1 // This file is Copyright its original authors, visible in version control
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
10 //! LDK sends, receives, and forwards onion messages via the [`OnionMessenger`]. See its docs for
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};
18 use crate::chain::keysinterface::{InMemorySigner, KeysInterface, KeysManager, Recipient, Sign};
19 use crate::ln::features::{InitFeatures, NodeFeatures};
20 use crate::ln::msgs::{self, OnionMessageHandler};
21 use crate::ln::onion_utils;
22 use crate::ln::peer_handler::IgnoringMessageHandler;
23 use super::blinded_route::{BlindedRoute, ForwardTlvs, ReceiveTlvs};
24 use super::packet::{CustomOnionMessageContents, OnionMessageContents};
25 use super::packet::{BIG_PACKET_HOP_DATA_LEN, ForwardControlTlvs, Packet, Payload, ReceiveControlTlvs, SMALL_PACKET_HOP_DATA_LEN};
27 use crate::util::events::OnionMessageProvider;
28 use crate::util::logger::Logger;
29 use crate::util::ser::Writeable;
33 use crate::sync::{Arc, Mutex};
34 use crate::prelude::*;
36 /// A sender, receiver and forwarder of onion messages. In upcoming releases, this object will be
37 /// used to retrieve invoices and fulfill invoice requests from [offers]. Currently, only sending
38 /// and receiving custom onion messages is supported.
43 /// # extern crate bitcoin;
44 /// # use bitcoin::hashes::_export::_core::time::Duration;
45 /// # use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
46 /// # use lightning::chain::keysinterface::{InMemorySigner, KeysManager, KeysInterface};
47 /// # use lightning::ln::msgs::DecodeError;
48 /// # use lightning::ln::peer_handler::IgnoringMessageHandler;
49 /// # use lightning::onion_message::messenger::{Destination, OnionMessenger};
50 /// # use lightning::onion_message::packet::CustomOnionMessageContents;
51 /// # use lightning::onion_message::blinded_route::BlindedRoute;
52 /// # use lightning::util::logger::{Logger, Record};
53 /// # use lightning::util::ser::{Writeable, Writer};
54 /// # use lightning::io;
55 /// # use std::sync::Arc;
56 /// # struct FakeLogger {};
57 /// # impl Logger for FakeLogger {
58 /// # fn log(&self, record: &Record) { unimplemented!() }
60 /// # let seed = [42u8; 32];
61 /// # let time = Duration::from_secs(123456);
62 /// # let keys_manager = KeysManager::new(&seed, time.as_secs(), time.subsec_nanos());
63 /// # let logger = Arc::new(FakeLogger {});
64 /// # let node_secret = SecretKey::from_slice(&hex::decode("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
65 /// # let secp_ctx = Secp256k1::new();
66 /// # let hop_node_id1 = PublicKey::from_secret_key(&secp_ctx, &node_secret);
67 /// # let (hop_node_id2, hop_node_id3, hop_node_id4) = (hop_node_id1, hop_node_id1, hop_node_id1);
68 /// # let destination_node_id = hop_node_id1;
69 /// # let your_custom_message_handler = IgnoringMessageHandler {};
70 /// // Create the onion messenger. This must use the same `keys_manager` as is passed to your
71 /// // ChannelManager.
72 /// let onion_messenger = OnionMessenger::new(&keys_manager, logger, your_custom_message_handler);
74 /// # #[derive(Clone)]
75 /// # struct YourCustomMessage {}
76 /// impl Writeable for YourCustomMessage {
77 /// fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
79 /// // Write your custom onion message to `w`
82 /// impl CustomOnionMessageContents for YourCustomMessage {
83 /// fn tlv_type(&self) -> u64 {
84 /// # let your_custom_message_type = 42;
85 /// your_custom_message_type
88 /// // Send a custom onion message to a node id.
89 /// let intermediate_hops = [hop_node_id1, hop_node_id2];
90 /// let reply_path = None;
91 /// # let your_custom_message = YourCustomMessage {};
92 /// onion_messenger.send_custom_onion_message(&intermediate_hops, Destination::Node(destination_node_id), your_custom_message, reply_path);
94 /// // Create a blinded route to yourself, for someone to send an onion message to.
