_ 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::channelmanager::CounterpartyForwardingInfo;
  12 use crate::ln::features::BlindedHopFeatures;
  13 use crate::ln::msgs::DecodeError;
  14 use crate::offers::invoice::BlindedPayInfo;
  15 use crate::offers::offer::OfferId;
  16 use crate::util::ser::{HighZeroBytesDroppedBigSize, Readable, Writeable, Writer};
  17
  18 #[allow(unused_imports)]
  19 use crate::prelude::*;
  20
  21 /// An intermediate node, its outbound channel, and relay parameters.
  22 #[derive(Clone, Debug)]
  23 pub struct ForwardNode {
  24         /// The TLVs for this node's [`BlindedHop`], where the fee parameters contained within are also
  25         /// used for [`BlindedPayInfo`] construction.
  26         pub tlvs: ForwardTlvs,
  27         /// This node's pubkey.
  28         pub node_id: PublicKey,
  29         /// The maximum value, in msat, that may be accepted by this node.
  30         pub htlc_maximum_msat: u64,
  31 }
  32
  33 /// Data to construct a [`BlindedHop`] for forwarding a payment.
  34 #[derive(Clone, Debug)]
  35 pub struct ForwardTlvs {
  36         /// The short channel id this payment should be forwarded out over.
  37         pub short_channel_id: u64,
  38         /// Payment parameters for relaying over [`Self::short_channel_id`].
  39         pub payment_relay: PaymentRelay,
  40         /// Payment constraints for relaying over [`Self::short_channel_id`].
  41         pub payment_constraints: PaymentConstraints,
  42         /// Supported and required features when relaying a payment onion containing this object's
  43         /// corresponding [`BlindedHop::encrypted_payload`].
  44         ///
  45         /// [`BlindedHop::encrypted_payload`]: crate::blinded_path::BlindedHop::encrypted_payload
  46         pub features: BlindedHopFeatures,
  47 }
  48
  49 /// Data to construct a [`BlindedHop`] for receiving a payment. This payload is custom to LDK and
  50 /// may not be valid if received by another lightning implementation.
  51 #[derive(Clone, Debug)]
  52 pub struct ReceiveTlvs {
  53         /// Used to authenticate the sender of a payment to the receiver and tie MPP HTLCs together.
  54         pub payment_secret: PaymentSecret,
  55         /// Constraints for the receiver of this payment.
  56         pub payment_constraints: PaymentConstraints,
  57         /// Context for the receiver of this payment.
  58         pub payment_context: PaymentContext,
  59 }
  60
  61 /// Data to construct a [`BlindedHop`] for sending a payment over.
  62 ///
  63 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  64 pub(crate) enum BlindedPaymentTlvs {
  65         /// This blinded payment data is for a forwarding node.
  66         Forward(ForwardTlvs),
  67         /// This blinded payment data is for the receiving node.
  68         Receive(ReceiveTlvs),
  69 }
  70
  71 // Used to include forward and receive TLVs in the same iterator for encoding.
  72 enum BlindedPaymentTlvsRef<'a> {
  73         Forward(&'a ForwardTlvs),
  74         Receive(&'a ReceiveTlvs),
  75 }
  76
  77 /// Parameters for relaying over a given [`BlindedHop`].
  78 ///
  79 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  80 #[derive(Clone, Debug)]
  81 pub struct PaymentRelay {
  82         /// Number of blocks subtracted from an incoming HTLC's `cltv_expiry` for this [`BlindedHop`].
  83         pub cltv_expiry_delta: u16,
  84         /// Liquidity fee charged (in millionths of the amount transferred) for relaying a payment over
  85         /// this [`BlindedHop`], (i.e., 10,000 is 1%).
  86         pub fee_proportional_millionths: u32,
  87         /// Base fee charged (in millisatoshi) for relaying a payment over this [`BlindedHop`].
  88         pub fee_base_msat: u32,
  89 }
  90
  91 /// Constraints for relaying over a given [`BlindedHop`].
  92 ///
  93 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  94 #[derive(Clone, Debug)]
  95 pub struct PaymentConstraints {
  96         /// The maximum total CLTV that is acceptable when relaying a payment over this [`BlindedHop`].
