Wumbo!

lightning/src/ln/channel.rs

@@ -734,9 +734,13 @@ pub const COMMITMENT_TX_WEIGHT_PER_HTLC: u64 = 172;
 
 pub const ANCHOR_OUTPUT_VALUE_SATOSHI: u64 = 330;
 
-/// Maximum `funding_satoshis` value, according to the BOLT #2 specification
-/// it's 2^24.
-pub const MAX_FUNDING_SATOSHIS: u64 = 1 << 24;
+/// Maximum `funding_satoshis` value according to the BOLT #2 specification, if
+/// `option_support_large_channel` (aka wumbo channels) is not supported.
+/// It's 2^24 - 1.
+pub const MAX_FUNDING_SATOSHIS_NO_WUMBO: u64 = (1 << 24) - 1;
+
+/// Total bitcoin supply in satoshis.
+pub const TOTAL_BITCOIN_SUPPLY_SATOSHIS: u64 = 21_000_000 * 1_0000_0000;
 
 /// The maximum network dust limit for standard script formats. This currently represents the
 /// minimum output value for a P2SH output before Bitcoin Core 22 considers the entire
@@ -850,8 +854,11 @@ impl<Signer: Sign> Channel<Signer> {
 		let holder_signer = keys_provider.get_channel_signer(false, channel_value_satoshis);
 		let pubkeys = holder_signer.pubkeys().clone();
 
-		if channel_value_satoshis >= MAX_FUNDING_SATOSHIS {
-			return Err(APIError::APIMisuseError{err: format!("funding_value must be smaller than {}, it was {}", MAX_FUNDING_SATOSHIS, channel_value_satoshis)});
+		if !their_features.supports_wumbo() && channel_value_satoshis > MAX_FUNDING_SATOSHIS_NO_WUMBO {
+			return Err(APIError::APIMisuseError{err: format!("funding_value must not exceed {}, it was {}", MAX_FUNDING_SATOSHIS_NO_WUMBO, channel_value_satoshis)});
+		}
+		if channel_value_satoshis >= TOTAL_BITCOIN_SUPPLY_SATOSHIS {
+			return Err(APIError::APIMisuseError{err: format!("funding_value must be smaller than the total bitcoin supply, it was {}", channel_value_satoshis)});
 		}
 		let channel_value_msat = channel_value_satoshis * 1000;
 		if push_msat > channel_value_msat {
@@ -1076,8 +1083,11 @@ impl<Signer: Sign> Channel<Signer> {
 		}
 
 		// Check sanity of message fields:
-		if msg.funding_satoshis >= MAX_FUNDING_SATOSHIS {
-			return Err(ChannelError::Close(format!("Funding must be smaller than {}. It was {}", MAX_FUNDING_SATOSHIS, msg.funding_satoshis)));
+		if msg.funding_satoshis > config.peer_channel_config_limits.max_funding_satoshis {
+			return Err(ChannelError::Close(format!("Per our config, funding must be at most {}. It was {}", config.peer_channel_config_limits.max_funding_satoshis, msg.funding_satoshis)));
+		}
+		if msg.funding_satoshis >= TOTAL_BITCOIN_SUPPLY_SATOSHIS {
+			return Err(ChannelError::Close(format!("Funding must be smaller than the total bitcoin supply. It was {}", msg.funding_satoshis)));
 		}
 		if msg.channel_reserve_satoshis > msg.funding_satoshis {
 			return Err(ChannelError::Close(format!("Bogus channel_reserve_satoshis ({}). Must be not greater than funding_satoshis: {}", msg.channel_reserve_satoshis, msg.funding_satoshis)));
@@ -4110,7 +4120,7 @@ impl<Signer: Sign> Channel<Signer> {
 		if !self.pending_inbound_htlcs.is_empty() || !self.pending_outbound_htlcs.is_empty() {
 			return Err(ChannelError::Close("Remote end sent us a closing_signed while there were still pending HTLCs".to_owned()));
 		}
-		if msg.fee_satoshis > 21_000_000 * 1_0000_0000 { //this is required to stop potential overflow in build_closing_transaction
+		if msg.fee_satoshis > TOTAL_BITCOIN_SUPPLY_SATOSHIS { // this is required to stop potential overflow in build_closing_transaction
 			return Err(ChannelError::Close("Remote tried to send us a closing tx with > 21 million BTC fee".to_owned()));
 		}
 
@@ -6298,7 +6308,7 @@ mod tests {
 	use ln::PaymentHash;
 	use ln::channelmanager::{HTLCSource, PaymentId};
 	use ln::channel::{Channel, InboundHTLCOutput, OutboundHTLCOutput, InboundHTLCState, OutboundHTLCState, HTLCCandidate, HTLCInitiator};
-	use ln::channel::MAX_FUNDING_SATOSHIS;
+	use ln::channel::{MAX_FUNDING_SATOSHIS_NO_WUMBO, TOTAL_BITCOIN_SUPPLY_SATOSHIS};
 	use ln::features::InitFeatures;
 	use ln::msgs::{ChannelUpdate, DataLossProtect, DecodeError, OptionalField, UnsignedChannelUpdate};
 	use ln::script::ShutdownScript;
@@ -6334,9 +6344,10 @@ mod tests {
 	}
 
