Use BTreeMap in NegotiationContext to order inputs and outputs

When an interactive tx sessions aborts, the contributed inputs and
outputs will be given in the error in an upcoming commit. Use BTreeMap
instead in NegotiationContext to give a consisted ordering by SerialId.

Author: jkczyz

lightning/src/ln/interactivetxs.rs

@@ -35,6 +35,7 @@ use crate::ln::msgs::{MessageSendEvent, SerialId, TxSignatures};
 use crate::ln::types::ChannelId;
 use crate::sign::{EntropySource, P2TR_KEY_PATH_WITNESS_WEIGHT, P2WPKH_WITNESS_WEIGHT};
 
+use alloc::collections::{btree_map, BTreeMap};
 use core::fmt::Display;
 use core::ops::Deref;
 
@@ -818,7 +819,7 @@ struct NegotiationContext {
 	holder_is_initiator: bool,
 	received_tx_add_input_count: u16,
 	received_tx_add_output_count: u16,
-	inputs: HashMap<SerialId, InteractiveTxInput>,
+	inputs: BTreeMap<SerialId, InteractiveTxInput>,
 	/// Optional intended/expected funding input, used during splicing.
 	/// The funding input is shared, it is usually co-owned by both peers.
 	/// - For the initiator:
@@ -836,7 +837,7 @@ struct NegotiationContext {
 	shared_funding_output: SharedOwnedOutput,
 	prevtx_outpoints: HashSet<OutPoint>,
 	/// The outputs added so far.
-	outputs: HashMap<SerialId, InteractiveTxOutput>,
+	outputs: BTreeMap<SerialId, InteractiveTxOutput>,
 	/// The locktime of the funding transaction.
 	tx_locktime: AbsoluteLockTime,
 	/// The fee rate used for the transaction
@@ -881,11 +882,11 @@ impl NegotiationContext {
 			holder_is_initiator,
 			received_tx_add_input_count: 0,
 			received_tx_add_output_count: 0,
-			inputs: new_hash_map(),
+			inputs: BTreeMap::new(),
 			shared_funding_input,
 			shared_funding_output,
 			prevtx_outpoints: new_hash_set(),
-			outputs: new_hash_map(),
+			outputs: BTreeMap::new(),
 			tx_locktime,
 			feerate_sat_per_kw,
 		}
@@ -1030,13 +1031,13 @@ impl NegotiationContext {
 		};
 
 		match self.inputs.entry(msg.serial_id) {
-			hash_map::Entry::Occupied(_) => {
+			btree_map::Entry::Occupied(_) => {
 				// The receiving node:
 				//  - MUST fail the negotiation if:
 				//    - the `serial_id` is already included in the transaction
 				Err(AbortReason::DuplicateSerialId)
 			},
-			hash_map::Entry::Vacant(entry) => {
+			btree_map::Entry::Vacant(entry) => {
 				if !self.prevtx_outpoints.insert(prev_outpoint) {
 					// The receiving node:
 					//  - MUST fail the negotiation if:
@@ -1140,13 +1141,13 @@ impl NegotiationContext {
 		let output =
 			InteractiveTxOutput { serial_id: msg.serial_id, added_by: AddingRole::Remote, output };
 		match self.outputs.entry(msg.serial_id) {
-			hash_map::Entry::Occupied(_) => {
+			btree_map::Entry::Occupied(_) => {
 				// The receiving node:
 				//  - MUST fail the negotiation if:
 				//    - the `serial_id` is already included in the transaction
 				Err(AbortReason::DuplicateSerialId)
 			},
-			hash_map::Entry::Vacant(entry) => {
+			btree_map::Entry::Vacant(entry) => {
 				entry.insert(output);
 				Ok(())
 			},