_ Git - rust-lightning/blob - lightning/src/blinded_path/payment.rs

   1 //! Data structures and methods for constructing [`BlindedPath`]s to send a payment over.
   2 //!
   3 //! [`BlindedPath`]: crate::blinded_path::BlindedPath
   4
   5 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
   6
   7 use crate::blinded_path::BlindedHop;
   8 use crate::blinded_path::utils;
   9 use crate::io;
  10 use crate::ln::PaymentSecret;
  11 use crate::ln::features::BlindedHopFeatures;
  12 use crate::ln::msgs::DecodeError;
  13 use crate::offers::invoice::BlindedPayInfo;
  14 use crate::prelude::*;
  15 use crate::util::ser::{Readable, Writeable, Writer};
  16
  17 use core::convert::TryFrom;
  18
  19 /// An intermediate node, its outbound channel, and relay parameters.
  20 #[derive(Clone, Debug)]
  21 pub struct ForwardNode {
  22         /// The TLVs for this node's [`BlindedHop`], where the fee parameters contained within are also
  23         /// used for [`BlindedPayInfo`] construction.
  24         pub tlvs: ForwardTlvs,
  25         /// This node's pubkey.
  26         pub node_id: PublicKey,
  27         /// The maximum value, in msat, that may be accepted by this node.
  28         pub htlc_maximum_msat: u64,
  29 }
  30
  31 /// Data to construct a [`BlindedHop`] for forwarding a payment.
  32 #[derive(Clone, Debug)]
  33 pub struct ForwardTlvs {
  34         /// The short channel id this payment should be forwarded out over.
  35         pub short_channel_id: u64,
  36         /// Payment parameters for relaying over [`Self::short_channel_id`].
  37         pub payment_relay: PaymentRelay,
  38         /// Payment constraints for relaying over [`Self::short_channel_id`].
  39         pub payment_constraints: PaymentConstraints,
  40         /// Supported and required features when relaying a payment onion containing this object's
  41         /// corresponding [`BlindedHop::encrypted_payload`].
  42         ///
  43         /// [`BlindedHop::encrypted_payload`]: crate::blinded_path::BlindedHop::encrypted_payload
  44         pub features: BlindedHopFeatures,
  45 }
  46
  47 /// Data to construct a [`BlindedHop`] for receiving a payment. This payload is custom to LDK and
  48 /// may not be valid if received by another lightning implementation.
  49 #[derive(Clone, Debug)]
  50 pub struct ReceiveTlvs {
  51         /// Used to authenticate the sender of a payment to the receiver and tie MPP HTLCs together.
  52         pub payment_secret: PaymentSecret,
  53         /// Constraints for the receiver of this payment.
  54         pub payment_constraints: PaymentConstraints,
  55 }
  56
  57 /// Data to construct a [`BlindedHop`] for sending a payment over.
  58 ///
  59 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  60 pub(crate) enum BlindedPaymentTlvs {
  61         /// This blinded payment data is for a forwarding node.
  62         Forward(ForwardTlvs),
  63         /// This blinded payment data is for the receiving node.
  64         Receive(ReceiveTlvs),
  65 }
  66
  67 // Used to include forward and receive TLVs in the same iterator for encoding.
  68 enum BlindedPaymentTlvsRef<'a> {
  69         Forward(&'a ForwardTlvs),
  70         Receive(&'a ReceiveTlvs),
  71 }
  72
  73 /// Parameters for relaying over a given [`BlindedHop`].
  74 ///
  75 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  76 #[derive(Clone, Debug)]
  77 pub struct PaymentRelay {
  78         /// Number of blocks subtracted from an incoming HTLC's `cltv_expiry` for this [`BlindedHop`].
  79         pub cltv_expiry_delta: u16,
  80         /// Liquidity fee charged (in millionths of the amount transferred) for relaying a payment over
  81         /// this [`BlindedHop`], (i.e., 10,000 is 1%).
  82         pub fee_proportional_millionths: u32,
  83         /// Base fee charged (in millisatoshi) for relaying a payment over this [`BlindedHop`].
