From 6fa188610ce0959e0b61ecaf63f5babf826d2071 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Sat, 24 Oct 2026 04:23:38 +0200
Subject: pull missing changes

Nodes push changes to their neighbours but don't relay them directly.
In a partial mesh, nodes can learn about missing changes via keepalive
messages and can pull them from their neighbours.
---
 src/swarm/topology.rs | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

(limited to 'src/swarm/topology.rs')

diff --git a/src/swarm/topology.rs b/src/swarm/topology.rs
index b5880cf..dddf81b 100644
--- a/src/swarm/topology.rs
+++ b/src/swarm/topology.rs
@@ -33,6 +33,18 @@ pub(crate) struct NeighbourView {
     k: usize,
     unreachable: BTreeSet<String>,
     neighbours: BTreeSet<String>,
+    /// Every reachable member is a neighbour.
+    full_mesh: bool,
+}
+
+/// Whether every reachable member is our neighbour (also while the view is unknown).
+pub(crate) fn is_full_mesh(state: &AppState) -> bool {
+    state
+        .neighbours
+        .read()
+        .unwrap_or_else(|poisoned| poisoned.into_inner())
+        .as_ref()
+        .is_none_or(|view| view.full_mesh)
 }
 
 /// Whether we initiate contact with `peer`: HELLOs, keepalives, dormancy checks, sync
@@ -113,10 +125,15 @@ pub(crate) async fn refresh(state: &AppState) -> Option<NeighbourChange> {
         removed = change.removed.len(),
         "Neighbours computed from the member list"
     );
+    let reachable_others = current
+        .iter()
+        .filter(|m| m.as_str() != state.local_id() && !unreachable.contains(*m))
+        .count();
     *state
         .neighbours
         .write()
         .unwrap_or_else(|poisoned| poisoned.into_inner()) = Some(NeighbourView {
+        full_mesh: computed.len() >= reachable_others,
         members: current,
         k,
         unreachable,
-- 
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