Do not write outside TLV.

Do not write TLV if max htlcs is already 50.

Read configured max accepted htlcs when opening channels

Author: swilliamson5

lightning/src/ln/channel.rs

@@ -1026,7 +1026,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 			cur_counterparty_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
 			value_to_self_msat,
 
-			max_accepted_htlcs: 50,
+			max_accepted_htlcs: config.channel_handshake_config.max_accepted_htlcs,
 			pending_inbound_htlcs: Vec::new(),
 			pending_outbound_htlcs: Vec::new(),
 			holding_cell_htlc_updates: Vec::new(),
@@ -1373,7 +1373,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 			cur_counterparty_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
 			value_to_self_msat: msg.push_msat,
 
-			max_accepted_htlcs: msg.max_accepted_htlcs,
+			max_accepted_htlcs: config.channel_handshake_config.max_accepted_htlcs,
 			pending_inbound_htlcs: Vec::new(),
 			pending_outbound_htlcs: Vec::new(),
 			holding_cell_htlc_updates: Vec::new(),
@@ -6276,7 +6276,6 @@ impl<Signer: WriteableEcdsaChannelSigner> Writeable for Channel<Signer> {
 		self.cur_counterparty_commitment_transaction_number.write(writer)?;
 		self.value_to_self_msat.write(writer)?;
 
-		self.max_accepted_htlcs.write(writer)?;
 		let mut dropped_inbound_htlcs = 0;
 		for htlc in self.pending_inbound_htlcs.iter() {
 			if let InboundHTLCState::RemoteAnnounced(_) = htlc.state {
@@ -6498,6 +6497,8 @@ impl<Signer: WriteableEcdsaChannelSigner> Writeable for Channel<Signer> {
 		// we write the high bytes as an option here.
 		let user_id_high_opt = Some((self.user_id >> 64) as u64);
 
+		let max_accepted_htlcs = if self.max_accepted_htlcs == 50 { None } else { Some(self.max_accepted_htlcs) };
+
 		write_tlv_fields!(writer, {
 			(0, self.announcement_sigs, option),
 			// minimum_depth and counterparty_selected_channel_reserve_satoshis used to have a
@@ -6523,7 +6524,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Writeable for Channel<Signer> {
 			(23, channel_ready_event_emitted, option),
 			(25, user_id_high_opt, option),
 			(27, self.channel_keys_id, required),
-			(28, Some(self.max_accepted_htlcs), option),
+			(28, max_accepted_htlcs, option),
 			(29, self.temporary_channel_id, option),
 			(31, channel_pending_event_emitted, option),
 		});
@@ -6591,10 +6592,11 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 		let cur_counterparty_commitment_transaction_number = Readable::read(reader)?;
 		let value_to_self_msat = Readable::read(reader)?;
 
-		let max_accepted_htlcs = Readable::read(reader)?;
 		let pending_inbound_htlc_count: u64 = Readable::read(reader)?;
 
-		let mut pending_inbound_htlcs = Vec::with_capacity(cmp::min(pending_inbound_htlc_count as usize, max_accepted_htlcs as usize));
+		let channel_handshake_config = ChannelHandshakeConfig::default();
+
+		let mut pending_inbound_htlcs = Vec::with_capacity(cmp::min(pending_inbound_htlc_count as usize, channel_handshake_config.max_accepted_htlcs as usize));
 		for _ in 0..pending_inbound_htlc_count {
 			pending_inbound_htlcs.push(InboundHTLCOutput {
 				htlc_id: Readable::read(reader)?,
@@ -6612,7 +6614,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 		}
 
 		let pending_outbound_htlc_count: u64 = Readable::read(reader)?;
-		let mut pending_outbound_htlcs = Vec::with_capacity(cmp::min(pending_outbound_htlc_count as usize, max_accepted_htlcs as usize));
+		let mut pending_outbound_htlcs = Vec::with_capacity(cmp::min(pending_outbound_htlc_count as usize, channel_handshake_config.max_accepted_htlcs as usize));
 		for _ in 0..pending_outbound_htlc_count {
 			pending_outbound_htlcs.push(OutboundHTLCOutput {
 				htlc_id: Readable::read(reader)?,
@@ -6641,7 +6643,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 		}
 
