Define V2 channel structs & move out some shared methods as utils

Author: dunxen

lightning/src/ln/channel.rs

@@ -20,7 +20,7 @@ use bitcoin::hash_types::{Txid, BlockHash};
 use bitcoin::secp256k1::constants::PUBLIC_KEY_SIZE;
 use bitcoin::secp256k1::{PublicKey,SecretKey};
 use bitcoin::secp256k1::{Secp256k1,ecdsa::Signature};
-use bitcoin::secp256k1;
+use bitcoin::{secp256k1, TxOut};
 
 use crate::ln::{PaymentPreimage, PaymentHash};
 use crate::ln::features::{ChannelTypeFeatures, InitFeatures};
@@ -257,9 +257,11 @@ enum HTLCUpdateAwaitingACK {
 /// ChannelReady can then get all remaining flags set on it, until we finish shutdown, then we
 /// move on to ShutdownComplete, at which point most calls into this channel are disallowed.
 enum ChannelState {
-	/// Implies we have (or are prepared to) send our open_channel/accept_channel message
+	/// Implies we have (or are prepared to) send our open_channel/accept_channel message or in the
+	/// case of V2 establishment, our open_channel2/accept_channel2 message
 	OurInitSent = 1 << 0,
-	/// Implies we have received their open_channel/accept_channel message
+	/// Implies we have received their open_channel/accept_channel message or in the case of
+	/// V2 establishment, their open_channel2/accept_channel2 message
 	TheirInitSent = 1 << 1,
 	/// We have sent funding_created and are awaiting a funding_signed to advance to FundingSent.
 	/// Note that this is nonsense for an inbound channel as we immediately generate funding_signed
@@ -2009,6 +2011,20 @@ pub(crate) fn get_legacy_default_holder_selected_channel_reserve_satoshis(channe
 	cmp::min(channel_value_satoshis, cmp::max(q, 1000))
 }
 
+/// Returns a minimum channel reserve value each party needs to maintain, fixed in the spec to a
+/// default of 1% of the total channel value.
+///
+/// Guaranteed to return a value no larger than `channel_value_satoshis`
+///
+/// This is used both for outbound and inbound channels and has lower bound
+/// of `dust_limit_satoshis`.
+fn get_v2_channel_reserve_satoshis(channel_value_satoshis: u64, dust_limit_satoshis: u64) -> u64 {
+	let channel_reserve_proportional_millionths = 10_000; // Fixed at 1% in spec.
+	let calculated_reserve =
+		channel_value_satoshis.saturating_mul(channel_reserve_proportional_millionths) / 1_000_000;
+	cmp::min(channel_value_satoshis, cmp::max(calculated_reserve, dust_limit_satoshis))
+}
+
 // Get the fee cost in SATS of a commitment tx with a given number of HTLC outputs.
 // Note that num_htlcs should not include dust HTLCs.
 #[inline]
@@ -2024,6 +2040,39 @@ fn commit_tx_fee_msat(feerate_per_kw: u32, num_htlcs: usize, channel_type_featur
 	(commitment_tx_base_weight(channel_type_features) + num_htlcs as u64 * COMMITMENT_TX_WEIGHT_PER_HTLC) * feerate_per_kw as u64 / 1000 * 1000
 }
 
+/// Used when supplying inputs to contribute to an outbound or inbound dual-funded channel.
+/// It will be included in an interactively constructed funding transaction which must then
+/// be signed by the user.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct DualFundingUtxo {
+	/// The outpoint which is spendable.
+	pub outpoint: OutPoint,
+	/// The output which is referenced by the given outpoint.
+	pub output: TxOut,
+}
+
+/// A wrapper for the common [`ChannelContext`] that includes dual-funding-specific fields.
+pub(super) struct DualFundingChannelContext<Signer: ChannelSigner> {
+	/// The common channel context, not specific to a particular channel establishment version.
+	pub common: ChannelContext<Signer>,
+
+	/// The amount in satoshis we will be contributing to the channel.
+	pub our_funding_satoshis: u64,
+	/// The UTXOs we will be adding in interactive transaction construction.
+	pub our_funding_inputs: Vec<DualFundingUtxo>,
+	/// Flag indicating that we require our counterparty to use confirmed inputs for the construction
+	/// of the funding transaction.
+	pub we_require_confirmed_inputs: bool,
+	/// Flag indicating that our counterparty requires us to use confirmed inputs for the construction
+	/// of the funding transaction.
+	pub counterparty_requires_confirmed_inputs: bool,
+	/// The funding transaction locktime suggested by the initiator. If set by us, it is always set
+	/// to the current block height to align incentives against fee-sniping.
+	pub funding_tx_locktime: u32,
+	/// The destination for our change output, if one needs to be added.
+	pub our_change_script_pubkey: Script,
+}
+
 // TODO: We should refactor this to be an Inbound/OutboundChannel until initial setup handshaking
 // has been completed, and then turn into a Channel to get compiler-time enforcement of things like
 // calling channel_id() before we're set up or things like get_outbound_funding_signed on an
@@ -5499,7 +5548,7 @@ impl<Signer: WriteableEcdsaChannelSigner> OutboundV1Channel<Signer> {
 			return Err(APIError::APIMisuseError { err: format!("Holder selected channel  reserve below implemention limit dust_limit_satoshis {}", holder_selected_channel_reserve_satoshis) });
 		}
 
