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 pub 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;
32 use crate::sync::{Arc, Mutex};
33 use crate::prelude::*;
35 /// A sender, receiver and forwarder of onion messages. In upcoming releases, this object will be
36 /// used to retrieve invoices and fulfill invoice requests from [offers]. Currently, only sending
37 /// and receiving custom onion messages is supported.
42 /// # extern crate bitcoin;
43 /// # use bitcoin::hashes::_export::_core::time::Duration;
44 /// # use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
45 /// # use lightning::chain::keysinterface::{InMemorySigner, KeysManager, KeysInterface};
46 /// # use lightning::ln::msgs::DecodeError;
47 /// # use lightning::ln::peer_handler::IgnoringMessageHandler;
48 /// # use lightning::onion_message::{BlindedRoute, CustomOnionMessageContents, Destination, OnionMessageContents, OnionMessenger};
49 /// # use lightning::util::logger::{Logger, Record};
50 /// # use lightning::util::ser::{MaybeReadableArgs, Writeable, Writer};
51 /// # use lightning::io;
52 /// # use std::sync::Arc;
53 /// # struct FakeLogger {};
54 /// # impl Logger for FakeLogger {
55 /// # fn log(&self, record: &Record) { unimplemented!() }
57 /// # let seed = [42u8; 32];
58 /// # let time = Duration::from_secs(123456);
59 /// # let keys_manager = KeysManager::new(&seed, time.as_secs(), time.subsec_nanos());
60 /// # let logger = Arc::new(FakeLogger {});
61 /// # let node_secret = SecretKey::from_slice(&hex::decode("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
62 /// # let secp_ctx = Secp256k1::new();
63 /// # let hop_node_id1 = PublicKey::from_secret_key(&secp_ctx, &node_secret);
64 /// # let (hop_node_id2, hop_node_id3, hop_node_id4) = (hop_node_id1, hop_node_id1, hop_node_id1);
65 /// # let destination_node_id = hop_node_id1;
66 /// # let your_custom_message_handler = IgnoringMessageHandler {};
67 /// // Create the onion messenger. This must use the same `keys_manager` as is passed to your
68 /// // ChannelManager.
69 /// let onion_messenger = OnionMessenger::new(&keys_manager, logger, your_custom_message_handler);
71 /// # struct YourCustomMessage {}
72 /// impl Writeable for YourCustomMessage {
73 /// fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
75 /// // Write your custom onion message to `w`
78 /// impl CustomOnionMessageContents for YourCustomMessage {
79 /// fn tlv_type(&self) -> u64 {
80 /// # let your_custom_message_type = 42;
81 /// your_custom_message_type
84 /// impl MaybeReadableArgs<u64> for YourCustomMessage {
85 /// fn read<R: io::Read>(r: &mut R, message_type: u64) -> Result<Option<Self>, DecodeError> {
87 /// // Read your custom onion message of type `message_type` from `r`, or return `None`
88 /// // if the message type is unknown
91 /// // Send a custom onion message to a node id.
92 /// let intermediate_hops = [hop_node_id1, hop_node_id2];
93 /// let reply_path = None;
94 /// # let your_custom_message = YourCustomMessage {};
95 /// let message = OnionMessageContents::Custom(your_custom_message);
96 /// onion_messenger.send_onion_message(&intermediate_hops, Destination::Node(destination_node_id), message, reply_path);
98 /// // Create a blinded route to yourself, for someone to send an onion message to.
99 /// # let your_node_id = hop_node_id1;
100 /// let hops = [hop_node_id3, hop_node_id4, your_node_id];
101 /// let blinded_route = BlindedRoute::new(&hops, &keys_manager, &secp_ctx).unwrap();
103 /// // Send a custom onion message to a blinded route.
104 /// # let intermediate_hops = [hop_node_id1, hop_node_id2];
105 /// let reply_path = None;
106 /// # let your_custom_message = YourCustomMessage {};
107 /// let message = OnionMessageContents::Custom(your_custom_message);
108 /// onion_messenger.send_onion_message(&intermediate_hops, Destination::BlindedRoute(blinded_route), message, reply_path);
111 /// [offers]: <https://github.com/lightning/bolts/pull/798>
112 /// [`OnionMessenger`]: crate::onion_message::OnionMessenger
113 pub struct OnionMessenger<Signer: Sign, K: Deref, L: Deref, CMH: Deref>
114 where K::Target: KeysInterface<Signer = Signer>,
116 CMH:: Target: CustomOnionMessageHandler,
120 pending_messages: Mutex<HashMap<PublicKey, VecDeque<msgs::OnionMessage>>>,
121 secp_ctx: Secp256k1<secp256k1::All>,
124 // invoice_handler: InvoiceHandler,
127 /// The destination of an onion message.