  97         pub max_cltv_expiry: u32,
  98         /// The minimum value, in msat, that may be accepted by the node corresponding to this
  99         /// [`BlindedHop`].
 100         pub htlc_minimum_msat: u64,
 101 }
 102
 103 /// The context of an inbound payment, which is included in a [`BlindedPath`] via [`ReceiveTlvs`]
 104 /// and surfaced in [`PaymentPurpose`].
 105 ///
 106 /// [`BlindedPath`]: crate::blinded_path::BlindedPath
 107 /// [`PaymentPurpose`]: crate::events::PaymentPurpose
 108 #[derive(Clone, Debug, Eq, PartialEq)]
 109 pub enum PaymentContext {
 110         /// The payment context was unknown.
 111         Unknown(UnknownPaymentContext),
 112
 113         /// The payment was made for an invoice requested from a BOLT 12 [`Offer`].
 114         ///
 115         /// [`Offer`]: crate::offers::offer::Offer
 116         Bolt12Offer(Bolt12OfferContext),
 117 }
 118
 119 /// An unknown payment context.
 120 #[derive(Clone, Debug, Eq, PartialEq)]
 121 pub struct UnknownPaymentContext(());
 122
 123 /// The context of a payment made for an invoice requested from a BOLT 12 [`Offer`].
 124 ///
 125 /// [`Offer`]: crate::offers::offer::Offer
 126 #[derive(Clone, Debug, Eq, PartialEq)]
 127 pub struct Bolt12OfferContext {
 128         /// The identifier of the [`Offer`].
 129         ///
 130         /// [`Offer`]: crate::offers::offer::Offer
 131         pub offer_id: OfferId,
 132 }
 133
 134 impl PaymentContext {
 135         pub(crate) fn unknown() -> Self {
 136                 PaymentContext::Unknown(UnknownPaymentContext(()))
 137         }
 138 }
 139
 140 impl TryFrom<CounterpartyForwardingInfo> for PaymentRelay {
 141         type Error = ();
 142
 143         fn try_from(info: CounterpartyForwardingInfo) -> Result<Self, ()> {
 144                 let CounterpartyForwardingInfo {
 145                         fee_base_msat, fee_proportional_millionths, cltv_expiry_delta
 146                 } = info;
 147
 148                 // Avoid exposing esoteric CLTV expiry deltas
 149                 let cltv_expiry_delta = match cltv_expiry_delta {
 150                         0..=40 => 40,
 151                         41..=80 => 80,
 152                         81..=144 => 144,
 153                         145..=216 => 216,
 154                         _ => return Err(()),
 155                 };
 156
 157                 Ok(Self { cltv_expiry_delta, fee_proportional_millionths, fee_base_msat })
 158         }
 159 }
 160
 161 impl Writeable for ForwardTlvs {
 162         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 163                 let features_opt =
 164                         if self.features == BlindedHopFeatures::empty() { None }
 165                         else { Some(&self.features) };
 166                 encode_tlv_stream!(w, {
 167                         (2, self.short_channel_id, required),
 168                         (10, self.payment_relay, required),
 169                         (12, self.payment_constraints, required),
 170                         (14, features_opt, option)
 171                 });
 172                 Ok(())
 173         }
 174 }
 175
 176 impl Writeable for ReceiveTlvs {
 177         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 178                 encode_tlv_stream!(w, {
 179                         (12, self.payment_constraints, required),
 180                         (65536, self.payment_secret, required),
 181                         (65537, self.payment_context, required)
 182                 });
 183                 Ok(())
 184         }
 185 }
 186
 187 impl<'a> Writeable for BlindedPaymentTlvsRef<'a> {
 188         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 189                 // TODO: write padding
 190                 match self {
 191                         Self::Forward(tlvs) => tlvs.write(w)?,
 192                         Self::Receive(tlvs) => tlvs.write(w)?,
 193                 }
 194                 Ok(())
 195         }
 196 }
 197
 198 impl Readable for BlindedPaymentTlvs {
 199         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 200                 _init_and_read_tlv_stream!(r, {
 201                         (1, _padding, option),
 202                         (2, scid, option),
