Make the P2PGossipSync UtxoLookup exchangable without &mut self

Because a `UtxoLookup` implementation is likely to need a reference
to the `PeerManager` which contains a reference to the
`P2PGossipSync`, it is likely to be impossible to get a mutable
reference to the `P2PGossipSync` by the time we want to add a
`UtxoLookup` without a ton of boilerplate and trait wrapping.

Instead, we simply place the `UtxoLookup` in a `RwLock`, allowing
us to modify it without a mutable self reference.

The lifetime bounds updates in tests required in this commit are
entirely unclear to me, but do allow tests to continue building, so
somehow make rustc happier.

Author: TheBlueMatt

lightning/src/ln/functional_test_utils.rs

@@ -534,11 +534,11 @@ impl<'a, 'b, 'c> Drop for Node<'a, 'b, 'c> {
 	}
 }
 
-pub fn create_chan_between_nodes<'a, 'b, 'c, 'd>(node_a: &'a Node<'b, 'c, 'd>, node_b: &'a Node<'b, 'c, 'd>) -> (msgs::ChannelAnnouncement, msgs::ChannelUpdate, msgs::ChannelUpdate, [u8; 32], Transaction) {
+pub fn create_chan_between_nodes<'a, 'b, 'c: 'd, 'd>(node_a: &'a Node<'b, 'c, 'd>, node_b: &'a Node<'b, 'c, 'd>) -> (msgs::ChannelAnnouncement, msgs::ChannelUpdate, msgs::ChannelUpdate, [u8; 32], Transaction) {
 	create_chan_between_nodes_with_value(node_a, node_b, 100000, 10001)
 }
 
-pub fn create_chan_between_nodes_with_value<'a, 'b, 'c, 'd>(node_a: &'a Node<'b, 'c, 'd>, node_b: &'a Node<'b, 'c, 'd>, channel_value: u64, push_msat: u64) -> (msgs::ChannelAnnouncement, msgs::ChannelUpdate, msgs::ChannelUpdate, [u8; 32], Transaction) {
+pub fn create_chan_between_nodes_with_value<'a, 'b, 'c: 'd, 'd>(node_a: &'a Node<'b, 'c, 'd>, node_b: &'a Node<'b, 'c, 'd>, channel_value: u64, push_msat: u64) -> (msgs::ChannelAnnouncement, msgs::ChannelUpdate, msgs::ChannelUpdate, [u8; 32], Transaction) {
 	let (channel_ready, channel_id, tx) = create_chan_between_nodes_with_value_a(node_a, node_b, channel_value, push_msat);
 	let (announcement, as_update, bs_update) = create_chan_between_nodes_with_value_b(node_a, node_b, &channel_ready);
 	(announcement, as_update, bs_update, channel_id, tx)
@@ -1078,7 +1078,7 @@ pub fn create_chan_between_nodes_with_value_confirm_second<'a, 'b, 'c>(node_recv
 	}), channel_id)
 }
 
-pub fn create_chan_between_nodes_with_value_confirm<'a, 'b, 'c, 'd>(node_a: &'a Node<'b, 'c, 'd>, node_b: &'a Node<'b, 'c, 'd>, tx: &Transaction) -> ((msgs::ChannelReady, msgs::AnnouncementSignatures), [u8; 32]) {
+pub fn create_chan_between_nodes_with_value_confirm<'a, 'b, 'c: 'd, 'd>(node_a: &'a Node<'b, 'c, 'd>, node_b: &'a Node<'b, 'c, 'd>, tx: &Transaction) -> ((msgs::ChannelReady, msgs::AnnouncementSignatures), [u8; 32]) {
 	let conf_height = core::cmp::max(node_a.best_block_info().1 + 1, node_b.best_block_info().1 + 1);
 	create_chan_between_nodes_with_value_confirm_first(node_a, node_b, tx, conf_height);
 	confirm_transaction_at(node_a, tx, conf_height);
@@ -1087,7 +1087,7 @@ pub fn create_chan_between_nodes_with_value_confirm<'a, 'b, 'c, 'd>(node_a: &'a
 	create_chan_between_nodes_with_value_confirm_second(node_b, node_a)
 }
 
-pub fn create_chan_between_nodes_with_value_a<'a, 'b, 'c, 'd>(node_a: &'a Node<'b, 'c, 'd>, node_b: &'a Node<'b, 'c, 'd>, channel_value: u64, push_msat: u64) -> ((msgs::ChannelReady, msgs::AnnouncementSignatures), [u8; 32], Transaction) {
+pub fn create_chan_between_nodes_with_value_a<'a, 'b, 'c: 'd, 'd>(node_a: &'a Node<'b, 'c, 'd>, node_b: &'a Node<'b, 'c, 'd>, channel_value: u64, push_msat: u64) -> ((msgs::ChannelReady, msgs::AnnouncementSignatures), [u8; 32], Transaction) {
 	let tx = create_chan_between_nodes_with_value_init(node_a, node_b, channel_value, push_msat);
 	let (msgs, chan_id) = create_chan_between_nodes_with_value_confirm(node_a, node_b, &tx);
 	(msgs, chan_id, tx)
@@ -1127,11 +1127,11 @@ pub fn create_chan_between_nodes_with_value_b<'a, 'b, 'c>(node_a: &Node<'a, 'b,
 	((*announcement).clone(), as_update, bs_update)
 }
 
