Optional setting to dip into trampoline relay fees - #3372
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Many service providers (lightning nodes that provide services to mobile wallets that support it) get paid by adding a fee to the routing hints of the end user's invoices: this lets them be paid a fee that may be larger than their usual relay fees when wallet users receive payments. That can compete with the fees collected by intermediate trampoline nodes, so we provide a new setting (disabled by default) that lets trampoline nodes relay payments without collecting their full relay fee. It is up to each trampoline node to decide whether they are ok with having more payments succeed with a smaller per-payment revenue or not.
pm47
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Aug 28, 2026
| case p@PaymentPart(_, _, _, Some(route), _) => route.head.fee(p.amountWithFees) | ||
| }.sum | ||
| } else { | ||
| 0 msat |
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I figure we could maybe set a minimum relay fee here (and in PaymentLifeCycle), WDYT?
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Then I think we should repurpose the relay.fees.min-trampoline section of eclair.conf for that, shouldn't we?
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I've tried a different approach in 88102e1, which lets us more flexibly configure a threshold trampoline fee that's different from the channel fees.
Note that this is somewhat unrelated to the line of code you're commenting on, which just computes local vs total path fees for reporting.
Another approach, slightly different from the previous commit, where we instead set a floor for trampoline fees that may be different from our local channel fees when trampoline payments contain a routing hint.
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Many service providers (lightning nodes that provide services to mobile wallets that support it) get paid by adding a fee to the routing hints of the end user's invoices: this lets them be paid a fee that may be larger than their usual relay fees when wallet users receive payments.
That can compete with the fees collected by intermediate trampoline nodes, so we provide a new setting (disabled by default) that lets trampoline nodes relay payments without collecting their full relay fee. It is up to each trampoline node to decide whether they are ok with having more payments succeed with a smaller per-payment revenue or not.