From: Matt Corallo <git@bluematt.me>
Date: Sat, 21 Sep 2024 04:23:09 +0000 (+0000)
Subject: Avoid a `short_to_chan_info` read lock in `claim_funds_from_hop`
X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=b423a33bc7e90234b5b9b45a960c59d1d0d2fdc7;p=rust-lightning

Avoid a `short_to_chan_info` read lock in `claim_funds_from_hop`

In 453ed11f80b40f28b6e95a74b1f7ed2cd7f012ad we started tracking the
counterparty's `node_id` in `HTLCPreviousHopData`, however we were
still trying to look it up using `prev_short_channel_id` in
`claim_funds_from_hop`.

Because we now usually have the counterparty's `node_id` directly
accessible, we should skip the `prev_short_channel_id` lookup.

This will also be more important in the next commit where we need
to look up state for our counterparty to generate
`ChannelMonitorUpdate`s whether we have a live channel or not.
---

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 5315e6a4e..aab2ec031 100644
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -6928,11 +6928,10 @@ where
 		&self, prev_hop: HTLCPreviousHopData, payment_preimage: PaymentPreimage,
 		payment_info: Option<PaymentClaimDetails>, completion_action: ComplFunc,
 	) {
-		let counterparty_node_id =
-			match self.short_to_chan_info.read().unwrap().get(&prev_hop.short_channel_id) {
-				Some((cp_id, _dup_chan_id)) => Some(cp_id.clone()),
-				None => None
-			};
+		let counterparty_node_id = prev_hop.counterparty_node_id.or_else(|| {
+			let short_to_chan_info = self.short_to_chan_info.read().unwrap();
+			short_to_chan_info.get(&prev_hop.short_channel_id).map(|(cp_id, _)| *cp_id)
+		});
 
 		let htlc_source = HTLCClaimSource {
 			counterparty_node_id,