-pub fn create_announced_chan_between_nodes<'a, 'b, 'c, 'd>(nodes: &'a Vec<Node<'b, 'c, 'd>>, a: usize, b: usize) -> (msgs::ChannelUpdate, msgs::ChannelUpdate, [u8; 32], Transaction) {
+pub fn create_announced_chan_between_nodes<'a, 'b, 'c: 'd, 'd>(nodes: &'a Vec<Node<'b, 'c, 'd>>, a: usize, b: usize) -> (msgs::ChannelUpdate, msgs::ChannelUpdate, [u8; 32], Transaction) {
 	create_announced_chan_between_nodes_with_value(nodes, a, b, 100000, 10001)
 }
 
-pub fn create_announced_chan_between_nodes_with_value<'a, 'b, 'c, 'd>(nodes: &'a Vec<Node<'b, 'c, 'd>>, a: usize, b: usize, channel_value: u64, push_msat: u64) -> (msgs::ChannelUpdate, msgs::ChannelUpdate, [u8; 32], Transaction) {
+pub fn create_announced_chan_between_nodes_with_value<'a, 'b, 'c: 'd, 'd>(nodes: &'a Vec<Node<'b, 'c, 'd>>, a: usize, b: usize, channel_value: u64, push_msat: u64) -> (msgs::ChannelUpdate, msgs::ChannelUpdate, [u8; 32], Transaction) {
 	let chan_announcement = create_chan_between_nodes_with_value(&nodes[a], &nodes[b], channel_value, push_msat);
 	update_nodes_with_chan_announce(nodes, a, b, &chan_announcement.0, &chan_announcement.1, &chan_announcement.2);
 	(chan_announcement.1, chan_announcement.2, chan_announcement.3, chan_announcement.4)

lightning/src/routing/gossip.rs

@@ -254,7 +254,7 @@ pub struct P2PGossipSync<G: Deref<Target=NetworkGraph<L>>, U: Deref, L: Deref>
 where U::Target: UtxoLookup, L::Target: Logger
 {
 	network_graph: G,
-	utxo_lookup: Option<U>,
+	utxo_lookup: RwLock<Option<U>>,
 	#[cfg(feature = "std")]
 	full_syncs_requested: AtomicUsize,
 	pending_events: Mutex<Vec<MessageSendEvent>>,
@@ -273,7 +273,7 @@ where U::Target: UtxoLookup, L::Target: Logger
 			network_graph,
 			#[cfg(feature = "std")]
 			full_syncs_requested: AtomicUsize::new(0),
-			utxo_lookup,
+			utxo_lookup: RwLock::new(utxo_lookup),
 			pending_events: Mutex::new(vec![]),
 			logger,
 		}
@@ -282,8 +282,8 @@ where U::Target: UtxoLookup, L::Target: Logger
 	/// Adds a provider used to check new announcements. Does not affect
 	/// existing announcements unless they are updated.
 	/// Add, update or remove the provider would replace the current one.
-	pub fn add_utxo_lookup(&mut self, utxo_lookup: Option<U>) {
-		self.utxo_lookup = utxo_lookup;
+	pub fn add_utxo_lookup(&self, utxo_lookup: Option<U>) {
+		*self.utxo_lookup.write().unwrap() = utxo_lookup;
 	}
 
 	/// Gets a reference to the underlying [`NetworkGraph`] which was provided in
@@ -415,7 +415,7 @@ where U::Target: UtxoLookup, L::Target: Logger
 	}
 
 	fn handle_channel_announcement(&self, msg: &msgs::ChannelAnnouncement) -> Result<bool, LightningError> {
-		self.network_graph.update_channel_from_announcement(msg, &self.utxo_lookup)?;
+		self.network_graph.update_channel_from_announcement(msg, &*self.utxo_lookup.read().unwrap())?;
 		Ok(msg.contents.excess_data.len() <= MAX_EXCESS_BYTES_FOR_RELAY)
 	}
 

lightning/src/routing/router.rs

@@ -3495,7 +3495,7 @@ mod tests {
 	fn available_amount_while_routing_test() {
 		// Tests whether we choose the correct available channel amount while routing.
 
-		let (secp_ctx, network_graph, mut gossip_sync, chain_monitor, logger) = build_graph();
+		let (secp_ctx, network_graph, gossip_sync, chain_monitor, logger) = build_graph();
 		let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
 		let scorer = ln_test_utils::TestScorer::new();
 		let keys_manager = ln_test_utils::TestKeysInterface::new(&[0u8; 32], Network::Testnet);