The receiving node: ...
- MUST fail the channel if:
- the `witness_stack` weight lowers the effective `feerate`
below the agreed upon transaction `feerate`
We consolidate to the latest/singular RFC patch for dual-funding, so
there's just a single patchfile for the change. Plus we move back to the
opener setting the desired feerate, the accepter merely declines to
participate if they disagree with the set rate.
We were getting a memleak error that the open_attempt isnt' being
cleaned up in test_rbf_reconnect_tx_construct. I had some trouble
reproducing it, so I removed the reliance on using `tmpctx` to clean it
up and was more surgical about cleaning it up inline.
We move over to the new "warning" paradigm, instead of using
an "rbf_fail" message.
Every failure is either a warning or an error; on warnings we
hang up and reconnect later, effectively resetting the state.
We're *mostly* set up for both sides doing RBF, except that it reverses
the callback flow (using the plugin vs RPC calls) and we're not
currently smart enough to flip between them gracefully
We're going to move over to "unsaved channels" instead of using a
separate "uncommitted_channel" struct. This means a peer might have a
channel that's not saved to the database yet in its channel list
We need to make sure that there's at least one input that's represented
in every single RBF-attempt for this channel, to prevent "parallel"
subsequent RBFs from succeeding/opening (the multi-channel backdoor?!)
When the funding tx reaches depth, update the channel's data to the
"correct" funding transaction info from inflights (if necessary).
This will be necessary if:
- the transaction has been successfully RBF'd and
- the lesser fee transaction is the one successfully mined, OR
- the channel is in the process of being RBF'd
Nit: The underscore in "openchannel_hook" is wrong, bcause the name of
the hook is just "openchannel". The "_hook" implied this to be part of
the name.
Changelog-None
We weren't sending a channel_open notification for dual-funded channels.
This is only sent for the 'accepter' side. We send it as soon as both
funding_tx sigs have been exchanged, even though it's possible the
funding transaction might be published without this having been the case.
Since we fail the channel if this happens, only notifying for good/valid
channels reaching the broadcast state is the right way to handle this.
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.)
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.
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
Since this all stays in dualopend/dual_open_control, we can hold
onto the openchannel_signed command to wait for a response here locally.
Previously we were splitting across the channeld/openingd boundary.
We let the plugin decide what feerate to accept/whether or not to add
funds to the open. To aid this decision, we also send the plugin what we
(c-lightning) currently have as our max and min acceptable feerates.
We also now use these as our default for max/min acceptable feerate
range when sending an openchannel offer to a peer.
In the future, it might be a good idea to make these more easily
changeable, either via a config setting (?) or a command param.
Prior to this patch update, we expected a client to call
`openchannel_signed` before checking for peer's tx-sigs messages on the
wire.
When moving to a 'multifundchannel' approach, we'll need to be able to
collect sigs from our peers before sending our tx_sigs message. There's
no strict ordering on when tx-sigs messages are sent/received, so this
is fine.
To do this, we go ahead and start up channeld as soon as
commitment_sigs are secured, so that we process incoming tx-sigs from
our peers as soon as we get them.
This is handy/necessary for getting multifundchannel to work, as we need
to know what output to tell all the other peers about.
Changelog-Added: Experimental!! JSON-RPC: openchannel_init returns a field `funding_serial` that indicates the serial_id of the funding output in the provided PSBT
Rusty pointed out that having an empty channel_id is suboptimal; adding
another call is probably the right idea rather than re-using an existing
one.
Suggested-By: @rustyrussell
niftynei
Michael Schmoock
Rusty Russell
Antoine Poinsot