payloads_and_keys<T: OnionMessageContents, S: secp256k1::Signing + secp256k1::Verification>(
1428         secp_ctx: &Secp256k1<S>, unblinded_path: &[PublicKey], destination: Destination, message: T,
1429         mut reply_path: Option<BlindedPath>, session_priv: &SecretKey
1430 ) -> Result<(Vec<(Payload<T>, [u8; 32])>, Vec<onion_utils::OnionKeys>), SendError> {
1431         let num_hops = unblinded_path.len() + destination.num_hops();
1432         let mut payloads = Vec::with_capacity(num_hops);
1433         let mut onion_packet_keys = Vec::with_capacity(num_hops);
1434
1435         let (mut intro_node_id_blinding_pt, num_blinded_hops) = match &destination {
1436                 Destination::Node(_) => (None, 0),
1437                 Destination::BlindedPath(BlindedPath { introduction_node, blinding_point, blinded_hops }) => {
1438                         let introduction_node_id = match introduction_node {
1439                                 IntroductionNode::NodeId(pubkey) => pubkey,
1440                                 IntroductionNode::DirectedShortChannelId(..) => {
1441                                         return Err(SendError::UnresolvedIntroductionNode);
1442                                 },
1443                         };
1444                         (Some((*introduction_node_id, *blinding_point)), blinded_hops.len())
1445                 },
1446         };
1447         let num_unblinded_hops = num_hops - num_blinded_hops;
1448
1449         let mut unblinded_path_idx = 0;
1450         let mut blinded_path_idx = 0;
1451         let mut prev_control_tlvs_ss = None;
1452         let mut final_control_tlvs = None;
1453         utils::construct_keys_callback(secp_ctx, unblinded_path.iter(), Some(destination), session_priv,
1454                 |_, onion_packet_ss, ephemeral_pubkey, control_tlvs_ss, unblinded_pk_opt, enc_payload_opt| {
1455                         if num_unblinded_hops != 0 && unblinded_path_idx < num_unblinded_hops {
1456                                 if let Some(ss) = prev_control_tlvs_ss.take() {
1457                                         payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(
1458                                                 ForwardTlvs {
1459                                                         next_hop: NextMessageHop::NodeId(unblinded_pk_opt.unwrap()),
1460                                                         next_blinding_override: None,
1461                                                 }
1462                                         )), ss));
1463                                 }
1464                                 prev_control_tlvs_ss = Some(control_tlvs_ss);
1465                                 unblinded_path_idx += 1;
1466                         } else if let Some((intro_node_id, blinding_pt)) = intro_node_id_blinding_pt.take() {
1467                                 if let Some(control_tlvs_ss) = prev_control_tlvs_ss.take() {
1468                                         payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
1469                                                 next_hop: NextMessageHop::NodeId(intro_node_id),
1470                                                 next_blinding_override: Some(blinding_pt),
1471                                         })), control_tlvs_ss));
1472                                 }
1473                         }
1474                         if blinded_path_idx < num_blinded_hops.saturating_sub(1) && enc_payload_opt.is_some() {
1475                                 payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(enc_payload_opt.unwrap())),
1476                                         control_tlvs_ss));
1477                                 blinded_path_idx += 1;
1478                         } else if let Some(encrypted_payload) = enc_payload_opt {
1479                                 final_control_tlvs = Some(ReceiveControlTlvs::Blinded(encrypted_payload));
1480                                 prev_control_tlvs_ss = Some(control_tlvs_ss);
1481                         }
1482
1483                         let (rho, mu) = onion_utils::gen_rho_mu_from_shared_secret(onion_packet_ss.as_ref());
1484                         onion_packet_keys.push(onion_utils::OnionKeys {
1485                                 #[cfg(test)]
1486                                 shared_secret: onion_packet_ss,
1487                                 #[cfg(test)]
1488                                 blinding_factor: [0; 32],
1489                                 ephemeral_pubkey,
1490                                 rho,
1491                                 mu,
1492                         });
1493                 }
1494         ).map_err(|e| SendError::Secp256k1(e))?;
1495
1496         if let Some(control_tlvs) = final_control_tlvs {
1497                 payloads.push((Payload::Receive {
1498                         control_tlvs,
1499                         reply_path: reply_path.take(),
1500                         message,
1501                 }, prev_control_tlvs_ss.unwrap()));
1502         } else {
1503                 payloads.push((Payload::Receive {
1504                         control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id: None, }),
1505                         reply_path: reply_path.take(),
1506                         message,
1507                 }, prev_control_tlvs_ss.unwrap()));
1508         }
1509
1510         Ok((payloads, onion_packet_keys))
1511 }
1512
1513 /// Errors if the serialized payload size exceeds onion_message::BIG_PACKET_HOP_DATA_LEN
1514 fn construct_onion_message_packet<T: OnionMessageContents>(payloads: Vec<(Payload<T>, [u8; 32])>, onion_keys: Vec<onion_utils::OnionKeys>, prng_seed: [u8; 32]) -> Result<Packet, ()> {
1515         // Spec rationale:
1516         // "`len` allows larger messages to be sent than the standard 1300 bytes allowed for an HTLC
1517         // onion, but this should be used sparingly as it is reduces anonymity set, hence the
1518         // recommendation that it either look like an HTLC onion, or if larger, be a fixed size."
1519         let payloads_ser_len = onion_utils::payloads_serialized_length(&payloads);
1520         let hop_data_len = if payloads_ser_len <= SMALL_PACKET_HOP_DATA_LEN {
1521                 SMALL_PACKET_HOP_DATA_LEN
1522         } else if payloads_ser_len <= BIG_PACKET_HOP_DATA_LEN {
1523                 BIG_PACKET_HOP_DATA_LEN
1524         } else { return Err(()) };
1525
1526         onion_utils::construct_onion_message_packet::<_, _>(
1527                 payloads, onion_keys, prng_seed, hop_data_len)
1528 }