Remove Trampoline config flag

In this PR, we add end-to-end tests for Trampoline receive and forwarding
behavior (specifically rejection of payments for the latter), ensuring
sanity, no unexpected errors, and obviating the cfg-gating.

Author: arik-so

Cargo.toml

@@ -63,7 +63,6 @@ check-cfg = [
     "cfg(ldk_bench)",
     "cfg(ldk_test_vectors)",
     "cfg(taproot)",
-    "cfg(trampoline)",
     "cfg(require_route_graph_test)",
     "cfg(splicing)",
     "cfg(async_payments)",

ci/ci-tests.sh

@@ -134,8 +134,6 @@ RUSTFLAGS="--cfg=taproot" cargo test --verbose --color always -p lightning
 [ "$CI_MINIMIZE_DISK_USAGE" != "" ] && cargo clean
 RUSTFLAGS="--cfg=splicing" cargo test --verbose --color always -p lightning
 [ "$CI_MINIMIZE_DISK_USAGE" != "" ] && cargo clean
-RUSTFLAGS="--cfg=trampoline" cargo test --verbose --color always -p lightning
-[ "$CI_MINIMIZE_DISK_USAGE" != "" ] && cargo clean
 RUSTFLAGS="--cfg=async_payments" cargo test --verbose --color always -p lightning
 [ "$CI_MINIMIZE_DISK_USAGE" != "" ] && cargo clean
 RUSTFLAGS="--cfg=lsps1_service" cargo test --verbose --color always -p lightning-liquidity

lightning/src/blinded_path/payment.rs

@@ -298,7 +298,6 @@ pub struct ForwardTlvs {
 }
 
 /// Data to construct a [`BlindedHop`] for forwarding a Trampoline payment.
-#[cfg(trampoline)]
 #[derive(Clone, Debug)]
 pub struct TrampolineForwardTlvs {
 	/// The node id to which the trampoline node must find a route.
@@ -371,7 +370,6 @@ pub(crate) enum BlindedPaymentTlvs {
 /// Data to construct a [`BlindedHop`] for sending a Trampoline payment over.
 ///
 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
-#[cfg(trampoline)]
 pub(crate) enum BlindedTrampolineTlvs {
 	/// This blinded payment data is for a forwarding node.
 	Forward(TrampolineForwardTlvs),
@@ -591,7 +589,6 @@ impl Readable for BlindedPaymentTlvs {
 	}
 }
 
-#[cfg(trampoline)]
 impl Readable for BlindedTrampolineTlvs {
 	fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 		_init_and_read_tlv_stream!(r, {

lightning/src/ln/blinded_payment_tests.rs

@@ -1816,7 +1816,6 @@ fn test_combined_trampoline_onion_creation_vectors() {
 }
 
 #[test]
-#[cfg(trampoline)]
 fn test_trampoline_inbound_payment_decoding() {
 	let secp_ctx = Secp256k1::new();
 	let session_priv = secret_from_hex("0303030303030303030303030303030303030303030303030303030303030303");