  84         pub fee_base_msat: u32,
  85 }
  86
  87 /// Constraints for relaying over a given [`BlindedHop`].
  88 ///
  89 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  90 #[derive(Clone, Debug)]
  91 pub struct PaymentConstraints {
  92         /// The maximum total CLTV that is acceptable when relaying a payment over this [`BlindedHop`].
  93         pub max_cltv_expiry: u32,
  94         /// The minimum value, in msat, that may be accepted by the node corresponding to this
  95         /// [`BlindedHop`].
  96         pub htlc_minimum_msat: u64,
  97 }
  98
  99 impl Writeable for ForwardTlvs {
 100         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 101                 encode_tlv_stream!(w, {
 102                         (2, self.short_channel_id, required),
 103                         (10, self.payment_relay, required),
 104                         (12, self.payment_constraints, required),
 105                         (14, self.features, required)
 106                 });
 107                 Ok(())
 108         }
 109 }
 110
 111 impl Writeable for ReceiveTlvs {
 112         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 113                 encode_tlv_stream!(w, {
 114                         (12, self.payment_constraints, required),
 115                         (65536, self.payment_secret, required)
 116                 });
 117                 Ok(())
 118         }
 119 }
 120
 121 impl<'a> Writeable for BlindedPaymentTlvsRef<'a> {
 122         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 123                 // TODO: write padding
 124                 match self {
 125                         Self::Forward(tlvs) => tlvs.write(w)?,
 126                         Self::Receive(tlvs) => tlvs.write(w)?,
 127                 }
 128                 Ok(())
 129         }
 130 }
 131
 132 impl Readable for BlindedPaymentTlvs {
 133         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 134                 _init_and_read_tlv_stream!(r, {
 135                         (1, _padding, option),
 136                         (2, scid, option),
 137                         (10, payment_relay, option),
 138                         (12, payment_constraints, required),
 139                         (14, features, option),
 140                         (65536, payment_secret, option),
 141                 });
 142                 let _padding: Option<utils::Padding> = _padding;
 143
 144                 if let Some(short_channel_id) = scid {
 145                         if payment_secret.is_some() { return Err(DecodeError::InvalidValue) }
 146                         Ok(BlindedPaymentTlvs::Forward(ForwardTlvs {
 147                                 short_channel_id,
 148                                 payment_relay: payment_relay.ok_or(DecodeError::InvalidValue)?,
 149                                 payment_constraints: payment_constraints.0.unwrap(),
 150                                 features: features.ok_or(DecodeError::InvalidValue)?,
 151                         }))
 152                 } else {
 153                         if payment_relay.is_some() || features.is_some() { return Err(DecodeError::InvalidValue) }
 154                         Ok(BlindedPaymentTlvs::Receive(ReceiveTlvs {
 155                                 payment_secret: payment_secret.ok_or(DecodeError::InvalidValue)?,
 156                                 payment_constraints: payment_constraints.0.unwrap(),
 157                         }))
 158                 }
 159         }
 160 }
 161
 162 /// Construct blinded payment hops for the given `intermediate_nodes` and payee info.
 163 pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 164         secp_ctx: &Secp256k1<T>, intermediate_nodes: &[ForwardNode],
 165         payee_node_id: PublicKey, payee_tlvs: ReceiveTlvs, session_priv: &SecretKey
 166 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
 167         let pks = intermediate_nodes.iter().map(|node| &node.node_id)
 168                 .chain(core::iter::once(&payee_node_id));
 169         let tlvs = intermediate_nodes.iter().map(|node| BlindedPaymentTlvsRef::Forward(&node.tlvs))
 170                 .chain(core::iter::once(BlindedPaymentTlvsRef::Receive(&payee_tlvs)));
 171         utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
 172 }
 173
 174 /// `None` if underflow occurs.