128 pub enum Destination {
129 /// We're sending this onion message to a node.
131 /// We're sending this onion message to a blinded route.
132 BlindedRoute(BlindedRoute),
136 pub(super) fn num_hops(&self) -> usize {
138 Destination::Node(_) => 1,
139 Destination::BlindedRoute(BlindedRoute { blinded_hops, .. }) => blinded_hops.len(),
144 /// Errors that may occur when [sending an onion message].
146 /// [sending an onion message]: OnionMessenger::send_onion_message
147 #[derive(Debug, PartialEq, Eq)]
149 /// Errored computing onion message packet keys.
150 Secp256k1(secp256k1::Error),
151 /// Because implementations such as Eclair will drop onion messages where the message packet
152 /// exceeds 32834 bytes, we refuse to send messages where the packet exceeds this size.
154 /// The provided [`Destination`] was an invalid [`BlindedRoute`], due to having fewer than two
157 /// Our next-hop peer was offline or does not support onion message forwarding.
159 /// Onion message contents must have a TLV type >= 64.
161 /// Our next-hop peer's buffer was full or our total outbound buffer was full.
165 /// Handler for custom onion messages. If you are using [`SimpleArcOnionMessenger`],
166 /// [`SimpleRefOnionMessenger`], or prefer to ignore inbound custom onion messages,
167 /// [`IgnoringMessageHandler`] must be provided to [`OnionMessenger::new`]. Otherwise, a custom
168 /// implementation of this trait must be provided, with [`CustomMessage`] specifying the supported
171 /// See [`OnionMessenger`] for example usage.
173 /// [`IgnoringMessageHandler`]: crate::ln::peer_handler::IgnoringMessageHandler
174 /// [`CustomMessage`]: Self::CustomMessage
175 pub trait CustomOnionMessageHandler {
176 /// The message known to the handler. To support multiple message types, you may want to make this
177 /// an enum with a variant for each supported message.
178 type CustomMessage: CustomOnionMessageContents;
179 /// Called with the custom message that was received.
180 fn handle_custom_message(&self, msg: Self::CustomMessage);
183 impl<Signer: Sign, K: Deref, L: Deref, CMH: Deref> OnionMessenger<Signer, K, L, CMH>
184 where K::Target: KeysInterface<Signer = Signer>,
186 CMH::Target: CustomOnionMessageHandler,
188 /// Constructs a new `OnionMessenger` to send, forward, and delegate received onion messages to
189 /// their respective handlers.
190 pub fn new(keys_manager: K, logger: L, custom_handler: CMH) -> Self {
191 let mut secp_ctx = Secp256k1::new();
192 secp_ctx.seeded_randomize(&keys_manager.get_secure_random_bytes());
195 pending_messages: Mutex::new(HashMap::new()),
202 /// Send an onion message with contents `message` to `destination`, routing it through `intermediate_nodes`.
203 /// See [`OnionMessenger`] for example usage.
