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Delete CommitmentStats.total_anchors_sat
The upcoming `TxBuilder` API will sum the msat value of any anchors and custom outputs on commitment transactions into `{local, remote}_balance_before_fee_msat`.
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lightning/src/ln/channel.rs

Lines changed: 34 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -1130,10 +1130,12 @@ struct CommitmentData<'a> {
11301130

11311131
/// A struct gathering stats on a commitment transaction, either local or remote.
11321132
struct CommitmentStats {
1133-
total_fee_sat: u64, // the total fee included in the transaction
1134-
total_anchors_sat: u64, // the sum of the anchors' amounts
1135-
local_balance_before_fee_anchors_msat: u64, // local balance before fees and anchors *not* considering dust limits
1136-
remote_balance_before_fee_anchors_msat: u64, // remote balance before fees and anchors *not* considering dust limits
1133+
/// The total fee included in the commitment transaction
1134+
commit_tx_fee_sat: u64,
1135+
/// The local balance before fees *not* considering dust limits
1136+
local_balance_before_fee_msat: u64,
1137+
/// The remote balance before fees *not* considering dust limits
1138+
remote_balance_before_fee_msat: u64,
11371139
}
11381140

11391141
/// Used when calculating whether we or the remote can afford an additional HTLC.
@@ -4235,7 +4237,7 @@ where
42354237
if update_fee {
42364238
debug_assert!(!funding.is_outbound());
42374239
let counterparty_reserve_we_require_msat = funding.holder_selected_channel_reserve_satoshis * 1000;
4238-
if commitment_data.stats.remote_balance_before_fee_anchors_msat < commitment_data.stats.total_fee_sat * 1000 + commitment_data.stats.total_anchors_sat * 1000 + counterparty_reserve_we_require_msat {
4240+
if commitment_data.stats.remote_balance_before_fee_msat < commitment_data.stats.commit_tx_fee_sat * 1000 + counterparty_reserve_we_require_msat {
42394241
return Err(ChannelError::close("Funding remote cannot afford proposed new fee".to_owned()));
42404242
}
42414243
}
@@ -4251,7 +4253,7 @@ where
42514253
&& info.next_holder_htlc_id == self.next_holder_htlc_id
42524254
&& info.next_counterparty_htlc_id == self.next_counterparty_htlc_id
42534255
&& info.feerate == self.feerate_per_kw {
4254-
assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
4256+
assert_eq!(commitment_data.stats.commit_tx_fee_sat, info.fee / 1000);
42554257
}
42564258
}
42574259
}
@@ -4327,8 +4329,8 @@ where
43274329
&holder_commitment_point.current_point(), true, true, logger,
43284330
);
43294331
let buffer_fee_msat = commit_tx_fee_sat(feerate_per_kw, commitment_data.tx.nondust_htlcs().len() + htlc_stats.on_holder_tx_outbound_holding_cell_htlcs_count as usize + CONCURRENT_INBOUND_HTLC_FEE_BUFFER as usize, funding.get_channel_type()) * 1000;
4330-
let holder_balance_msat = commitment_data.stats.local_balance_before_fee_anchors_msat - htlc_stats.outbound_holding_cell_msat;
4331-
if holder_balance_msat < buffer_fee_msat + commitment_data.stats.total_anchors_sat * 1000 + funding.counterparty_selected_channel_reserve_satoshis.unwrap() * 1000 {
4332+
let holder_balance_msat = commitment_data.stats.local_balance_before_fee_msat - htlc_stats.outbound_holding_cell_msat;
4333+
if holder_balance_msat < buffer_fee_msat + funding.counterparty_selected_channel_reserve_satoshis.unwrap() * 1000 {
43324334
//TODO: auto-close after a number of failures?
43334335
log_debug!(logger, "Cannot afford to send new feerate at {}", feerate_per_kw);
43344336
return false;
@@ -4506,14 +4508,26 @@ where
45064508
broadcaster_max_commitment_tx_output.1 = cmp::max(broadcaster_max_commitment_tx_output.1, value_to_remote_msat);
45074509
}
45084510

