bump ltc payment limit

[Jasonhcwong]

increase litecoin payment limit to (0.04 * 60) as BTC is about 60 times more expensive than LTC
fixes #980

[Empact]

Instead of dropping the const, how about initializing in either case in Start? In any case, I doubt you'd want to drop const on those that can carry it.

[Jasonhcwong]

Isn't the value of const must be known at compile time?
The limit depends on the chain(btc or ltc) which is a "deploy time" / "run-time" decision.

[cfromknecht]

This would require modifying the spec or adding a feature bit to signal support for larger payments

[Jasonhcwong]

You are right, according to Bolt #2, the payment limit should be less than 2^24 satoshi which is about 0.16777216 BTC / LTC. So the max payment limit for litecoin will be 0.16777216 LTC (about 19 USD when LTC price is 113 USD)?

[Jasonhcwong]

@cfromknecht I just added a local feature with feature bit 7 to support larger payment up to 1 BTC/LTC. There is also a config flag "largerpayment" to enable this feature.

[wpaulino]

Thanks for the PR @Jasonhcwong! We won't be going forward with the feature bit since we are really the only implementation that fully supports Litecoin. We'll need to bump up the channel capacity by 60x when running on the Litecoin chain.

[Jasonhcwong]

@wpaulino, I think c-lightning support Litecoin too and BTCPayServer is using c-lightning as backend. Simply bump up channel capacity by 60x may break interoperability.

[Roasbeef]

Closed as the other PR bumped up by 60x, we'll need to create a proper feature bit in the near future, but this at least lets lnd nodes use LN on Litecoin rn.