 203                         (10, payment_relay, option),
 204                         (12, payment_constraints, required),
 205                         (14, features, option),
 206                         (65536, payment_secret, option),
 207                         (65537, payment_context, (default_value, PaymentContext::unknown())),
 208                 });
 209                 let _padding: Option<utils::Padding> = _padding;
 210
 211                 if let Some(short_channel_id) = scid {
 212                         if payment_secret.is_some() {
 213                                 return Err(DecodeError::InvalidValue)
 214                         }
 215                         Ok(BlindedPaymentTlvs::Forward(ForwardTlvs {
 216                                 short_channel_id,
 217                                 payment_relay: payment_relay.ok_or(DecodeError::InvalidValue)?,
 218                                 payment_constraints: payment_constraints.0.unwrap(),
 219                                 features: features.unwrap_or_else(BlindedHopFeatures::empty),
 220                         }))
 221                 } else {
 222                         if payment_relay.is_some() || features.is_some() { return Err(DecodeError::InvalidValue) }
 223                         Ok(BlindedPaymentTlvs::Receive(ReceiveTlvs {
 224                                 payment_secret: payment_secret.ok_or(DecodeError::InvalidValue)?,
 225                                 payment_constraints: payment_constraints.0.unwrap(),
 226                                 payment_context: payment_context.0.unwrap(),
 227                         }))
 228                 }
 229         }
 230 }
 231
 232 /// Construct blinded payment hops for the given `intermediate_nodes` and payee info.
 233 pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 234         secp_ctx: &Secp256k1<T>, intermediate_nodes: &[ForwardNode],
 235         payee_node_id: PublicKey, payee_tlvs: ReceiveTlvs, session_priv: &SecretKey
 236 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
 237         let pks = intermediate_nodes.iter().map(|node| &node.node_id)
 238                 .chain(core::iter::once(&payee_node_id));
 239         let tlvs = intermediate_nodes.iter().map(|node| BlindedPaymentTlvsRef::Forward(&node.tlvs))
 240                 .chain(core::iter::once(BlindedPaymentTlvsRef::Receive(&payee_tlvs)));
 241         utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
 242 }
 243
 244 /// `None` if underflow occurs.
 245 pub(crate) fn amt_to_forward_msat(inbound_amt_msat: u64, payment_relay: &PaymentRelay) -> Option<u64> {
 246         let inbound_amt = inbound_amt_msat as u128;
 247         let base = payment_relay.fee_base_msat as u128;
 248         let prop = payment_relay.fee_proportional_millionths as u128;
 249
 250         let post_base_fee_inbound_amt =
 251                 if let Some(amt) = inbound_amt.checked_sub(base) { amt } else { return None };
 252         let mut amt_to_forward =
 253                 (post_base_fee_inbound_amt * 1_000_000 + 1_000_000 + prop - 1) / (prop + 1_000_000);
 254
 255         let fee = ((amt_to_forward * prop) / 1_000_000) + base;
 256         if inbound_amt - fee < amt_to_forward {
 257                 // Rounding up the forwarded amount resulted in underpaying this node, so take an extra 1 msat
 258                 // in fee to compensate.
 259                 amt_to_forward -= 1;
 260         }
 261         debug_assert_eq!(amt_to_forward + fee, inbound_amt);
 262         u64::try_from(amt_to_forward).ok()
 263 }
 264
 265 pub(super) fn compute_payinfo(
 266         intermediate_nodes: &[ForwardNode], payee_tlvs: &ReceiveTlvs, payee_htlc_maximum_msat: u64,
 267         min_final_cltv_expiry_delta: u16
 268 ) -> Result<BlindedPayInfo, ()> {
 269         let mut curr_base_fee: u64 = 0;
 270         let mut curr_prop_mil: u64 = 0;
 271         let mut cltv_expiry_delta: u16 = min_final_cltv_expiry_delta;
 272         for tlvs in intermediate_nodes.iter().rev().map(|n| &n.tlvs) {
 273                 // In the future, we'll want to take the intersection of all supported features for the
 274                 // `BlindedPayInfo`, but there are no features in that context right now.
