Add InboundV2Channel struct

lightning/src/ln/channel.rs

@@ -269,9 +269,11 @@ 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`
@@ -2651,6 +2653,20 @@ 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]
@@ -2684,6 +2700,8 @@ pub(super) struct DualFundingChannelContext {
 // Counterparty designates channel data owned by the another channel participant entity.
 pub(super) struct Channel<SP: Deref> where SP::Target: SignerProvider {
 	pub context: ChannelContext<SP>,
+	#[cfg(dual_funding)]
+	pub dual_funding_channel_context: Option<DualFundingChannelContext>,
 }
 
 #[cfg(any(test, fuzzing))]
@@ -6617,6 +6635,8 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {
 
 		let channel = Channel {
 			context: self.context,
+			#[cfg(dual_funding)]
+			dual_funding_channel_context: None,
 		};
 
 		Ok((channel, funding_created))
@@ -7089,6 +7109,8 @@ impl<SP: Deref> InboundV1Channel<SP> where SP::Target: SignerProvider {
 		// `ChannelMonitor`.
 		let mut channel = Channel {
 			context: self.context,
+			#[cfg(dual_funding)]
+			dual_funding_channel_context: None,
 		};
 		let need_channel_ready = channel.check_get_channel_ready(0).is_some();
 		channel.monitor_updating_paused(false, false, need_channel_ready, Vec::new(), Vec::new(), Vec::new());
@@ -7097,6 +7119,159 @@ impl<SP: Deref> InboundV1Channel<SP> where SP::Target: SignerProvider {
 	}
 }
 