lightning/src/ln/channelmanager.rs

@@ -170,7 +170,6 @@ pub enum PendingHTLCRouting {
 		incoming_cltv_expiry: Option<u32>,
 	},
 	/// An HTLC which should be forwarded on to another Trampoline node.
-	#[cfg(trampoline)]
 	TrampolineForward {
 		/// The onion shared secret we build with the sender (or the preceding Trampoline node) used
 		/// to decrypt the onion.
@@ -288,7 +287,6 @@ impl PendingHTLCRouting {
 	fn blinded_failure(&self) -> Option<BlindedFailure> {
 		match self {
 			Self::Forward { blinded: Some(BlindedForward { failure, .. }), .. } => Some(*failure),
-			#[cfg(trampoline)]
 			Self::TrampolineForward { blinded: Some(BlindedForward { failure, .. }), .. } => Some(*failure),
 			Self::Receive { requires_blinded_error: true, .. } => Some(BlindedFailure::FromBlindedNode),
 			Self::ReceiveKeysend { requires_blinded_error: true, .. } => Some(BlindedFailure::FromBlindedNode),
@@ -299,7 +297,6 @@ impl PendingHTLCRouting {
 	fn incoming_cltv_expiry(&self) -> Option<u32> {
 		match self {
 			Self::Forward { incoming_cltv_expiry, .. } => *incoming_cltv_expiry,
-			#[cfg(trampoline)]
 			Self::TrampolineForward { incoming_cltv_expiry, .. } => Some(*incoming_cltv_expiry),
 			Self::Receive { incoming_cltv_expiry, .. } => Some(*incoming_cltv_expiry),
 			Self::ReceiveKeysend { incoming_cltv_expiry, .. } => Some(*incoming_cltv_expiry),
@@ -4510,24 +4507,7 @@ where
 			}
 		}
 		match decoded_hop {
-			onion_utils::Hop::Receive { .. } | onion_utils::Hop::BlindedReceive { .. } => {
-				// OUR PAYMENT!
-				let current_height: u32 = self.best_block.read().unwrap().height;
-				match create_recv_pending_htlc_info(decoded_hop, shared_secret, msg.payment_hash,
-					msg.amount_msat, msg.cltv_expiry, None, allow_underpay, msg.skimmed_fee_msat,
-					current_height)
-				{
-					Ok(info) => {
-						// Note that we could obviously respond immediately with an update_fulfill_htlc
-						// message, however that would leak that we are the recipient of this payment, so
-						// instead we stay symmetric with the forwarding case, only responding (after a
-						// delay) once they've sent us a commitment_signed!
-						PendingHTLCStatus::Forward(info)
-					},
-					Err(InboundHTLCErr { err_code, err_data, msg }) => return_err!(msg, err_code, &err_data)
-				}
-			},
-			#[cfg(trampoline)]
+			onion_utils::Hop::Receive { .. } | onion_utils::Hop::BlindedReceive { .. } |
 			onion_utils::Hop::TrampolineReceive { .. } | onion_utils::Hop::TrampolineBlindedReceive { .. } => {
 				// OUR PAYMENT!
 				let current_height: u32 = self.best_block.read().unwrap().height;
@@ -4551,7 +4531,6 @@ where
 					Err(InboundHTLCErr { err_code, err_data, msg }) => return_err!(msg, err_code, &err_data)
 				}
 			},
-			#[cfg(trampoline)]
 			onion_utils::Hop::TrampolineForward { .. } | onion_utils::Hop::TrampolineBlindedForward { .. } => {
 				match create_fwd_pending_htlc_info(msg, decoded_hop, shared_secret, next_packet_pubkey_opt) {
 					Ok(info) => PendingHTLCStatus::Forward(info),
@@ -9067,7 +9046,6 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 				for (forward_info, prev_htlc_id) in pending_forwards.drain(..) {
 					let scid = match forward_info.routing {
 						PendingHTLCRouting::Forward { short_channel_id, .. } => short_channel_id,
-						#[cfg(trampoline)]
 						PendingHTLCRouting::TrampolineForward { .. } => 0,
 						PendingHTLCRouting::Receive { .. } => 0,
 						PendingHTLCRouting::ReceiveKeysend { .. } => 0,
@@ -12888,36 +12866,6 @@ impl_writeable_tlv_based!(BlindedForward, {
 	(3, next_blinding_override, option),
 });
 
-#[cfg(not(trampoline))]
-impl_writeable_tlv_based_enum!(PendingHTLCRouting,
-	(0, Forward) => {
-		(0, onion_packet, required),
-		(1, blinded, option),
-		(2, short_channel_id, required),
-		(3, incoming_cltv_expiry, option),
-	},
-	(1, Receive) => {
-		(0, payment_data, required),
-		(1, phantom_shared_secret, option),
-		(2, incoming_cltv_expiry, required),
-		(3, payment_metadata, option),
-		(5, custom_tlvs, optional_vec),
-		(7, requires_blinded_error, (default_value, false)),
-		(9, payment_context, option),
-	},
-	(2, ReceiveKeysend) => {
-		(0, payment_preimage, required),
-		(1, requires_blinded_error, (default_value, false)),
-		(2, incoming_cltv_expiry, required),
-		(3, payment_metadata, option),
-		(4, payment_data, option), // Added in 0.0.116
-		(5, custom_tlvs, optional_vec),
-		(7, has_recipient_created_payment_secret, (default_value, false)),
-		(9, payment_context, option),
-		(11, invoice_request, option),
-	},
-);
-#[cfg(trampoline)]
 impl_writeable_tlv_based_enum!(PendingHTLCRouting,
 	(0, Forward) => {
 		(0, onion_packet, required),

lightning/src/ln/msgs.rs

@@ -32,7 +32,6 @@ use bitcoin::script::ScriptBuf;
 use bitcoin::hash_types::Txid;
 
 use crate::blinded_path::payment::{BlindedPaymentTlvs, ForwardTlvs, ReceiveTlvs, UnauthenticatedReceiveTlvs};
-#[cfg(trampoline)]
 use crate::blinded_path::payment::{BlindedTrampolineTlvs, TrampolineForwardTlvs};
 use crate::ln::channelmanager::Verification;
 use crate::ln::types::ChannelId;
@@ -2075,8 +2074,7 @@ mod fuzzy_internal_msgs {
 		pub outgoing_cltv_value: u32,
 	}
 
