If the latest splice transaction doesn't confirm, we allow exchanging
`tx_init_rbf` and `tx_ack_rbf` to create another splice transaction to
replace it. We use the same funding contribution as the previous splice.
When 0-conf isn't used, we reject `splice_init` while the previous
splice transaction hasn't confirmed. Our peer should either use RBF
instead of creating a new splice, or they should wait for our node
to receive the block that confirmed the previous transaction. This
protects against chains of unconfirmed transactions.
When using 0-conf, we reject `tx_init_rbf` and allow creating chains of
unconfirmed splice transactions: using RBF with 0-conf can lead to one
side stealing funds, which is why we prevent it.
If our peer was buying liquidity but tries to cancel the purchase with
an RBF attempt, we reject it: this prevents edge cases where the seller
may end up adding liquidity to the channel without being paid in return.
When providing on-the-fly funding with the `from_future_htlc` payment
type, the liquidity provider is paying mining fees for the funding
transaction while trusting that the remote node will accept the HTLCs
afterwards and thus pay a liquidity fees. If the remote node fails the
HTLCs, the liquidity provider doesn't get paid. At that point it can
disable the channel and try to actively double-spend it. When we detect
such behavior, we immediately disable `from_future_htlc` to limit the
exposure to liquidity griefing: it can then be re-enabled by using the
`enableFromFutureHtlc` RPC, or will be automatically re-enabled if the
remote node fulfills the HTLCs after a retry.
We record whether a liquidity purchase happened as part of every funding
transaction with the purchased amount and fees. We don't record how the
payment was made, because:
- it creates more backwards-compatibility risk if the liquidity ads spec
changes
- it's most likely unnecessary once the purchase happened, and can only
be stored in the liquidity DB for auditing
We initially supported splicing with a poor man's quiescence, where we
allowed splice messages if the commitments were already quiescent.
We've shipped support for quiescence since then, which means that new
even nodes relying on experimental splicing should support quiescence.
We can thus remove support for the non-quiescent version.
Independently of target and tolerance ratios, transactions must be
publishable in our local mempool. We must be careful that fee ranges
stay above this min fee level.
In theory we shouldn't need to care about the upper range, but I'm not
sure that, depending on the fee estimator, the min fee is always lower
than arbitrary block targets.
We add an optional feature that lets on-the-fly funding clients accept
payments that are too small to pay the fees for an on-the-fly funding.
When that happens, the payment amount is added as "fee credit" without
performing an on-chain operation. Once enough fee credit has been
obtained, we can initiate an on-chain operation to create a channel or
a splice by paying part of the fees from the fee credit.
This feature makes more efficient use of on-chain transactions by
trusting that the seller will honor our fee credit in the future. The
fee credit takes precedence over other ways of paying the fees (from
the channel balance or future HTLCs), which guarantees that the fee
credit eventually converges to 0.
Co-authored-by: Pierre-Marie Padiou <pm47@users.noreply.github.com>
* Add `on_the_fly_funding` feature bit and messages
Add the (disabled by default) `on_the_fly_funding` feature bit and
codecs for the corresponding messages:
- `will_add_htlc`
- `will_fail_htlc`
- `will_fail_malformed_htlc`
- `cancel_on_the_fly_funding`
We also add a TLV to `update_add_htlc` to notify the recipient that we
relayed less data than what the onion encodes, in exchange for the fees
of the specified funding transaction.
* Add `non_initiator_pays_commit_fees` channel flag
We add a non-standard channel flag to `open_channel2` to allow wallets
to ask their peer to pay the commit tx fees, even when they're not the
channel opener. This is necessary for on-the-fly funding, until we can
move to 0-fee commit txs which will make it obsolete.
* Allow underpaying feerate when using future HTLCs
When an interactive-tx session is created for a liquidity purchase that
uses future HTLCs to pay fees, the initiator may not have enough funds
to honor the target feerate. We allow the transaction anyway, because
we want to get paid for the liquidity we're providing. If the feerate
is too low and the transaction doesn't confirm, we can double-spend it
if we need that liquidity elsewhere.
* Add `funding_fee` field to `CMD_ADD_HTLC`
This commit adds the funding fee field to HTLCs, but never sets it.
We update a lot of test files, but there is no functional change.
* Implement on-the-fly funding
Implement the on-the-fly funding protocol: when a payment cannot be
relayed because of a liquidity issue, we notify the `Peer` actor that
we'd like to trigger on-the-fly funding if available. If available, we
we send a funding proposal to our peer and keep track of its status.
