_ 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         /// The payment was made for an invoice sent for a BOLT 12 [`Refund`].
 119         ///
 120         /// [`Refund`]: crate::offers::refund::Refund
 121         Bolt12Refund(Bolt12RefundContext),
 122 }
 123
 124 /// An unknown payment context.
 125 #[derive(Clone, Debug, Eq, PartialEq)]
 126 pub struct UnknownPaymentContext(());
 127
 128 /// The context of a payment made for an invoice requested from a BOLT 12 [`Offer`].
 129 ///
 130 /// [`Offer`]: crate::offers::offer::Offer
 131 #[derive(Clone, Debug, Eq, PartialEq)]
 132 pub struct Bolt12OfferContext {
 133         /// The identifier of the [`Offer`].
 134         ///
 135         /// [`Offer`]: crate::offers::offer::Offer
 136         pub offer_id: OfferId,
 137 }
 138
 139 /// The context of a payment made for an invoice sent for a BOLT 12 [`Refund`].
 140 ///
 141 /// [`Refund`]: crate::offers::refund::Refund
 142 #[derive(Clone, Debug, Eq, PartialEq)]
 143 pub struct Bolt12RefundContext {}
 144
 145 impl PaymentContext {
 146         pub(crate) fn unknown() -> Self {
 147                 PaymentContext::Unknown(UnknownPaymentContext(()))
 148         }
 149 }
 150
 151 impl TryFrom<CounterpartyForwardingInfo> for PaymentRelay {
 152         type Error = ();
 153
 154         fn try_from(info: CounterpartyForwardingInfo) -> Result<Self, ()> {
 155                 let CounterpartyForwardingInfo {
 156                         fee_base_msat, fee_proportional_millionths, cltv_expiry_delta
 157                 } = info;
 158
 159                 // Avoid exposing esoteric CLTV expiry deltas
 160                 let cltv_expiry_delta = match cltv_expiry_delta {
 161                         0..=40 => 40,
 162                         41..=80 => 80,
 163                         81..=144 => 144,
 164                         145..=216 => 216,
 165                         _ => return Err(()),
 166                 };
 167
 168                 Ok(Self { cltv_expiry_delta, fee_proportional_millionths, fee_base_msat })
 169         }
 170 }
 171
 172 impl Writeable for ForwardTlvs {
 173         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 174                 let features_opt =
 175                         if self.features == BlindedHopFeatures::empty() { None }
 176                         else { Some(&self.features) };
 177                 encode_tlv_stream!(w, {
 178                         (2, self.short_channel_id, required),
 179                         (10, self.payment_relay, required),
 180                         (12, self.payment_constraints, required),
 181                         (14, features_opt, option)
 182                 });
 183                 Ok(())
 184         }
 185 }
 186
 187 impl Writeable for ReceiveTlvs {
 188         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 189                 encode_tlv_stream!(w, {
 190                         (12, self.payment_constraints, required),
 191                         (65536, self.payment_secret, required),
 192                         (65537, self.payment_context, required)
 193                 });
 194                 Ok(())
 195         }
 196 }
 197
 198 impl<'a> Writeable for BlindedPaymentTlvsRef<'a> {
 199         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 200                 // TODO: write padding
 201                 match self {
 202                         Self::Forward(tlvs) => tlvs.write(w)?,
 203                         Self::Receive(tlvs) => tlvs.write(w)?,
 204                 }
 205                 Ok(())
 206         }
 207 }
 208
 209 impl Readable for BlindedPaymentTlvs {
 210         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 211                 _init_and_read_tlv_stream!(r, {
 212                         (1, _padding, option),
 213                         (2, scid, option),
 214                         (10, payment_relay, option),
 215                         (12, payment_constraints, required),
 216                         (14, features, option),
 217                         (65536, payment_secret, option),
 218                         (65537, payment_context, (default_value, PaymentContext::unknown())),
 219                 });
 220                 let _padding: Option<utils::Padding> = _padding;
 221
 222                 if let Some(short_channel_id) = scid {
 223                         if payment_secret.is_some() {
 224                                 return Err(DecodeError::InvalidValue)
 225                         }
 226                         Ok(BlindedPaymentTlvs::Forward(ForwardTlvs {
 227                                 short_channel_id,
 228                                 payment_relay: payment_relay.ok_or(DecodeError::InvalidValue)?,
 229                                 payment_constraints: payment_constraints.0.unwrap(),
 230                                 features: features.unwrap_or_else(BlindedHopFeatures::empty),
 231                         }))
 232                 } else {
 233                         if payment_relay.is_some() || features.is_some() { return Err(DecodeError::InvalidValue) }
 234                         Ok(BlindedPaymentTlvs::Receive(ReceiveTlvs {
 235                                 payment_secret: payment_secret.ok_or(DecodeError::InvalidValue)?,
 236                                 payment_constraints: payment_constraints.0.unwrap(),
 237                                 payment_context: payment_context.0.unwrap(),
 238                         }))
 239                 }
 240         }
 241 }
 242
 243 /// Construct blinded payment hops for the given `intermediate_nodes` and payee info.
