Determine if we have lost data

Deserialise the ChannelMonitors and compare the data to determine if we have
lost some states.

Author: adi2011

lightning/src/ln/channelmanager.rs

@@ -81,7 +81,7 @@ use crate::ln::onion_utils::{
 	decode_fulfill_attribution_data, HTLCFailReason, LocalHTLCFailureReason,
 };
 use crate::ln::onion_utils::{process_fulfill_attribution_data, AttributionData};
-use crate::ln::our_peer_storage::EncryptedOurPeerStorage;
+use crate::ln::our_peer_storage::{EncryptedOurPeerStorage, PeerStorageMonitorHolderList};
 #[cfg(test)]
 use crate::ln::outbound_payment;
 use crate::ln::outbound_payment::{
@@ -2959,6 +2959,7 @@ pub(super) const MAX_UNFUNDED_CHANNEL_PEERS: usize = 50;
 /// This constant defines the upper limit for the size of data
 /// that can be stored for a peer. It is set to 1024 bytes (1 kilobyte)
 /// to prevent excessive resource consumption.
+#[cfg(not(test))]
 const MAX_PEER_STORAGE_SIZE: usize = 1024;
 
 /// The maximum number of peers which we do not have a (funded) channel with. Once we reach this
@@ -9332,7 +9333,54 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 		};
 
 		log_trace!(logger, "Got valid {}-byte peer backup from {}", decrypted.len(), peer_node_id);
+		let per_peer_state = self.per_peer_state.read().unwrap();
+
+		let mut cursor = io::Cursor::new(decrypted);
+		let mon_list = <PeerStorageMonitorHolderList as Readable>::read(&mut cursor).unwrap_or_else(|e| {
+			// This should NEVER happen.
+			log_debug!(self.logger, "Unable to unpack the retrieved peer storage {:?}", e);
+			PeerStorageMonitorHolderList { monitors: Vec::new() }
+		});
+
+		for mon_holder in mon_list.monitors.iter() {
+			let peer_state_mutex =
+				match per_peer_state.get(&mon_holder.counterparty_node_id) {
+					Some(mutex) => mutex,
+					None => {
+						log_debug!(
+							logger,
+							"Not able to find peer_state for the counterparty {}, channelId {}",
+							log_pubkey!(mon_holder.counterparty_node_id),
+							mon_holder.channel_id
+						);
+						continue;
+					},
+				};
 
+			let peer_state_lock = peer_state_mutex.lock().unwrap();
+			let peer_state = &*peer_state_lock;
+
+			match peer_state.channel_by_id.get(&mon_holder.channel_id) {
+				Some(chan) => {
+					if let Some(funded_chan) = chan.as_funded() {
+						if funded_chan
+							.get_revoked_counterparty_commitment_transaction_number()
+							> mon_holder.min_seen_secret
+						{
+							panic!(
+								"Lost channel state for channel {}.\n\
+								Received peer storage with a more recent state than what our node had.\n\
+								Use the FundRecoverer to initiate a force close and sweep the funds.",
+								&mon_holder.channel_id
+							);
+						}
+					}
+				},
+				None => {
+					log_debug!(logger, "Found an unknown channel {}", &mon_holder.channel_id);
+				},
+			}
+		}
 		Ok(())
 	}
 
@@ -9358,6 +9406,7 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 			), ChannelId([0; 32])));
 		}
 
+		#[cfg(not(test))]
 		if msg.data.len() > MAX_PEER_STORAGE_SIZE {
 			log_debug!(logger, "Sending warning to peer and ignoring peer storage request from {} as its over 1KiB", log_pubkey!(counterparty_node_id));