1 // This file is Copyright its original authors, visible in version control
4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
7 // You may not use this file except in accordance with one or both of these
10 //! Various utilities to assemble claimable outpoints in package of one or more transactions. Those
11 //! packages are attached metadata, guiding their aggregable or fee-bumping re-schedule. This file
12 //! also includes witness weight computation and fee computation methods.
14 use bitcoin::blockdata::constants::WITNESS_SCALE_FACTOR;
15 use bitcoin::blockdata::transaction::{TxOut,TxIn, Transaction, SigHashType};
16 use bitcoin::blockdata::transaction::OutPoint as BitcoinOutPoint;
17 use bitcoin::blockdata::script::Script;
19 use bitcoin::hash_types::Txid;
21 use bitcoin::secp256k1::key::{SecretKey,PublicKey};
23 use ln::PaymentPreimage;
24 use ln::chan_utils::{TxCreationKeys, HTLCOutputInCommitment};
26 use ln::msgs::DecodeError;
27 use chain::chaininterface::{FeeEstimator, ConfirmationTarget, MIN_RELAY_FEE_SAT_PER_1000_WEIGHT};
28 use chain::keysinterface::Sign;
29 use chain::onchaintx::OnchainTxHandler;
31 use util::logger::Logger;
32 use util::ser::{Readable, Writer, Writeable};
40 const MAX_ALLOC_SIZE: usize = 64*1024;
43 // number_of_witness_elements + sig_length + revocation_sig + pubkey_length + revocationpubkey + witness_script_length + witness_script
44 pub(crate) const WEIGHT_REVOKED_OFFERED_HTLC: u64 = 1 + 1 + 73 + 1 + 33 + 1 + 133;
45 // number_of_witness_elements + sig_length + revocation_sig + pubkey_length + revocationpubkey + witness_script_length + witness_script
46 pub(crate) const WEIGHT_REVOKED_RECEIVED_HTLC: u64 = 1 + 1 + 73 + 1 + 33 + 1 + 139;
47 // number_of_witness_elements + sig_length + counterpartyhtlc_sig + preimage_length + preimage + witness_script_length + witness_script
48 pub(crate) const WEIGHT_OFFERED_HTLC: u64 = 1 + 1 + 73 + 1 + 32 + 1 + 133;
49 // number_of_witness_elements + sig_length + revocation_sig + pubkey_length + revocationpubkey + witness_script_length + witness_script
50 pub(crate) const WEIGHT_RECEIVED_HTLC: u64 = 1 + 1 + 73 + 1 + 1 + 1 + 139;
51 // number_of_witness_elements + sig_length + revocation_sig + true_length + op_true + witness_script_length + witness_script
52 pub(crate) const WEIGHT_REVOKED_OUTPUT: u64 = 1 + 1 + 73 + 1 + 1 + 1 + 77;
54 /// Height delay at which transactions are fee-bumped/rebroadcasted with a low priority.
55 const LOW_FREQUENCY_BUMP_INTERVAL: u32 = 15;
56 /// Height delay at which transactions are fee-bumped/rebroadcasted with a middle priority.
57 const MIDDLE_FREQUENCY_BUMP_INTERVAL: u32 = 3;
58 /// Height delay at which transactions are fee-bumped/rebroadcasted with a high priority.
59 const HIGH_FREQUENCY_BUMP_INTERVAL: u32 = 1;
61 /// A struct to describe a revoked output and corresponding information to generate a solving
62 /// witness spending a commitment `to_local` output or a second-stage HTLC transaction output.
64 /// CSV and pubkeys are used as part of a witnessScript redeeming a balance output, amount is used
65 /// as part of the signature hash and revocation secret to generate a satisfying witness.
66 #[derive(Clone, PartialEq)]
67 pub(crate) struct RevokedOutput {
68 per_commitment_point: PublicKey,
69 counterparty_delayed_payment_base_key: PublicKey,
70 counterparty_htlc_base_key: PublicKey,
71 per_commitment_key: SecretKey,
74 on_counterparty_tx_csv: u16,
78 pub(crate) fn build(per_commitment_point: PublicKey, counterparty_delayed_payment_base_key: PublicKey, counterparty_htlc_base_key: PublicKey, per_commitment_key: SecretKey, amount: u64, on_counterparty_tx_csv: u16) -> Self {
81 counterparty_delayed_payment_base_key,
82 counterparty_htlc_base_key,
84 weight: WEIGHT_REVOKED_OUTPUT,
86 on_counterparty_tx_csv
91 impl_writeable_tlv_based!(RevokedOutput, {
92 (0, per_commitment_point, required),
93 (2, counterparty_delayed_payment_base_key, required),
94 (4, counterparty_htlc_base_key, required),
95 (6, per_commitment_key, required),
96 (8, weight, required),
97 (10, amount, required),
98 (12, on_counterparty_tx_csv, required),
101 /// A struct to describe a revoked offered output and corresponding information to generate a
104 /// HTLCOuputInCommitment (hash timelock, direction) and pubkeys are used to generate a suitable
107 /// CSV is used as part of a witnessScript redeeming a balance output, amount is used as part
108 /// of the signature hash and revocation secret to generate a satisfying witness.
