Allow a user to switch on dual-funding without needing to compile
as EXPERIMENTAL_FEATURES.
Doesn't work yet, since everything is still behind
'EXPERIMENTAL_FEATURES' compile time flags... but useful for testing
Let plugins know when a channel open has failed.
We need to notify accepters now too, so we remove the check on who's
funding the channel before sending the 'failed' message from
dualopend->master.
We already know what the channel id is, we should go ahead and pass it
on to any listening plugins -- this makes clean up easier/possible
if a open fails early on and we've got reserved utxos.
When we're the opener, we get the upfront shutdown scriptpubkey (if
there is one) from the `close_to` param of `openchannel_init`.
We were passing it through dualopend, but we need to break the update
chain so that our test_option_upfront_shutdown_script test works (same
as on the openingd flow.)
There's a case where a dropped funding_locked will result in the peer
moving onto channeld, while we stay in dualopend. As we haven't
received their funding_locked, we retransmit tx_sigs, which channeld
will need to handle.
With the patch the peer drops it on the floor; the peer will resend
funding_locked on reconnect, which will correctly advance us to
channeld and CHANNELD_NORMAL
Prior to this, all reconnect logic lived in channeld. If you
disconnected before we finished building a funding transaction, that was
no big deal. Now, however, we're waiting for the funding to lock in in
dualopend, instead of handing straight to channeld to wait.
So we need a way to restart dualopend.
We delegate the decision about what to do about 'out of bound' feerates
to the plugin (if one exists), however in the case that the plugin
doesnt exist or doesnt want to figure it out, we default to using the
'best' as their intended feerate, and rejecting if it's out of bounds.
We need to know if they've sent us their sigs message yet. Ideally, we'd
be able to check the 'finalness' of the PSBT, however if the peer
doesn't have any inputs to the channel this doesn't work.
We were incorrectly saving the *remote's* commitment transaction as the
'last_tx' for a peer, not our own local one.
When we applied the 'remote_commit_sig' to it, it would fail since the
remote's signature doesn't validate for their commitment transaction.
Back in the days before dual-funding, the `channel` struct on subd was
only every one type per daemon (either struct channel or struct
uncommitted_channel)
The RBF requirement on dualopend means that dualopend's channel,
however, can now be two different things -- either channel or
uncommitted_channel.
To track the difference/disambiguate, we now track the channel type on a
flag on the subd. It gets updated when we swap out the channel.
This will make it possible to do RBF, since we can re-start the opening
process in dualopend while waiting for lock-in.
Note the new channel states are being used, DUALOPEND_INIT and
DUALOPEND_AWAITING_LOCKIN, to differentiate from openingd/channeld opens
v2 channel opens are going to happen over in dualopend. In order
to make sure that these don't end up in the wrong place/to keep track of
the difference between "waiting for sigs" and "have merely initiatlized
a channel", we add two new states to the channel state machine.
A channel that 'originates' in dualopend will only ever arrive at
channeld in the state CHANNELD_NORMAL.