Once a matching funding transaction is signed, we persist this funding
attempt and wait for the additional liquidity to be available (once the
channel is ready or the splice locked). We will then frequently try to
relay the payment to get paid our liquidity fees. If the payment keeps
getting rejected, or we cannot connect to our peer, we abandon the
payment when it reaches its CLTV expiry, which ensures that the upstream
channels are not at risk.
When using on-the-fly funding, we use a single channel with our peer.
If they try to open another channel while one is available, we reject
their request and expect a splice instead.
We send to our peers an optional message that tells them the feerates
we'd like to use for funding channels. This lets them know which values
are acceptable to us, in case we reject their funding requests.
This is using an odd type and will be automatically ignored by existing
nodes who don't support that feature.
Co-authored-by: Pierre-Marie Padiou <pm47@users.noreply.github.com>
* Add support for extensible liquidity ads
The initiator of `open_channel2`, `tx_init_rbf` and `splice_init` can
request funding from the remote node. The non-initiator node will:
- let the open-channel-interceptor plugin decide whether to provide
liquidity for new channels or not, and how much
- always honor liquidity requests on existing channels (RBF and splice)
when funding rates have been configured
Liquidity ads are included in the `node_announcement` message, which
lets buyers compare sellers and connect to sellers that provide rates
they are comfortable with. They are also included in the `init` message
which allows providing different rates to specific peers.
This implements https://github.com/lightning/bolts/pull/1153. We
currently use the temporary tlv tag 1339 while we're waiting for
feedback on the spec proposal.
* Add `channelCreationFee` to liquidity ads
Creating a new channel has an additional cost compared to adding
liquidity to an existing channel: the channel will be closed in the
future, which will require paying on-chain fees. Node operators can
include a `channel-creation-fee-satoshis` in their liquidity ads to
cover some of that future cost.
* Add liquidity purchases to the `AuditDb`
Whenever liquidity is purchased, we store it in the `AuditDb`. This lets
node operators gather useful statistics on their peers, and which ones
are actively using the liquidity that is purchased.
We store minimal information about the liquidity ads itself to be more
easily compatible with potential changes in the spec.
When nodes only have private channels, they must include routing hints
in their Bolt 11 invoices to be able to receive payments. We add a
parameter to the `createinvoice` RPC for this. Note that this may leak
the channel outpoint if `scid_alias` isn't used.
Fixes#2802
We have a couple of such errors in our logs for blinded payment relay,
and we currently don't know what the sender did wrong because we don't
log the faulty TLV tag. This should make it easier to debug.
Older lnd nodes are unable to mutual close channels while HTLCs are
in-flight. This triggers unexpected force-closes which can be costly
for node operators. We ignore the errors coming from lnd that match
this case to avoid that.
* Update CI test with latest bitcoin core (switch from autotools to cmake)
bitcoin core now uses cmake instead of autotools.
CI test is triggered by a cron job but can now also be triggered manually.
* Don't spawn anchor tx publisher if commit is confirmed
It is inefficient to spawn a tx publisher for anchor txs if we already
know that the commit tx is confirmed: we will make calls to our bitcoin
node that can easily be avoided. This can matter when force-closing a
large number of channels with frequent disconnections (e.g. wallets).
* Improve `TxTimeLocksMonitor` performance
When publishing a transaction that has CSV delays, we previously used
the watcher and set a `minDepth` on the parent transaction matching
the CSV delay of the child transaction. While this was very simple,
it was unnecessarily expensive for large CSV delays: the watcher would
check for tx confirmations at every block, even when the CSV delay is
very large. When we force-close a large number of channels, it results
in a very large number of RPC calls to our `bitcoind` node.
We don't use the watcher in the `TxTimeLocksMonitor` anymore: instead
we check the parent confirmations once, and then we check again after
the CSV delay.
* Add relative delay hints to `ZmqWatcher`
When we tell the `ZmqWatcher` to watch for confirmations on transactions
that have a relative delay, it is highly inefficient to call our bitcoin
node at every new block to check for confirmations (especially when the
parent transaction isn't even confirmed). We now tell the watcher about
the relative delay, which lets it check for confirmations only at block
heights where we expect the transaction to reach its minimum depth. This
is especially useful to improve performance for delayed transactions
that usually use a CSV of at least 720 blocks.
We refactor `NodeRelay.scala` to re-order some steps. The steps are:
1. Fully receive the incoming payment
2. Resolve the next node (unwrap blinded paths if needed)
3. Wake-up the next node if necessary (mobile wallet)
4. Relay outgoing payment
Note that we introduce a wake-up step, that can be extended to include
mobile notifications. We introduce that same wake-up step in channel
relay and message relay. We also allow relaying data to contain a wallet
`node_id` instead of an scid. When that's the case, we start by waking
up that wallet node before we try relaying onion messages or payments.