 244 pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 245         secp_ctx: &Secp256k1<T>, intermediate_nodes: &[ForwardNode],
 246         payee_node_id: PublicKey, payee_tlvs: ReceiveTlvs, session_priv: &SecretKey
 247 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
 248         let pks = intermediate_nodes.iter().map(|node| &node.node_id)
 249                 .chain(core::iter::once(&payee_node_id));
 250         let tlvs = intermediate_nodes.iter().map(|node| BlindedPaymentTlvsRef::Forward(&node.tlvs))
 251                 .chain(core::iter::once(BlindedPaymentTlvsRef::Receive(&payee_tlvs)));
 252         utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
 253 }
 254
 255 /// `None` if underflow occurs.
 256 pub(crate) fn amt_to_forward_msat(inbound_amt_msat: u64, payment_relay: &PaymentRelay) -> Option<u64> {
 257         let inbound_amt = inbound_amt_msat as u128;
 258         let base = payment_relay.fee_base_msat as u128;
 259         let prop = payment_relay.fee_proportional_millionths as u128;
 260
 261         let post_base_fee_inbound_amt =
 262                 if let Some(amt) = inbound_amt.checked_sub(base) { amt } else { return None };
 263         let mut amt_to_forward =
 264                 (post_base_fee_inbound_amt * 1_000_000 + 1_000_000 + prop - 1) / (prop + 1_000_000);
 265
 266         let fee = ((amt_to_forward * prop) / 1_000_000) + base;
 267         if inbound_amt - fee < amt_to_forward {
 268                 // Rounding up the forwarded amount resulted in underpaying this node, so take an extra 1 msat
 269                 // in fee to compensate.
 270                 amt_to_forward -= 1;
 271         }
 272         debug_assert_eq!(amt_to_forward + fee, inbound_amt);
 273         u64::try_from(amt_to_forward).ok()
 274 }
 275
 276 pub(super) fn compute_payinfo(
 277         intermediate_nodes: &[ForwardNode], payee_tlvs: &ReceiveTlvs, payee_htlc_maximum_msat: u64,
 278         min_final_cltv_expiry_delta: u16
 279 ) -> Result<BlindedPayInfo, ()> {
 280         let mut curr_base_fee: u64 = 0;
 281         let mut curr_prop_mil: u64 = 0;
 282         let mut cltv_expiry_delta: u16 = min_final_cltv_expiry_delta;
 283         for tlvs in intermediate_nodes.iter().rev().map(|n| &n.tlvs) {
 284                 // In the future, we'll want to take the intersection of all supported features for the
 285                 // `BlindedPayInfo`, but there are no features in that context right now.
