In spec commit 498f104fd399488c77f449d05cb21c0b604636a2 (August 2021),
Bastien Teinturier removed the requirement that the mutual close fee be
less than or equal the final commitment tx.
We adopted that change in v0.10.2, but we made sure to never offer a fee
under the final commitment tx's fee, so we didn't break older nodes.
However, the closing tx can actually be larger than the final commitment tx!
The final commit tx has a 22-byte P2WKH output and a 34-byte P2WSH output;
the closing can have two 34-byte outputs, making it 4*8 = 32 Sipa heavier.
Previously this would only happen if both sides asked for P2WSH outputs,
but now it happens with P2TR, which we now do.
The result is that we create a tx which is below the finally commitment
tx fee, and may be below minrelayfee (as it was in regtest).
So it's time to remove that backwards-compatibility hack.
Changelog-Fixed: Protocol: We may propose mutual close transaction which has a slightly higher fee than the final commitment tx (depending on the outputs, e.g. two taproot outputs).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Fixes: #6545
We now let gossipd do it.
This also means there's nothing left in 'struct per_peer_state' to
send across the wire (the fds are sent separately), so that gets
removed from wire messages too.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This allows cmdline users to have more idea what's going on.
Inspired-by: https://github.com/ElementsProject/lightning/issues/4777
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: `close` now notifies about the feeranges each side uses.
This follows https://github.com/lightningnetwork/lightning-rfc/pull/847.
For anchor_outputs, we pass down a max_feerate to closingd, and set the
fee ceiling to MAX. It uses that to estimate the desired closing fee.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-EXPERIMENTAL: Anchor output mutual close allow a fee higher than the final commitment transaction (as per lightning-rfc #847)
Based on a commit by @niftynei, but:
- Separated quickclose logic from main loop.
- I made it indep of anchor_outputs, use and option instead.
- Disable if they've specified how to negotiate.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We were actually using the last commit tx's size, since we were
setting it in lightningd. Instead, hand the min and desired feerates
to closingd, and (as it knows the weight of the closing tx), and have
it start negotiation from there.
This can be significantly less when anchor outputs are enabled: for
example in test_closing.py, the commit tx weight is 1124 Sipa, the
close is 672 Sipa!
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Changed: Protocol: Use a more accurate fee for mutual close negotiation.
It handles all the cases of retransmission, and in the normal case
retransmits shutdown and immediately returns for us to run closingd.
This is actually far simpler and reduces code duplication.
[ Includes fixup to stop warn_unused_result from Christian ]
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Fixed: Protocol: We could get stuck on signature exchange if we needed to retransmit the final revoke_and_ack.
v2 channel open uses a different method to derive the channel_id, so now
we save it to the database so that we dont have to remember how to
derive it for each.
includes a migration for existing channels