109 #[derive(Clone, PartialEq)]
110 pub(crate) struct RevokedHTLCOutput {
111 per_commitment_point: PublicKey,
112 counterparty_delayed_payment_base_key: PublicKey,
113 counterparty_htlc_base_key: PublicKey,
114 per_commitment_key: SecretKey,
117 htlc: HTLCOutputInCommitment,
120 impl RevokedHTLCOutput {
121 pub(crate) fn build(per_commitment_point: PublicKey, counterparty_delayed_payment_base_key: PublicKey, counterparty_htlc_base_key: PublicKey, per_commitment_key: SecretKey, amount: u64, htlc: HTLCOutputInCommitment) -> Self {
122 let weight = if htlc.offered { WEIGHT_REVOKED_OFFERED_HTLC } else { WEIGHT_REVOKED_RECEIVED_HTLC };
124 per_commitment_point,
125 counterparty_delayed_payment_base_key,
126 counterparty_htlc_base_key,
135 impl_writeable_tlv_based!(RevokedHTLCOutput, {
136 (0, per_commitment_point, required),
137 (2, counterparty_delayed_payment_base_key, required),
138 (4, counterparty_htlc_base_key, required),
139 (6, per_commitment_key, required),
140 (8, weight, required),
141 (10, amount, required),
142 (12, htlc, required),
145 /// A struct to describe a HTLC output on a counterparty commitment transaction.
147 /// HTLCOutputInCommitment (hash, timelock, directon) and pubkeys are used to generate a suitable
150 /// The preimage is used as part of the witness.
151 #[derive(Clone, PartialEq)]
152 pub(crate) struct CounterpartyOfferedHTLCOutput {
153 per_commitment_point: PublicKey,
154 counterparty_delayed_payment_base_key: PublicKey,
155 counterparty_htlc_base_key: PublicKey,
156 preimage: PaymentPreimage,
157 htlc: HTLCOutputInCommitment
160 impl CounterpartyOfferedHTLCOutput {
161 pub(crate) fn build(per_commitment_point: PublicKey, counterparty_delayed_payment_base_key: PublicKey, counterparty_htlc_base_key: PublicKey, preimage: PaymentPreimage, htlc: HTLCOutputInCommitment) -> Self {
162 CounterpartyOfferedHTLCOutput {
163 per_commitment_point,
164 counterparty_delayed_payment_base_key,
165 counterparty_htlc_base_key,
172 impl_writeable_tlv_based!(CounterpartyOfferedHTLCOutput, {
173 (0, per_commitment_point, required),
174 (2, counterparty_delayed_payment_base_key, required),
175 (4, counterparty_htlc_base_key, required),
176 (6, preimage, required),
180 /// A struct to describe a HTLC output on a counterparty commitment transaction.
182 /// HTLCOutputInCommitment (hash, timelock, directon) and pubkeys are used to generate a suitable
184 #[derive(Clone, PartialEq)]
185 pub(crate) struct CounterpartyReceivedHTLCOutput {
186 per_commitment_point: PublicKey,
187 counterparty_delayed_payment_base_key: PublicKey,
188 counterparty_htlc_base_key: PublicKey,
189 htlc: HTLCOutputInCommitment
192 impl CounterpartyReceivedHTLCOutput {
193 pub(crate) fn build(per_commitment_point: PublicKey, counterparty_delayed_payment_base_key: PublicKey, counterparty_htlc_base_key: PublicKey, htlc: HTLCOutputInCommitment) -> Self {
194 CounterpartyReceivedHTLCOutput {
195 per_commitment_point,
196 counterparty_delayed_payment_base_key,
197 counterparty_htlc_base_key,
203 impl_writeable_tlv_based!(CounterpartyReceivedHTLCOutput, {
204 (0, per_commitment_point, required),
205 (2, counterparty_delayed_payment_base_key, required),
206 (4, counterparty_htlc_base_key, required),
210 /// A struct to describe a HTLC output on holder commitment transaction.
212 /// Either offered or received, the amount is always used as part of the bip143 sighash.
213 /// Preimage is only included as part of the witness in former case.
214 #[derive(Clone, PartialEq)]
215 pub(crate) struct HolderHTLCOutput {
216 preimage: Option<PaymentPreimage>,
218 /// Defaults to 0 for HTLC-Success transactions, which have no expiry
222 impl HolderHTLCOutput {
223 pub(crate) fn build_offered(amount: u64, cltv_expiry: u32) -> Self {
231 pub(crate) fn build_accepted(preimage: PaymentPreimage, amount: u64) -> Self {
233 preimage: Some(preimage),
240 impl_writeable_tlv_based!(HolderHTLCOutput, {
241 (0, amount, required),
242 (2, cltv_expiry, required),
243 (4, preimage, option)
246 /// A struct to describe the channel output on the funding transaction.
248 /// witnessScript is used as part of the witness redeeming the funding utxo.
249 #[derive(Clone, PartialEq)]
250 pub(crate) struct HolderFundingOutput {
251 funding_redeemscript: Script,
254 impl HolderFundingOutput {
255 pub(crate) fn build(funding_redeemscript: Script) -> Self {
256 HolderFundingOutput {
257 funding_redeemscript,
262 impl_writeable_tlv_based!(HolderFundingOutput, {
263 (0, funding_redeemscript, required),
266 /// A wrapper encapsulating all in-protocol differing outputs types.
268 /// The generic API offers access to an outputs common attributes or allow transformation such as
269 /// finalizing an input claiming the output.
270 #[derive(Clone, PartialEq)]
271 pub(crate) enum PackageSolvingData {
272 RevokedOutput(RevokedOutput),
273 RevokedHTLCOutput(RevokedHTLCOutput),
274 CounterpartyOfferedHTLCOutput(CounterpartyOfferedHTLCOutput),
275 CounterpartyReceivedHTLCOutput(CounterpartyReceivedHTLCOutput),
276 HolderHTLCOutput(HolderHTLCOutput),
277 HolderFundingOutput(HolderFundingOutput),
280 impl PackageSolvingData {
281 fn amount(&self) -> u64 {
282 let amt = match self {
283 PackageSolvingData::RevokedOutput(ref outp) => { outp.amount },
284 PackageSolvingData::RevokedHTLCOutput(ref outp) => { outp.amount },
285 PackageSolvingData::CounterpartyOfferedHTLCOutput(ref outp) => { outp.htlc.amount_msat / 1000 },
286 PackageSolvingData::CounterpartyReceivedHTLCOutput(ref outp) => { outp.htlc.amount_msat / 1000 },
287 // Note: Currently, amounts of holder outputs spending witnesses aren't used
288 // as we can't malleate spending package to increase their feerate. This
289 // should change with the remaining anchor output patchset.