 286                 if tlvs.features.requires_unknown_bits_from(&BlindedHopFeatures::empty()) { return Err(()) }
 287
 288                 let next_base_fee = tlvs.payment_relay.fee_base_msat as u64;
 289                 let next_prop_mil = tlvs.payment_relay.fee_proportional_millionths as u64;
 290                 // Use integer arithmetic to compute `ceil(a/b)` as `(a+b-1)/b`
 291                 // ((curr_base_fee * (1_000_000 + next_prop_mil)) / 1_000_000) + next_base_fee
 292                 curr_base_fee = curr_base_fee.checked_mul(1_000_000 + next_prop_mil)
 293                         .and_then(|f| f.checked_add(1_000_000 - 1))
 294                         .map(|f| f / 1_000_000)
 295                         .and_then(|f| f.checked_add(next_base_fee))
 296                         .ok_or(())?;
 297                 // ceil(((curr_prop_mil + 1_000_000) * (next_prop_mil + 1_000_000)) / 1_000_000) - 1_000_000
 298                 curr_prop_mil = curr_prop_mil.checked_add(1_000_000)
 299                         .and_then(|f1| next_prop_mil.checked_add(1_000_000).and_then(|f2| f2.checked_mul(f1)))
 300                         .and_then(|f| f.checked_add(1_000_000 - 1))
 301                         .map(|f| f / 1_000_000)
 302                         .and_then(|f| f.checked_sub(1_000_000))
 303                         .ok_or(())?;
 304
 305                 cltv_expiry_delta = cltv_expiry_delta.checked_add(tlvs.payment_relay.cltv_expiry_delta).ok_or(())?;
 306         }
 307
 308         let mut htlc_minimum_msat: u64 = 1;
 309         let mut htlc_maximum_msat: u64 = 21_000_000 * 100_000_000 * 1_000; // Total bitcoin supply
 310         for node in intermediate_nodes.iter() {
 311                 // The min htlc for an intermediate node is that node's min minus the fees charged by all of the
 312                 // following hops for forwarding that min, since that fee amount will automatically be included
 313                 // in the amount that this node receives and contribute towards reaching its min.
 314                 htlc_minimum_msat = amt_to_forward_msat(
 315                         core::cmp::max(node.tlvs.payment_constraints.htlc_minimum_msat, htlc_minimum_msat),
 316                         &node.tlvs.payment_relay
 317                 ).unwrap_or(1); // If underflow occurs, we definitely reached this node's min
 318                 htlc_maximum_msat = amt_to_forward_msat(
 319                         core::cmp::min(node.htlc_maximum_msat, htlc_maximum_msat), &node.tlvs.payment_relay
 320                 ).ok_or(())?; // If underflow occurs, we cannot send to this hop without exceeding their max
 321         }
 322         htlc_minimum_msat = core::cmp::max(
 323                 payee_tlvs.payment_constraints.htlc_minimum_msat, htlc_minimum_msat
 324         );
 325         htlc_maximum_msat = core::cmp::min(payee_htlc_maximum_msat, htlc_maximum_msat);
 326
 327         if htlc_maximum_msat < htlc_minimum_msat { return Err(()) }
 328         Ok(BlindedPayInfo {
 329                 fee_base_msat: u32::try_from(curr_base_fee).map_err(|_| ())?,
 330                 fee_proportional_millionths: u32::try_from(curr_prop_mil).map_err(|_| ())?,
 331                 cltv_expiry_delta,
 332                 htlc_minimum_msat,
 333                 htlc_maximum_msat,
 334                 features: BlindedHopFeatures::empty(),
 335         })
 336 }
 337
 338 impl Writeable for PaymentRelay {
 339         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 340                 self.cltv_expiry_delta.write(w)?;
 341                 self.fee_proportional_millionths.write(w)?;
 342                 HighZeroBytesDroppedBigSize(self.fee_base_msat).write(w)
 343         }
 344 }
 345 impl Readable for PaymentRelay {
 346         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 347                 let cltv_expiry_delta: u16 = Readable::read(r)?;
 348                 let fee_proportional_millionths: u32 = Readable::read(r)?;
 349                 let fee_base_msat: HighZeroBytesDroppedBigSize<u32> = Readable::read(r)?;
 350                 Ok(Self { cltv_expiry_delta, fee_proportional_millionths, fee_base_msat: fee_base_msat.0 })
 351         }
 352 }
 353
 354 impl Writeable for PaymentConstraints {
 355         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 356                 self.max_cltv_expiry.write(w)?;
 357                 HighZeroBytesDroppedBigSize(self.htlc_minimum_msat).write(w)
 358         }