 275                 if tlvs.features.requires_unknown_bits_from(&BlindedHopFeatures::empty()) { return Err(()) }
 276
 277                 let next_base_fee = tlvs.payment_relay.fee_base_msat as u64;
 278                 let next_prop_mil = tlvs.payment_relay.fee_proportional_millionths as u64;
 279                 // Use integer arithmetic to compute `ceil(a/b)` as `(a+b-1)/b`
 280                 // ((curr_base_fee * (1_000_000 + next_prop_mil)) / 1_000_000) + next_base_fee
 281                 curr_base_fee = curr_base_fee.checked_mul(1_000_000 + next_prop_mil)
 282                         .and_then(|f| f.checked_add(1_000_000 - 1))
 283                         .map(|f| f / 1_000_000)
 284                         .and_then(|f| f.checked_add(next_base_fee))
 285                         .ok_or(())?;
 286                 // ceil(((curr_prop_mil + 1_000_000) * (next_prop_mil + 1_000_000)) / 1_000_000) - 1_000_000
 287                 curr_prop_mil = curr_prop_mil.checked_add(1_000_000)
 288                         .and_then(|f1| next_prop_mil.checked_add(1_000_000).and_then(|f2| f2.checked_mul(f1)))
 289                         .and_then(|f| f.checked_add(1_000_000 - 1))
 290                         .map(|f| f / 1_000_000)
 291                         .and_then(|f| f.checked_sub(1_000_000))
 292                         .ok_or(())?;
 293
 294                 cltv_expiry_delta = cltv_expiry_delta.checked_add(tlvs.payment_relay.cltv_expiry_delta).ok_or(())?;
 295         }
 296
 297         let mut htlc_minimum_msat: u64 = 1;
 298         let mut htlc_maximum_msat: u64 = 21_000_000 * 100_000_000 * 1_000; // Total bitcoin supply
 299         for node in intermediate_nodes.iter() {
 300                 // The min htlc for an intermediate node is that node's min minus the fees charged by all of the
 301                 // following hops for forwarding that min, since that fee amount will automatically be included
 302                 // in the amount that this node receives and contribute towards reaching its min.
 303                 htlc_minimum_msat = amt_to_forward_msat(
 304                         core::cmp::max(node.tlvs.payment_constraints.htlc_minimum_msat, htlc_minimum_msat),
 305                         &node.tlvs.payment_relay
 306                 ).unwrap_or(1); // If underflow occurs, we definitely reached this node's min
 307                 htlc_maximum_msat = amt_to_forward_msat(
 308                         core::cmp::min(node.htlc_maximum_msat, htlc_maximum_msat), &node.tlvs.payment_relay
 309                 ).ok_or(())?; // If underflow occurs, we cannot send to this hop without exceeding their max
 310         }
 311         htlc_minimum_msat = core::cmp::max(
 312                 payee_tlvs.payment_constraints.htlc_minimum_msat, htlc_minimum_msat
 313         );
 314         htlc_maximum_msat = core::cmp::min(payee_htlc_maximum_msat, htlc_maximum_msat);
 315
 316         if htlc_maximum_msat < htlc_minimum_msat { return Err(()) }
 317         Ok(BlindedPayInfo {
 318                 fee_base_msat: u32::try_from(curr_base_fee).map_err(|_| ())?,
 319                 fee_proportional_millionths: u32::try_from(curr_prop_mil).map_err(|_| ())?,
 320                 cltv_expiry_delta,
 321                 htlc_minimum_msat,
 322                 htlc_maximum_msat,
 323                 features: BlindedHopFeatures::empty(),
 324         })
 325 }
 326
 327 impl Writeable for PaymentRelay {
 328         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 329                 self.cltv_expiry_delta.write(w)?;
 330                 self.fee_proportional_millionths.write(w)?;
 331                 HighZeroBytesDroppedBigSize(self.fee_base_msat).write(w)
 332         }
 333 }
 334 impl Readable for PaymentRelay {
 335         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 336                 let cltv_expiry_delta: u16 = Readable::read(r)?;
 337                 let fee_proportional_millionths: u32 = Readable::read(r)?;
 338                 let fee_base_msat: HighZeroBytesDroppedBigSize<u32> = Readable::read(r)?;
 339                 Ok(Self { cltv_expiry_delta, fee_proportional_millionths, fee_base_msat: fee_base_msat.0 })
 340         }
 341 }
 342
 343 impl Writeable for PaymentConstraints {
 344         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 345                 self.max_cltv_expiry.write(w)?;
 346                 HighZeroBytesDroppedBigSize(self.htlc_minimum_msat).write(w)