 175 pub(crate) fn amt_to_forward_msat(inbound_amt_msat: u64, payment_relay: &PaymentRelay) -> Option<u64> {
 176         let inbound_amt = inbound_amt_msat as u128;
 177         let base = payment_relay.fee_base_msat as u128;
 178         let prop = payment_relay.fee_proportional_millionths as u128;
 179
 180         let post_base_fee_inbound_amt =
 181                 if let Some(amt) = inbound_amt.checked_sub(base) { amt } else { return None };
 182         let mut amt_to_forward =
 183                 (post_base_fee_inbound_amt * 1_000_000 + 1_000_000 + prop - 1) / (prop + 1_000_000);
 184
 185         let fee = ((amt_to_forward * prop) / 1_000_000) + base;
 186         if inbound_amt - fee < amt_to_forward {
 187                 // Rounding up the forwarded amount resulted in underpaying this node, so take an extra 1 msat
 188                 // in fee to compensate.
 189                 amt_to_forward -= 1;
 190         }
 191         debug_assert_eq!(amt_to_forward + fee, inbound_amt);
 192         u64::try_from(amt_to_forward).ok()
 193 }
 194
 195 pub(super) fn compute_payinfo(
 196         intermediate_nodes: &[ForwardNode], payee_tlvs: &ReceiveTlvs, payee_htlc_maximum_msat: u64
 197 ) -> Result<BlindedPayInfo, ()> {
 198         let mut curr_base_fee: u64 = 0;
 199         let mut curr_prop_mil: u64 = 0;
 200         let mut cltv_expiry_delta: u16 = 0;
 201         for tlvs in intermediate_nodes.iter().rev().map(|n| &n.tlvs) {
 202                 // In the future, we'll want to take the intersection of all supported features for the
 203                 // `BlindedPayInfo`, but there are no features in that context right now.
 204                 if tlvs.features.requires_unknown_bits_from(&BlindedHopFeatures::empty()) { return Err(()) }
 205
 206                 let next_base_fee = tlvs.payment_relay.fee_base_msat as u64;
 207                 let next_prop_mil = tlvs.payment_relay.fee_proportional_millionths as u64;
 208                 // Use integer arithmetic to compute `ceil(a/b)` as `(a+b-1)/b`
 209                 // ((curr_base_fee * (1_000_000 + next_prop_mil)) / 1_000_000) + next_base_fee
 210                 curr_base_fee = curr_base_fee.checked_mul(1_000_000 + next_prop_mil)
 211                         .and_then(|f| f.checked_add(1_000_000 - 1))
 212                         .map(|f| f / 1_000_000)
 213                         .and_then(|f| f.checked_add(next_base_fee))
 214                         .ok_or(())?;
 215                 // ceil(((curr_prop_mil + 1_000_000) * (next_prop_mil + 1_000_000)) / 1_000_000) - 1_000_000
 216                 curr_prop_mil = curr_prop_mil.checked_add(1_000_000)
 217                         .and_then(|f1| next_prop_mil.checked_add(1_000_000).and_then(|f2| f2.checked_mul(f1)))
 218                         .and_then(|f| f.checked_add(1_000_000 - 1))
 219                         .map(|f| f / 1_000_000)
 220                         .and_then(|f| f.checked_sub(1_000_000))
 221                         .ok_or(())?;
 222
 223                 cltv_expiry_delta = cltv_expiry_delta.checked_add(tlvs.payment_relay.cltv_expiry_delta).ok_or(())?;
 224         }
 225
 226         let mut htlc_minimum_msat: u64 = 1;
 227         let mut htlc_maximum_msat: u64 = 21_000_000 * 100_000_000 * 1_000; // Total bitcoin supply
 228         for node in intermediate_nodes.iter() {
 229                 // The min htlc for an intermediate node is that node's min minus the fees charged by all of the
 230                 // following hops for forwarding that min, since that fee amount will automatically be included
 231                 // in the amount that this node receives and contribute towards reaching its min.