-		let channel_type = Self::get_initial_channel_type(&config, their_features);
+		let channel_type = get_initial_channel_type(&config, their_features);
 		debug_assert!(channel_type.is_subset(&channelmanager::provided_channel_type_features(&config)));
 
 		let feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Normal);
@@ -5727,29 +5776,6 @@ impl<Signer: WriteableEcdsaChannelSigner> OutboundV1Channel<Signer> {
 		}))
 	}
 
-	fn get_initial_channel_type(config: &UserConfig, their_features: &InitFeatures) -> ChannelTypeFeatures {
-		// The default channel type (ie the first one we try) depends on whether the channel is
-		// public - if it is, we just go with `only_static_remotekey` as it's the only option
-		// available. If it's private, we first try `scid_privacy` as it provides better privacy
-		// with no other changes, and fall back to `only_static_remotekey`.
-		let mut ret = ChannelTypeFeatures::only_static_remote_key();
-		if !config.channel_handshake_config.announced_channel &&
-			config.channel_handshake_config.negotiate_scid_privacy &&
-			their_features.supports_scid_privacy() {
-			ret.set_scid_privacy_required();
-		}
-
-		// Optionally, if the user would like to negotiate the `anchors_zero_fee_htlc_tx` option, we
-		// set it now. If they don't understand it, we'll fall back to our default of
-		// `only_static_remotekey`.
-		if config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx &&
-			their_features.supports_anchors_zero_fee_htlc_tx() {
-			ret.set_anchors_zero_fee_htlc_tx_required();
-		}
-
-		ret
-	}
-
 	/// If we receive an error message, it may only be a rejection of the channel type we tried,
 	/// not of our ability to open any channel at all. Thus, on error, we should first call this
 	/// and see if we get a new `OpenChannel` message, otherwise the channel is failed.
@@ -6498,6 +6524,41 @@ impl<Signer: WriteableEcdsaChannelSigner> InboundV1Channel<Signer> {
 	}
 }
 
+// A not-yet-funded outbound (from holder) channel using V2 channel establishment.
+pub(super) struct OutboundV2Channel<Signer: ChannelSigner> {
+	pub context: DualFundingChannelContext<Signer>,
+}
+
+// A not-yet-funded inbound (from counterparty) channel using V2 channel establishment.
+pub(super) struct InboundV2Channel<Signer: ChannelSigner> {
+	pub context: DualFundingChannelContext<Signer>,
+}
+
+// Prefunded channel utilities
+
+fn get_initial_channel_type(config: &UserConfig, their_features: &InitFeatures) -> ChannelTypeFeatures {
+	// The default channel type (ie the first one we try) depends on whether the channel is
+	// public - if it is, we just go with `only_static_remotekey` as it's the only option
+	// available. If it's private, we first try `scid_privacy` as it provides better privacy
+	// with no other changes, and fall back to `only_static_remotekey`.
+	let mut ret = ChannelTypeFeatures::only_static_remote_key();
+	if !config.channel_handshake_config.announced_channel &&
+		config.channel_handshake_config.negotiate_scid_privacy &&
+		their_features.supports_scid_privacy() {
+		ret.set_scid_privacy_required();
+	}
+
+	// Optionally, if the user would like to negotiate the `anchors_zero_fee_htlc_tx` option, we
+	// set it now. If they don't understand it, we'll fall back to our default of
+	// `only_static_remotekey`.
+	if config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx &&
+		their_features.supports_anchors_zero_fee_htlc_tx() {
+		ret.set_anchors_zero_fee_htlc_tx_required();
+	}
+
+	ret
+}
+
 const SERIALIZATION_VERSION: u8 = 3;
 const MIN_SERIALIZATION_VERSION: u8 = 2;