290 PackageSolvingData::HolderHTLCOutput(..) => { unreachable!() },
291 PackageSolvingData::HolderFundingOutput(..) => { unreachable!() },
295 fn weight(&self) -> usize {
296 let weight = match self {
297 PackageSolvingData::RevokedOutput(ref outp) => { outp.weight as usize },
298 PackageSolvingData::RevokedHTLCOutput(ref outp) => { outp.weight as usize },
299 PackageSolvingData::CounterpartyOfferedHTLCOutput(..) => { WEIGHT_OFFERED_HTLC as usize },
300 PackageSolvingData::CounterpartyReceivedHTLCOutput(..) => { WEIGHT_RECEIVED_HTLC as usize },
301 // Note: Currently, weights of holder outputs spending witnesses aren't used
302 // as we can't malleate spending package to increase their feerate. This
303 // should change with the remaining anchor output patchset.
304 PackageSolvingData::HolderHTLCOutput(..) => { unreachable!() },
305 PackageSolvingData::HolderFundingOutput(..) => { unreachable!() },
309 fn is_compatible(&self, input: &PackageSolvingData) -> bool {
311 PackageSolvingData::RevokedOutput(..) => {
313 PackageSolvingData::RevokedHTLCOutput(..) => { true },
314 PackageSolvingData::RevokedOutput(..) => { true },
318 PackageSolvingData::RevokedHTLCOutput(..) => {
320 PackageSolvingData::RevokedOutput(..) => { true },
321 PackageSolvingData::RevokedHTLCOutput(..) => { true },
325 _ => { mem::discriminant(self) == mem::discriminant(&input) }
328 fn finalize_input<Signer: Sign>(&self, bumped_tx: &mut Transaction, i: usize, onchain_handler: &mut OnchainTxHandler<Signer>) -> bool {
330 PackageSolvingData::RevokedOutput(ref outp) => {
331 if let Ok(chan_keys) = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint) {
332 let witness_script = chan_utils::get_revokeable_redeemscript(&chan_keys.revocation_key, outp.on_counterparty_tx_csv, &chan_keys.broadcaster_delayed_payment_key);
333 //TODO: should we panic on signer failure ?
334 if let Ok(sig) = onchain_handler.signer.sign_justice_revoked_output(&bumped_tx, i, outp.amount, &outp.per_commitment_key, &onchain_handler.secp_ctx) {
335 bumped_tx.input[i].witness.push(sig.serialize_der().to_vec());
336 bumped_tx.input[i].witness[0].push(SigHashType::All as u8);
337 bumped_tx.input[i].witness.push(vec!(1));
338 bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
339 } else { return false; }
342 PackageSolvingData::RevokedHTLCOutput(ref outp) => {
343 if let Ok(chan_keys) = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint) {
344 let witness_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&outp.htlc, &chan_keys.broadcaster_htlc_key, &chan_keys.countersignatory_htlc_key, &chan_keys.revocation_key);
345 //TODO: should we panic on signer failure ?
346 if let Ok(sig) = onchain_handler.signer.sign_justice_revoked_htlc(&bumped_tx, i, outp.amount, &outp.per_commitment_key, &outp.htlc, &onchain_handler.secp_ctx) {
347 bumped_tx.input[i].witness.push(sig.serialize_der().to_vec());
348 bumped_tx.input[i].witness[0].push(SigHashType::All as u8);
349 bumped_tx.input[i].witness.push(chan_keys.revocation_key.clone().serialize().to_vec());
350 bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
351 } else { return false; }
354 PackageSolvingData::CounterpartyOfferedHTLCOutput(ref outp) => {
355 if let Ok(chan_keys) = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint) {
356 let witness_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&outp.htlc, &chan_keys.broadcaster_htlc_key, &chan_keys.countersignatory_htlc_key, &chan_keys.revocation_key);
358 if let Ok(sig) = onchain_handler.signer.sign_counterparty_htlc_transaction(&bumped_tx, i, &outp.htlc.amount_msat / 1000, &outp.per_commitment_point, &outp.htlc, &onchain_handler.secp_ctx) {
359 bumped_tx.input[i].witness.push(sig.serialize_der().to_vec());
360 bumped_tx.input[i].witness[0].push(SigHashType::All as u8);
361 bumped_tx.input[i].witness.push(outp.preimage.0.to_vec());
362 bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
366 PackageSolvingData::CounterpartyReceivedHTLCOutput(ref outp) => {
367 if let Ok(chan_keys) = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint) {
368 let witness_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&outp.htlc, &chan_keys.broadcaster_htlc_key, &chan_keys.countersignatory_htlc_key, &chan_keys.revocation_key);
370 bumped_tx.lock_time = outp.htlc.cltv_expiry; // Right now we don't aggregate time-locked transaction, if we do we should set lock_time before to avoid breaking hash computation
371 if let Ok(sig) = onchain_handler.signer.sign_counterparty_htlc_transaction(&bumped_tx, i, &outp.htlc.amount_msat / 1000, &outp.per_commitment_point, &outp.htlc, &onchain_handler.secp_ctx) {
372 bumped_tx.input[i].witness.push(sig.serialize_der().to_vec());
373 bumped_tx.input[i].witness[0].push(SigHashType::All as u8);
374 // Due to BIP146 (MINIMALIF) this must be a zero-length element to relay.
