routing: Support Pathfinding to Blinded Routes #7267

This commit adds a representation of blinded payments, which include a blinded path and aggregate routing parameters to be used in payment to the path.

This commit adds the encrypted_data, blinding_point and total_amt_msat tlvs to the known set of even tlvs for the onion payload. These TLVs are added in two places (the onion payload and hop struct) because lnd uses the same set of TLV types for both structs (and they inherently represent the same thing). Note: in some places, unit tests intentionally mimic the style of older tests, so as to be more consistently readable.

With the addition of blinded routes, we now need to account for the possibility that intermediate nodes payloads will not have an amount and expiry set because that information is provided by the recipient encrypted data blob. This commit updates our payload packing to only optionally include those fields.

When we introduce blinded routes, some of our hops are expected to have zero amounts to forward in their hop payload. This commit updates our hop fee logic to attribute the full blinded route's fees to the introduction node. We can't actually know where/how these fees are distributed, so we collect them all at the introduction node.

This commit introduces a single struct to hold all of the parameters that are passed to FindRoute. This cleans up an already overloaded function signature and prepares us for handling requests with blinded routes where we need to perform some additional processing on our para (such as extracting the target node from the blinded path).

Add the option to include a blinded route in a route request (exclusive to including hop hints, because it's incongruous to include both), and express the route as a chain of hop hints. Using a chain of hints over a single hint to represent the whole path allows us to re-use our route construction to fill in a lot of the path on our behalf.

This commit updates route construction to backfill the fields required for payment to blinded paths and set amount to forward and expiry fields to zero for intermediate hops (as is instructed in the route blinding specification). We could attempt to do this in the first pass, but that loop relies on fields like amount to forward and expiry to calculate each hop backwards, so we keep it simple (stupid) and post processes the blinded portion, since it's computationally cheap and more readable.

Blinded routes can now have "hints" that have zero value edges, so we remove this log to avoid spamming logs.

Note: This commit can be dropped before merge, it's mostly added to make the PR easier to manually test against other implementations that have bolt 12 invoices implemented already!

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routing: Support Pathfinding to Blinded Routes #7267

routing: Support Pathfinding to Blinded Routes #7267

Commits on Sep 27, 2023