-	#[cfg(trampoline)]
-	#[cfg_attr(trampoline, allow(unused))]
+	#[allow(unused)]
 	pub struct InboundTrampolineEntrypointPayload {
 		pub amt_to_forward: u64,
 		pub outgoing_cltv_value: u32,
@@ -2118,23 +2116,19 @@ mod fuzzy_internal_msgs {
 
 	pub enum InboundOnionPayload {
 		Forward(InboundOnionForwardPayload),
-		#[cfg(trampoline)]
-		#[cfg_attr(trampoline, allow(unused))]
 		TrampolineEntrypoint(InboundTrampolineEntrypointPayload),
 		Receive(InboundOnionReceivePayload),
 		BlindedForward(InboundOnionBlindedForwardPayload),
 		BlindedReceive(InboundOnionBlindedReceivePayload),
 	}
 
-	#[cfg(trampoline)]
 	pub struct InboundTrampolineForwardPayload {
 		pub next_trampoline: PublicKey,
 		/// The value, in msat, of the payment after this hop's fee is deducted.
 		pub amt_to_forward: u64,
 		pub outgoing_cltv_value: u32,
 	}
 
-	#[cfg(trampoline)]
 	pub struct InboundTrampolineBlindedForwardPayload {
 		pub next_trampoline: PublicKey,
 		pub payment_relay: PaymentRelay,
@@ -2144,7 +2138,6 @@ mod fuzzy_internal_msgs {
 		pub next_blinding_override: Option<PublicKey>,
 	}
 
-	#[cfg(trampoline)]
 	pub enum InboundTrampolinePayload {
 		Forward(InboundTrampolineForwardPayload),
 		BlindedForward(InboundTrampolineBlindedForwardPayload),
@@ -3239,15 +3232,13 @@ impl<NS: Deref> ReadableArgs<(Option<PublicKey>, NS)> for InboundOnionPayload wh
 		let mut payment_metadata: Option<WithoutLength<Vec<u8>>> = None;
 		let mut total_msat = None;
 		let mut keysend_preimage: Option<PaymentPreimage> = None;
-		#[cfg(trampoline)]
 		let mut trampoline_onion_packet: Option<TrampolineOnionPacket> = None;
 		let mut invoice_request: Option<InvoiceRequest> = None;
 		let mut custom_tlvs = Vec::new();
 
 		let tlv_len = BigSize::read(r)?;
 		let mut rd = FixedLengthReader::new(r, tlv_len.0);
 
-		#[cfg(trampoline)]
 		decode_tlv_stream_with_custom_tlv_decode!(&mut rd, {
 			(2, amt, (option, encoding: (u64, HighZeroBytesDroppedBigSize))),
 			(4, cltv_value, (option, encoding: (u32, HighZeroBytesDroppedBigSize))),
@@ -3268,33 +3259,12 @@ impl<NS: Deref> ReadableArgs<(Option<PublicKey>, NS)> for InboundOnionPayload wh
 			custom_tlvs.push((msg_type, value));
 			Ok(true)
 		});
-		#[cfg(not(trampoline))]
-		decode_tlv_stream_with_custom_tlv_decode!(&mut rd, {
-			(2, amt, (option, encoding: (u64, HighZeroBytesDroppedBigSize))),
-			(4, cltv_value, (option, encoding: (u32, HighZeroBytesDroppedBigSize))),
-			(6, short_id, option),
-			(8, payment_data, option),
-			(10, encrypted_tlvs_opt, option),
-			(12, intro_node_blinding_point, option),
-			(16, payment_metadata, option),
-			(18, total_msat, (option, encoding: (u64, HighZeroBytesDroppedBigSize))),
-			(77_777, invoice_request, option),
-			// See https://github.com/lightning/blips/blob/master/blip-0003.md
-			(5482373484, keysend_preimage, option)
-		}, |msg_type: u64, msg_reader: &mut FixedLengthReader<_>| -> Result<bool, DecodeError> {
-			if msg_type < 1 << 16 { return Ok(false) }
-			let mut value = Vec::new();
-			msg_reader.read_to_limit(&mut value, u64::MAX)?;
-			custom_tlvs.push((msg_type, value));
-			Ok(true)
-		});
 
 		if amt.unwrap_or(0) > MAX_VALUE_MSAT { return Err(DecodeError::InvalidValue) }
 		if intro_node_blinding_point.is_some() && update_add_blinding_point.is_some() {
 			return Err(DecodeError::InvalidValue)
 		}
 
-		#[cfg(trampoline)]
 		if let Some(trampoline_onion_packet) = trampoline_onion_packet {
 			if payment_metadata.is_some() || encrypted_tlvs_opt.is_some() ||
 				total_msat.is_some()
@@ -3391,7 +3361,6 @@ impl<NS: Deref> ReadableArgs<(Option<PublicKey>, NS)> for InboundOnionPayload wh
 	}
 }
 