375 bumped_tx.input[i].witness.push(vec![]);
376 bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
380 _ => { panic!("API Error!"); }
384 fn get_finalized_tx<Signer: Sign>(&self, outpoint: &BitcoinOutPoint, onchain_handler: &mut OnchainTxHandler<Signer>) -> Option<Transaction> {
386 PackageSolvingData::HolderHTLCOutput(ref outp) => { return onchain_handler.get_fully_signed_htlc_tx(outpoint, &outp.preimage); }
387 PackageSolvingData::HolderFundingOutput(ref outp) => { return Some(onchain_handler.get_fully_signed_holder_tx(&outp.funding_redeemscript)); }
388 _ => { panic!("API Error!"); }
391 fn absolute_tx_timelock(&self, output_conf_height: u32) -> u32 {
392 // Get the absolute timelock at which this output can be spent given the height at which
393 // this output was confirmed. We use `output_conf_height + 1` as a safe default as we can
394 // be confirmed in the next block and transactions with time lock `current_height + 1`
396 let absolute_timelock = match self {
397 PackageSolvingData::RevokedOutput(_) => output_conf_height + 1,
398 PackageSolvingData::RevokedHTLCOutput(_) => output_conf_height + 1,
399 PackageSolvingData::CounterpartyOfferedHTLCOutput(_) => output_conf_height + 1,
400 PackageSolvingData::CounterpartyReceivedHTLCOutput(ref outp) => cmp::max(outp.htlc.cltv_expiry, output_conf_height + 1),
401 PackageSolvingData::HolderHTLCOutput(ref outp) => cmp::max(outp.cltv_expiry, output_conf_height + 1),
402 PackageSolvingData::HolderFundingOutput(_) => output_conf_height + 1,
408 impl_writeable_tlv_based_enum!(PackageSolvingData, ;
410 (1, RevokedHTLCOutput),
411 (2, CounterpartyOfferedHTLCOutput),
412 (3, CounterpartyReceivedHTLCOutput),
413 (4, HolderHTLCOutput),
414 (5, HolderFundingOutput),
417 /// A malleable package might be aggregated with other packages to save on fees.
418 /// A untractable package has been counter-signed and aggregable will break cached counterparty
420 #[derive(Clone, PartialEq)]
421 pub(crate) enum PackageMalleability {
426 /// A structure to describe a package content that is generated by ChannelMonitor and
427 /// used by OnchainTxHandler to generate and broadcast transactions settling onchain claims.
429 /// A package is defined as one or more transactions claiming onchain outputs in reaction
430 /// to confirmation of a channel transaction. Those packages might be aggregated to save on
431 /// fees, if satisfaction of outputs's witnessScript let's us do so.
433 /// As packages are time-sensitive, we fee-bump and rebroadcast them at scheduled intervals.
434 /// Failing to confirm a package translate as a loss of funds for the user.
435 #[derive(Clone, PartialEq)]
436 pub struct PackageTemplate {
437 // List of onchain outputs and solving data to generate satisfying witnesses.
438 inputs: Vec<(BitcoinOutPoint, PackageSolvingData)>,
439 // Packages are deemed as malleable if we have local knwoledge of at least one set of
440 // private keys yielding a satisfying witnesses. Malleability implies that we can aggregate
441 // packages among them to save on fees or rely on RBF to bump their feerates.
442 // Untractable packages have been counter-signed and thus imply that we can't aggregate
443 // them without breaking signatures. Fee-bumping strategy will also rely on CPFP.
444 malleability: PackageMalleability,
445 // Block height after which the earlier-output belonging to this package is mature for a
446 // competing claim by the counterparty. As our chain tip becomes nearer from the timelock,
447 // the fee-bumping frequency will increase. See `OnchainTxHandler::get_height_timer`.
448 soonest_conf_deadline: u32,
449 // Determines if this package can be aggregated.
450 // Timelocked outputs belonging to the same transaction might have differing
451 // satisfying heights. Picking up the later height among the output set would be a valid
452 // aggregable strategy but it comes with at least 2 trade-offs :
453 // * earlier-output fund are going to take longer to come back
454 // * CLTV delta backing up a corresponding HTLC on an upstream channel could be swallowed
455 // by the requirement of the later-output part of the set
456 // For now, we mark such timelocked outputs as non-aggregable, though we might introduce
457 // smarter aggregable strategy in the future.
459 // Cache of package feerate committed at previous (re)broadcast. If bumping resources
460 // (either claimed output value or external utxo), it will keep increasing until holder
461 // or counterparty successful claim.
462 feerate_previous: u64,
463 // Cache of next height at which fee-bumping and rebroadcast will be attempted. In
464 // the future, we might abstract it to an observed mempool fluctuation.
465 height_timer: Option<u32>,
466 // Confirmation height of the claimed outputs set transaction. In case of reorg reaching
467 // it, we wipe out and forget the package.
468 height_original: u32,
471 impl PackageTemplate {
472 pub(crate) fn is_malleable(&self) -> bool {
473 self.malleability == PackageMalleability::Malleable
475 pub(crate) fn timelock(&self) -> u32 {
476 self.soonest_conf_deadline
478 pub(crate) fn aggregable(&self) -> bool {
481 pub(crate) fn set_feerate(&mut self, new_feerate: u64) {
482 self.feerate_previous = new_feerate;
484 pub(crate) fn timer(&self) -> Option<u32> {
485 if let Some(ref timer) = self.height_timer {
490 pub(crate) fn set_timer(&mut self, new_timer: Option<u32>) {
491 self.height_timer = new_timer;
493 pub(crate) fn outpoints(&self) -> Vec<&BitcoinOutPoint> {
494 self.inputs.iter().map(|(o, _)| o).collect()
496 pub(crate) fn split_package(&mut self, split_outp: &BitcoinOutPoint) -> Option<PackageTemplate> {
497 match self.malleability {
498 PackageMalleability::Malleable => {
499 let mut split_package = None;
500 let timelock = self.soonest_conf_deadline;
501 let aggregable = self.aggregable;
502 let feerate_previous = self.feerate_previous;
503 let height_timer = self.height_timer;
504 let height_original = self.height_original;
505 self.inputs.retain(|outp| {
506 if *split_outp == outp.0 {
507 split_package = Some(PackageTemplate {
508 inputs: vec![(outp.0, outp.1.clone())],
509 malleability: PackageMalleability::Malleable,
510 soonest_conf_deadline: timelock,
520 return split_package;
523 // Note, we may try to split on remote transaction for
524 // which we don't have a competing one (HTLC-Success before
525 // timelock expiration). This explain we don't panic!
