Feature to allow shutdown of channels opened with the wrong funding txid / output number. #4421
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rustyrussell
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cdecker
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Very good, just found an assert that seems to be triggerable (followed by the same check in an if block) and minor wording.
CI failures seem unrelated, restarted.
ACK 599113e
I was initially curious about why we'd want to remember the funding
alias in the first place, but it is being used to track the funding
instead. I'm wondering if this is worth generalizing into an alias
tracking feature: record tx outpoint aliases in a new table, if an
alias gets confirmed look at the txo_watches and call that with the
alias transaction instead. It'd require a bit of care in the watch
callbacks in case we build on top of that TX, but it could allow us to
use the aliasing to unify outpoint tracking across variants of
transactions for things like HTLC-transactions being re-assembled into
larger batches, these malleation cases and some others.
Not for this PR, but might be a nice cleanup for the next release if we go
more into the direction of babysitting our txs.
| \fBexperimental-shutdown-wrong-funding\fR | ||
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| Specifying this allows the \fBwrong_funding\fR field in shutdown: if a |
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For the spec we probably want to call this funding_malleated_txid or funding_alias_txid but for now this is ok.
doc/lightningd-config.5
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| Specifying this allows the \fBwrong_funding\fR field in shutdown: if a | ||
| remote node has opened a channel using the incorrect txid (and it | ||
| hasn't been used yet at all) this allows them to negotiate a clean |
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Isn't specifying that it hasn't been used implied? We can't perform updates unless we find the correct funding.
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Yes, I should clarify. "If the remote node has opened a channel but claims it used the incorrect txid (and the channel hasn't been used at all)"?
| @@ -90,6 +90,10 @@ msgtype,shutdown,38 | |||
| msgdata,shutdown,channel_id,channel_id, | |||
| msgdata,shutdown,len,u16, | |||
| msgdata,shutdown,scriptpubkey,byte,len | |||
| msgdata,shutdown,tlvs,shutdown_tlvs, | |||
| tlvtype,shutdown_tlvs,wrong_funding,100 | |||
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Shall we use 104 here as well to match the option featurebit?
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Sure, why not.
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(I didn't change this, actually, since @openoms is actively testing now, and easier not to break him).
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| ", shutdown_wrong_txid" // 57 | ||
| ", shutdown_wrong_outnum" // 58 |
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At some point I'll add an outpoint primitive that subsumes (txid, outnum) since it's a very common thing, and they rarely get queried individually :-)
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If only ALTER TABLE DROP COLUMN were something that sqlite3 can do...
closingd/closingd.c
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| @@ -75,6 +76,7 @@ static struct bitcoin_tx *close_tx(const tal_t *ctx, | |||
| out_minus_fee[LOCAL], | |||
| out_minus_fee[REMOTE], | |||
| dust_limit); | |||
| assert(tx); | |||
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Whoops, this looks like it could trigger, taking closingd with it.
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Oops, that was me trying to track a bug and force a backtrace.
Good catch!
closingd/closingd.c
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| @@ -669,6 +695,11 @@ int main(int argc, char *argv[]) | |||
| status_debug("fee = %s", | |||
| type_to_string(tmpctx, struct amount_sat, &offer[LOCAL])); | |||
| status_debug("fee negotiation step = %s", fee_negotiation_step_str); | |||
| if (wrong_funding) | |||
| status_unusual("Seting wrong_funding_txid to %s:%u", | |||
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Suggested change
| status_unusual("Seting wrong_funding_txid to %s:%u", | |
| status_unusual("Setting wrong_funding_txid to %s:%u", |
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Tried but seems to break unless it is me doing something wrong. built with: And lightningd is running with: Build output: https://pastebin.com/raw/AD6U8RNG The signet transaction sent (with the wrong txid passed to In the log: |
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Good catch, fix coming! |
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Tested sucessfully on signet! Log of the remote peer: Log of the funding peer: And the recovered funds in the wallet: |
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Minor breakage in the test, otherwise perfect: |
Obvious fix applied. Rebased and folded previous fixes... |
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… up! It's not unheard of for people to give the wrong funding tx to us, getting their funds stuck. Interestingly, we can allow mutual close using a different txid and output number as long as they (solely) funded the channel, and the channel hasn't been used. This defines a "play area" feature to do just that. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
…tpoint. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
If it passes checks, lightningd puts it in the database. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: lightningd: experimental-shutdown-wrong-funding to allow remote nodes to close incorrectly opened channels. Changelog-Added: JSON-RPC: close has a new `wrong_funding` option to try to close out unused channels where we messed up the funding tx. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Fairly easy to do, though we also have to add the watch when we load from the database. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Trivial rebase to fix generated file conflicts |
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Ack 06d04f8 |
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See #4416, though it may not help soon enough for that (the peer will forget the channel after 2016 blocks, so they need to upgrade and try this before then!)
Next step is to remove the footgun which caused it, but @TBast also reported that he had similar problems with users trying to RBF their funding tx...