95 /// # let your_node_id = hop_node_id1;
96 /// let hops = [hop_node_id3, hop_node_id4, your_node_id];
97 /// let blinded_route = BlindedRoute::new(&hops, &keys_manager, &secp_ctx).unwrap();
99 /// // Send a custom onion message to a blinded route.
100 /// # let intermediate_hops = [hop_node_id1, hop_node_id2];
101 /// let reply_path = None;
102 /// # let your_custom_message = YourCustomMessage {};
103 /// onion_messenger.send_custom_onion_message(&intermediate_hops, Destination::BlindedRoute(blinded_route), your_custom_message, reply_path);
106 /// [offers]: <https://github.com/lightning/bolts/pull/798>
107 /// [`OnionMessenger`]: crate::onion_message::OnionMessenger
108 pub struct OnionMessenger<Signer: Sign, K: Deref, L: Deref, CMH: Deref>
109 where K::Target: KeysInterface<Signer = Signer>,
111 CMH:: Target: CustomOnionMessageHandler,
115 pending_messages: Mutex<HashMap<PublicKey, VecDeque<msgs::OnionMessage>>>,
116 secp_ctx: Secp256k1<secp256k1::All>,
119 // invoice_handler: InvoiceHandler,
122 /// The destination of an onion message.
123 pub enum Destination {
124 /// We're sending this onion message to a node.
126 /// We're sending this onion message to a blinded route.
127 BlindedRoute(BlindedRoute),
131 pub(super) fn num_hops(&self) -> usize {
133 Destination::Node(_) => 1,
134 Destination::BlindedRoute(BlindedRoute { blinded_hops, .. }) => blinded_hops.len(),
139 /// Errors that may occur when [sending an onion message].
141 /// [sending an onion message]: OnionMessenger::send_custom_onion_message
142 #[derive(Debug, PartialEq, Eq)]
144 /// Errored computing onion message packet keys.
145 Secp256k1(secp256k1::Error),
146 /// Because implementations such as Eclair will drop onion messages where the message packet
147 /// exceeds 32834 bytes, we refuse to send messages where the packet exceeds this size.
149 /// The provided [`Destination`] was an invalid [`BlindedRoute`], due to having fewer than two
152 /// Our next-hop peer was offline or does not support onion message forwarding.
154 /// Onion message contents must have a TLV type >= 64.
156 /// Our next-hop peer's buffer was full or our total outbound buffer was full.
160 /// Handler for custom onion messages. If you are using [`SimpleArcOnionMessenger`],
161 /// [`SimpleRefOnionMessenger`], or prefer to ignore inbound custom onion messages,
162 /// [`IgnoringMessageHandler`] must be provided to [`OnionMessenger::new`]. Otherwise, a custom
163 /// implementation of this trait must be provided, with [`CustomMessage`] specifying the supported
166 /// See [`OnionMessenger`] for example usage.
168 /// [`IgnoringMessageHandler`]: crate::ln::peer_handler::IgnoringMessageHandler
169 /// [`CustomMessage`]: Self::CustomMessage
170 pub trait CustomOnionMessageHandler {
171 /// The message known to the handler. To support multiple message types, you may want to make this
172 /// an enum with a variant for each supported message.
173 type CustomMessage: CustomOnionMessageContents;
174 /// Called with the custom message that was received.
175 fn handle_custom_message(&self, msg: Self::CustomMessage);
176 /// Read a custom message of type `message_type` from `buffer`, returning `Ok(None)` if the
177 /// message type is unknown.
178 fn read_custom_message<R: io::Read>(&self, message_type: u64, buffer: &mut R) -> Result<Option<Self::CustomMessage>, msgs::DecodeError>;
181 impl<Signer: Sign, K: Deref, L: Deref, CMH: Deref> OnionMessenger<Signer, K, L, CMH>
182 where K::Target: KeysInterface<Signer = Signer>,
184 CMH::Target: CustomOnionMessageHandler,
186 /// Constructs a new `OnionMessenger` to send, forward, and delegate received onion messages to
187 /// their respective handlers.
