router: Use aggregate capacity for first-hop fragmentation check#2
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martinsaposnic wants to merge 1 commit intolsp-0.1.8from
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router: Use aggregate capacity for first-hop fragmentation check#2martinsaposnic wants to merge 1 commit intolsp-0.1.8from
martinsaposnic wants to merge 1 commit intolsp-0.1.8from
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The routing fragmentation mitigation heuristic requires each channel to contribute at least `payment_amount / max_path_count` to avoid excessive path splitting. This makes sense for network paths where each additional path incurs base fees and increases failure probability. However, for first hops this is overly restrictive. Multiple channels to the same peer converge immediately at the first hop - there's no actual network-level fragmentation. A 2M sat channel and a 48M sat channel to the same peer should be usable together for a 50M sat payment, but currently the small channel gets rejected (threshold would be 5M sat with default max_path_count=10), leaving only 48M available. This change checks the aggregate capacity across all first-hop channels to a peer. If the aggregate meets the contribution threshold, individual channels are allowed regardless of their size.
amackillop
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Mar 18, 2026
When the counterparty initiates an RBF and we have no new contribution queued via QuiescentAction, we must re-use our prior contribution so that our splice is not lost. Track contributions in a new field on PendingFunding so the last entry can be re-used in this scenario. Each entry stores the feerate-adjusted version because that reflects what was actually negotiated and allows correct feerate re-adjustment on subsequent RBFs. Only explicitly provided contributions (from a QuiescentAction) append to the vec. Re-used contributions are replaced in-place with the version adjusted for the new feerate so they remain accurate for further RBF rounds, without growing the vec. Add test_splice_rbf_acceptor_recontributes to verify that when the counterparty initiates an RBF and we have no new QuiescentAction queued, our prior contribution is automatically re-used so the splice is preserved. Add test_splice_rbf_recontributes_feerate_too_high to verify that when the counterparty RBFs at a feerate too high for our prior contribution to cover, the RBF is rejected rather than proceeding without our contribution. Add test for sequential RBF splice attempts Add test_splice_rbf_sequential that exercises three consecutive RBF rounds on the same splice (initial → RBF #1 → RBF #2) to verify: - Each round requires the 25/24 feerate increase (253 → 264 → 275) - DiscardFunding events reference the correct funding txid from each replaced candidate - The final RBF splice can be mined and splice_locked successfully Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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The routing fragmentation mitigation heuristic requires each channel to contribute at least
payment_amount / max_path_countto avoid excessive path splitting. This makes sense for network paths where each additional path incurs base fees and increases failure probability.However, for first hops this is overly restrictive. Multiple channels to the same peer converge immediately at the first hop - there's no actual network-level fragmentation. A 2M sat channel and a 48M sat channel to the same peer should be usable together for a 50M sat payment, but currently the small channel gets rejected (threshold would be 5M sat with default max_path_count=10), leaving only 48M available.
This change checks the aggregate capacity across all first-hop channels to a peer. If the aggregate meets the contribution threshold, individual channels are allowed regardless of their size.