_ 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::invoice_request::InvoiceRequestFields;
  16 use crate::offers::offer::OfferId;
  17 use crate::util::ser::{HighZeroBytesDroppedBigSize, Readable, Writeable, Writer};
  18
  19 #[allow(unused_imports)]
  20 use crate::prelude::*;
  21
  22 /// An intermediate node, its outbound channel, and relay parameters.
  23 #[derive(Clone, Debug)]
  24 pub struct ForwardNode {
  25         /// The TLVs for this node's [`BlindedHop`], where the fee parameters contained within are also
  26         /// used for [`BlindedPayInfo`] construction.
  27         pub tlvs: ForwardTlvs,
  28         /// This node's pubkey.
  29         pub node_id: PublicKey,
  30         /// The maximum value, in msat, that may be accepted by this node.
  31         pub htlc_maximum_msat: u64,
  32 }
  33
  34 /// Data to construct a [`BlindedHop`] for forwarding a payment.
  35 #[derive(Clone, Debug)]
  36 pub struct ForwardTlvs {
  37         /// The short channel id this payment should be forwarded out over.
  38         pub short_channel_id: u64,
  39         /// Payment parameters for relaying over [`Self::short_channel_id`].
  40         pub payment_relay: PaymentRelay,
  41         /// Payment constraints for relaying over [`Self::short_channel_id`].
  42         pub payment_constraints: PaymentConstraints,
  43         /// Supported and required features when relaying a payment onion containing this object's
  44         /// corresponding [`BlindedHop::encrypted_payload`].
  45         ///
  46         /// [`BlindedHop::encrypted_payload`]: crate::blinded_path::BlindedHop::encrypted_payload
  47         pub features: BlindedHopFeatures,
  48 }
  49
  50 /// Data to construct a [`BlindedHop`] for receiving a payment. This payload is custom to LDK and
  51 /// may not be valid if received by another lightning implementation.
  52 #[derive(Clone, Debug)]
  53 pub struct ReceiveTlvs {
  54         /// Used to authenticate the sender of a payment to the receiver and tie MPP HTLCs together.
  55         pub payment_secret: PaymentSecret,
  56         /// Constraints for the receiver of this payment.
  57         pub payment_constraints: PaymentConstraints,
  58         /// Context for the receiver of this payment.
  59         pub payment_context: PaymentContext,
  60 }
  61
  62 /// Data to construct a [`BlindedHop`] for sending a payment over.
  63 ///
  64 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  65 pub(crate) enum BlindedPaymentTlvs {
  66         /// This blinded payment data is for a forwarding node.
  67         Forward(ForwardTlvs),
  68         /// This blinded payment data is for the receiving node.
  69         Receive(ReceiveTlvs),
  70 }
  71
  72 // Used to include forward and receive TLVs in the same iterator for encoding.
  73 enum BlindedPaymentTlvsRef<'a> {
  74         Forward(&'a ForwardTlvs),
  75         Receive(&'a ReceiveTlvs),
  76 }
  77
  78 /// Parameters for relaying over a given [`BlindedHop`].
  79 ///
  80 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  81 #[derive(Clone, Debug)]
  82 pub struct PaymentRelay {
  83         /// Number of blocks subtracted from an incoming HTLC's `cltv_expiry` for this [`BlindedHop`].
  84         pub cltv_expiry_delta: u16,
  85         /// Liquidity fee charged (in millionths of the amount transferred) for relaying a payment over
  86         /// this [`BlindedHop`], (i.e., 10,000 is 1%).
  87         pub fee_proportional_millionths: u32,
  88         /// Base fee charged (in millisatoshi) for relaying a payment over this [`BlindedHop`].
  89         pub fee_base_msat: u32,
  90 }
  91
  92 /// Constraints for relaying over a given [`BlindedHop`].
  93 ///
  94 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  95 #[derive(Clone, Debug)]
  96 pub struct PaymentConstraints {
  97         /// The maximum total CLTV that is acceptable when relaying a payment over this [`BlindedHop`].
  98         pub max_cltv_expiry: u32,
  99         /// The minimum value, in msat, that may be accepted by the node corresponding to this
 100         /// [`BlindedHop`].
 101         pub htlc_minimum_msat: u64,
 102 }
 103
 104 /// The context of an inbound payment, which is included in a [`BlindedPath`] via [`ReceiveTlvs`]
 105 /// and surfaced in [`PaymentPurpose`].
