From c12ce1a67e387474d17419bb252211bf04b2e443 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Tue, 3 Nov 2026 01:19:05 +0100
Subject: always announce new heads

---
 src/simtest/relay.rs | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

(limited to 'src/simtest')

diff --git a/src/simtest/relay.rs b/src/simtest/relay.rs
index 9b016b8..dadeed3 100644
--- a/src/simtest/relay.rs
+++ b/src/simtest/relay.rs
@@ -64,3 +64,56 @@ async fn changes_reach_members_the_writer_cant_reach_at_once() {
         .await;
     }
 }
+
+/// One transport, a full mesh by the member list, but the writer x reaches b alone (as
+/// one behind NAT may): what x writes reaches c through b, at once, though the member
+/// list makes c x's neighbour too.
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn changes_reach_members_the_writer_fails_to_reach_at_once() {
+    let keepalive = Duration::from_secs(5);
+    let slow = move |config: &mut crate::node::NodeConfig| {
+        config.timing = Timing::new(keepalive, SYNC_REPLY_TIMEOUT, DELIVERY_LIMIT);
+    };
+    let sim = Sim::with_identity(63);
+    // Nothing between x and c, either way.
+    let cut = crate::transport::sim::LinkParams {
+        loss: 1.0,
+        ..Default::default()
+    };
+    sim.net.set_link("x", "c", cut.clone());
+    sim.net.set_link("c", "x", cut);
+    let b = sim.start_on_with("b", &["sim"], &[], Start::Genesis, slow);
+    let c = sim.start_on_with("c", &["sim"], &["b"], Start::Join, slow);
+    let x = sim.start_on_with("x", &["sim"], &["b"], Start::Join, slow);
+    sim.wait_ready(&[&b, &c, &x], SOON).await;
+    let (c_id, x_id) = (c.local_id().to_owned(), x.local_id().to_owned());
+    {
+        let (b, c_id, x_id) = (&b, c_id.clone(), x_id.clone());
+        sim.wait_until(
+            "b knows its neighbours, a full mesh, x and c among them",
+            SOON,
+            move || {
+                let (c_id, x_id) = (c_id.clone(), x_id.clone());
+                async move {
+                    topology::view_known(b)
+                        && topology::is_full_mesh(b)
+                        && topology::is_neighbour(b, &c_id)
+                        && topology::is_neighbour(b, &x_id)
+                }
+            },
+        )
+        .await;
+    }
+    sim.wait_converged(&[&b, &c, &x], SOON).await;
+
+    write(&x, "y", json!(1)).await;
+    {
+        let c = &c;
+        sim.wait_until(
+            "c has x's write within a second",
+            Duration::from_secs(1),
+            move || async move { read(c, "y").await == Some(json!(1)) },
+        )
+        .await;
+    }
+}
-- 
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