 	#[test]
-	fn test_max_funding_satoshis() {
-		assert!(MAX_FUNDING_SATOSHIS <= 21_000_000 * 100_000_000,
-		        "MAX_FUNDING_SATOSHIS is greater than all satoshis in existence");
+	fn test_max_funding_satoshis_no_wumbo() {
+		assert_eq!(TOTAL_BITCOIN_SUPPLY_SATOSHIS, 21_000_000 * 100_000_000);
+		assert!(MAX_FUNDING_SATOSHIS_NO_WUMBO <= TOTAL_BITCOIN_SUPPLY_SATOSHIS,
+		        "MAX_FUNDING_SATOSHIS_NO_WUMBO is greater than all satoshis in existence");
 	}
 
 	#[test]

lightning/src/ln/channelmanager.rs

@@ -1498,8 +1498,6 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 	///
 	/// Non-proportional fees are fixed according to our risk using the provided fee estimator.
 	///
-	/// panics if channel_value_satoshis is >= `MAX_FUNDING_SATOSHIS`!
-	///
 	/// Users need to notify the new ChannelManager when a new block is connected or
 	/// disconnected using its `block_connected` and `block_disconnected` methods, starting
 	/// from after `params.latest_hash`.

lightning/src/ln/features.rs

@@ -137,7 +137,7 @@ mod sealed {
 			// Byte 1
 			,
 			// Byte 2
-			BasicMPP,
+			BasicMPP | Wumbo,
 			// Byte 3
 			ShutdownAnySegwit,
 			// Byte 4
@@ -169,7 +169,7 @@ mod sealed {
 			// Byte 1
 			,
 			// Byte 2
-			BasicMPP,
+			BasicMPP | Wumbo,
 			// Byte 3
 			ShutdownAnySegwit,
 			// Byte 4
@@ -390,6 +390,9 @@ mod sealed {
 	define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
 		"Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
 		supports_basic_mpp, requires_basic_mpp);
+	define_feature!(19, Wumbo, [InitContext, NodeContext],
+		"Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
+		supports_wumbo, requires_wumbo);
 	define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 		"Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 		set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
@@ -740,6 +743,15 @@ impl<T: sealed::ShutdownAnySegwit> Features<T> {
 		self
 	}
 }
+
+impl<T: sealed::Wumbo> Features<T> {
+	#[cfg(test)]
+	pub(crate) fn clear_wumbo(mut self) -> Self {
+		<T as sealed::Wumbo>::clear_bits(&mut self.flags);
+		self
+	}
+}
+
 macro_rules! impl_feature_len_prefixed_write {
 	($features: ident) => {
 		impl Writeable for $features {
@@ -843,6 +855,11 @@ mod tests {
 		assert!(!InitFeatures::known().requires_scid_privacy());
 		assert!(!NodeFeatures::known().requires_scid_privacy());
 
+		assert!(InitFeatures::known().supports_wumbo());
+		assert!(NodeFeatures::known().supports_wumbo());
+		assert!(!InitFeatures::known().requires_wumbo());
+		assert!(!NodeFeatures::known().requires_wumbo());
+
 		let mut init_features = InitFeatures::known();
 		assert!(init_features.initial_routing_sync());
 		init_features.clear_initial_routing_sync();
@@ -878,14 +895,14 @@ mod tests {
 			// Check that the flags are as expected:
 			// - option_data_loss_protect
 			// - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
-			// - basic_mpp
+			// - basic_mpp | wumbo
 			// - opt_shutdown_anysegwit
 			// -
 			// - option_channel_type | option_scid_alias
 			assert_eq!(node_features.flags.len(), 6);
 			assert_eq!(node_features.flags[0], 0b00000010);
 			assert_eq!(node_features.flags[1], 0b01010001);
-			assert_eq!(node_features.flags[2], 0b00000010);
+			assert_eq!(node_features.flags[2], 0b00001010);
 			assert_eq!(node_features.flags[3], 0b00001000);
 			assert_eq!(node_features.flags[4], 0b00000000);
 			assert_eq!(node_features.flags[5], 0b10100000);

lightning/src/ln/functional_tests.rs

@@ -58,9 +58,12 @@ use ln::chan_utils::CommitmentTransaction;
 #[test]
 fn test_insane_channel_opens() {
 	// Stand up a network of 2 nodes
+	use ln::channel::TOTAL_BITCOIN_SUPPLY_SATOSHIS;
+	let mut cfg = UserConfig::default();
+	cfg.peer_channel_config_limits.max_funding_satoshis = TOTAL_BITCOIN_SUPPLY_SATOSHIS + 1;
 	let chanmon_cfgs = create_chanmon_cfgs(2);
 	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
-	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, Some(cfg)]);
 	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
 