 106 ///
 107 /// [`BlindedPath`]: crate::blinded_path::BlindedPath
 108 /// [`PaymentPurpose`]: crate::events::PaymentPurpose
 109 #[derive(Clone, Debug, Eq, PartialEq)]
 110 pub enum PaymentContext {
 111         /// The payment context was unknown.
 112         Unknown(UnknownPaymentContext),
 113
 114         /// The payment was made for an invoice requested from a BOLT 12 [`Offer`].
 115         ///
 116         /// [`Offer`]: crate::offers::offer::Offer
 117         Bolt12Offer(Bolt12OfferContext),
 118
 119         /// The payment was made for an invoice sent for a BOLT 12 [`Refund`].
 120         ///
 121         /// [`Refund`]: crate::offers::refund::Refund
 122         Bolt12Refund(Bolt12RefundContext),
 123 }
 124
 125 // Used when writing PaymentContext in Event::PaymentClaimable to avoid cloning.
 126 pub(crate) enum PaymentContextRef<'a> {
 127         Bolt12Offer(&'a Bolt12OfferContext),
 128         Bolt12Refund(&'a Bolt12RefundContext),
 129 }
 130
 131 /// An unknown payment context.
 132 #[derive(Clone, Debug, Eq, PartialEq)]
 133 pub struct UnknownPaymentContext(());
 134
 135 /// The context of a payment made for an invoice requested from a BOLT 12 [`Offer`].
 136 ///
 137 /// [`Offer`]: crate::offers::offer::Offer
 138 #[derive(Clone, Debug, Eq, PartialEq)]
 139 pub struct Bolt12OfferContext {
 140         /// The identifier of the [`Offer`].
 141         ///
 142         /// [`Offer`]: crate::offers::offer::Offer
 143         pub offer_id: OfferId,
 144
 145         /// Fields from an [`InvoiceRequest`] sent for a [`Bolt12Invoice`].
 146         ///
 147         /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 148         /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 149         pub invoice_request: InvoiceRequestFields,
 150 }
 151
 152 /// The context of a payment made for an invoice sent for a BOLT 12 [`Refund`].
 153 ///
 154 /// [`Refund`]: crate::offers::refund::Refund
 155 #[derive(Clone, Debug, Eq, PartialEq)]
 156 pub struct Bolt12RefundContext {}
 157
 158 impl PaymentContext {
 159         pub(crate) fn unknown() -> Self {
 160                 PaymentContext::Unknown(UnknownPaymentContext(()))
 161         }
 162 }
 163
 164 impl TryFrom<CounterpartyForwardingInfo> for PaymentRelay {
 165         type Error = ();
 166
 167         fn try_from(info: CounterpartyForwardingInfo) -> Result<Self, ()> {
 168                 let CounterpartyForwardingInfo {
 169                         fee_base_msat, fee_proportional_millionths, cltv_expiry_delta
 170                 } = info;
 171
 172                 // Avoid exposing esoteric CLTV expiry deltas
 173                 let cltv_expiry_delta = match cltv_expiry_delta {
 174                         0..=40 => 40,
 175                         41..=80 => 80,
 176                         81..=144 => 144,
 177                         145..=216 => 216,
 178                         _ => return Err(()),
 179                 };
 180
 181                 Ok(Self { cltv_expiry_delta, fee_proportional_millionths, fee_base_msat })
 182         }
 183 }
 184
 185 impl Writeable for ForwardTlvs {
 186         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 187                 let features_opt =
 188                         if self.features == BlindedHopFeatures::empty() { None }
 189                         else { Some(&self.features) };
 190                 encode_tlv_stream!(w, {
 191                         (2, self.short_channel_id, required),
 192                         (10, self.payment_relay, required),
 193                         (12, self.payment_constraints, required),
 194                         (14, features_opt, option)
 195                 });
 196                 Ok(())
 197         }
 198 }
 199
 200 impl Writeable for ReceiveTlvs {
 201         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 202                 encode_tlv_stream!(w, {
 203                         (12, self.payment_constraints, required),
 204                         (65536, self.payment_secret, required),
 205                         (65537, self.payment_context, required)
 206                 });
 207                 Ok(())
 208         }
 209 }
 210
 211 impl<'a> Writeable for BlindedPaymentTlvsRef<'a> {
 212         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 213                 // TODO: write padding
 214                 match self {
 215                         Self::Forward(tlvs) => tlvs.write(w)?,
 216                         Self::Receive(tlvs) => tlvs.write(w)?,
 217                 }