 359 }
 360 impl Readable for PaymentConstraints {
 361         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 362                 let max_cltv_expiry: u32 = Readable::read(r)?;
 363                 let htlc_minimum_msat: HighZeroBytesDroppedBigSize<u64> = Readable::read(r)?;
 364                 Ok(Self { max_cltv_expiry, htlc_minimum_msat: htlc_minimum_msat.0 })
 365         }
 366 }
 367
 368 impl_writeable_tlv_based_enum!(PaymentContext,
 369         ;
 370         (0, Unknown),
 371         (1, Bolt12Offer),
 372         (2, Bolt12Refund),
 373 );
 374
 375 impl Writeable for UnknownPaymentContext {
 376         fn write<W: Writer>(&self, _w: &mut W) -> Result<(), io::Error> {
 377                 Ok(())
 378         }
 379 }
 380
 381 impl Readable for UnknownPaymentContext {
 382         fn read<R: io::Read>(_r: &mut R) -> Result<Self, DecodeError> {
 383                 Ok(UnknownPaymentContext(()))
 384         }
 385 }
 386
 387 impl_writeable_tlv_based!(Bolt12OfferContext, {
 388         (0, offer_id, required),
 389 });
 390
 391 impl_writeable_tlv_based!(Bolt12RefundContext, {});
 392
 393 #[cfg(test)]
 394 mod tests {
 395         use bitcoin::secp256k1::PublicKey;
 396         use crate::blinded_path::payment::{ForwardNode, ForwardTlvs, ReceiveTlvs, PaymentConstraints, PaymentContext, PaymentRelay};
 397         use crate::ln::PaymentSecret;
 398         use crate::ln::features::BlindedHopFeatures;
 399         use crate::ln::functional_test_utils::TEST_FINAL_CLTV;
 400
 401         #[test]
 402         fn compute_payinfo() {
 403                 // Taken from the spec example for aggregating blinded payment info. See
 404                 // https://github.com/lightning/bolts/blob/master/proposals/route-blinding.md#blinded-payments
 405                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 406                 let intermediate_nodes = vec![ForwardNode {
 407                         node_id: dummy_pk,
 408                         tlvs: ForwardTlvs {
 409                                 short_channel_id: 0,
 410                                 payment_relay: PaymentRelay {
 411                                         cltv_expiry_delta: 144,
 412                                         fee_proportional_millionths: 500,
 413                                         fee_base_msat: 100,
 414                                 },
 415                                 payment_constraints: PaymentConstraints {
 416                                         max_cltv_expiry: 0,
 417                                         htlc_minimum_msat: 100,
 418                                 },
 419                                 features: BlindedHopFeatures::empty(),
 420                         },
 421                         htlc_maximum_msat: u64::max_value(),
 422                 }, ForwardNode {
 423                         node_id: dummy_pk,
 424                         tlvs: ForwardTlvs {
 425                                 short_channel_id: 0,
 426                                 payment_relay: PaymentRelay {
 427                                         cltv_expiry_delta: 144,
 428                                         fee_proportional_millionths: 500,
 429                                         fee_base_msat: 100,
 430                                 },
 431                                 payment_constraints: PaymentConstraints {
 432                                         max_cltv_expiry: 0,
 433                                         htlc_minimum_msat: 1_000,
 434                                 },
 435                                 features: BlindedHopFeatures::empty(),
 436                         },
 437                         htlc_maximum_msat: u64::max_value(),
 438                 }];
 439                 let recv_tlvs = ReceiveTlvs {
 440                         payment_secret: PaymentSecret([0; 32]),
 441                         payment_constraints: PaymentConstraints {
 442                                 max_cltv_expiry: 0,
 443                                 htlc_minimum_msat: 1,
 444                         },
 445                         payment_context: PaymentContext::unknown(),
 446                 };
 447                 let htlc_maximum_msat = 100_000;
 448                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat, 12).unwrap();
 449                 assert_eq!(blinded_payinfo.fee_base_msat, 201);
 450                 assert_eq!(blinded_payinfo.fee_proportional_millionths, 1001);
