where the user has the preimage.
The CLTV requirements between old and new flow are imcompatible.
With the current locktime value, the server was vulnerable to an
attack where the client does not settle the lightning payment
and claims a refund. In order to support both old and new flows,
one would need to use different locktimes.
- client requests payment_hash from the server
- client sends an invoice with that hash
- client waits to receive HTLCs, then broadcasts funding tx
This means that we now use same script for normal and reverse swaps.
The new flow is enabled by setting option LIGHTNING_SWAP_HTLC_FIRST
in the client. The old protocol is still supported server-side.