 218                 Ok(())
 219         }
 220 }
 221
 222 impl Readable for BlindedPaymentTlvs {
 223         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 224                 _init_and_read_tlv_stream!(r, {
 225                         (1, _padding, option),
 226                         (2, scid, option),
 227                         (10, payment_relay, option),
 228                         (12, payment_constraints, required),
 229                         (14, features, option),
 230                         (65536, payment_secret, option),
 231                         (65537, payment_context, (default_value, PaymentContext::unknown())),
 232                 });
 233                 let _padding: Option<utils::Padding> = _padding;
 234
 235                 if let Some(short_channel_id) = scid {
 236                         if payment_secret.is_some() {
 237                                 return Err(DecodeError::InvalidValue)
 238                         }
 239                         Ok(BlindedPaymentTlvs::Forward(ForwardTlvs {
 240                                 short_channel_id,
 241                                 payment_relay: payment_relay.ok_or(DecodeError::InvalidValue)?,
 242                                 payment_constraints: payment_constraints.0.unwrap(),
 243                                 features: features.unwrap_or_else(BlindedHopFeatures::empty),
 244                         }))
 245                 } else {
 246                         if payment_relay.is_some() || features.is_some() { return Err(DecodeError::InvalidValue) }
 247                         Ok(BlindedPaymentTlvs::Receive(ReceiveTlvs {
 248                                 payment_secret: payment_secret.ok_or(DecodeError::InvalidValue)?,
 249                                 payment_constraints: payment_constraints.0.unwrap(),
 250                                 payment_context: payment_context.0.unwrap(),
 251                         }))
 252                 }
 253         }
 254 }
 255
 256 /// Construct blinded payment hops for the given `intermediate_nodes` and payee info.
 257 pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 258         secp_ctx: &Secp256k1<T>, intermediate_nodes: &[ForwardNode],
 259         payee_node_id: PublicKey, payee_tlvs: ReceiveTlvs, session_priv: &SecretKey
 260 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
 261         let pks = intermediate_nodes.iter().map(|node| &node.node_id)
 262                 .chain(core::iter::once(&payee_node_id));
 263         let tlvs = intermediate_nodes.iter().map(|node| BlindedPaymentTlvsRef::Forward(&node.tlvs))
 264                 .chain(core::iter::once(BlindedPaymentTlvsRef::Receive(&payee_tlvs)));
 265         utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
 266 }
 267
 268 /// `None` if underflow occurs.
 269 pub(crate) fn amt_to_forward_msat(inbound_amt_msat: u64, payment_relay: &PaymentRelay) -> Option<u64> {
 270         let inbound_amt = inbound_amt_msat as u128;
 271         let base = payment_relay.fee_base_msat as u128;
 272         let prop = payment_relay.fee_proportional_millionths as u128;
 273
 274         let post_base_fee_inbound_amt =
 275                 if let Some(amt) = inbound_amt.checked_sub(base) { amt } else { return None };
 276         let mut amt_to_forward =
 277                 (post_base_fee_inbound_amt * 1_000_000 + 1_000_000 + prop - 1) / (prop + 1_000_000);
 278
 279         let fee = ((amt_to_forward * prop) / 1_000_000) + base;
 280         if inbound_amt - fee < amt_to_forward {
 281                 // Rounding up the forwarded amount resulted in underpaying this node, so take an extra 1 msat
 282                 // in fee to compensate.
 283                 amt_to_forward -= 1;
 284         }
 285         debug_assert_eq!(amt_to_forward + fee, inbound_amt);
 286         u64::try_from(amt_to_forward).ok()
 287 }
 288
 289 pub(super) fn compute_payinfo(
 290         intermediate_nodes: &[ForwardNode], payee_tlvs: &ReceiveTlvs, payee_htlc_maximum_msat: u64,
 291         min_final_cltv_expiry_delta: u16
 292 ) -> Result<BlindedPayInfo, ()> {
 293         let mut curr_base_fee: u64 = 0;
 294         let mut curr_prop_mil: u64 = 0;
 295         let mut cltv_expiry_delta: u16 = min_final_cltv_expiry_delta;
 296         for tlvs in intermediate_nodes.iter().rev().map(|n| &n.tlvs) {
 297                 // In the future, we'll want to take the intersection of all supported features for the
 298                 // `BlindedPayInfo`, but there are no features in that context right now.