188 pub fn new(keys_manager: K, logger: L, custom_handler: CMH) -> Self {
189 let mut secp_ctx = Secp256k1::new();
190 secp_ctx.seeded_randomize(&keys_manager.get_secure_random_bytes());
193 pending_messages: Mutex::new(HashMap::new()),
200 /// Send an onion message with contents `message` to `destination`, routing it through `intermediate_nodes`.
201 /// See [`OnionMessenger`] for example usage.
202 pub(crate) fn send_onion_message<T: CustomOnionMessageContents>(&self, intermediate_nodes: &[PublicKey], destination: Destination, msg: OnionMessageContents<T>, reply_path: Option<BlindedRoute>) -> Result<(), SendError> {
203 let OnionMessageContents::Custom(message) = msg;
204 self.send_custom_onion_message(intermediate_nodes, destination, message, reply_path)
207 /// Send an onion message with contents `message` to `destination`, routing it through `intermediate_nodes`.
208 /// See [`OnionMessenger`] for example usage.
209 pub fn send_custom_onion_message<T: CustomOnionMessageContents>(&self, intermediate_nodes: &[PublicKey], destination: Destination, msg: T, reply_path: Option<BlindedRoute>) -> Result<(), SendError> {
210 if let Destination::BlindedRoute(BlindedRoute { ref blinded_hops, .. }) = destination {
211 if blinded_hops.len() < 2 {
212 return Err(SendError::TooFewBlindedHops);
215 if msg.tlv_type() < 64 { return Err(SendError::InvalidMessage) }
217 let blinding_secret_bytes = self.keys_manager.get_secure_random_bytes();
218 let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
219 let (introduction_node_id, blinding_point) = if intermediate_nodes.len() != 0 {
220 (intermediate_nodes[0], PublicKey::from_secret_key(&self.secp_ctx, &blinding_secret))
223 Destination::Node(pk) => (pk, PublicKey::from_secret_key(&self.secp_ctx, &blinding_secret)),
224 Destination::BlindedRoute(BlindedRoute { introduction_node_id, blinding_point, .. }) =>
225 (introduction_node_id, blinding_point),
228 let (packet_payloads, packet_keys) = packet_payloads_and_keys(
229 &self.secp_ctx, intermediate_nodes, destination, OnionMessageContents::Custom(msg), reply_path, &blinding_secret)
230 .map_err(|e| SendError::Secp256k1(e))?;
232 let prng_seed = self.keys_manager.get_secure_random_bytes();
233 let onion_routing_packet = construct_onion_message_packet(
234 packet_payloads, packet_keys, prng_seed).map_err(|()| SendError::TooBigPacket)?;
236 let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
237 if outbound_buffer_full(&introduction_node_id, &pending_per_peer_msgs) { return Err(SendError::BufferFull) }
238 match pending_per_peer_msgs.entry(introduction_node_id) {
239 hash_map::Entry::Vacant(_) => Err(SendError::InvalidFirstHop),
240 hash_map::Entry::Occupied(mut e) => {
241 e.get_mut().push_back(msgs::OnionMessage { blinding_point, onion_routing_packet });
248 pub(super) fn release_pending_msgs(&self) -> HashMap<PublicKey, VecDeque<msgs::OnionMessage>> {
249 let mut pending_msgs = self.pending_messages.lock().unwrap();
250 let mut msgs = HashMap::new();
251 // We don't want to disconnect the peers by removing them entirely from the original map, so we
252 // swap the pending message buffers individually.
