From rusty at rustcorp.com.au  Fri Oct 19 10:42:31 2018
From: rusty at rustcorp.com.au (Rusty Russell)
Date: Fri, 19 Oct 2018 21:12:31 +1030
Subject: [Lightning-dev] Commitment Transaction Format Update Proposals?
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Message-ID: <87va5ycj54.fsf@rustcorp.com.au>

Fabrice Drouin <fabrice.drouin at acinq.fr> writes:
> Hello,
>
>> 1.  Rather than trying to agree on what fees will be in the future, we
>  >     should use an OP_TRUE-style output to allow CPFP (Roasbeef)
>
> We could also use SIGHASH_ANYONECANPAY|SIGHASH_SINGLE for HTLC txs, without
> adding the "OP_TRUE" output to the commitment transaction. We would still
> need the update_fee message to manage onchain fees for the commit tx (but
> not the HTLC txs) but there would be no reason anymore to refuse fee rates
> that are too high and channels would not get closed anymore when there's a
> spike in onchain fees.

Agreed, that was in the details below:

- HTLC-timeout and HTLC-success txs sigs are 
  SIGHASH_ANYONECANPAY|SIGHASH_SINGLE, so you can Bring Your Own Fees.

The only problem with these proposals is that it requires you have an
available UTXO to make the CPFP etc.

Cheers,
Rusty.