This wake-up step doesn't contain any logic right now apart from waiting
for the peer to connect, if it isn't connected already. But it can easily be
extended to send a mobile notification to prompt the wallet to connect.
* Reject new static_remote_key channels
We will still load and use existing static_remote_key channels, we can still open static_remote_key channels, but we will not accept new static_remote_key channels.
This behaviour can be overridden by setting `eclair.channel.accept-incoming-static-remote-key-channels` to `true`.
* Reject new obsolete incoming channels
We reject new incoming channels that don't even support `option_static_remotekey` (which is assumed to be on in the BOLTs).
Unit tests have been modified to use static_remote_key or anchor channels (default used to be the obsolete "standard" channel).
---------
Co-authored-by: Bastien Teinturier <31281497+t-bast@users.noreply.github.com>
There weren't any logs when relaying onion messages, which makes it
impossible to troubleshoot. While we're working on cross-compatibility,
we keep those logs at the `INFO` level, and will change some of them to
`DEBUG` once stabilized.
We move the `Upstream` trait closer to the `Origin`, and make it more
obvious than a hot `Origin` is:
- an `Upstream` referencing the upstream HTLCs
- an actor requesting the outgoing payment
We also improve the cold trampoline relay class to record the incoming
HTLC amount, which we previously didn't bother encoding but is useful to
compute the fees collected during relay. To ensure backwards-compat, it
is set to `0 msat` for pending HTLCs. It will only affect HTLCs that
were pending during the upgrade, which is acceptable.
When we require inputs to be confirmed, we can reliably check whether
they are unspent. We can't reliably check this for unconfirmed inputs,
because they could be valid but simply not in our mempool, in which
case bitcoind would incorrectly consider them unspendable.
We want to reject unspendable inputs early to immediately fail the
funding attempt, instead of waiting to detect the double-spend later.
A race exists because node C can publish the txs to spend the htlcs from the revoked commitment *before* F publishes their txs to spend two of the htlc outputs.
Instead we handle the rare case of a `txn-mempool-conflict` failure.
We will sometimes miss testing that C claims those two htlcs via 3rd stage txs.
The channel initiator traditionally pays the commit tx fees, but we may
want to override that when providing services to wallet users. We thus
split the current `isInitiator` flag into two flags:
- `isChannelOpener`
- `paysCommitTxFees`
We always set `paysCommitTxFees` to the same value as `isChannelOpener`.
Custom feature bits may override that behavior if necessary.
Note that backwards compatibility is preserved since our previous `bool8`
codec encodes `true` as `0xff` and `false` as `0x00`.
We do log all incoming/outgoing messages, including `TxAddInput`, but
the `toString()` prints the whole serialized tx, not the txid, making
grepping more difficult.
Co-authored-by: Bastien Teinturier <31281497+t-bast@users.noreply.github.com>
Sending a payment to a blinded route that starts at our node can be tricky, we remove this problem by unwrapping such routes before starting the payment flow.
---------
Co-authored-by: t-bast <bastien@acinq.fr>
https://github.com/lightning/bolts/pull/1163 makes the channel update in
onion failures optional. One reason for this change is that it can be a
privacy issue: by applying a `channel_update` received from an payment
attempt, you may reveal that you are the sender. Another reason is that
some nodes have been omitting that field for years (which was arguably
a bug), and it's better to be able to correctly handle such failures.
To save space in the offer, we can skip the node id for offers that use blinded paths.
The node id used to sign the invoice will be the last blinded node id of the path used to request the invoice.
We also make the description optional for offers without amount.
Bitcoin Core 26.1 contains ancestor-aware funding: it will automatically
fetch unconfirmed ancestors during funding and adapt the fee to apply
the target feerate to the whole unconfirmed package.
We had custom code to implement this entirely in eclair, which we can
now remove.
https://github.com/lightning/bolts/pull/1092 initially made the
`gossip_queries` feature mandatory and assumed: however it generally
doesn't make sense for mobile wallets. It was thus relaxed in the last
commits of this BOLTs PR, so we revert our change to `mandatory` to
make this optional and avoid sending gossip queries to nodes who don't
activate the feature.
If the peer had `option_shutdown_anysegwit` enabled when they initially sent their `remoteScriptPubkey`, but reconnected later with `option_shutdown_anysegwit` disabled, then `isValidFinalScriptPubkey` may not pass anymore.