526 // We should refactor OnchainTxHandler::block_connected to
527 // only test equality on competing claims.
532 pub(crate) fn merge_package(&mut self, mut merge_from: PackageTemplate) {
533 assert_eq!(self.height_original, merge_from.height_original);
534 if self.malleability == PackageMalleability::Untractable || merge_from.malleability == PackageMalleability::Untractable {
535 panic!("Merging template on untractable packages");
537 if !self.aggregable || !merge_from.aggregable {
538 panic!("Merging non aggregatable packages");
540 if let Some((_, lead_input)) = self.inputs.first() {
541 for (_, v) in merge_from.inputs.iter() {
542 if !lead_input.is_compatible(v) { panic!("Merging outputs from differing types !"); }
544 } else { panic!("Merging template on an empty package"); }
545 for (k, v) in merge_from.inputs.drain(..) {
546 self.inputs.push((k, v));
548 //TODO: verify coverage and sanity?
549 if self.soonest_conf_deadline > merge_from.soonest_conf_deadline {
550 self.soonest_conf_deadline = merge_from.soonest_conf_deadline;
552 if self.feerate_previous > merge_from.feerate_previous {
553 self.feerate_previous = merge_from.feerate_previous;
555 self.height_timer = cmp::min(self.height_timer, merge_from.height_timer);
557 /// Gets the amount of all outptus being spent by this package, only valid for malleable
559 fn package_amount(&self) -> u64 {
561 for (_, outp) in self.inputs.iter() {
562 amounts += outp.amount();
566 pub(crate) fn package_timelock(&self) -> u32 {
567 self.inputs.iter().map(|(_, outp)| outp.absolute_tx_timelock(self.height_original))
568 .max().expect("There must always be at least one output to spend in a PackageTemplate")
570 pub(crate) fn package_weight(&self, destination_script: &Script) -> usize {
571 let mut inputs_weight = 0;
572 let mut witnesses_weight = 2; // count segwit flags
573 for (_, outp) in self.inputs.iter() {
574 // previous_out_point: 36 bytes ; var_int: 1 byte ; sequence: 4 bytes
575 inputs_weight += 41 * WITNESS_SCALE_FACTOR;
576 witnesses_weight += outp.weight();
578 // version: 4 bytes ; count_tx_in: 1 byte ; count_tx_out: 1 byte ; lock_time: 4 bytes
579 let transaction_weight = 10 * WITNESS_SCALE_FACTOR;
580 // value: 8 bytes ; var_int: 1 byte ; pk_script: `destination_script.len()`
581 let output_weight = (8 + 1 + destination_script.len()) * WITNESS_SCALE_FACTOR;
582 inputs_weight + witnesses_weight + transaction_weight + output_weight
584 pub(crate) fn finalize_package<L: Deref, Signer: Sign>(&self, onchain_handler: &mut OnchainTxHandler<Signer>, value: u64, destination_script: Script, logger: &L) -> Option<Transaction>
585 where L::Target: Logger,
587 match self.malleability {
588 PackageMalleability::Malleable => {
589 let mut bumped_tx = Transaction {
594 script_pubkey: destination_script,
598 for (outpoint, _) in self.inputs.iter() {
599 bumped_tx.input.push(TxIn {
600 previous_output: *outpoint,
601 script_sig: Script::new(),
602 sequence: 0xfffffffd,
606 for (i, (outpoint, out)) in self.inputs.iter().enumerate() {
607 log_debug!(logger, "Adding claiming input for outpoint {}:{}", outpoint.txid, outpoint.vout);
608 if !out.finalize_input(&mut bumped_tx, i, onchain_handler) { return None; }
610 log_debug!(logger, "Finalized transaction {} ready to broadcast", bumped_tx.txid());
611 return Some(bumped_tx);
613 PackageMalleability::Untractable => {
614 debug_assert_eq!(value, 0, "value is ignored for non-malleable packages, should be zero to ensure callsites are correct");
615 if let Some((outpoint, outp)) = self.inputs.first() {
616 if let Some(final_tx) = outp.get_finalized_tx(outpoint, onchain_handler) {
617 log_debug!(logger, "Adding claiming input for outpoint {}:{}", outpoint.txid, outpoint.vout);
618 log_debug!(logger, "Finalized transaction {} ready to broadcast", final_tx.txid());
619 return Some(final_tx);
622 } else { panic!("API Error: Package must not be inputs empty"); }
626 /// In LN, output claimed are time-sensitive, which means we have to spend them before reaching some timelock expiration. At in-channel
627 /// output detection, we generate a first version of a claim tx and associate to it a height timer. A height timer is an absolute block
628 /// height that once reached we should generate a new bumped "version" of the claim tx to be sure that we safely claim outputs before
629 /// that our counterparty can do so. If timelock expires soon, height timer is going to be scaled down in consequence to increase
630 /// frequency of the bump and so increase our bets of success.