204 pub fn send_onion_message<T: CustomOnionMessageContents>(&self, intermediate_nodes: &[PublicKey], destination: Destination, message: OnionMessageContents<T>, reply_path: Option<BlindedRoute>) -> Result<(), SendError> {
205 if let Destination::BlindedRoute(BlindedRoute { ref blinded_hops, .. }) = destination {
206 if blinded_hops.len() < 2 {
207 return Err(SendError::TooFewBlindedHops);
210 let OnionMessageContents::Custom(ref msg) = message;
211 if msg.tlv_type() < 64 { return Err(SendError::InvalidMessage) }
213 let blinding_secret_bytes = self.keys_manager.get_secure_random_bytes();
214 let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
215 let (introduction_node_id, blinding_point) = if intermediate_nodes.len() != 0 {
216 (intermediate_nodes[0], PublicKey::from_secret_key(&self.secp_ctx, &blinding_secret))
219 Destination::Node(pk) => (pk, PublicKey::from_secret_key(&self.secp_ctx, &blinding_secret)),
220 Destination::BlindedRoute(BlindedRoute { introduction_node_id, blinding_point, .. }) =>
221 (introduction_node_id, blinding_point),
224 let (packet_payloads, packet_keys) = packet_payloads_and_keys(
225 &self.secp_ctx, intermediate_nodes, destination, message, reply_path, &blinding_secret)
226 .map_err(|e| SendError::Secp256k1(e))?;
228 let prng_seed = self.keys_manager.get_secure_random_bytes();
229 let onion_routing_packet = construct_onion_message_packet(
230 packet_payloads, packet_keys, prng_seed).map_err(|()| SendError::TooBigPacket)?;
232 let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
233 if outbound_buffer_full(&introduction_node_id, &pending_per_peer_msgs) { return Err(SendError::BufferFull) }
234 match pending_per_peer_msgs.entry(introduction_node_id) {
235 hash_map::Entry::Vacant(_) => Err(SendError::InvalidFirstHop),
236 hash_map::Entry::Occupied(mut e) => {
237 e.get_mut().push_back(msgs::OnionMessage { blinding_point, onion_routing_packet });
244 pub(super) fn release_pending_msgs(&self) -> HashMap<PublicKey, VecDeque<msgs::OnionMessage>> {
245 let mut pending_msgs = self.pending_messages.lock().unwrap();
246 let mut msgs = HashMap::new();
247 // We don't want to disconnect the peers by removing them entirely from the original map, so we
248 // swap the pending message buffers individually.
249 for (peer_node_id, pending_messages) in &mut *pending_msgs {
250 msgs.insert(*peer_node_id, core::mem::take(pending_messages));
256 fn outbound_buffer_full(peer_node_id: &PublicKey, buffer: &HashMap<PublicKey, VecDeque<msgs::OnionMessage>>) -> bool {
257 const MAX_TOTAL_BUFFER_SIZE: usize = (1 << 20) * 128;
258 const MAX_PER_PEER_BUFFER_SIZE: usize = (1 << 10) * 256;
259 let mut total_buffered_bytes = 0;
260 let mut peer_buffered_bytes = 0;
261 for (pk, peer_buf) in buffer {
263 let om_len = om.serialized_length();
264 if pk == peer_node_id {
265 peer_buffered_bytes += om_len;
267 total_buffered_bytes += om_len;
269 if total_buffered_bytes >= MAX_TOTAL_BUFFER_SIZE ||
270 peer_buffered_bytes >= MAX_PER_PEER_BUFFER_SIZE
279 impl<Signer: Sign, K: Deref, L: Deref, CMH: Deref> OnionMessageHandler for OnionMessenger<Signer, K, L, CMH>
280 where K::Target: KeysInterface<Signer = Signer>,
282 CMH::Target: CustomOnionMessageHandler,
284 /// Handle an incoming onion message. Currently, if a message was destined for us we will log, but
285 /// soon we'll delegate the onion message to a handler that can generate invoices or send
287 fn handle_onion_message(&self, _peer_node_id: &PublicKey, msg: &msgs::OnionMessage) {
288 let control_tlvs_ss = match self.keys_manager.ecdh(Recipient::Node, &msg.blinding_point, None) {
291 log_error!(self.logger, "Failed to retrieve node secret: {:?}", e);
295 let onion_decode_ss = {
296 let blinding_factor = {
297 let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
298 hmac.input(control_tlvs_ss.as_ref());
299 Hmac::from_engine(hmac).into_inner()
301 match self.keys_manager.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
302 Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
304 Ok(ss) => ss.secret_bytes(),
306 log_trace!(self.logger, "Failed to compute onion packet shared secret");
311 match onion_utils::decode_next_hop(onion_decode_ss, &msg.onion_routing_packet.hop_data[..],
312 msg.onion_routing_packet.hmac, control_tlvs_ss)
314 Ok((Payload::Receive::<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage> {
315 message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
317 log_info!(self.logger,
318 "Received an onion message with path_id {:02x?} and {} reply_path",
319 path_id, if reply_path.is_some() { "a" } else { "no" });
321 OnionMessageContents::Custom(msg) => self.custom_handler.handle_custom_message(msg),
324 Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