253 for (peer_node_id, pending_messages) in &mut *pending_msgs {
254 msgs.insert(*peer_node_id, core::mem::take(pending_messages));
260 fn outbound_buffer_full(peer_node_id: &PublicKey, buffer: &HashMap<PublicKey, VecDeque<msgs::OnionMessage>>) -> bool {
261 const MAX_TOTAL_BUFFER_SIZE: usize = (1 << 20) * 128;
262 const MAX_PER_PEER_BUFFER_SIZE: usize = (1 << 10) * 256;
263 let mut total_buffered_bytes = 0;
264 let mut peer_buffered_bytes = 0;
265 for (pk, peer_buf) in buffer {
267 let om_len = om.serialized_length();
268 if pk == peer_node_id {
269 peer_buffered_bytes += om_len;
271 total_buffered_bytes += om_len;
273 if total_buffered_bytes >= MAX_TOTAL_BUFFER_SIZE ||
274 peer_buffered_bytes >= MAX_PER_PEER_BUFFER_SIZE
283 impl<Signer: Sign, K: Deref, L: Deref, CMH: Deref> OnionMessageHandler for OnionMessenger<Signer, K, L, CMH>
284 where K::Target: KeysInterface<Signer = Signer>,
286 CMH::Target: CustomOnionMessageHandler + Sized,
288 /// Handle an incoming onion message. Currently, if a message was destined for us we will log, but
289 /// soon we'll delegate the onion message to a handler that can generate invoices or send
291 fn handle_onion_message(&self, _peer_node_id: &PublicKey, msg: &msgs::OnionMessage) {
292 let control_tlvs_ss = match self.keys_manager.ecdh(Recipient::Node, &msg.blinding_point, None) {
295 log_error!(self.logger, "Failed to retrieve node secret: {:?}", e);
299 let onion_decode_ss = {
300 let blinding_factor = {
301 let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
302 hmac.input(control_tlvs_ss.as_ref());
303 Hmac::from_engine(hmac).into_inner()
305 match self.keys_manager.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
306 Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
308 Ok(ss) => ss.secret_bytes(),
310 log_trace!(self.logger, "Failed to compute onion packet shared secret");
315 match onion_utils::decode_next_untagged_hop(onion_decode_ss, &msg.onion_routing_packet.hop_data[..],
316 msg.onion_routing_packet.hmac, (control_tlvs_ss, &*self.custom_handler))
318 Ok((Payload::Receive::<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage> {
319 message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
321 log_info!(self.logger,
322 "Received an onion message with path_id {:02x?} and {} reply_path",
323 path_id, if reply_path.is_some() { "a" } else { "no" });
325 OnionMessageContents::Custom(msg) => self.custom_handler.handle_custom_message(msg),
328 Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
329 next_node_id, next_blinding_override
330 })), Some((next_hop_hmac, new_packet_bytes)))) => {
331 // TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
332 // blinded hop and this onion message is destined for us. In this situation, we should keep
333 // unwrapping the onion layers to get to the final payload. Since we don't have the option
334 // of creating blinded routes with dummy hops currently, we should be ok to not handle this
336 let new_pubkey = match onion_utils::next_hop_packet_pubkey(&self.secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
339 log_trace!(self.logger, "Failed to compute next hop packet pubkey: {}", e);
343 let outgoing_packet = Packet {
345 public_key: new_pubkey,
346 hop_data: new_packet_bytes,
349 let onion_message = msgs::OnionMessage {
350 blinding_point: match next_blinding_override {
351 Some(blinding_point) => blinding_point,
353 let blinding_factor = {
354 let mut sha = Sha256::engine();
355 sha.input(&msg.blinding_point.serialize()[..]);
356 sha.input(control_tlvs_ss.as_ref());
357 Sha256::from_engine(sha).into_inner()