 232                 htlc_minimum_msat = amt_to_forward_msat(
 233                         core::cmp::max(node.tlvs.payment_constraints.htlc_minimum_msat, htlc_minimum_msat),
 234                         &node.tlvs.payment_relay
 235                 ).unwrap_or(1); // If underflow occurs, we definitely reached this node's min
 236                 htlc_maximum_msat = amt_to_forward_msat(
 237                         core::cmp::min(node.htlc_maximum_msat, htlc_maximum_msat), &node.tlvs.payment_relay
 238                 ).ok_or(())?; // If underflow occurs, we cannot send to this hop without exceeding their max
 239         }
 240         htlc_minimum_msat = core::cmp::max(
 241                 payee_tlvs.payment_constraints.htlc_minimum_msat, htlc_minimum_msat
 242         );
 243         htlc_maximum_msat = core::cmp::min(payee_htlc_maximum_msat, htlc_maximum_msat);
 244
 245         if htlc_maximum_msat < htlc_minimum_msat { return Err(()) }
 246         Ok(BlindedPayInfo {
 247                 fee_base_msat: u32::try_from(curr_base_fee).map_err(|_| ())?,
 248                 fee_proportional_millionths: u32::try_from(curr_prop_mil).map_err(|_| ())?,
 249                 cltv_expiry_delta,
 250                 htlc_minimum_msat,
 251                 htlc_maximum_msat,
 252                 features: BlindedHopFeatures::empty(),
 253         })
 254 }
 255
 256 impl_writeable_msg!(PaymentRelay, {
 257         cltv_expiry_delta,
 258         fee_proportional_millionths,
 259         fee_base_msat
 260 }, {});
 261
 262 impl_writeable_msg!(PaymentConstraints, {
 263         max_cltv_expiry,
 264         htlc_minimum_msat
 265 }, {});
 266
 267 #[cfg(test)]
 268 mod tests {
 269         use bitcoin::secp256k1::PublicKey;
 270         use crate::blinded_path::payment::{ForwardNode, ForwardTlvs, ReceiveTlvs, PaymentConstraints, PaymentRelay};
 271         use crate::ln::PaymentSecret;
 272         use crate::ln::features::BlindedHopFeatures;
 273
 274         #[test]
 275         fn compute_payinfo() {
 276                 // Taken from the spec example for aggregating blinded payment info. See
 277                 // https://github.com/lightning/bolts/blob/master/proposals/route-blinding.md#blinded-payments
 278                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 279                 let intermediate_nodes = vec![ForwardNode {
 280                         node_id: dummy_pk,
 281                         tlvs: ForwardTlvs {
 282                                 short_channel_id: 0,
 283                                 payment_relay: PaymentRelay {
 284                                         cltv_expiry_delta: 144,
 285                                         fee_proportional_millionths: 500,
 286                                         fee_base_msat: 100,
 287                                 },
 288                                 payment_constraints: PaymentConstraints {
 289                                         max_cltv_expiry: 0,
 290                                         htlc_minimum_msat: 100,
 291                                 },
 292                                 features: BlindedHopFeatures::empty(),
 293                         },
 294                         htlc_maximum_msat: u64::max_value(),
 295                 }, ForwardNode {
 296                         node_id: dummy_pk,
 297                         tlvs: ForwardTlvs {
 298                                 short_channel_id: 0,
 299                                 payment_relay: PaymentRelay {
 300                                         cltv_expiry_delta: 144,
 301                                         fee_proportional_millionths: 500,
 302                                         fee_base_msat: 100,
 303                                 },
 304                                 payment_constraints: PaymentConstraints {
 305                                         max_cltv_expiry: 0,
 306                                         htlc_minimum_msat: 1_000,
 307                                 },
 308                                 features: BlindedHopFeatures::empty(),
 309                         },
 310                         htlc_maximum_msat: u64::max_value(),
 311                 }];
 312                 let recv_tlvs = ReceiveTlvs {
 313                         payment_secret: PaymentSecret([0; 32]),
 314                         payment_constraints: PaymentConstraints {
 315                                 max_cltv_expiry: 0,
 316                                 htlc_minimum_msat: 1,
 317                         },