 451                 assert_eq!(blinded_payinfo.cltv_expiry_delta, 300);
 452                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 900);
 453                 assert_eq!(blinded_payinfo.htlc_maximum_msat, htlc_maximum_msat);
 454         }
 455
 456         #[test]
 457         fn compute_payinfo_1_hop() {
 458                 let recv_tlvs = ReceiveTlvs {
 459                         payment_secret: PaymentSecret([0; 32]),
 460                         payment_constraints: PaymentConstraints {
 461                                 max_cltv_expiry: 0,
 462                                 htlc_minimum_msat: 1,
 463                         },
 464                         payment_context: PaymentContext::unknown(),
 465                 };
 466                 let blinded_payinfo = super::compute_payinfo(&[], &recv_tlvs, 4242, TEST_FINAL_CLTV as u16).unwrap();
 467                 assert_eq!(blinded_payinfo.fee_base_msat, 0);
 468                 assert_eq!(blinded_payinfo.fee_proportional_millionths, 0);
 469                 assert_eq!(blinded_payinfo.cltv_expiry_delta, TEST_FINAL_CLTV as u16);
 470                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 1);
 471                 assert_eq!(blinded_payinfo.htlc_maximum_msat, 4242);
 472         }
 473
 474         #[test]
 475         fn simple_aggregated_htlc_min() {
 476                 // If no hops charge fees, the htlc_minimum_msat should just be the maximum htlc_minimum_msat
 477                 // along the path.
 478                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 479                 let intermediate_nodes = vec![ForwardNode {
 480                         node_id: dummy_pk,
 481                         tlvs: ForwardTlvs {
 482                                 short_channel_id: 0,
 483                                 payment_relay: PaymentRelay {
 484                                         cltv_expiry_delta: 0,
 485                                         fee_proportional_millionths: 0,
 486                                         fee_base_msat: 0,
 487                                 },
 488                                 payment_constraints: PaymentConstraints {
 489                                         max_cltv_expiry: 0,
 490                                         htlc_minimum_msat: 1,
 491                                 },
 492                                 features: BlindedHopFeatures::empty(),
 493                         },
 494                         htlc_maximum_msat: u64::max_value()
 495                 }, ForwardNode {
 496                         node_id: dummy_pk,
 497                         tlvs: ForwardTlvs {
 498                                 short_channel_id: 0,
 499                                 payment_relay: PaymentRelay {
 500                                         cltv_expiry_delta: 0,
 501                                         fee_proportional_millionths: 0,
 502                                         fee_base_msat: 0,
 503                                 },
 504                                 payment_constraints: PaymentConstraints {
 505                                         max_cltv_expiry: 0,
 506                                         htlc_minimum_msat: 2_000,
 507                                 },
 508                                 features: BlindedHopFeatures::empty(),
 509                         },
 510                         htlc_maximum_msat: u64::max_value()
 511                 }];
 512                 let recv_tlvs = ReceiveTlvs {
 513                         payment_secret: PaymentSecret([0; 32]),
 514                         payment_constraints: PaymentConstraints {
 515                                 max_cltv_expiry: 0,
 516                                 htlc_minimum_msat: 3,
 517                         },
 518                         payment_context: PaymentContext::unknown(),
 519                 };
 520                 let htlc_maximum_msat = 100_000;
 521                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat, TEST_FINAL_CLTV as u16).unwrap();
 522                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 2_000);
 523         }
 524
 525         #[test]
 526         fn aggregated_htlc_min() {
 527                 // Create a path with varying fees and htlc_mins, and make sure htlc_minimum_msat ends up as the
 528                 // max (htlc_min - following_fees) along the path.
