We want to re-use the logic that determines what change amount is left
over depending on whether we add or don't add a change output to a
transaction, respecting the change output's dust limit.
We'll want to be able to tell the coin selection algorithm that we
intend to add any change to an existing output instead of assuming that
a change output is always created.
If we add any left over change to an existing output, we can skip the
dust amount check as we assume the selected existing output already has
a non-dust amount requested (responsibility of the caller to assert).
Before this commit the coin selection logic in the chanfunding package
would always assume that there is a P2WSH funding output and potentially
a P2TR change output. But because we want to re-use the coin selection
for things other than just channel funding, we make the logic more
generic by allowing us to specify both the existing weight of the
transaction (the already known, static parts of the TX) as well as the
type of the potential change output we would use.
Allows to define a maximum amount to provision a channel
opening with using a new field `FundUpToMaxAmt` on the
`Request` struct. Also adds a new coin select function
`CoinSelectUpToAmount` to select coins up to a maximum
amount respecting a minimum amount.
With this commit we support fee calculation in coin selection for p2tr
inputs. We assume that coins in our UTXO selection are only BIP0086
coins. Any other input types with different spend paths won't be
selected by the wallet assembler.
This commit was previously split into the following parts to ease
review:
- 2d746f68: replace imports
- 4008f0fd: use ecdsa.Signature
- 849e33d1: remove btcec.S256()
- b8f6ebbd: use v2 library correctly
- fa80bca9: bump go modules
This commit updates call-sites to use the proper dust limits for
various script types. This also updates the default dust limit used
in the funding flow to be 354 satoshis instead of 573 satoshis.
Add a dust-limit to `CoinSelect` and let the fee estimation consider if a change output is needed or not, assuring that if the change is below the dust-limit it will go towards the fee instead.
In this commit, we make an incremental change to move the existing coin
selection code into a new chanfunding package. In later commits, this
package will grow to serve all the lower level channel funding needs in
the daemon.
