Peer Storage (Part 3): Identifying Lost Channel States

Cargo.toml

@@ -68,4 +68,5 @@ check-cfg = [
     "cfg(splicing)",
     "cfg(async_payments)",
     "cfg(simple_close)",
+    "cfg(peer_storage)",
 ]

ci/ci-tests.sh

@@ -158,3 +158,5 @@ RUSTFLAGS="--cfg=async_payments" cargo test --verbose --color always -p lightnin
 RUSTFLAGS="--cfg=simple_close" cargo test --verbose --color always -p lightning
 [ "$CI_MINIMIZE_DISK_USAGE" != "" ] && cargo clean
 RUSTFLAGS="--cfg=lsps1_service" cargo test --verbose --color always -p lightning-liquidity
+[ "$CI_MINIMIZE_DISK_USAGE" != "" ] && cargo clean
+RUSTFLAGS="--cfg=peer_storage" cargo test --verbose --color always -p lightning

lightning/src/chain/chainmonitor.rs

@@ -28,6 +28,8 @@ use bitcoin::hash_types::{BlockHash, Txid};
 
 use crate::chain;
 use crate::chain::chaininterface::{BroadcasterInterface, FeeEstimator};
+#[cfg(peer_storage)]
+use crate::chain::channelmonitor::write_chanmon_internal;
 use crate::chain::channelmonitor::{
 	Balance, ChannelMonitor, ChannelMonitorUpdate, MonitorEvent, TransactionOutputs,
 	WithChannelMonitor,
@@ -37,7 +39,7 @@ use crate::chain::{ChannelMonitorUpdateStatus, Filter, WatchedOutput};
 use crate::events::{self, Event, EventHandler, ReplayEvent};
 use crate::ln::channel_state::ChannelDetails;
 use crate::ln::msgs::{self, BaseMessageHandler, Init, MessageSendEvent, SendOnlyMessageHandler};
-use crate::ln::our_peer_storage::DecryptedOurPeerStorage;
+use crate::ln::our_peer_storage::{DecryptedOurPeerStorage, PeerStorageMonitorHolder};
 use crate::ln::types::ChannelId;
 use crate::prelude::*;
 use crate::sign::ecdsa::EcdsaChannelSigner;
@@ -47,6 +49,8 @@ use crate::types::features::{InitFeatures, NodeFeatures};
 use crate::util::errors::APIError;
 use crate::util::logger::{Logger, WithContext};
 use crate::util::persist::MonitorName;
+#[cfg(peer_storage)]
+use crate::util::ser::{VecWriter, Writeable};
 use crate::util::wakers::{Future, Notifier};
 use bitcoin::secp256k1::PublicKey;
 use core::ops::Deref;
@@ -809,11 +813,57 @@ where
 		mon.values().map(|monitor| monitor.monitor.get_counterparty_node_id()).collect()
 	}
 
+	#[cfg(peer_storage)]
 	fn send_peer_storage(&self, their_node_id: PublicKey) {
-		// TODO: Serialize `ChannelMonitor`s inside `our_peer_storage`.
-
+		#[allow(unused_mut)]
+		let mut monitors_list: Vec<PeerStorageMonitorHolder> = Vec::new();
 		let random_bytes = self.entropy_source.get_secure_random_bytes();
-		let serialised_channels = Vec::new();
+
+		const MAX_PEER_STORAGE_SIZE: usize = 65531;
+		const USIZE_LEN: usize = core::mem::size_of::<usize>();
+		let mut usize_bytes = [0u8; USIZE_LEN];
+		usize_bytes.copy_from_slice(&random_bytes[0..USIZE_LEN]);
+		let random_usize = usize::from_le_bytes(usize_bytes);
+
+		let mut curr_size = 0;
+		let monitors = self.monitors.read().unwrap();
+		let mut stored_chanmon_idx = alloc::collections::BTreeSet::<usize>::new();
+		// Used as a fallback reference if the set is empty
+		let zero = 0;
+
+		while curr_size < MAX_PEER_STORAGE_SIZE
+			&& *stored_chanmon_idx.last().unwrap_or(&zero) < monitors.len()
+		{
+			let idx = random_usize % monitors.len();
+			stored_chanmon_idx.insert(idx + 1);
+			let (cid, mon) = monitors.iter().skip(idx).next().unwrap();
+
+			let mut ser_chan = VecWriter(Vec::new());
+			let min_seen_secret = mon.monitor.get_min_seen_secret();
+			let counterparty_node_id = mon.monitor.get_counterparty_node_id();
+			{
+				let chan_mon = mon.monitor.inner.lock().unwrap();
+
+				write_chanmon_internal(&chan_mon, true, &mut ser_chan)
+					.expect("can not write Channel Monitor for peer storage message");
+			}
+			let peer_storage_monitor = PeerStorageMonitorHolder {
+				channel_id: *cid,
+				min_seen_secret,
+				counterparty_node_id,
+				monitor_bytes: ser_chan.0,
+			};
+
+			// Adding size of peer_storage_monitor.
+			curr_size += peer_storage_monitor.serialized_length();
+
+			if curr_size > MAX_PEER_STORAGE_SIZE {
+				break;
+			}
+			monitors_list.push(peer_storage_monitor);
+		}
+
+		let serialised_channels = monitors_list.encode();
 		let our_peer_storage = DecryptedOurPeerStorage::new(serialised_channels);
 		let cipher = our_peer_storage.encrypt(&self.our_peerstorage_encryption_key, &random_bytes);
 
@@ -920,6 +970,7 @@ where
 			)
 		});
 
+		#[cfg(peer_storage)]
 		// Send peer storage everytime a new block arrives.
 		for node_id in self.all_counterparty_node_ids() {
 			self.send_peer_storage(node_id);
@@ -1021,6 +1072,7 @@ where
 			)
 		});
 
+		#[cfg(peer_storage)]
 		// Send peer storage everytime a new block arrives.
 		for node_id in self.all_counterparty_node_ids() {
 			self.send_peer_storage(node_id);