325 next_node_id, next_blinding_override
326 })), Some((next_hop_hmac, new_packet_bytes)))) => {
327 // TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
328 // blinded hop and this onion message is destined for us. In this situation, we should keep
329 // unwrapping the onion layers to get to the final payload. Since we don't have the option
330 // of creating blinded routes with dummy hops currently, we should be ok to not handle this
332 let new_pubkey = match onion_utils::next_hop_packet_pubkey(&self.secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
335 log_trace!(self.logger, "Failed to compute next hop packet pubkey: {}", e);
339 let outgoing_packet = Packet {
341 public_key: new_pubkey,
342 hop_data: new_packet_bytes,
345 let onion_message = msgs::OnionMessage {
346 blinding_point: match next_blinding_override {
347 Some(blinding_point) => blinding_point,
349 let blinding_factor = {
350 let mut sha = Sha256::engine();
351 sha.input(&msg.blinding_point.serialize()[..]);
352 sha.input(control_tlvs_ss.as_ref());
353 Sha256::from_engine(sha).into_inner()
355 let next_blinding_point = msg.blinding_point;
356 match next_blinding_point.mul_tweak(&self.secp_ctx, &Scalar::from_be_bytes(blinding_factor).unwrap()) {
359 log_trace!(self.logger, "Failed to compute next blinding point: {}", e);
365 onion_routing_packet: outgoing_packet,
368 let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
369 if outbound_buffer_full(&next_node_id, &pending_per_peer_msgs) {
370 log_trace!(self.logger, "Dropping forwarded onion message to peer {:?}: outbound buffer full", next_node_id);
375 pending_per_peer_msgs.entry(next_node_id).or_insert_with(VecDeque::new);
377 match pending_per_peer_msgs.entry(next_node_id) {
378 hash_map::Entry::Vacant(_) => {
379 log_trace!(self.logger, "Dropping forwarded onion message to disconnected peer {:?}", next_node_id);
382 hash_map::Entry::Occupied(mut e) => {
383 e.get_mut().push_back(onion_message);
384 log_trace!(self.logger, "Forwarding an onion message to peer {}", next_node_id);
389 log_trace!(self.logger, "Errored decoding onion message packet: {:?}", e);
392 log_trace!(self.logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
397 fn peer_connected(&self, their_node_id: &PublicKey, init: &msgs::Init) -> Result<(), ()> {
398 if init.features.supports_onion_messages() {
399 let mut peers = self.pending_messages.lock().unwrap();
400 peers.insert(their_node_id.clone(), VecDeque::new());
405 fn peer_disconnected(&self, their_node_id: &PublicKey, _no_connection_possible: bool) {
406 let mut pending_msgs = self.pending_messages.lock().unwrap();
407 pending_msgs.remove(their_node_id);
410 fn provided_node_features(&self) -> NodeFeatures {
411 let mut features = NodeFeatures::empty();
412 features.set_onion_messages_optional();
416 fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
417 let mut features = InitFeatures::empty();
418 features.set_onion_messages_optional();
423 impl<Signer: Sign, K: Deref, L: Deref, CMH: Deref> OnionMessageProvider for OnionMessenger<Signer, K, L, CMH>
424 where K::Target: KeysInterface<Signer = Signer>,
426 CMH::Target: CustomOnionMessageHandler,
428 fn next_onion_message_for_peer(&self, peer_node_id: PublicKey) -> Option<msgs::OnionMessage> {
429 let mut pending_msgs = self.pending_messages.lock().unwrap();
430 if let Some(msgs) = pending_msgs.get_mut(&peer_node_id) {
431 return msgs.pop_front()
437 // TODO: parameterize the below Simple* types with OnionMessenger and handle the messages it
439 /// Useful for simplifying the parameters of [`SimpleArcChannelManager`] and
440 /// [`SimpleArcPeerManager`]. See their docs for more details.
442 /// (C-not exported) as `Arc`s don't make sense in bindings.
444 /// [`SimpleArcChannelManager`]: crate::ln::channelmanager::SimpleArcChannelManager
445 /// [`SimpleArcPeerManager`]: crate::ln::peer_handler::SimpleArcPeerManager
446 pub type SimpleArcOnionMessenger<L> = OnionMessenger<InMemorySigner, Arc<KeysManager>, Arc<L>, IgnoringMessageHandler>;
447 /// Useful for simplifying the parameters of [`SimpleRefChannelManager`] and
448 /// [`SimpleRefPeerManager`]. See their docs for more details.
450 /// (C-not exported) as general type aliases don't make sense in bindings.
452 /// [`SimpleRefChannelManager`]: crate::ln::channelmanager::SimpleRefChannelManager
453 /// [`SimpleRefPeerManager`]: crate::ln::peer_handler::SimpleRefPeerManager
454 pub type SimpleRefOnionMessenger<'a, 'b, L> = OnionMessenger<InMemorySigner, &'a KeysManager, &'b L, IgnoringMessageHandler>;
456 /// Construct onion packet payloads and keys for sending an onion message along the given
457 /// `unblinded_path` to the given `destination`.