359 let next_blinding_point = msg.blinding_point;
360 match next_blinding_point.mul_tweak(&self.secp_ctx, &Scalar::from_be_bytes(blinding_factor).unwrap()) {
363 log_trace!(self.logger, "Failed to compute next blinding point: {}", e);
369 onion_routing_packet: outgoing_packet,
372 let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
373 if outbound_buffer_full(&next_node_id, &pending_per_peer_msgs) {
374 log_trace!(self.logger, "Dropping forwarded onion message to peer {:?}: outbound buffer full", next_node_id);
379 pending_per_peer_msgs.entry(next_node_id).or_insert_with(VecDeque::new);
381 match pending_per_peer_msgs.entry(next_node_id) {
382 hash_map::Entry::Vacant(_) => {
383 log_trace!(self.logger, "Dropping forwarded onion message to disconnected peer {:?}", next_node_id);
386 hash_map::Entry::Occupied(mut e) => {
387 e.get_mut().push_back(onion_message);
388 log_trace!(self.logger, "Forwarding an onion message to peer {}", next_node_id);
393 log_trace!(self.logger, "Errored decoding onion message packet: {:?}", e);
396 log_trace!(self.logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
401 fn peer_connected(&self, their_node_id: &PublicKey, init: &msgs::Init) -> Result<(), ()> {
402 if init.features.supports_onion_messages() {
403 let mut peers = self.pending_messages.lock().unwrap();
404 peers.insert(their_node_id.clone(), VecDeque::new());
409 fn peer_disconnected(&self, their_node_id: &PublicKey, _no_connection_possible: bool) {
410 let mut pending_msgs = self.pending_messages.lock().unwrap();
411 pending_msgs.remove(their_node_id);
414 fn provided_node_features(&self) -> NodeFeatures {
415 let mut features = NodeFeatures::empty();
416 features.set_onion_messages_optional();
420 fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
421 let mut features = InitFeatures::empty();
422 features.set_onion_messages_optional();
427 impl<Signer: Sign, K: Deref, L: Deref, CMH: Deref> OnionMessageProvider for OnionMessenger<Signer, K, L, CMH>
428 where K::Target: KeysInterface<Signer = Signer>,
430 CMH::Target: CustomOnionMessageHandler,
432 fn next_onion_message_for_peer(&self, peer_node_id: PublicKey) -> Option<msgs::OnionMessage> {
433 let mut pending_msgs = self.pending_messages.lock().unwrap();
434 if let Some(msgs) = pending_msgs.get_mut(&peer_node_id) {
435 return msgs.pop_front()
441 // TODO: parameterize the below Simple* types with OnionMessenger and handle the messages it
443 /// Useful for simplifying the parameters of [`SimpleArcChannelManager`] and
444 /// [`SimpleArcPeerManager`]. See their docs for more details.
446 /// (C-not exported) as `Arc`s don't make sense in bindings.
448 /// [`SimpleArcChannelManager`]: crate::ln::channelmanager::SimpleArcChannelManager
449 /// [`SimpleArcPeerManager`]: crate::ln::peer_handler::SimpleArcPeerManager
450 pub type SimpleArcOnionMessenger<L> = OnionMessenger<InMemorySigner, Arc<KeysManager>, Arc<L>, IgnoringMessageHandler>;
451 /// Useful for simplifying the parameters of [`SimpleRefChannelManager`] and
452 /// [`SimpleRefPeerManager`]. See their docs for more details.
454 /// (C-not exported) as general type aliases don't make sense in bindings.
456 /// [`SimpleRefChannelManager`]: crate::ln::channelmanager::SimpleRefChannelManager
457 /// [`SimpleRefPeerManager`]: crate::ln::peer_handler::SimpleRefPeerManager
458 pub type SimpleRefOnionMessenger<'a, 'b, L> = OnionMessenger<InMemorySigner, &'a KeysManager, &'b L, IgnoringMessageHandler>;
460 /// Construct onion packet payloads and keys for sending an onion message along the given
461 /// `unblinded_path` to the given `destination`.