 318                 };
 319                 let htlc_maximum_msat = 100_000;
 320                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat).unwrap();
 321                 assert_eq!(blinded_payinfo.fee_base_msat, 201);
 322                 assert_eq!(blinded_payinfo.fee_proportional_millionths, 1001);
 323                 assert_eq!(blinded_payinfo.cltv_expiry_delta, 288);
 324                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 900);
 325                 assert_eq!(blinded_payinfo.htlc_maximum_msat, htlc_maximum_msat);
 326         }
 327
 328         #[test]
 329         fn compute_payinfo_1_hop() {
 330                 let recv_tlvs = ReceiveTlvs {
 331                         payment_secret: PaymentSecret([0; 32]),
 332                         payment_constraints: PaymentConstraints {
 333                                 max_cltv_expiry: 0,
 334                                 htlc_minimum_msat: 1,
 335                         },
 336                 };
 337                 let blinded_payinfo = super::compute_payinfo(&[], &recv_tlvs, 4242).unwrap();
 338                 assert_eq!(blinded_payinfo.fee_base_msat, 0);
 339                 assert_eq!(blinded_payinfo.fee_proportional_millionths, 0);
 340                 assert_eq!(blinded_payinfo.cltv_expiry_delta, 0);
 341                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 1);
 342                 assert_eq!(blinded_payinfo.htlc_maximum_msat, 4242);
 343         }
 344
 345         #[test]
 346         fn simple_aggregated_htlc_min() {
 347                 // If no hops charge fees, the htlc_minimum_msat should just be the maximum htlc_minimum_msat
 348                 // along the path.
 349                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 350                 let intermediate_nodes = vec![ForwardNode {
 351                         node_id: dummy_pk,
 352                         tlvs: ForwardTlvs {
 353                                 short_channel_id: 0,
 354                                 payment_relay: PaymentRelay {
 355                                         cltv_expiry_delta: 0,
 356                                         fee_proportional_millionths: 0,
 357                                         fee_base_msat: 0,
 358                                 },
 359                                 payment_constraints: PaymentConstraints {
 360                                         max_cltv_expiry: 0,
 361                                         htlc_minimum_msat: 1,
 362                                 },
 363                                 features: BlindedHopFeatures::empty(),
 364                         },
 365                         htlc_maximum_msat: u64::max_value()
 366                 }, ForwardNode {
 367                         node_id: dummy_pk,
 368                         tlvs: ForwardTlvs {
 369                                 short_channel_id: 0,
 370                                 payment_relay: PaymentRelay {
 371                                         cltv_expiry_delta: 0,
 372                                         fee_proportional_millionths: 0,
 373                                         fee_base_msat: 0,
 374                                 },
 375                                 payment_constraints: PaymentConstraints {
 376                                         max_cltv_expiry: 0,
 377                                         htlc_minimum_msat: 2_000,
 378                                 },
 379                                 features: BlindedHopFeatures::empty(),
 380                         },
 381                         htlc_maximum_msat: u64::max_value()
 382                 }];
 383                 let recv_tlvs = ReceiveTlvs {
 384                         payment_secret: PaymentSecret([0; 32]),
 385                         payment_constraints: PaymentConstraints {
 386                                 max_cltv_expiry: 0,
 387                                 htlc_minimum_msat: 3,
 388                         },
 389                 };
 390                 let htlc_maximum_msat = 100_000;
 391                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat).unwrap();
 392                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 2_000);
 393         }
 394
 395         #[test]
 396         fn aggregated_htlc_min() {
 397                 // Create a path with varying fees and htlc_mins, and make sure htlc_minimum_msat ends up as the
 398                 // max (htlc_min - following_fees) along the path.
