Add a comment describing the timestamp field's use

diff --git a/lightning/src/routing/network_graph.rs b/lightning/src/routing/network_graph.rs
index 2dba12b630f38c98035ebe980aec39f1e4e31adb..10c0ba57b58b05e2a6875795773e4a19188c6cb1 100644 (file)
--- a/lightning/src/routing/network_graph.rs
+++ b/lightning/src/routing/network_graph.rs
@@ -847,6 +847,9 @@ impl NetworkGraph {
                        None => Err(LightningError{err: "No existing channels for node_announcement".to_owned(), action: ErrorAction::IgnoreError}),
                        Some(node) => {
                                if let Some(node_info) = node.announcement_info.as_ref() {
+                                       // The timestamp field is somewhat of a misnomer - the BOLTs use it to order
+                                       // updates to ensure you always have the latest one, only vaguely suggesting
+                                       // that it be at least the current time.
                                        if node_info.last_update  > msg.timestamp {
                                                return Err(LightningError{err: "Update older than last processed update".to_owned(), action: ErrorAction::IgnoreAndLog(Level::Gossip)});
                                        } else if node_info.last_update  == msg.timestamp {
@@ -1084,6 +1087,12 @@ impl NetworkGraph {
                                macro_rules! maybe_update_channel_info {
                                        ( $target: expr, $src_node: expr) => {
                                                if let Some(existing_chan_info) = $target.as_ref() {
+                                                       // The timestamp field is somewhat of a misnomer - the BOLTs use it to
+                                                       // order updates to ensure you always have the latest one, only
+                                                       // suggesting  that it be at least the current time. For
+                                                       // channel_updates specifically, the BOLTs discuss the possibility of
+                                                       // pruning based on the timestamp field being more than two weeks old,
+                                                       // but only in the non-normative section.
                                                        if existing_chan_info.last_update > msg.timestamp {
                                                                return Err(LightningError{err: "Update older than last processed update".to_owned(), action: ErrorAction::IgnoreAndLog(Level::Gossip)});
                                                        } else if existing_chan_info.last_update == msg.timestamp {