 299                 if tlvs.features.requires_unknown_bits_from(&BlindedHopFeatures::empty()) { return Err(()) }
 300
 301                 let next_base_fee = tlvs.payment_relay.fee_base_msat as u64;
 302                 let next_prop_mil = tlvs.payment_relay.fee_proportional_millionths as u64;
 303                 // Use integer arithmetic to compute `ceil(a/b)` as `(a+b-1)/b`
 304                 // ((curr_base_fee * (1_000_000 + next_prop_mil)) / 1_000_000) + next_base_fee
 305                 curr_base_fee = curr_base_fee.checked_mul(1_000_000 + next_prop_mil)
 306                         .and_then(|f| f.checked_add(1_000_000 - 1))
 307                         .map(|f| f / 1_000_000)
 308                         .and_then(|f| f.checked_add(next_base_fee))
 309                         .ok_or(())?;
 310                 // ceil(((curr_prop_mil + 1_000_000) * (next_prop_mil + 1_000_000)) / 1_000_000) - 1_000_000
 311                 curr_prop_mil = curr_prop_mil.checked_add(1_000_000)
 312                         .and_then(|f1| next_prop_mil.checked_add(1_000_000).and_then(|f2| f2.checked_mul(f1)))
 313                         .and_then(|f| f.checked_add(1_000_000 - 1))
 314                         .map(|f| f / 1_000_000)
 315                         .and_then(|f| f.checked_sub(1_000_000))
 316                         .ok_or(())?;
 317
 318                 cltv_expiry_delta = cltv_expiry_delta.checked_add(tlvs.payment_relay.cltv_expiry_delta).ok_or(())?;
 319         }
 320
 321         let mut htlc_minimum_msat: u64 = 1;
 322         let mut htlc_maximum_msat: u64 = 21_000_000 * 100_000_000 * 1_000; // Total bitcoin supply
 323         for node in intermediate_nodes.iter() {
 324                 // The min htlc for an intermediate node is that node's min minus the fees charged by all of the
 325                 // following hops for forwarding that min, since that fee amount will automatically be included
 326                 // in the amount that this node receives and contribute towards reaching its min.
 327                 htlc_minimum_msat = amt_to_forward_msat(
 328                         core::cmp::max(node.tlvs.payment_constraints.htlc_minimum_msat, htlc_minimum_msat),
 329                         &node.tlvs.payment_relay
 330                 ).unwrap_or(1); // If underflow occurs, we definitely reached this node's min
 331                 htlc_maximum_msat = amt_to_forward_msat(
 332                         core::cmp::min(node.htlc_maximum_msat, htlc_maximum_msat), &node.tlvs.payment_relay
 333                 ).ok_or(())?; // If underflow occurs, we cannot send to this hop without exceeding their max
 334         }
 335         htlc_minimum_msat = core::cmp::max(
 336                 payee_tlvs.payment_constraints.htlc_minimum_msat, htlc_minimum_msat
 337         );
 338         htlc_maximum_msat = core::cmp::min(payee_htlc_maximum_msat, htlc_maximum_msat);
 339
 340         if htlc_maximum_msat < htlc_minimum_msat { return Err(()) }
 341         Ok(BlindedPayInfo {
 342                 fee_base_msat: u32::try_from(curr_base_fee).map_err(|_| ())?,
 343                 fee_proportional_millionths: u32::try_from(curr_prop_mil).map_err(|_| ())?,
 344                 cltv_expiry_delta,
 345                 htlc_minimum_msat,
 346                 htlc_maximum_msat,
 347                 features: BlindedHopFeatures::empty(),
 348         })
 349 }
 350
 351 impl Writeable for PaymentRelay {
 352         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 353                 self.cltv_expiry_delta.write(w)?;
 354                 self.fee_proportional_millionths.write(w)?;
 355                 HighZeroBytesDroppedBigSize(self.fee_base_msat).write(w)
 356         }
 357 }
 358 impl Readable for PaymentRelay {
 359         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 360                 let cltv_expiry_delta: u16 = Readable::read(r)?;
 361                 let fee_proportional_millionths: u32 = Readable::read(r)?;
 362                 let fee_base_msat: HighZeroBytesDroppedBigSize<u32> = Readable::read(r)?;
 363                 Ok(Self { cltv_expiry_delta, fee_proportional_millionths, fee_base_msat: fee_base_msat.0 })
 364         }
 365 }
 366
 367 impl Writeable for PaymentConstraints {
 368         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 369                 self.max_cltv_expiry.write(w)?;
 370                 HighZeroBytesDroppedBigSize(self.htlc_minimum_msat).write(w)
 371         }
 372 }
 373 impl Readable for PaymentConstraints {
 374         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 375                 let max_cltv_expiry: u32 = Readable::read(r)?;
