From d7959009790a422ebb17d4c4ab1d9be3d48dc511 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Wed, 28 Oct 2026 17:38:16 +0100
Subject: list libp2p relays in document

---
 src/swarm/members.rs  | 32 ++++++++++++++++++++++++++++++++
 src/swarm/topology.rs |  1 +
 2 files changed, 33 insertions(+)

(limited to 'src/swarm')

diff --git a/src/swarm/members.rs b/src/swarm/members.rs
index c2edd01..3bfb9cf 100644
--- a/src/swarm/members.rs
+++ b/src/swarm/members.rs
@@ -146,6 +146,27 @@ pub(crate) fn learn_addresses(state: &AppState, doc: &AutoCommit) {
     }
 }
 
+/// Relays listed for the swarm, at most this many.
+const MAX_RELAYS: usize = 32;
+
+/// The relays listed for the swarm under `_continuum/relays` (by `--protocol-writers`):
+/// addresses (`libp2p:<multiaddr>`, with or without the relay's peer ID) of relays that
+/// aren't members, e.g. nodes that only relay. Every member's transport may
+/// pick them (`Transport::learn_relays`), after the relays it is configured with.
+pub(crate) fn relays(doc: &AutoCommit) -> Vec<String> {
+    match store::read_path(doc, &meta::path(&[meta::RELAYS])) {
+        Ok(Some(JsonValue::Array(items))) => items
+            .into_iter()
+            .filter_map(|item| match item {
+                JsonValue::String(address) => Some(address),
+                _ => None,
+            })
+            .take(MAX_RELAYS)
+            .collect(),
+        _ => Vec::new(),
+    }
+}
+
 fn alive_path(pk: &str) -> Vec<String> {
     let mut path = member_path(pk);
     path.push("alive".to_owned());
@@ -302,6 +323,17 @@ mod tests {
         );
     }
 
+    #[test]
+    fn listed_relays() {
+        let mut doc = AutoCommit::new();
+        assert!(relays(&doc).is_empty());
+        let relay = "libp2p:/ip6/fd00::1/tcp/9661";
+        store::write_path(&mut doc, &meta::path(&[meta::RELAYS]), &json!([relay, 7])).unwrap();
+        assert_eq!(relays(&doc), [relay]); // Anything but text is ignored.
+        store::write_path(&mut doc, &meta::path(&[meta::RELAYS]), &json!(relay)).unwrap();
+        assert!(relays(&doc).is_empty()); // Not a list.
+    }
+
     #[test]
     fn renewal_interval() {
         let day = Duration::from_secs(24 * 3600);
diff --git a/src/swarm/topology.rs b/src/swarm/topology.rs
index 1e4f5b9..1d98637 100644
--- a/src/swarm/topology.rs
+++ b/src/swarm/topology.rs
@@ -163,6 +163,7 @@ pub(crate) async fn refresh(state: &AppState) -> Option<NeighbourChange> {
         let replica = state.doc.read().await;
         members::learn_addresses(state, &replica.doc);
         set_aliases(state, members::aliases(&replica.doc));
+        state.transport.learn_relays(&members::relays(&replica.doc));
         let current = members::members(&replica.doc);
         // Those that said they are alive within the electorate window.
         let alive: BTreeSet<String> = members::electorate(
-- 
cgit v1.3.1