631 pub(crate) fn get_height_timer(&self, current_height: u32) -> u32 {
632 if self.soonest_conf_deadline <= current_height + MIDDLE_FREQUENCY_BUMP_INTERVAL {
633 return current_height + HIGH_FREQUENCY_BUMP_INTERVAL
634 } else if self.soonest_conf_deadline - current_height <= LOW_FREQUENCY_BUMP_INTERVAL {
635 return current_height + MIDDLE_FREQUENCY_BUMP_INTERVAL
637 current_height + LOW_FREQUENCY_BUMP_INTERVAL
640 /// Returns value in satoshis to be included as package outgoing output amount and feerate
641 /// which was used to generate the value. Will not return less than `dust_limit_sats` for the
643 pub(crate) fn compute_package_output<F: Deref, L: Deref>(&self, predicted_weight: usize, dust_limit_sats: u64, fee_estimator: &F, logger: &L) -> Option<(u64, u64)>
644 where F::Target: FeeEstimator,
647 debug_assert!(self.malleability == PackageMalleability::Malleable, "The package output is fixed for non-malleable packages");
648 let input_amounts = self.package_amount();
649 assert!(dust_limit_sats as i64 > 0, "Output script must be broadcastable/have a 'real' dust limit.");
650 // If old feerate is 0, first iteration of this claim, use normal fee calculation
651 if self.feerate_previous != 0 {
652 if let Some((new_fee, feerate)) = feerate_bump(predicted_weight, input_amounts, self.feerate_previous, fee_estimator, logger) {
653 return Some((cmp::max(input_amounts as i64 - new_fee as i64, dust_limit_sats as i64) as u64, feerate));
656 if let Some((new_fee, feerate)) = compute_fee_from_spent_amounts(input_amounts, predicted_weight, fee_estimator, logger) {
657 return Some((cmp::max(input_amounts as i64 - new_fee as i64, dust_limit_sats as i64) as u64, feerate));
662 pub (crate) fn build_package(txid: Txid, vout: u32, input_solving_data: PackageSolvingData, soonest_conf_deadline: u32, aggregable: bool, height_original: u32) -> Self {
663 let malleability = match input_solving_data {
664 PackageSolvingData::RevokedOutput(..) => { PackageMalleability::Malleable },
665 PackageSolvingData::RevokedHTLCOutput(..) => { PackageMalleability::Malleable },
666 PackageSolvingData::CounterpartyOfferedHTLCOutput(..) => { PackageMalleability::Malleable },
667 PackageSolvingData::CounterpartyReceivedHTLCOutput(..) => { PackageMalleability::Malleable },
668 PackageSolvingData::HolderHTLCOutput(..) => { PackageMalleability::Untractable },
669 PackageSolvingData::HolderFundingOutput(..) => { PackageMalleability::Untractable },
671 let mut inputs = Vec::with_capacity(1);
672 inputs.push((BitcoinOutPoint { txid, vout }, input_solving_data));
676 soonest_conf_deadline,
685 impl Writeable for PackageTemplate {
686 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
687 writer.write_all(&byte_utils::be64_to_array(self.inputs.len() as u64))?;
688 for (ref outpoint, ref rev_outp) in self.inputs.iter() {
689 outpoint.write(writer)?;
690 rev_outp.write(writer)?;
692 write_tlv_fields!(writer, {
693 (0, self.soonest_conf_deadline, required),
694 (2, self.feerate_previous, required),
695 (4, self.height_original, required),
696 (6, self.height_timer, option)
702 impl Readable for PackageTemplate {
703 fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
704 let inputs_count = <u64 as Readable>::read(reader)?;
705 let mut inputs: Vec<(BitcoinOutPoint, PackageSolvingData)> = Vec::with_capacity(cmp::min(inputs_count as usize, MAX_ALLOC_SIZE / 128));
706 for _ in 0..inputs_count {
707 let outpoint = Readable::read(reader)?;
708 let rev_outp = Readable::read(reader)?;
709 inputs.push((outpoint, rev_outp));
711 let (malleability, aggregable) = if let Some((_, lead_input)) = inputs.first() {
713 PackageSolvingData::RevokedOutput(..) => { (PackageMalleability::Malleable, true) },
714 PackageSolvingData::RevokedHTLCOutput(..) => { (PackageMalleability::Malleable, true) },
715 PackageSolvingData::CounterpartyOfferedHTLCOutput(..) => { (PackageMalleability::Malleable, true) },
716 PackageSolvingData::CounterpartyReceivedHTLCOutput(..) => { (PackageMalleability::Malleable, false) },
717 PackageSolvingData::HolderHTLCOutput(..) => { (PackageMalleability::Untractable, false) },
718 PackageSolvingData::HolderFundingOutput(..) => { (PackageMalleability::Untractable, false) },
720 } else { return Err(DecodeError::InvalidValue); };
721 let mut soonest_conf_deadline = 0;
722 let mut feerate_previous = 0;
723 let mut height_timer = None;
724 let mut height_original = 0;
725 read_tlv_fields!(reader, {
726 (0, soonest_conf_deadline, required),
727 (2, feerate_previous, required),
728 (4, height_original, required),
729 (6, height_timer, option),
734 soonest_conf_deadline,
743 /// Attempt to propose a bumping fee for a transaction from its spent output's values and predicted
744 /// weight. We start with the highest priority feerate returned by the node's fee estimator then
745 /// fall-back to lower priorities until we have enough value available to suck from.
747 /// If the proposed fee is less than the available spent output's values, we return the proposed
748 /// fee and the corresponding updated feerate. If the proposed fee is equal or more than the
749 /// available spent output's values, we return nothing
750 fn compute_fee_from_spent_amounts<F: Deref, L: Deref>(input_amounts: u64, predicted_weight: usize, fee_estimator: &F, logger: &L) -> Option<(u64, u64)>
751 where F::Target: FeeEstimator,
754 let mut updated_feerate = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::HighPriority) as u64;
755 let mut fee = updated_feerate * (predicted_weight as u64) / 1000;
756 if input_amounts <= fee {
757 updated_feerate = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Normal) as u64;
758 fee = updated_feerate * (predicted_weight as u64) / 1000;
759 if input_amounts <= fee {
760 updated_feerate = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Background) as u64;
761 fee = updated_feerate * (predicted_weight as u64) / 1000;
762 if input_amounts <= fee {
763 log_error!(logger, "Failed to generate an on-chain punishment tx as even low priority fee ({} sat) was more than the entire claim balance ({} sat)",
767 log_warn!(logger, "Used low priority fee for on-chain punishment tx as high priority fee was more than the entire claim balance ({} sat)",
769 Some((fee, updated_feerate))
772 log_warn!(logger, "Used medium priority fee for on-chain punishment tx as high priority fee was more than the entire claim balance ({} sat)",
774 Some((fee, updated_feerate))
777 Some((fee, updated_feerate))
781 /// Attempt to propose a bumping fee for a transaction from its spent output's values and predicted
782 /// weight. If feerates proposed by the fee-estimator have been increasing since last fee-bumping
783 /// attempt, use them. Otherwise, blindly bump the feerate by 25% of the previous feerate. We also
784 /// verify that those bumping heuristics respect BIP125 rules 3) and 4) and if required adjust
785 /// the new fee to meet the RBF policy requirement.