462 fn packet_payloads_and_keys<T: CustomOnionMessageContents, S: secp256k1::Signing + secp256k1::Verification>(
463 secp_ctx: &Secp256k1<S>, unblinded_path: &[PublicKey], destination: Destination,
464 message: OnionMessageContents<T>, mut reply_path: Option<BlindedRoute>, session_priv: &SecretKey
465 ) -> Result<(Vec<(Payload<T>, [u8; 32])>, Vec<onion_utils::OnionKeys>), secp256k1::Error> {
466 let num_hops = unblinded_path.len() + destination.num_hops();
467 let mut payloads = Vec::with_capacity(num_hops);
468 let mut onion_packet_keys = Vec::with_capacity(num_hops);
470 let (mut intro_node_id_blinding_pt, num_blinded_hops) = if let Destination::BlindedRoute(BlindedRoute {
471 introduction_node_id, blinding_point, blinded_hops }) = &destination {
472 (Some((*introduction_node_id, *blinding_point)), blinded_hops.len()) } else { (None, 0) };
473 let num_unblinded_hops = num_hops - num_blinded_hops;
475 let mut unblinded_path_idx = 0;
476 let mut blinded_path_idx = 0;
477 let mut prev_control_tlvs_ss = None;
478 let mut final_control_tlvs = None;
479 utils::construct_keys_callback(secp_ctx, unblinded_path, Some(destination), session_priv, |_, onion_packet_ss, ephemeral_pubkey, control_tlvs_ss, unblinded_pk_opt, enc_payload_opt| {
480 if num_unblinded_hops != 0 && unblinded_path_idx < num_unblinded_hops {
481 if let Some(ss) = prev_control_tlvs_ss.take() {
482 payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(
484 next_node_id: unblinded_pk_opt.unwrap(),
485 next_blinding_override: None,
489 prev_control_tlvs_ss = Some(control_tlvs_ss);
490 unblinded_path_idx += 1;
491 } else if let Some((intro_node_id, blinding_pt)) = intro_node_id_blinding_pt.take() {
492 if let Some(control_tlvs_ss) = prev_control_tlvs_ss.take() {
493 payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
494 next_node_id: intro_node_id,
495 next_blinding_override: Some(blinding_pt),
496 })), control_tlvs_ss));
498 if let Some(encrypted_payload) = enc_payload_opt {
499 payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(encrypted_payload)),
501 } else { debug_assert!(false); }
502 blinded_path_idx += 1;
503 } else if blinded_path_idx < num_blinded_hops - 1 && enc_payload_opt.is_some() {
504 payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(enc_payload_opt.unwrap())),
506 blinded_path_idx += 1;
507 } else if let Some(encrypted_payload) = enc_payload_opt {
508 final_control_tlvs = Some(ReceiveControlTlvs::Blinded(encrypted_payload));
509 prev_control_tlvs_ss = Some(control_tlvs_ss);
512 let (rho, mu) = onion_utils::gen_rho_mu_from_shared_secret(onion_packet_ss.as_ref());
513 onion_packet_keys.push(onion_utils::OnionKeys {
515 shared_secret: onion_packet_ss,
517 blinding_factor: [0; 32],
524 if let Some(control_tlvs) = final_control_tlvs {
525 payloads.push((Payload::Receive {
527 reply_path: reply_path.take(),
529 }, prev_control_tlvs_ss.unwrap()));
531 payloads.push((Payload::Receive {
532 control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id: None, }),
533 reply_path: reply_path.take(),
535 }, prev_control_tlvs_ss.unwrap()));
538 Ok((payloads, onion_packet_keys))
541 /// Errors if the serialized payload size exceeds onion_message::BIG_PACKET_HOP_DATA_LEN
542 fn construct_onion_message_packet<T: CustomOnionMessageContents>(payloads: Vec<(Payload<T>, [u8; 32])>, onion_keys: Vec<onion_utils::OnionKeys>, prng_seed: [u8; 32]) -> Result<Packet, ()> {
544 // "`len` allows larger messages to be sent than the standard 1300 bytes allowed for an HTLC
545 // onion, but this should be used sparingly as it is reduces anonymity set, hence the
546 // recommendation that it either look like an HTLC onion, or if larger, be a fixed size."
547 let payloads_ser_len = onion_utils::payloads_serialized_length(&payloads);
548 let hop_data_len = if payloads_ser_len <= SMALL_PACKET_HOP_DATA_LEN {
549 SMALL_PACKET_HOP_DATA_LEN
550 } else if payloads_ser_len <= BIG_PACKET_HOP_DATA_LEN {
551 BIG_PACKET_HOP_DATA_LEN
552 } else { return Err(()) };
554 Ok(onion_utils::construct_onion_message_packet::<_, _>(
555 payloads, onion_keys, prng_seed, hop_data_len))