 	// Instantiate channel parameters where we push the maximum msats given our
@@ -92,11 +95,11 @@ fn test_insane_channel_opens() {
 		} else { assert!(false); }
 	};
 
-	use ln::channel::MAX_FUNDING_SATOSHIS;
 	use ln::channelmanager::MAX_LOCAL_BREAKDOWN_TIMEOUT;
 
 	// Test all mutations that would make the channel open message insane
-	insane_open_helper(format!("Funding must be smaller than {}. It was {}", MAX_FUNDING_SATOSHIS, MAX_FUNDING_SATOSHIS).as_str(), |mut msg| { msg.funding_satoshis = MAX_FUNDING_SATOSHIS; msg });
+	insane_open_helper(format!("Per our config, funding must be at most {}. It was {}", TOTAL_BITCOIN_SUPPLY_SATOSHIS + 1, TOTAL_BITCOIN_SUPPLY_SATOSHIS + 2).as_str(), |mut msg| { msg.funding_satoshis = TOTAL_BITCOIN_SUPPLY_SATOSHIS + 2; msg });
+	insane_open_helper(format!("Funding must be smaller than the total bitcoin supply. It was {}", TOTAL_BITCOIN_SUPPLY_SATOSHIS).as_str(), |mut msg| { msg.funding_satoshis = TOTAL_BITCOIN_SUPPLY_SATOSHIS; msg });
 
 	insane_open_helper("Bogus channel_reserve_satoshis", |mut msg| { msg.channel_reserve_satoshis = msg.funding_satoshis + 1; msg });
 
@@ -113,6 +116,25 @@ fn test_insane_channel_opens() {
 	insane_open_helper("max_accepted_htlcs was 484. It must not be larger than 483", |mut msg| { msg.max_accepted_htlcs = 484; msg });
 }
 
+#[test]
+fn test_funding_exceeds_no_wumbo_limit() {
+	// Test that if a peer does not support wumbo channels, we'll refuse to open a wumbo channel to
+	// them.
+	use ln::channel::MAX_FUNDING_SATOSHIS_NO_WUMBO;
+	let chanmon_cfgs = create_chanmon_cfgs(2);
+	let mut node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+	node_cfgs[1].features = InitFeatures::known().clear_wumbo();
+	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+
+	match nodes[0].node.create_channel(nodes[1].node.get_our_node_id(), MAX_FUNDING_SATOSHIS_NO_WUMBO + 1, 0, 42, None) {
+		Err(APIError::APIMisuseError { err }) => {
+			assert_eq!(format!("funding_value must not exceed {}, it was {}", MAX_FUNDING_SATOSHIS_NO_WUMBO, MAX_FUNDING_SATOSHIS_NO_WUMBO + 1), err);
+		},
+		_ => panic!()
+	}
+}
+
 fn do_test_counterparty_no_reserve(send_from_initiator: bool) {
 	// A peer providing a channel_reserve_satoshis of 0 (or less than our dust limit) is insecure,
 	// but only for them. Because some LSPs do it with some level of trust of the clients (for a

lightning/src/util/config.rs

@@ -10,6 +10,7 @@
 //! Various user-configurable channel limits and settings which ChannelManager
 //! applies for you.
 
+use ln::channel::MAX_FUNDING_SATOSHIS_NO_WUMBO;
 use ln::channelmanager::{BREAKDOWN_TIMEOUT, MAX_LOCAL_BREAKDOWN_TIMEOUT};
 
 /// Configuration we set when applicable.
@@ -95,11 +96,16 @@ impl Default for ChannelHandshakeConfig {
 /// are applied mostly only to incoming channels that's not much of a problem.
 #[derive(Copy, Clone, Debug)]
 pub struct ChannelHandshakeLimits {
-	/// Minimum allowed satoshis when a channel is funded, this is supplied by the sender and so
+	/// Minimum allowed satoshis when a channel is funded. This is supplied by the sender and so
 	/// only applies to inbound channels.
 	///
 	/// Default value: 0.
 	pub min_funding_satoshis: u64,
+	/// Maximum allowed satoshis when a channel is funded. This is supplied by the sender and so
+	/// only applies to inbound channels.
+	///
+	/// Default value: 2^24 - 1.
+	pub max_funding_satoshis: u64,
 	/// The remote node sets a limit on the minimum size of HTLCs we can send to them. This allows
 	/// you to limit the maximum minimum-size they can require.
 	///
@@ -151,6 +157,7 @@ impl Default for ChannelHandshakeLimits {
 	fn default() -> Self {
 		ChannelHandshakeLimits {
 			min_funding_satoshis: 0,
+			max_funding_satoshis: MAX_FUNDING_SATOSHIS_NO_WUMBO,
 			max_htlc_minimum_msat: <u64>::max_value(),
 			min_max_htlc_value_in_flight_msat: 0,
 			max_channel_reserve_satoshis: <u64>::max_value(),