 376                 let htlc_minimum_msat: HighZeroBytesDroppedBigSize<u64> = Readable::read(r)?;
 377                 Ok(Self { max_cltv_expiry, htlc_minimum_msat: htlc_minimum_msat.0 })
 378         }
 379 }
 380
 381 impl_writeable_tlv_based_enum!(PaymentContext,
 382         ;
 383         (0, Unknown),
 384         (1, Bolt12Offer),
 385         (2, Bolt12Refund),
 386 );
 387
 388 impl<'a> Writeable for PaymentContextRef<'a> {
 389         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 390                 match self {
 391                         PaymentContextRef::Bolt12Offer(context) => {
 392                                 1u8.write(w)?;
 393                                 context.write(w)?;
 394                         },
 395                         PaymentContextRef::Bolt12Refund(context) => {
 396                                 2u8.write(w)?;
 397                                 context.write(w)?;
 398                         },
 399                 }
 400
 401                 Ok(())
 402         }
 403 }
 404
 405 impl Writeable for UnknownPaymentContext {
 406         fn write<W: Writer>(&self, _w: &mut W) -> Result<(), io::Error> {
 407                 Ok(())
 408         }
 409 }
 410
 411 impl Readable for UnknownPaymentContext {
 412         fn read<R: io::Read>(_r: &mut R) -> Result<Self, DecodeError> {
 413                 Ok(UnknownPaymentContext(()))
 414         }
 415 }
 416
 417 impl_writeable_tlv_based!(Bolt12OfferContext, {
 418         (0, offer_id, required),
 419         (2, invoice_request, required),
 420 });
 421
 422 impl_writeable_tlv_based!(Bolt12RefundContext, {});
 423
 424 #[cfg(test)]
 425 mod tests {
 426         use bitcoin::secp256k1::PublicKey;
 427         use crate::blinded_path::payment::{ForwardNode, ForwardTlvs, ReceiveTlvs, PaymentConstraints, PaymentContext, PaymentRelay};
 428         use crate::ln::PaymentSecret;
 429         use crate::ln::features::BlindedHopFeatures;
 430         use crate::ln::functional_test_utils::TEST_FINAL_CLTV;
 431
 432         #[test]
 433         fn compute_payinfo() {
 434                 // Taken from the spec example for aggregating blinded payment info. See
 435                 // https://github.com/lightning/bolts/blob/master/proposals/route-blinding.md#blinded-payments
 436                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 437                 let intermediate_nodes = vec![ForwardNode {
 438                         node_id: dummy_pk,
 439                         tlvs: ForwardTlvs {
 440                                 short_channel_id: 0,
 441                                 payment_relay: PaymentRelay {
 442                                         cltv_expiry_delta: 144,
 443                                         fee_proportional_millionths: 500,
 444                                         fee_base_msat: 100,
 445                                 },
 446                                 payment_constraints: PaymentConstraints {
 447                                         max_cltv_expiry: 0,
 448                                         htlc_minimum_msat: 100,
 449                                 },
 450                                 features: BlindedHopFeatures::empty(),
 451                         },
 452                         htlc_maximum_msat: u64::max_value(),
 453                 }, ForwardNode {
 454                         node_id: dummy_pk,
 455                         tlvs: ForwardTlvs {
 456                                 short_channel_id: 0,
 457                                 payment_relay: PaymentRelay {
 458                                         cltv_expiry_delta: 144,
 459                                         fee_proportional_millionths: 500,
 460                                         fee_base_msat: 100,
 461                                 },
 462                                 payment_constraints: PaymentConstraints {
 463                                         max_cltv_expiry: 0,
 464                                         htlc_minimum_msat: 1_000,
 465                                 },
 466                                 features: BlindedHopFeatures::empty(),
 467                         },
 468                         htlc_maximum_msat: u64::max_value(),
 469                 }];
 470                 let recv_tlvs = ReceiveTlvs {
 471                         payment_secret: PaymentSecret([0; 32]),
 472                         payment_constraints: PaymentConstraints {
 473                                 max_cltv_expiry: 0,
 474                                 htlc_minimum_msat: 1,
 475                         },
 476                         payment_context: PaymentContext::unknown(),
 477                 };
