+// This file is Copyright its original authors, visible in version control
+// history.
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+//! This module contains traits for LDK to access UTXOs to check gossip data is correct.
+//!
+//! When lightning nodes gossip channel information, they resist DoS attacks by checking that each
+//! channel matches a UTXO on-chain, requiring at least some marginal on-chain transacting in
+//! order to announce a channel. This module handles that checking.
+
+use bitcoin::{BlockHash, TxOut};
+
+/// An error when accessing the chain via [`UtxoLookup`].
+#[derive(Clone, Debug)]
+pub enum UtxoLookupError {
+ /// The requested chain is unknown.
+ UnknownChain,
+
+ /// The requested transaction doesn't exist or hasn't confirmed.
+ UnknownTx,
+}
+
+/// The `UtxoLookup` trait defines behavior for accessing on-chain UTXOs.
+pub trait UtxoLookup {
+ /// Returns the transaction output of a funding transaction encoded by [`short_channel_id`].
+ /// Returns an error if `genesis_hash` is for a different chain or if such a transaction output
+ /// is unknown.
+ ///
+ /// [`short_channel_id`]: https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#definition-of-short_channel_id
+ fn get_utxo(&self, genesis_hash: &BlockHash, short_channel_id: u64) -> Result<TxOut, UtxoLookupError>;
+}