 347         }
 348 }
 349 impl Readable for PaymentConstraints {
 350         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 351                 let max_cltv_expiry: u32 = Readable::read(r)?;
 352                 let htlc_minimum_msat: HighZeroBytesDroppedBigSize<u64> = Readable::read(r)?;
 353                 Ok(Self { max_cltv_expiry, htlc_minimum_msat: htlc_minimum_msat.0 })
 354         }
 355 }
 356
 357 impl_writeable_tlv_based_enum!(PaymentContext,
 358         ;
 359         (0, Unknown),
 360         (1, Bolt12Offer),
 361 );
 362
 363 impl Writeable for UnknownPaymentContext {
 364         fn write<W: Writer>(&self, _w: &mut W) -> Result<(), io::Error> {
 365                 Ok(())
 366         }
 367 }
 368
 369 impl Readable for UnknownPaymentContext {
 370         fn read<R: io::Read>(_r: &mut R) -> Result<Self, DecodeError> {
 371                 Ok(UnknownPaymentContext(()))
 372         }
 373 }
 374
 375 impl_writeable_tlv_based!(Bolt12OfferContext, {
 376         (0, offer_id, required),
 377 });
 378
 379 #[cfg(test)]
 380 mod tests {
 381         use bitcoin::secp256k1::PublicKey;
 382         use crate::blinded_path::payment::{ForwardNode, ForwardTlvs, ReceiveTlvs, PaymentConstraints, PaymentContext, PaymentRelay};
 383         use crate::ln::PaymentSecret;
 384         use crate::ln::features::BlindedHopFeatures;
 385         use crate::ln::functional_test_utils::TEST_FINAL_CLTV;
 386
 387         #[test]
 388         fn compute_payinfo() {
 389                 // Taken from the spec example for aggregating blinded payment info. See
 390                 // https://github.com/lightning/bolts/blob/master/proposals/route-blinding.md#blinded-payments
 391                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 392                 let intermediate_nodes = vec![ForwardNode {
 393                         node_id: dummy_pk,
 394                         tlvs: ForwardTlvs {
 395                                 short_channel_id: 0,
 396                                 payment_relay: PaymentRelay {
 397                                         cltv_expiry_delta: 144,
 398                                         fee_proportional_millionths: 500,
 399                                         fee_base_msat: 100,
 400                                 },
 401                                 payment_constraints: PaymentConstraints {
 402                                         max_cltv_expiry: 0,
 403                                         htlc_minimum_msat: 100,
 404                                 },
 405                                 features: BlindedHopFeatures::empty(),
 406                         },
 407                         htlc_maximum_msat: u64::max_value(),
 408                 }, ForwardNode {
 409                         node_id: dummy_pk,
 410                         tlvs: ForwardTlvs {
 411                                 short_channel_id: 0,
 412                                 payment_relay: PaymentRelay {
 413                                         cltv_expiry_delta: 144,
 414                                         fee_proportional_millionths: 500,
 415                                         fee_base_msat: 100,
 416                                 },
 417                                 payment_constraints: PaymentConstraints {
 418                                         max_cltv_expiry: 0,
 419                                         htlc_minimum_msat: 1_000,
 420                                 },
 421                                 features: BlindedHopFeatures::empty(),
 422                         },
 423                         htlc_maximum_msat: u64::max_value(),
 424                 }];
 425                 let recv_tlvs = ReceiveTlvs {
 426                         payment_secret: PaymentSecret([0; 32]),
 427                         payment_constraints: PaymentConstraints {
 428                                 max_cltv_expiry: 0,
 429                                 htlc_minimum_msat: 1,
 430                         },
 431                         payment_context: PaymentContext::unknown(),
 432                 };
 433                 let htlc_maximum_msat = 100_000;
 434                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat, 12).unwrap();
 435                 assert_eq!(blinded_payinfo.fee_base_msat, 201);
 436                 assert_eq!(blinded_payinfo.fee_proportional_millionths, 1001);