 399                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 400                 let intermediate_nodes = vec![ForwardNode {
 401                         node_id: dummy_pk,
 402                         tlvs: ForwardTlvs {
 403                                 short_channel_id: 0,
 404                                 payment_relay: PaymentRelay {
 405                                         cltv_expiry_delta: 0,
 406                                         fee_proportional_millionths: 500,
 407                                         fee_base_msat: 1_000,
 408                                 },
 409                                 payment_constraints: PaymentConstraints {
 410                                         max_cltv_expiry: 0,
 411                                         htlc_minimum_msat: 5_000,
 412                                 },
 413                                 features: BlindedHopFeatures::empty(),
 414                         },
 415                         htlc_maximum_msat: u64::max_value()
 416                 }, ForwardNode {
 417                         node_id: dummy_pk,
 418                         tlvs: ForwardTlvs {
 419                                 short_channel_id: 0,
 420                                 payment_relay: PaymentRelay {
 421                                         cltv_expiry_delta: 0,
 422                                         fee_proportional_millionths: 500,
 423                                         fee_base_msat: 200,
 424                                 },
 425                                 payment_constraints: PaymentConstraints {
 426                                         max_cltv_expiry: 0,
 427                                         htlc_minimum_msat: 2_000,
 428                                 },
 429                                 features: BlindedHopFeatures::empty(),
 430                         },
 431                         htlc_maximum_msat: u64::max_value()
 432                 }];
 433                 let recv_tlvs = ReceiveTlvs {
 434                         payment_secret: PaymentSecret([0; 32]),
 435                         payment_constraints: PaymentConstraints {
 436                                 max_cltv_expiry: 0,
 437                                 htlc_minimum_msat: 1,
 438                         },
 439                 };
 440                 let htlc_minimum_msat = 3798;
 441                 assert!(super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_minimum_msat - 1).is_err());
 442
 443                 let htlc_maximum_msat = htlc_minimum_msat + 1;
 444                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat).unwrap();
 445                 assert_eq!(blinded_payinfo.htlc_minimum_msat, htlc_minimum_msat);
 446                 assert_eq!(blinded_payinfo.htlc_maximum_msat, htlc_maximum_msat);
 447         }
 448
 449         #[test]
 450         fn aggregated_htlc_max() {
 451                 // Create a path with varying fees and `htlc_maximum_msat`s, and make sure the aggregated max
 452                 // htlc ends up as the min (htlc_max - following_fees) along the path.
 453                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 454                 let intermediate_nodes = vec![ForwardNode {
 455                         node_id: dummy_pk,
 456                         tlvs: ForwardTlvs {
 457                                 short_channel_id: 0,
 458                                 payment_relay: PaymentRelay {
 459                                         cltv_expiry_delta: 0,
 460                                         fee_proportional_millionths: 500,
 461                                         fee_base_msat: 1_000,
 462                                 },
 463                                 payment_constraints: PaymentConstraints {
 464                                         max_cltv_expiry: 0,
 465                                         htlc_minimum_msat: 1,
 466                                 },
 467                                 features: BlindedHopFeatures::empty(),
 468                         },
 469                         htlc_maximum_msat: 5_000,
 470                 }, ForwardNode {
 471                         node_id: dummy_pk,
 472                         tlvs: ForwardTlvs {
 473                                 short_channel_id: 0,
 474                                 payment_relay: PaymentRelay {
 475                                         cltv_expiry_delta: 0,
 476                                         fee_proportional_millionths: 500,
 477                                         fee_base_msat: 1,
 478                                 },
 479                                 payment_constraints: PaymentConstraints {
 480                                         max_cltv_expiry: 0,
 481                                         htlc_minimum_msat: 1,
 482                                 },
 483                                 features: BlindedHopFeatures::empty(),
 484                         },
 485                         htlc_maximum_msat: 10_000
 486                 }];
 487                 let recv_tlvs = ReceiveTlvs {
 488                         payment_secret: PaymentSecret([0; 32]),
 489                         payment_constraints: PaymentConstraints {
 490                                 max_cltv_expiry: 0,
 491                                 htlc_minimum_msat: 1,
 492                         },
 493                 };
 494
 495                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, 10_000).unwrap();
 496                 assert_eq!(blinded_payinfo.htlc_maximum_msat, 3997);
 497         }
 498 }