From 0c949dcd04d8e94e2fe4fd9d9d867825822176a7 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Wed, 13 Dec 2023 16:05:43 +1030
Subject: [PATCH] lightningd: permit wrong-alias lookups for private
 channel_update.

This is wrong, but we send them for now in zeroconf!

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 lightningd/gossip_control.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/lightningd/gossip_control.c b/lightningd/gossip_control.c
index 4378f6c1a..b4083c29a 100644
--- a/lightningd/gossip_control.c
+++ b/lightningd/gossip_control.c
@@ -205,6 +205,30 @@ static void set_channel_remote_update(struct lightningd *ld,
 	wallet_channel_save(ld->wallet, channel);
 }
 
+/* One of the few places where we look up by *remote* id.  It's not unique,
+ * but it is unique for a specific peer. */
+static struct channel *lookup_by_peer_remote_alias(struct lightningd *ld,
+						   const struct node_id *source,
+						   struct short_channel_id scid)
+{
+	const struct peer *p;
+	struct channel *chan;
+
+	if (!source)
+		return NULL;
+
+	p = peer_by_id(ld, source);
+	if (!p)
+		return NULL;
+
+	list_for_each(&p->channels, chan, list) {
+		if (chan->alias[REMOTE]
+		    && short_channel_id_eq(&scid, chan->alias[REMOTE]))
+			return chan;
+	}
+	return NULL;
+}
+
 static void handle_peer_update_data(struct lightningd *ld, const u8 *msg)
 {
 	struct channel *channel;
@@ -216,8 +240,10 @@ static void handle_peer_update_data(struct lightningd *ld, const u8 *msg)
 		fatal("Gossip gave bad GOSSIPD_REMOTE_CHANNEL_UPDATE %s",
 		      tal_hex(msg, msg));
 	channel = any_channel_by_scid(ld, &update->scid, true);
+	if (!channel)
+		channel = lookup_by_peer_remote_alias(ld, source, update->scid);
 	if (!channel) {
-		log_unusual(ld->log, "Bad gossip: could not find channel %s for peer's "
+		log_unusual(ld->log, "Bad gossip order: could not find channel %s for peer's "
 			    "channel update",
 			    short_channel_id_to_str(tmpctx, &update->scid));
 		return;