 437                 assert_eq!(blinded_payinfo.cltv_expiry_delta, 300);
 438                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 900);
 439                 assert_eq!(blinded_payinfo.htlc_maximum_msat, htlc_maximum_msat);
 440         }
 441
 442         #[test]
 443         fn compute_payinfo_1_hop() {
 444                 let recv_tlvs = ReceiveTlvs {
 445                         payment_secret: PaymentSecret([0; 32]),
 446                         payment_constraints: PaymentConstraints {
 447                                 max_cltv_expiry: 0,
 448                                 htlc_minimum_msat: 1,
 449                         },
 450                         payment_context: PaymentContext::unknown(),
 451                 };
 452                 let blinded_payinfo = super::compute_payinfo(&[], &recv_tlvs, 4242, TEST_FINAL_CLTV as u16).unwrap();
 453                 assert_eq!(blinded_payinfo.fee_base_msat, 0);
 454                 assert_eq!(blinded_payinfo.fee_proportional_millionths, 0);
 455                 assert_eq!(blinded_payinfo.cltv_expiry_delta, TEST_FINAL_CLTV as u16);
 456                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 1);
 457                 assert_eq!(blinded_payinfo.htlc_maximum_msat, 4242);
 458         }
 459
 460         #[test]
 461         fn simple_aggregated_htlc_min() {
 462                 // If no hops charge fees, the htlc_minimum_msat should just be the maximum htlc_minimum_msat
 463                 // along the path.
 464                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 465                 let intermediate_nodes = vec![ForwardNode {
 466                         node_id: dummy_pk,
 467                         tlvs: ForwardTlvs {
 468                                 short_channel_id: 0,
 469                                 payment_relay: PaymentRelay {
 470                                         cltv_expiry_delta: 0,
 471                                         fee_proportional_millionths: 0,
 472                                         fee_base_msat: 0,
 473                                 },
 474                                 payment_constraints: PaymentConstraints {
 475                                         max_cltv_expiry: 0,
 476                                         htlc_minimum_msat: 1,
 477                                 },
 478                                 features: BlindedHopFeatures::empty(),
 479                         },
 480                         htlc_maximum_msat: u64::max_value()
 481                 }, ForwardNode {
 482                         node_id: dummy_pk,
 483                         tlvs: ForwardTlvs {
 484                                 short_channel_id: 0,
 485                                 payment_relay: PaymentRelay {
 486                                         cltv_expiry_delta: 0,
 487                                         fee_proportional_millionths: 0,
 488                                         fee_base_msat: 0,
 489                                 },
 490                                 payment_constraints: PaymentConstraints {
 491                                         max_cltv_expiry: 0,
 492                                         htlc_minimum_msat: 2_000,
 493                                 },
 494                                 features: BlindedHopFeatures::empty(),
 495                         },
 496                         htlc_maximum_msat: u64::max_value()
 497                 }];
 498                 let recv_tlvs = ReceiveTlvs {
 499                         payment_secret: PaymentSecret([0; 32]),
 500                         payment_constraints: PaymentConstraints {
 501                                 max_cltv_expiry: 0,
 502                                 htlc_minimum_msat: 3,
 503                         },
 504                         payment_context: PaymentContext::unknown(),
 505                 };
 506                 let htlc_maximum_msat = 100_000;
 507                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat, TEST_FINAL_CLTV as u16).unwrap();
 508                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 2_000);
 509         }
 510
 511         #[test]
 512         fn aggregated_htlc_min() {
 513                 // Create a path with varying fees and htlc_mins, and make sure htlc_minimum_msat ends up as the
 514                 // max (htlc_min - following_fees) along the path.