786 fn feerate_bump<F: Deref, L: Deref>(predicted_weight: usize, input_amounts: u64, previous_feerate: u64, fee_estimator: &F, logger: &L) -> Option<(u64, u64)>
787 where F::Target: FeeEstimator,
790 // If old feerate inferior to actual one given back by Fee Estimator, use it to compute new fee...
791 let new_fee = if let Some((new_fee, _)) = compute_fee_from_spent_amounts(input_amounts, predicted_weight, fee_estimator, logger) {
792 let updated_feerate = new_fee / (predicted_weight as u64 * 1000);
793 if updated_feerate > previous_feerate {
796 // ...else just increase the previous feerate by 25% (because that's a nice number)
797 let new_fee = previous_feerate * (predicted_weight as u64) / 750;
798 if input_amounts <= new_fee {
799 log_warn!(logger, "Can't 25% bump new claiming tx, amount {} is too small", input_amounts);
805 log_warn!(logger, "Can't new-estimation bump new claiming tx, amount {} is too small", input_amounts);
809 let previous_fee = previous_feerate * (predicted_weight as u64) / 1000;
810 let min_relay_fee = MIN_RELAY_FEE_SAT_PER_1000_WEIGHT * (predicted_weight as u64) / 1000;
811 // BIP 125 Opt-in Full Replace-by-Fee Signaling
812 // * 3. The replacement transaction pays an absolute fee of at least the sum paid by the original transactions.
813 // * 4. The replacement transaction must also pay for its own bandwidth at or above the rate set by the node's minimum relay fee setting.
814 let new_fee = if new_fee < previous_fee + min_relay_fee {
815 new_fee + previous_fee + min_relay_fee - new_fee
819 Some((new_fee, new_fee * 1000 / (predicted_weight as u64)))
824 use chain::package::{CounterpartyReceivedHTLCOutput, HolderHTLCOutput, PackageTemplate, PackageSolvingData, RevokedOutput, WEIGHT_REVOKED_OUTPUT};
826 use ln::chan_utils::HTLCOutputInCommitment;
827 use ln::{PaymentPreimage, PaymentHash};
829 use bitcoin::blockdata::constants::WITNESS_SCALE_FACTOR;
830 use bitcoin::blockdata::script::Script;
831 use bitcoin::blockdata::transaction::OutPoint as BitcoinOutPoint;
833 use bitcoin::hashes::hex::FromHex;
835 use bitcoin::secp256k1::key::{PublicKey,SecretKey};
836 use bitcoin::secp256k1::Secp256k1;
838 macro_rules! dumb_revk_output {
839 ($secp_ctx: expr) => {
841 let dumb_scalar = SecretKey::from_slice(&hex::decode("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
842 let dumb_point = PublicKey::from_secret_key(&$secp_ctx, &dumb_scalar);
843 PackageSolvingData::RevokedOutput(RevokedOutput::build(dumb_point, dumb_point, dumb_point, dumb_scalar, 0, 0))
848 macro_rules! dumb_counterparty_output {
849 ($secp_ctx: expr, $amt: expr) => {
851 let dumb_scalar = SecretKey::from_slice(&hex::decode("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
852 let dumb_point = PublicKey::from_secret_key(&$secp_ctx, &dumb_scalar);
853 let hash = PaymentHash([1; 32]);
854 let htlc = HTLCOutputInCommitment { offered: true, amount_msat: $amt, cltv_expiry: 0, payment_hash: hash, transaction_output_index: None };
855 PackageSolvingData::CounterpartyReceivedHTLCOutput(CounterpartyReceivedHTLCOutput::build(dumb_point, dumb_point, dumb_point, htlc))
860 macro_rules! dumb_htlc_output {
863 let preimage = PaymentPreimage([2;32]);
864 PackageSolvingData::HolderHTLCOutput(HolderHTLCOutput::build_accepted(preimage, 0))
871 fn test_package_differing_heights() {
872 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
873 let secp_ctx = Secp256k1::new();
874 let revk_outp = dumb_revk_output!(secp_ctx);
876 let mut package_one_hundred = PackageTemplate::build_package(txid, 0, revk_outp.clone(), 1000, true, 100);
877 let package_two_hundred = PackageTemplate::build_package(txid, 1, revk_outp.clone(), 1000, true, 200);
878 package_one_hundred.merge_package(package_two_hundred);
883 fn test_package_untractable_merge_to() {
884 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
885 let secp_ctx = Secp256k1::new();
886 let revk_outp = dumb_revk_output!(secp_ctx);
887 let htlc_outp = dumb_htlc_output!();
889 let mut untractable_package = PackageTemplate::build_package(txid, 0, revk_outp.clone(), 1000, true, 100);
890 let malleable_package = PackageTemplate::build_package(txid, 1, htlc_outp.clone(), 1000, true, 100);
891 untractable_package.merge_package(malleable_package);
896 fn test_package_untractable_merge_from() {
897 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
898 let secp_ctx = Secp256k1::new();
899 let htlc_outp = dumb_htlc_output!();
900 let revk_outp = dumb_revk_output!(secp_ctx);
902 let mut malleable_package = PackageTemplate::build_package(txid, 0, htlc_outp.clone(), 1000, true, 100);
903 let untractable_package = PackageTemplate::build_package(txid, 1, revk_outp.clone(), 1000, true, 100);
904 malleable_package.merge_package(untractable_package);
909 fn test_package_noaggregation_to() {
910 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
911 let secp_ctx = Secp256k1::new();
912 let revk_outp = dumb_revk_output!(secp_ctx);