 529                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 530                 let intermediate_nodes = vec![ForwardNode {
 531                         node_id: dummy_pk,
 532                         tlvs: ForwardTlvs {
 533                                 short_channel_id: 0,
 534                                 payment_relay: PaymentRelay {
 535                                         cltv_expiry_delta: 0,
 536                                         fee_proportional_millionths: 500,
 537                                         fee_base_msat: 1_000,
 538                                 },
 539                                 payment_constraints: PaymentConstraints {
 540                                         max_cltv_expiry: 0,
 541                                         htlc_minimum_msat: 5_000,
 542                                 },
 543                                 features: BlindedHopFeatures::empty(),
 544                         },
 545                         htlc_maximum_msat: u64::max_value()
 546                 }, ForwardNode {
 547                         node_id: dummy_pk,
 548                         tlvs: ForwardTlvs {
 549                                 short_channel_id: 0,
 550                                 payment_relay: PaymentRelay {
 551                                         cltv_expiry_delta: 0,
 552                                         fee_proportional_millionths: 500,
 553                                         fee_base_msat: 200,
 554                                 },
 555                                 payment_constraints: PaymentConstraints {
 556                                         max_cltv_expiry: 0,
 557                                         htlc_minimum_msat: 2_000,
 558                                 },
 559                                 features: BlindedHopFeatures::empty(),
 560                         },
 561                         htlc_maximum_msat: u64::max_value()
 562                 }];
 563                 let recv_tlvs = ReceiveTlvs {
 564                         payment_secret: PaymentSecret([0; 32]),
 565                         payment_constraints: PaymentConstraints {
 566                                 max_cltv_expiry: 0,
 567                                 htlc_minimum_msat: 1,
 568                         },
 569                         payment_context: PaymentContext::unknown(),
 570                 };
 571                 let htlc_minimum_msat = 3798;
 572                 assert!(super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_minimum_msat - 1, TEST_FINAL_CLTV as u16).is_err());
 573
 574                 let htlc_maximum_msat = htlc_minimum_msat + 1;
 575                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat, TEST_FINAL_CLTV as u16).unwrap();
 576                 assert_eq!(blinded_payinfo.htlc_minimum_msat, htlc_minimum_msat);
 577                 assert_eq!(blinded_payinfo.htlc_maximum_msat, htlc_maximum_msat);
 578         }
 579
 580         #[test]
 581         fn aggregated_htlc_max() {
 582                 // Create a path with varying fees and `htlc_maximum_msat`s, and make sure the aggregated max
 583                 // htlc ends up as the min (htlc_max - following_fees) along the path.
 584                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 585                 let intermediate_nodes = vec![ForwardNode {
 586                         node_id: dummy_pk,
 587                         tlvs: ForwardTlvs {
 588                                 short_channel_id: 0,
 589                                 payment_relay: PaymentRelay {
 590                                         cltv_expiry_delta: 0,
 591                                         fee_proportional_millionths: 500,
 592                                         fee_base_msat: 1_000,
 593                                 },
 594                                 payment_constraints: PaymentConstraints {
 595                                         max_cltv_expiry: 0,
 596                                         htlc_minimum_msat: 1,
 597                                 },
 598                                 features: BlindedHopFeatures::empty(),
 599                         },
 600                         htlc_maximum_msat: 5_000,
 601                 }, ForwardNode {
 602                         node_id: dummy_pk,
 603                         tlvs: ForwardTlvs {
 604                                 short_channel_id: 0,
 605                                 payment_relay: PaymentRelay {
 606                                         cltv_expiry_delta: 0,
 607                                         fee_proportional_millionths: 500,
 608                                         fee_base_msat: 1,
 609                                 },
 610                                 payment_constraints: PaymentConstraints {
 611                                         max_cltv_expiry: 0,
 612                                         htlc_minimum_msat: 1,
 613                                 },
 614                                 features: BlindedHopFeatures::empty(),
 615                         },
 616                         htlc_maximum_msat: 10_000
 617                 }];
 618                 let recv_tlvs = ReceiveTlvs {
 619                         payment_secret: PaymentSecret([0; 32]),
 620                         payment_constraints: PaymentConstraints {
 621                                 max_cltv_expiry: 0,
 622                                 htlc_minimum_msat: 1,
 623                         },
 624                         payment_context: PaymentContext::unknown(),
 625                 };
 626
 627                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, 10_000, TEST_FINAL_CLTV as u16).unwrap();
 628                 assert_eq!(blinded_payinfo.htlc_maximum_msat, 3997);
 629         }
 630 }