[enhancement] Set inbound_fee_offset relativ to outbound fee of a peer

[warioishere]

Hello,

Would it be possible to implement a feature in charge-lnd that allows setting inbound fees dynamically based on the outbound fee of a channel?

For example, if a channel has an externally set outbound feerate of 400 ppm, charge-lnd should be able to apply a predefined negative fee offset, such as -40 ppm, resulting in an inbound fee of -360 ppm.

The idea is to let charge-lnd retrieve the outbound feerate and then apply a custom discount to determine the inbound fee.

A potential configuration could look like this:

[inbound-fee-policy]

node.id = file:///home/lnd/inbound_discount_peers.list

strategy = discount from outboundfee
inbound_base_fee_msat_offset = -40

This would allow defining a list of peers in a file, for whom charge-lnd automatically applies an inbound fee offset based on their outbound fee.

A similar approach has reportedly led to significant liquidity flow improvements and a 20-25% profit increase in another project, and would let to a better atumatization of the liquidy managment of a routing node making things a bit easy for a noderunner :)

Would this be feasible for charge-lnd?

Greetings from wario

[feelancer21]

The parameter you are looking for is called inbound_level_ppm. If you set it, the inbound fee rate is calculated by min(inbound_level_ppm - fee_ppm; 0). Hence you have to set it to 40.

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