Remote fees

[hosiawak]

I think remote fees are not calculated correcty:

https://github.com/prusnak/suez/blob/master/lndclient.py#L75

self.channels[cin].remote_fees += fee

The fee on the incoming channel (the remote party fee) is their base fee + amount * fee_rate but here you're using our fee.

This should be:

`self.channels[cin].remote_fees += (self.channels[cin].remote_fee_base + forward_amount * self.channels[cin].remote_fee_base / 10000) / 1000

or something along these lines.

What do you think @prusnak ?

[hosiawak]

The above is just an estimate that assumes fixed remote fees for the given forwarding period. To get the exact number we'd have to track remote fee changes.

[prusnak]

I am thinking of dropping remote fees completely, because these are not accurate. Also I am not that sure whether these should be an important factor whether to keep/close/rebalance the channel.

[hosiawak]

I think they're better than nothing though (after my fix below). I was able to quickly identify which remote nodes made more sats by forwarding than my node. Unless people actively manage their fees they don't change often so I think it's a reasonable assumption to make these days.

The exact fix is below (you have to adapt it to LND, I'm running this on C-Lightning):

        for fe in fwd_events:
            cin = fe["in_channel"]
            cout = fe["out_channel"]
            ts = int(fe["resolved_time"])
            fee = int(fe["fee"] / 1000)
            amount_in = int(fe["in_msatoshi"] / 1000)
            if cin in self.channels:
                self.channels[cin].last_forward = max(
                    ts, self.channels[cin].last_forward
                )
                self.channels[cin].remote_fees += int((self.channels[cin].remote_base_fee + (self.channels[cin].remote_fee_rate * amount_in / 1000)) / 1000)
            if cout in self.channels:
                self.channels[cout].last_forward = max(
                    ts, self.channels[cout].last_forward
                )
                self.channels[cout].local_fees += fee

[prusnak]

Fixed in 8f07c6f7e9987c8107467f15856d4336e6907157

Thanks!