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Enforce Trampoline Constraints (replacement) #4226

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Merged
carlaKC merged 5 commits into from
Dec 1, 2025
Merged

Enforce Trampoline Constraints (replacement) #4226

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e11b30c
ln/fmt: move rustfmt_skip to per-function in blinded_payment_tests
carlaKC Nov 17, 2025
8c9e01e
ln/fmt: remove rustfmt::skip from do_test_trampoline_unblinded_receive
carlaKC Nov 17, 2025
26a2222
ln/fmt: clean up ugly formatting of do_test_trampoline_unblinded_receive
carlaKC Nov 17, 2025
269eb6b
ln: add trampoline LocalHTLCFailureReason variants per spec
a-mpch Aug 14, 2025
785c781
ln: enforce trampoline onion recipient constraints
carlaKC Nov 14, 2025
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20 changes: 19 additions & 1 deletion lightning/src/ln/onion_utils.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1663,6 +1663,13 @@ pub enum LocalHTLCFailureReason {
PeerOffline,
/// The HTLC was failed because the channel balance was overdrawn.
ChannelBalanceOverdrawn,
/// We have been unable to forward a payment to the next Trampoline node but may be able to
/// do it later.
TemporaryTrampolineFailure,
/// The amount or CLTV expiry were insufficient to route the payment to the next Trampoline.
TrampolineFeeOrExpiryInsufficient,
/// The specified next Trampoline node cannot be reached from our node.
UnknownNextTrampoline,
}

impl LocalHTLCFailureReason {
Expand Down Expand Up @@ -1704,6 +1711,9 @@ impl LocalHTLCFailureReason {
Self::InvalidOnionPayload | Self::InvalidTrampolinePayload => PERM | 22,
Self::MPPTimeout => 23,
Self::InvalidOnionBlinding => BADONION | PERM | 24,
Self::TemporaryTrampolineFailure => NODE | 25,
Self::TrampolineFeeOrExpiryInsufficient => NODE | 26,
Self::UnknownNextTrampoline => PERM | 27,
Self::UnknownFailureCode { code } => *code,
}
}
Expand Down Expand Up @@ -1863,7 +1873,10 @@ ser_failure_reasons!(
(39, HTLCMinimum),
(40, HTLCMaximum),
(41, PeerOffline),
(42, ChannelBalanceOverdrawn)
(42, ChannelBalanceOverdrawn),
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@valentinewallace valentinewallace Dec 1, 2025

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Sorry I just noticed this, on line 1778 we have a macro that says "Error codes that represent BOLT04 error codes must be included here", which looks like it should include these new errors

(43, TemporaryTrampolineFailure),
(44, TrampolineFeeOrExpiryInsufficient),
(45, UnknownNextTrampoline)
);

impl From<&HTLCFailReason> for HTLCHandlingFailureReason {
Expand Down Expand Up @@ -2031,6 +2044,11 @@ impl HTLCFailReason {
debug_assert!(false, "Unknown failure code: {}", code)
}
},
LocalHTLCFailureReason::TemporaryTrampolineFailure => debug_assert!(data.is_empty()),
LocalHTLCFailureReason::TrampolineFeeOrExpiryInsufficient => {
debug_assert_eq!(data.len(), 10)
},
LocalHTLCFailureReason::UnknownNextTrampoline => debug_assert!(data.is_empty()),
}

Self(HTLCFailReasonRepr::Reason { data, failure_reason })
Expand Down