+// A not-yet-funded inbound (from counterparty) channel using V2 channel establishment.
+#[cfg(dual_funding)]
+pub(super) struct InboundV2Channel<SP: Deref> where SP::Target: SignerProvider {
+	pub context: ChannelContext<SP>,
+	pub unfunded_context: UnfundedChannelContext,
+	pub dual_funding_context: DualFundingChannelContext,
+}
+
+#[cfg(dual_funding)]
+impl<SP: Deref> InboundV2Channel<SP> where SP::Target: SignerProvider {
+	/// Creates a new dual-funded channel from a remote side's request for one.
+	/// Assumes chain_hash has already been checked and corresponds with what we expect!
+	pub fn new<ES: Deref, F: Deref, L: Deref>(
+		fee_estimator: &LowerBoundedFeeEstimator<F>, entropy_source: &ES, signer_provider: &SP,
+		counterparty_node_id: PublicKey, our_supported_features: &ChannelTypeFeatures,
+		their_features: &InitFeatures, msg: &msgs::OpenChannelV2, funding_satoshis: u64, user_id: u128,
+		config: &UserConfig, current_chain_height: u32, logger: &L,
+	) -> Result<InboundV2Channel<SP>, ChannelError>
+		where ES::Target: EntropySource,
+			  F::Target: FeeEstimator,
+			  L::Target: Logger,
+	{
+		// TODO(dual_funding): Fix this
+		let channel_value_satoshis = funding_satoshis * 1000 + msg.funding_satoshis;
+		let counterparty_selected_channel_reserve_satoshis = get_v2_channel_reserve_satoshis(
+			channel_value_satoshis, msg.dust_limit_satoshis);
+		let holder_selected_channel_reserve_satoshis = get_v2_channel_reserve_satoshis(
+			channel_value_satoshis, MIN_CHAN_DUST_LIMIT_SATOSHIS);
+
+		let counterparty_pubkeys = ChannelPublicKeys {
+			funding_pubkey: msg.funding_pubkey,
+			revocation_basepoint: RevocationBasepoint(msg.revocation_basepoint),
+			payment_point: msg.payment_basepoint,
+			delayed_payment_basepoint: DelayedPaymentBasepoint(msg.delayed_payment_basepoint),
+			htlc_basepoint: HtlcBasepoint(msg.htlc_basepoint)
+		};
+
+		let mut context = ChannelContext::new_for_inbound_channel(
+			fee_estimator,
+			entropy_source,
+			signer_provider,
+			counterparty_node_id,
+			our_supported_features,
+			their_features,
+			user_id,
+			config,
+			current_chain_height,
+			logger,
+			false,
+
+			funding_satoshis,
+
+			counterparty_pubkeys,
+			msg.channel_flags,
+			msg.channel_type.clone(),
+			msg.funding_satoshis,
+			msg.to_self_delay,
+			holder_selected_channel_reserve_satoshis,
+			counterparty_selected_channel_reserve_satoshis,
+			0 /* push_msat not used in dual-funding */,
+			msg.dust_limit_satoshis,
+			msg.htlc_minimum_msat,
+			msg.commitment_feerate_sat_per_1000_weight,
+			msg.max_accepted_htlcs,
+			msg.shutdown_scriptpubkey.clone(),
+			msg.max_htlc_value_in_flight_msat,
+			msg.temporary_channel_id,
+			msg.first_per_commitment_point,
+		)?;
+		let channel_id = ChannelId::v2_from_revocation_basepoints(
+			&context.get_holder_pubkeys().revocation_basepoint,
+			&context.get_counterparty_pubkeys().revocation_basepoint);
+		context.channel_id = channel_id;
+
+		let chan = Self {
+			context,
+			unfunded_context: UnfundedChannelContext { unfunded_channel_age_ticks: 0 },
+			dual_funding_context: DualFundingChannelContext {
+				our_funding_satoshis: funding_satoshis,
+				their_funding_satoshis: msg.funding_satoshis,
+				funding_tx_locktime: msg.locktime,
+				funding_feerate_sat_per_1000_weight: msg.funding_feerate_sat_per_1000_weight,
+			}
+		};
+
+		Ok(chan)
+	}
+
+	/// Marks an inbound channel as accepted and generates a [`msgs::AcceptChannelV2`] message which
+	/// should be sent back to the counterparty node.
+	///
+	/// [`msgs::AcceptChannelV2`]: crate::ln::msgs::AcceptChannelV2
+	pub fn accept_inbound_dual_funded_channel(&mut self) -> msgs::AcceptChannelV2 {
+		if self.context.is_outbound() {
+			panic!("Tried to send accept_channel2 for an outbound channel?");
+		}
+		if self.context.channel_state != (ChannelState::OurInitSent as u32) | (ChannelState::TheirInitSent as u32) {
+			panic!("Tried to send accept_channel2 after channel had moved forward");
+		}
+		if self.context.cur_holder_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER {
+			panic!("Tried to send an accept_channel2 for a channel that has already advanced");
+		}
+
+		self.generate_accept_channel_v2_message()
+	}
+
+	/// This function is used to explicitly generate a [`msgs::AcceptChannel`] message for an
+	/// inbound channel. If the intention is to accept an inbound channel, use
+	/// [`InboundV1Channel::accept_inbound_channel`] instead.
+	///
+	/// [`msgs::AcceptChannelV2`]: crate::ln::msgs::AcceptChannelV2
+	fn generate_accept_channel_v2_message(&self) -> msgs::AcceptChannelV2 {
+		let first_per_commitment_point = self.context.holder_signer.as_ref().get_per_commitment_point(
+			self.context.cur_holder_commitment_transaction_number, &self.context.secp_ctx);
+		let second_per_commitment_point = self.context.holder_signer.as_ref().get_per_commitment_point(
+			self.context.cur_holder_commitment_transaction_number - 1, &self.context.secp_ctx);
+		let keys = self.context.get_holder_pubkeys();
+
+		msgs::AcceptChannelV2 {
+			temporary_channel_id: self.context.temporary_channel_id.unwrap(),
+			funding_satoshis: self.dual_funding_context.our_funding_satoshis,
+			dust_limit_satoshis: self.context.holder_dust_limit_satoshis,
+			max_htlc_value_in_flight_msat: self.context.holder_max_htlc_value_in_flight_msat,
+			htlc_minimum_msat: self.context.holder_htlc_minimum_msat,
+			minimum_depth: self.context.minimum_depth.unwrap(),
+			to_self_delay: self.context.get_holder_selected_contest_delay(),
+			max_accepted_htlcs: self.context.holder_max_accepted_htlcs,
+			funding_pubkey: keys.funding_pubkey,
+			revocation_basepoint: keys.revocation_basepoint.to_public_key(),
+			payment_basepoint: keys.payment_point,
+			delayed_payment_basepoint: keys.delayed_payment_basepoint.to_public_key(),
+			htlc_basepoint: keys.htlc_basepoint.to_public_key(),
+			first_per_commitment_point,
+			second_per_commitment_point,
+			shutdown_scriptpubkey: Some(match &self.context.shutdown_scriptpubkey {
+				Some(script) => script.clone().into_inner(),
+				None => Builder::new().into_script(),
+			}),
+			channel_type: Some(self.context.channel_type.clone()),
+			require_confirmed_inputs: None,
+		}
+	}
+
+	/// Enables the possibility for tests to extract a [`msgs::AcceptChannelV2`] message for an
+	/// inbound channel without accepting it.
+	///
+	/// [`msgs::AcceptChannelV2`]: crate::ln::msgs::AcceptChannelV2
+	#[cfg(test)]
+	pub fn get_accept_channel_v2_message(&self) -> msgs::AcceptChannelV2 {
+		self.generate_accept_channel_v2_message()
+	}
+}
+
 const SERIALIZATION_VERSION: u8 = 3;
 const MIN_SERIALIZATION_VERSION: u8 = 3;
 
@@ -8006,7 +8181,9 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 				channel_keys_id,
 
 				blocked_monitor_updates: blocked_monitor_updates.unwrap(),
-			}
+			},
+			#[cfg(dual_funding)]
+			dual_funding_channel_context: None,
 		})
 	}
 }
@@ -8564,7 +8741,11 @@ mod tests {
 		let config = UserConfig::default();
 		let features = channelmanager::provided_init_features(&config);
 		let outbound_chan = OutboundV1Channel::<&TestKeysInterface>::new(&feeest, &&keys_provider, &&keys_provider, node_b_node_id, &features, 10000000, 100000, 42, &config, 0, 42, None).unwrap();
-		let mut chan = Channel { context: outbound_chan.context };
+		let mut chan = Channel {
+			context: outbound_chan.context,
+			#[cfg(dual_funding)]
+			dual_funding_channel_context: None,
+		};
 
 		let dummy_htlc_source = HTLCSource::OutboundRoute {
 			path: Path {