 478                 let htlc_maximum_msat = 100_000;
 479                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat, 12).unwrap();
 480                 assert_eq!(blinded_payinfo.fee_base_msat, 201);
 481                 assert_eq!(blinded_payinfo.fee_proportional_millionths, 1001);
 482                 assert_eq!(blinded_payinfo.cltv_expiry_delta, 300);
 483                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 900);
 484                 assert_eq!(blinded_payinfo.htlc_maximum_msat, htlc_maximum_msat);
 485         }
 486
 487         #[test]
 488         fn compute_payinfo_1_hop() {
 489                 let recv_tlvs = ReceiveTlvs {
 490                         payment_secret: PaymentSecret([0; 32]),
 491                         payment_constraints: PaymentConstraints {
 492                                 max_cltv_expiry: 0,
 493                                 htlc_minimum_msat: 1,
 494                         },
 495                         payment_context: PaymentContext::unknown(),
 496                 };
 497                 let blinded_payinfo = super::compute_payinfo(&[], &recv_tlvs, 4242, TEST_FINAL_CLTV as u16).unwrap();
 498                 assert_eq!(blinded_payinfo.fee_base_msat, 0);
 499                 assert_eq!(blinded_payinfo.fee_proportional_millionths, 0);
 500                 assert_eq!(blinded_payinfo.cltv_expiry_delta, TEST_FINAL_CLTV as u16);
 501                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 1);
 502                 assert_eq!(blinded_payinfo.htlc_maximum_msat, 4242);
 503         }
 504
 505         #[test]
 506         fn simple_aggregated_htlc_min() {
 507                 // If no hops charge fees, the htlc_minimum_msat should just be the maximum htlc_minimum_msat
 508                 // along the path.
 509                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 510                 let intermediate_nodes = vec![ForwardNode {
 511                         node_id: dummy_pk,
 512                         tlvs: ForwardTlvs {
 513                                 short_channel_id: 0,
 514                                 payment_relay: PaymentRelay {
 515                                         cltv_expiry_delta: 0,
 516                                         fee_proportional_millionths: 0,
 517                                         fee_base_msat: 0,
 518                                 },
 519                                 payment_constraints: PaymentConstraints {
 520                                         max_cltv_expiry: 0,
 521                                         htlc_minimum_msat: 1,
 522                                 },
 523                                 features: BlindedHopFeatures::empty(),
 524                         },
 525                         htlc_maximum_msat: u64::max_value()
 526                 }, ForwardNode {
 527                         node_id: dummy_pk,
 528                         tlvs: ForwardTlvs {
 529                                 short_channel_id: 0,
 530                                 payment_relay: PaymentRelay {
 531                                         cltv_expiry_delta: 0,
 532                                         fee_proportional_millionths: 0,
 533                                         fee_base_msat: 0,
 534                                 },
 535                                 payment_constraints: PaymentConstraints {
 536                                         max_cltv_expiry: 0,
 537                                         htlc_minimum_msat: 2_000,
 538                                 },
 539                                 features: BlindedHopFeatures::empty(),
 540                         },
 541                         htlc_maximum_msat: u64::max_value()
 542                 }];
 543                 let recv_tlvs = ReceiveTlvs {
 544                         payment_secret: PaymentSecret([0; 32]),
 545                         payment_constraints: PaymentConstraints {
 546                                 max_cltv_expiry: 0,
 547                                 htlc_minimum_msat: 3,
 548                         },
 549                         payment_context: PaymentContext::unknown(),
 550                 };
 551                 let htlc_maximum_msat = 100_000;
 552                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat, TEST_FINAL_CLTV as u16).unwrap();
 553                 assert_eq!(blinded_payinfo.htlc_minimum_msat, 2_000);
 554         }
 555
 556         #[test]
 557         fn aggregated_htlc_min() {
 558                 // Create a path with varying fees and htlc_mins, and make sure htlc_minimum_msat ends up as the
 559                 // max (htlc_min - following_fees) along the path.