 515                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 516                 let intermediate_nodes = vec![ForwardNode {
 517                         node_id: dummy_pk,
 518                         tlvs: ForwardTlvs {
 519                                 short_channel_id: 0,
 520                                 payment_relay: PaymentRelay {
 521                                         cltv_expiry_delta: 0,
 522                                         fee_proportional_millionths: 500,
 523                                         fee_base_msat: 1_000,
 524                                 },
 525                                 payment_constraints: PaymentConstraints {
 526                                         max_cltv_expiry: 0,
 527                                         htlc_minimum_msat: 5_000,
 528                                 },
 529                                 features: BlindedHopFeatures::empty(),
 530                         },
 531                         htlc_maximum_msat: u64::max_value()
 532                 }, ForwardNode {
 533                         node_id: dummy_pk,
 534                         tlvs: ForwardTlvs {
 535                                 short_channel_id: 0,
 536                                 payment_relay: PaymentRelay {
 537                                         cltv_expiry_delta: 0,
 538                                         fee_proportional_millionths: 500,
 539                                         fee_base_msat: 200,
 540                                 },
 541                                 payment_constraints: PaymentConstraints {
 542                                         max_cltv_expiry: 0,
 543                                         htlc_minimum_msat: 2_000,
 544                                 },
 545                                 features: BlindedHopFeatures::empty(),
 546                         },
 547                         htlc_maximum_msat: u64::max_value()
 548                 }];
 549                 let recv_tlvs = ReceiveTlvs {
 550                         payment_secret: PaymentSecret([0; 32]),
 551                         payment_constraints: PaymentConstraints {
 552                                 max_cltv_expiry: 0,
 553                                 htlc_minimum_msat: 1,
 554                         },
 555                         payment_context: PaymentContext::unknown(),
 556                 };
 557                 let htlc_minimum_msat = 3798;
 558                 assert!(super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_minimum_msat - 1, TEST_FINAL_CLTV as u16).is_err());
 559
 560                 let htlc_maximum_msat = htlc_minimum_msat + 1;
 561                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat, TEST_FINAL_CLTV as u16).unwrap();
 562                 assert_eq!(blinded_payinfo.htlc_minimum_msat, htlc_minimum_msat);
 563                 assert_eq!(blinded_payinfo.htlc_maximum_msat, htlc_maximum_msat);
 564         }
 565
 566         #[test]
 567         fn aggregated_htlc_max() {
 568                 // Create a path with varying fees and `htlc_maximum_msat`s, and make sure the aggregated max
 569                 // htlc ends up as the min (htlc_max - following_fees) along the path.
 570                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 571                 let intermediate_nodes = vec![ForwardNode {
 572                         node_id: dummy_pk,
 573                         tlvs: ForwardTlvs {
 574                                 short_channel_id: 0,
 575                                 payment_relay: PaymentRelay {
 576                                         cltv_expiry_delta: 0,
 577                                         fee_proportional_millionths: 500,
 578                                         fee_base_msat: 1_000,
 579                                 },
 580                                 payment_constraints: PaymentConstraints {
 581                                         max_cltv_expiry: 0,
 582                                         htlc_minimum_msat: 1,
 583                                 },
 584                                 features: BlindedHopFeatures::empty(),
 585                         },
 586                         htlc_maximum_msat: 5_000,
 587                 }, ForwardNode {
 588                         node_id: dummy_pk,
 589                         tlvs: ForwardTlvs {
 590                                 short_channel_id: 0,
 591                                 payment_relay: PaymentRelay {
 592                                         cltv_expiry_delta: 0,
 593                                         fee_proportional_millionths: 500,
 594                                         fee_base_msat: 1,
 595                                 },
 596                                 payment_constraints: PaymentConstraints {
 597                                         max_cltv_expiry: 0,
 598                                         htlc_minimum_msat: 1,
 599                                 },
 600                                 features: BlindedHopFeatures::empty(),
 601                         },
 602                         htlc_maximum_msat: 10_000
 603                 }];
 604                 let recv_tlvs = ReceiveTlvs {
 605                         payment_secret: PaymentSecret([0; 32]),
 606                         payment_constraints: PaymentConstraints {
 607                                 max_cltv_expiry: 0,
 608                                 htlc_minimum_msat: 1,
 609                         },
 610                         payment_context: PaymentContext::unknown(),
 611                 };
 612
 613                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, 10_000, TEST_FINAL_CLTV as u16).unwrap();
 614                 assert_eq!(blinded_payinfo.htlc_maximum_msat, 3997);
 615         }
 616 }