4509-
let total_fee_sat = commit_tx_fee_sat(feerate_per_kw, non_dust_htlc_count, &funding.channel_transaction_parameters.channel_type_features);
4511+
let commit_tx_fee_sat = commit_tx_fee_sat(feerate_per_kw, non_dust_htlc_count, &funding.channel_transaction_parameters.channel_type_features);
45104512
let total_anchors_sat = if funding.channel_transaction_parameters.channel_type_features.supports_anchors_zero_fee_htlc_tx() { ANCHOR_OUTPUT_VALUE_SATOSHI * 2 } else { 0 };
45114513

4514+
// We MUST use saturating subs here, as the funder's balance is not guaranteed to be greater
4515+
// than or equal to `total_anchors_sat`.
4516+
//
4517+
// This is because when the remote party sends an `update_fee` message, we build the new
4518+
// commitment transaction *before* checking whether the remote party's balance is enough to
4519+
// cover the total anchor sum.
4520+
4521+
if funding.is_outbound() {
4522+
value_to_self_msat = value_to_self_msat.saturating_sub(total_anchors_sat * 1000);
4523+
} else {
4524+
value_to_remote_msat = value_to_remote_msat.saturating_sub(total_anchors_sat * 1000);
4525+
}
4526+
45124527
CommitmentStats {
4513-
total_fee_sat,
4514-
total_anchors_sat,
4515-
local_balance_before_fee_anchors_msat: value_to_self_msat,
4516-
remote_balance_before_fee_anchors_msat: value_to_remote_msat,
4528+
commit_tx_fee_sat,
4529+
local_balance_before_fee_msat: value_to_self_msat,
4530+
remote_balance_before_fee_msat: value_to_remote_msat,
45174531
}
45184532
}
45194533

@@ -4540,10 +4554,9 @@ where
45404554

45414555
let stats = self.build_commitment_stats(funding, local, generated_by_local);
45424556
let CommitmentStats {
4543-
total_fee_sat,
4544-
total_anchors_sat,
4545-
local_balance_before_fee_anchors_msat,
4546-
remote_balance_before_fee_anchors_msat
4557+
commit_tx_fee_sat,
4558+
local_balance_before_fee_msat,
4559+
remote_balance_before_fee_msat
45474560
} = stats;
45484561

45494562
let num_htlcs = self.pending_inbound_htlcs.len() + self.pending_outbound_htlcs.len();
@@ -4607,16 +4620,16 @@ where
46074620
};
46084621

46094622
// We MUST use saturating subs here, as the funder's balance is not guaranteed to be greater
4610-
// than or equal to the sum of `total_fee_sat` and `total_anchors_sat`.
4623+
// than or equal to `commit_tx_fee_sat`.
46114624
//
46124625
// This is because when the remote party sends an `update_fee` message, we build the new
46134626
// commitment transaction *before* checking whether the remote party's balance is enough to
4614-
// cover the total fee and the anchors.
4627+
// cover the total fee.
46154628

46164629
let (value_to_self, value_to_remote) = if funding.is_outbound() {
4617-
((local_balance_before_fee_anchors_msat / 1000).saturating_sub(total_anchors_sat).saturating_sub(total_fee_sat), remote_balance_before_fee_anchors_msat / 1000)
4630+
((local_balance_before_fee_msat / 1000).saturating_sub(commit_tx_fee_sat), remote_balance_before_fee_msat / 1000)
46184631
} else {
4619-
(local_balance_before_fee_anchors_msat / 1000, (remote_balance_before_fee_anchors_msat / 1000).saturating_sub(total_anchors_sat).saturating_sub(total_fee_sat))
4632+
(local_balance_before_fee_msat / 1000, (remote_balance_before_fee_msat / 1000).saturating_sub(commit_tx_fee_sat))
46204633
};
46214634

46224635
let mut to_broadcaster_value_sat = if local { value_to_self } else { value_to_remote };

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