 		let holding_cell_htlc_update_count: u64 = Readable::read(reader)?;
-		let mut holding_cell_htlc_updates = Vec::with_capacity(cmp::min(holding_cell_htlc_update_count as usize, max_accepted_htlcs as usize*2));
+		let mut holding_cell_htlc_updates = Vec::with_capacity(cmp::min(holding_cell_htlc_update_count as usize, channel_handshake_config.max_accepted_htlcs as usize*2));
 		for _ in 0..holding_cell_htlc_update_count {
 			holding_cell_htlc_updates.push(match <u8 as Readable>::read(reader)? {
 				0 => HTLCUpdateAwaitingACK::AddHTLC {
@@ -6674,13 +6676,13 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 		let monitor_pending_commitment_signed = Readable::read(reader)?;
 
 		let monitor_pending_forwards_count: u64 = Readable::read(reader)?;
-		let mut monitor_pending_forwards = Vec::with_capacity(cmp::min(monitor_pending_forwards_count as usize, max_accepted_htlcs as usize));
+		let mut monitor_pending_forwards = Vec::with_capacity(cmp::min(monitor_pending_forwards_count as usize, channel_handshake_config.max_accepted_htlcs as usize));
 		for _ in 0..monitor_pending_forwards_count {
 			monitor_pending_forwards.push((Readable::read(reader)?, Readable::read(reader)?));
 		}
 
 		let monitor_pending_failures_count: u64 = Readable::read(reader)?;
-		let mut monitor_pending_failures = Vec::with_capacity(cmp::min(monitor_pending_failures_count as usize, max_accepted_htlcs as usize));
+		let mut monitor_pending_failures = Vec::with_capacity(cmp::min(monitor_pending_failures_count as usize, channel_handshake_config.max_accepted_htlcs as usize));
 		for _ in 0..monitor_pending_failures_count {
 			monitor_pending_failures.push((Readable::read(reader)?, Readable::read(reader)?, Readable::read(reader)?));
 		}
@@ -6801,6 +6803,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 		let mut user_id_high_opt: Option<u64> = None;
 		let mut channel_keys_id: Option<[u8; 32]> = None;
 		let mut temporary_channel_id: Option<[u8; 32]> = None;
+		let mut max_accepted_htlcs: Option<u16> = None;
 
 		read_tlv_fields!(reader, {
 			(0, announcement_sigs, option),
@@ -6821,6 +6824,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 			(23, channel_ready_event_emitted, option),
 			(25, user_id_high_opt, option),
 			(27, channel_keys_id, option),
+			(28, max_accepted_htlcs, option),
 			(29, temporary_channel_id, option),
 			(31, channel_pending_event_emitted, option),
 		});
@@ -6875,6 +6879,8 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 		// separate u64 values.
 		let user_id = user_id_low as u128 + ((user_id_high_opt.unwrap_or(0) as u128) << 64);
 
+		let max_accepted_htlcs = max_accepted_htlcs.unwrap_or(channel_handshake_config.max_accepted_htlcs);
+
 		Ok(Channel {
 			user_id,
 

lightning/src/util/config.rs

@@ -170,6 +170,8 @@ pub struct ChannelHandshakeConfig {
 	/// [`DecodeError::InvalidValue`]: crate::ln::msgs::DecodeError::InvalidValue
 	/// [`SIGHASH_SINGLE + update_fee Considered Harmful`]: https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-September/002796.html
 	pub negotiate_anchors_zero_fee_htlc_tx: bool,
+	/// Default value: 50
+	pub max_accepted_htlcs: u16,
 }
 
 impl Default for ChannelHandshakeConfig {
@@ -185,6 +187,7 @@ impl Default for ChannelHandshakeConfig {
 			their_channel_reserve_proportional_millionths: 10_000,
 			#[cfg(anchors)]
 			negotiate_anchors_zero_fee_htlc_tx: false,
+			max_accepted_htlcs: 50,
 		}
 	}
 }