 560                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 561                 let intermediate_nodes = vec![ForwardNode {
 562                         node_id: dummy_pk,
 563                         tlvs: ForwardTlvs {
 564                                 short_channel_id: 0,
 565                                 payment_relay: PaymentRelay {
 566                                         cltv_expiry_delta: 0,
 567                                         fee_proportional_millionths: 500,
 568                                         fee_base_msat: 1_000,
 569                                 },
 570                                 payment_constraints: PaymentConstraints {
 571                                         max_cltv_expiry: 0,
 572                                         htlc_minimum_msat: 5_000,
 573                                 },
 574                                 features: BlindedHopFeatures::empty(),
 575                         },
 576                         htlc_maximum_msat: u64::max_value()
 577                 }, ForwardNode {
 578                         node_id: dummy_pk,
 579                         tlvs: ForwardTlvs {
 580                                 short_channel_id: 0,
 581                                 payment_relay: PaymentRelay {
 582                                         cltv_expiry_delta: 0,
 583                                         fee_proportional_millionths: 500,
 584                                         fee_base_msat: 200,
 585                                 },
 586                                 payment_constraints: PaymentConstraints {
 587                                         max_cltv_expiry: 0,
 588                                         htlc_minimum_msat: 2_000,
 589                                 },
 590                                 features: BlindedHopFeatures::empty(),
 591                         },
 592                         htlc_maximum_msat: u64::max_value()
 593                 }];
 594                 let recv_tlvs = ReceiveTlvs {
 595                         payment_secret: PaymentSecret([0; 32]),
 596                         payment_constraints: PaymentConstraints {
 597                                 max_cltv_expiry: 0,
 598                                 htlc_minimum_msat: 1,
 599                         },
 600                         payment_context: PaymentContext::unknown(),
 601                 };
 602                 let htlc_minimum_msat = 3798;
 603                 assert!(super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_minimum_msat - 1, TEST_FINAL_CLTV as u16).is_err());
 604
 605                 let htlc_maximum_msat = htlc_minimum_msat + 1;
 606                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat, TEST_FINAL_CLTV as u16).unwrap();
 607                 assert_eq!(blinded_payinfo.htlc_minimum_msat, htlc_minimum_msat);
 608                 assert_eq!(blinded_payinfo.htlc_maximum_msat, htlc_maximum_msat);
 609         }
 610
 611         #[test]
 612         fn aggregated_htlc_max() {
 613                 // Create a path with varying fees and `htlc_maximum_msat`s, and make sure the aggregated max
 614                 // htlc ends up as the min (htlc_max - following_fees) along the path.
 615                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 616                 let intermediate_nodes = vec![ForwardNode {
 617                         node_id: dummy_pk,
 618                         tlvs: ForwardTlvs {
 619                                 short_channel_id: 0,
 620                                 payment_relay: PaymentRelay {
 621                                         cltv_expiry_delta: 0,
 622                                         fee_proportional_millionths: 500,
 623                                         fee_base_msat: 1_000,
 624                                 },
 625                                 payment_constraints: PaymentConstraints {
 626                                         max_cltv_expiry: 0,
 627                                         htlc_minimum_msat: 1,
 628                                 },
 629                                 features: BlindedHopFeatures::empty(),
 630                         },
 631                         htlc_maximum_msat: 5_000,
 632                 }, ForwardNode {
 633                         node_id: dummy_pk,
 634                         tlvs: ForwardTlvs {
 635                                 short_channel_id: 0,
 636                                 payment_relay: PaymentRelay {
 637                                         cltv_expiry_delta: 0,
 638                                         fee_proportional_millionths: 500,
 639                                         fee_base_msat: 1,
 640                                 },
 641                                 payment_constraints: PaymentConstraints {
 642                                         max_cltv_expiry: 0,
 643                                         htlc_minimum_msat: 1,
 644                                 },
 645                                 features: BlindedHopFeatures::empty(),
 646                         },
 647                         htlc_maximum_msat: 10_000
 648                 }];
 649                 let recv_tlvs = ReceiveTlvs {
 650                         payment_secret: PaymentSecret([0; 32]),
 651                         payment_constraints: PaymentConstraints {
 652                                 max_cltv_expiry: 0,
 653                                 htlc_minimum_msat: 1,
 654                         },
 655                         payment_context: PaymentContext::unknown(),
 656                 };
 657
 658                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, 10_000, TEST_FINAL_CLTV as u16).unwrap();
 659                 assert_eq!(blinded_payinfo.htlc_maximum_msat, 3997);
 660         }
 661 }