458 fn packet_payloads_and_keys<T: CustomOnionMessageContents, S: secp256k1::Signing + secp256k1::Verification>(
459 secp_ctx: &Secp256k1<S>, unblinded_path: &[PublicKey], destination: Destination,
460 message: OnionMessageContents<T>, mut reply_path: Option<BlindedRoute>, session_priv: &SecretKey
461 ) -> Result<(Vec<(Payload<T>, [u8; 32])>, Vec<onion_utils::OnionKeys>), secp256k1::Error> {
462 let num_hops = unblinded_path.len() + destination.num_hops();
463 let mut payloads = Vec::with_capacity(num_hops);
464 let mut onion_packet_keys = Vec::with_capacity(num_hops);
466 let (mut intro_node_id_blinding_pt, num_blinded_hops) = if let Destination::BlindedRoute(BlindedRoute {
467 introduction_node_id, blinding_point, blinded_hops }) = &destination {
468 (Some((*introduction_node_id, *blinding_point)), blinded_hops.len()) } else { (None, 0) };
469 let num_unblinded_hops = num_hops - num_blinded_hops;
471 let mut unblinded_path_idx = 0;
472 let mut blinded_path_idx = 0;
473 let mut prev_control_tlvs_ss = None;
474 let mut final_control_tlvs = None;
475 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| {
476 if num_unblinded_hops != 0 && unblinded_path_idx < num_unblinded_hops {
477 if let Some(ss) = prev_control_tlvs_ss.take() {
478 payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(
480 next_node_id: unblinded_pk_opt.unwrap(),
481 next_blinding_override: None,
485 prev_control_tlvs_ss = Some(control_tlvs_ss);
486 unblinded_path_idx += 1;
487 } else if let Some((intro_node_id, blinding_pt)) = intro_node_id_blinding_pt.take() {
488 if let Some(control_tlvs_ss) = prev_control_tlvs_ss.take() {
489 payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
490 next_node_id: intro_node_id,
491 next_blinding_override: Some(blinding_pt),
492 })), control_tlvs_ss));
494 if let Some(encrypted_payload) = enc_payload_opt {
495 payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(encrypted_payload)),
497 } else { debug_assert!(false); }
498 blinded_path_idx += 1;
499 } else if blinded_path_idx < num_blinded_hops - 1 && enc_payload_opt.is_some() {
500 payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(enc_payload_opt.unwrap())),
502 blinded_path_idx += 1;
503 } else if let Some(encrypted_payload) = enc_payload_opt {
504 final_control_tlvs = Some(ReceiveControlTlvs::Blinded(encrypted_payload));
505 prev_control_tlvs_ss = Some(control_tlvs_ss);
508 let (rho, mu) = onion_utils::gen_rho_mu_from_shared_secret(onion_packet_ss.as_ref());
509 onion_packet_keys.push(onion_utils::OnionKeys {
511 shared_secret: onion_packet_ss,
513 blinding_factor: [0; 32],
520 if let Some(control_tlvs) = final_control_tlvs {
521 payloads.push((Payload::Receive {
523 reply_path: reply_path.take(),
525 }, prev_control_tlvs_ss.unwrap()));
527 payloads.push((Payload::Receive {
528 control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id: None, }),
529 reply_path: reply_path.take(),
531 }, prev_control_tlvs_ss.unwrap()));
534 Ok((payloads, onion_packet_keys))
537 /// Errors if the serialized payload size exceeds onion_message::BIG_PACKET_HOP_DATA_LEN
538 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, ()> {
540 // "`len` allows larger messages to be sent than the standard 1300 bytes allowed for an HTLC
541 // onion, but this should be used sparingly as it is reduces anonymity set, hence the
542 // recommendation that it either look like an HTLC onion, or if larger, be a fixed size."
543 let payloads_ser_len = onion_utils::payloads_serialized_length(&payloads);
544 let hop_data_len = if payloads_ser_len <= SMALL_PACKET_HOP_DATA_LEN {
545 SMALL_PACKET_HOP_DATA_LEN
546 } else if payloads_ser_len <= BIG_PACKET_HOP_DATA_LEN {
547 BIG_PACKET_HOP_DATA_LEN
548 } else { return Err(()) };
550 Ok(onion_utils::construct_onion_message_packet::<_, _>(
551 payloads, onion_keys, prng_seed, hop_data_len))