-#[cfg(trampoline)]
 impl<NS: Deref> ReadableArgs<(Option<PublicKey>, NS)> for InboundTrampolinePayload where NS::Target: NodeSigner {
 	fn read<R: Read>(r: &mut R, args: (Option<PublicKey>, NS)) -> Result<Self, DecodeError> {
 		let (update_add_blinding_point, node_signer) = args;

lightning/src/ln/onion_payment.rs

@@ -6,8 +6,6 @@
 use bitcoin::hashes::Hash;
 use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::secp256k1::{self, PublicKey, Secp256k1};
-
-#[cfg(trampoline)]
 use bitcoin::secp256k1::ecdh::SharedSecret;
 
 use crate::blinded_path;
@@ -69,7 +67,6 @@ enum RoutingInfo {
 		new_packet_bytes: [u8; ONION_DATA_LEN],
 		next_hop_hmac: [u8; 32]
 	},
-	#[cfg(trampoline)]
 	Trampoline {
 		next_trampoline: PublicKey,
 		// Trampoline onions are currently variable length
@@ -118,14 +115,12 @@ pub(super) fn create_fwd_pending_htlc_info(
 				err_code: 0x4000 | 22,
 				err_data: Vec::new(),
 			}),
-		#[cfg(trampoline)]
 		onion_utils::Hop::TrampolineReceive { .. } | onion_utils::Hop::TrampolineBlindedReceive { .. } =>
 			return Err(InboundHTLCErr {
 				msg: "Final Node OnionHopData provided for us as an intermediary node",
 				err_code: 0x4000 | 22,
 				err_data: Vec::new(),
 			}),
-		#[cfg(trampoline)]
 		onion_utils::Hop::TrampolineForward { next_trampoline_hop_data, next_trampoline_hop_hmac, new_trampoline_packet_bytes, trampoline_shared_secret, .. } => {
 			(
 				RoutingInfo::Trampoline {
@@ -141,7 +136,6 @@ pub(super) fn create_fwd_pending_htlc_info(
 				None
 			)
 		},
-		#[cfg(trampoline)]
 		onion_utils::Hop::TrampolineBlindedForward { outer_hop_data, next_trampoline_hop_data, next_trampoline_hop_hmac, new_trampoline_packet_bytes, trampoline_shared_secret, .. } => {
 			let (amt_to_forward, outgoing_cltv_value) = check_blinded_forward(
 				msg.amount_msat, msg.cltv_expiry, &next_trampoline_hop_data.payment_relay, &next_trampoline_hop_data.payment_constraints, &next_trampoline_hop_data.features
@@ -192,7 +186,6 @@ pub(super) fn create_fwd_pending_htlc_info(
 					}),
 			}
 		}
-		#[cfg(trampoline)]
 		RoutingInfo::Trampoline { next_trampoline, new_packet_bytes, next_hop_hmac, shared_secret, current_path_key } => {
 			let next_trampoline_packet_pubkey = match next_packet_pubkey_opt {
 				Some(Ok(pubkey)) => pubkey,
@@ -272,7 +265,6 @@ pub(super) fn create_recv_pending_htlc_info(
 			 sender_intended_htlc_amt_msat, cltv_expiry_height, None, Some(payment_context),
 			 intro_node_blinding_point.is_none(), true, invoice_request)
 		}
-		#[cfg(trampoline)]
 		onion_utils::Hop::TrampolineReceive { .. } | onion_utils::Hop::TrampolineBlindedReceive { .. } => todo!(),
 		onion_utils::Hop::Forward { .. } => {
 			return Err(InboundHTLCErr {
@@ -288,7 +280,6 @@ pub(super) fn create_recv_pending_htlc_info(
 				msg: "Got blinded non final data with an HMAC of 0",
 			})
 		},
-		#[cfg(trampoline)]
 		onion_utils::Hop::TrampolineForward { .. } | onion_utils::Hop::TrampolineBlindedForward { .. } => {
 			return Err(InboundHTLCErr {
 				err_code: 0x4000|22,
@@ -560,7 +551,6 @@ where
 				outgoing_cltv_value
 			})
 		}
-		#[cfg(trampoline)]
 		onion_utils::Hop::TrampolineForward { next_trampoline_hop_data: msgs::InboundTrampolineForwardPayload { amt_to_forward, outgoing_cltv_value, next_trampoline }, trampoline_shared_secret, incoming_trampoline_public_key, .. } => {
 			let next_trampoline_packet_pubkey = onion_utils::next_hop_pubkey(secp_ctx,
 				incoming_trampoline_public_key, &trampoline_shared_secret.secret_bytes());