914 let mut noaggregation_package = PackageTemplate::build_package(txid, 0, revk_outp.clone(), 1000, false, 100);
915 let aggregation_package = PackageTemplate::build_package(txid, 1, revk_outp.clone(), 1000, true, 100);
916 noaggregation_package.merge_package(aggregation_package);
921 fn test_package_noaggregation_from() {
922 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
923 let secp_ctx = Secp256k1::new();
924 let revk_outp = dumb_revk_output!(secp_ctx);
926 let mut aggregation_package = PackageTemplate::build_package(txid, 0, revk_outp.clone(), 1000, true, 100);
927 let noaggregation_package = PackageTemplate::build_package(txid, 1, revk_outp.clone(), 1000, false, 100);
928 aggregation_package.merge_package(noaggregation_package);
933 fn test_package_empty() {
934 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
935 let secp_ctx = Secp256k1::new();
936 let revk_outp = dumb_revk_output!(secp_ctx);
938 let mut empty_package = PackageTemplate::build_package(txid, 0, revk_outp.clone(), 1000, true, 100);
939 empty_package.inputs = vec![];
940 let package = PackageTemplate::build_package(txid, 1, revk_outp.clone(), 1000, true, 100);
941 empty_package.merge_package(package);
946 fn test_package_differing_categories() {
947 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
948 let secp_ctx = Secp256k1::new();
949 let revk_outp = dumb_revk_output!(secp_ctx);
950 let counterparty_outp = dumb_counterparty_output!(secp_ctx, 0);
952 let mut revoked_package = PackageTemplate::build_package(txid, 0, revk_outp, 1000, true, 100);
953 let counterparty_package = PackageTemplate::build_package(txid, 1, counterparty_outp, 1000, true, 100);
954 revoked_package.merge_package(counterparty_package);
958 fn test_package_split_malleable() {
959 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
960 let secp_ctx = Secp256k1::new();
961 let revk_outp_one = dumb_revk_output!(secp_ctx);
962 let revk_outp_two = dumb_revk_output!(secp_ctx);
963 let revk_outp_three = dumb_revk_output!(secp_ctx);
965 let mut package_one = PackageTemplate::build_package(txid, 0, revk_outp_one, 1000, true, 100);
966 let package_two = PackageTemplate::build_package(txid, 1, revk_outp_two, 1000, true, 100);
967 let package_three = PackageTemplate::build_package(txid, 2, revk_outp_three, 1000, true, 100);
969 package_one.merge_package(package_two);
970 package_one.merge_package(package_three);
971 assert_eq!(package_one.outpoints().len(), 3);
973 if let Some(split_package) = package_one.split_package(&BitcoinOutPoint { txid, vout: 1 }) {
974 // Packages attributes should be identical
975 assert!(split_package.is_malleable());
976 assert_eq!(split_package.soonest_conf_deadline, package_one.soonest_conf_deadline);
977 assert_eq!(split_package.aggregable, package_one.aggregable);
978 assert_eq!(split_package.feerate_previous, package_one.feerate_previous);
979 assert_eq!(split_package.height_timer, package_one.height_timer);
980 assert_eq!(split_package.height_original, package_one.height_original);
982 assert_eq!(package_one.outpoints().len(), 2);
986 fn test_package_split_untractable() {
987 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
988 let htlc_outp_one = dumb_htlc_output!();
990 let mut package_one = PackageTemplate::build_package(txid, 0, htlc_outp_one, 1000, true, 100);
991 let ret_split = package_one.split_package(&BitcoinOutPoint { txid, vout: 0});
992 assert!(ret_split.is_none());
996 fn test_package_timer() {
997 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
998 let secp_ctx = Secp256k1::new();
999 let revk_outp = dumb_revk_output!(secp_ctx);
1001 let mut package = PackageTemplate::build_package(txid, 0, revk_outp, 1000, true, 100);
1002 let timer_none = package.timer();
1003 assert!(timer_none.is_none());
1004 package.set_timer(Some(100));
1005 if let Some(timer_some) = package.timer() {
1006 assert_eq!(timer_some, 100);
1011 fn test_package_amounts() {
1012 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
1013 let secp_ctx = Secp256k1::new();
1014 let counterparty_outp = dumb_counterparty_output!(secp_ctx, 1_000_000);
1016 let package = PackageTemplate::build_package(txid, 0, counterparty_outp, 1000, true, 100);
1017 assert_eq!(package.package_amount(), 1000);
1021 fn test_package_weight() {
1022 let txid = Txid::from_hex("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap();
1023 let secp_ctx = Secp256k1::new();
1024 let revk_outp = dumb_revk_output!(secp_ctx);
1026 let package = PackageTemplate::build_package(txid, 0, revk_outp, 0, true, 100);
1027 // (nVersion (4) + nLocktime (4) + count_tx_in (1) + prevout (36) + sequence (4) + script_length (1) + count_tx_out (1) + value (8) + var_int (1)) * WITNESS_SCALE_FACTOR
1028 // + witness marker (2) + WEIGHT_REVOKED_OUTPUT
1029 assert_eq!(package.package_weight(&Script::new()), (4 + 4 + 1 + 36 + 4 + 1 + 1 + 8 + 1) * WITNESS_SCALE_FACTOR + 2 + WEIGHT_REVOKED_OUTPUT as usize);