gossipd: replay old spent UTXOs when restarting.

This may help the cases we see where gossipd doesn't realize channels
are closed (because of shutdown before it processed the closing).

Signed-off-by: Rusty Russell <[email protected]>
Changelog-Fixed: `gossipd` will no longer miss some channel closes on restart.

Author: rustyrussell

gossipd/gossmap_manage.c

@@ -1242,6 +1242,12 @@ void gossmap_manage_channel_spent(struct gossmap_manage *gm,
 		return;
 	}
 
+	/* Is it already dying?  It's lightningd re-telling us */
+	for (size_t i = 0; i < tal_count(gm->dying_channels); i++) {
+		if (short_channel_id_eq(gm->dying_channels[i].scid, scid))
+			return;
+	}
+
 	/* BOLT #7:
 	 *   - once its funding output has been spent OR reorganized out:
 	 *     - SHOULD forget a channel after a 12-block delay.

lightningd/gossip_control.c

@@ -251,9 +251,25 @@ static void gossipd_init_done(struct subd *gossipd,
 			      const int *fds,
 			      void *unused)
 {
+	struct lightningd *ld = gossipd->ld;
+	u32 oldspends;
+
 	/* Any channels without channel_updates, we populate now: gossipd
 	 * might have lost its gossip_store. */
-	channel_gossip_init_done(gossipd->ld);
+	channel_gossip_init_done(ld);
+
+	/* Tell it about any closures it might have missed! */
+	oldspends = wallet_utxoset_oldest_spentheight(tmpctx, ld->wallet);
+	if (oldspends) {
+		while (oldspends <= get_block_height(ld->topology)) {
+			const struct short_channel_id *scids;
+
+			scids = wallet_utxoset_get_spent(tmpctx, ld->wallet,
+							 oldspends);
+			gossipd_notify_spends(ld, oldspends, scids);
+			oldspends++;
+		}
+	}
 
 	/* Break out of loop, so we can begin */
 	log_debug(gossipd->ld->log, "io_break: %s", __func__);

wallet/wallet.c

@@ -4462,6 +4462,26 @@ wallet_utxoset_get_spent(const tal_t *ctx, struct wallet *w,
 	return db_scids(ctx, stmt);
 }
 
+u32 wallet_utxoset_oldest_spentheight(const tal_t *ctx, struct wallet *w)
+{
+	struct db_stmt *stmt;
+	u32 height;
+	stmt = db_prepare_v2(w->db, SQL("SELECT"
+					" spendheight "
+					"FROM utxoset "
+					"WHERE spendheight IS NOT NULL "
+					"ORDER BY spendheight ASC "
+					"LIMIT 1"));
+	db_query_prepared(stmt);
+
+	if (db_step(stmt))
+		height = db_col_int(stmt, "spendheight");
+	else
+		height = 0;
+	tal_free(stmt);
+	return height;
+}
+
 const struct short_channel_id *
 wallet_utxoset_get_created(const tal_t *ctx, struct wallet *w,
 			   u32 blockheight)

wallet/wallet.h

@@ -1138,6 +1138,9 @@ wallet_utxoset_get_spent(const tal_t *ctx, struct wallet *w, u32 blockheight);
 /* Prune all UTXO entries spent (far) below this block height */
 void wallet_utxoset_prune(struct wallet *w, u32 blockheight);
 
+/* Get oldest spendheight (or 0 if none), to catch up */
+u32 wallet_utxoset_oldest_spentheight(const tal_t *ctx, struct wallet *w);
+
 /**
  * Retrieve all UTXO entries that were created at a given blockheight.
  */