From 67a476525bf23fec7aa10a962668cc77cce6c685 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Sun, 1 Nov 2026 05:00:43 +0100
Subject: libp2p: dial newly announced peer addresses

---
 src/transport/libp2p/book.rs | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

(limited to 'src/transport/libp2p/book.rs')

diff --git a/src/transport/libp2p/book.rs b/src/transport/libp2p/book.rs
index 44b2694..7de4be7 100644
--- a/src/transport/libp2p/book.rs
+++ b/src/transport/libp2p/book.rs
@@ -41,6 +41,9 @@ pub(super) struct Book {
     /// connection to the peer closes, as a peer restarted elsewhere is found by what
     /// the others say.
     pub(super) identified: HashMap<PeerId, Vec<Multiaddr>>,
+    /// Addresses of directly connected peers dialled for a better path (`explore`):
+    /// not again while connected, unless our own interfaces change.
+    pub(super) explored: HashMap<PeerId, std::collections::HashSet<Multiaddr>>,
     pub(super) listening: Vec<Multiaddr>,
     /// Where the router forwards to our listen addresses (UPnP, `Libp2pConfig::upnp`).
     pub(super) mapped: Vec<Multiaddr>,
@@ -213,6 +216,7 @@ impl Book {
         for peer in &stale {
             self.addresses.remove(peer);
             self.identified.remove(peer);
+            self.explored.remove(peer);
             self.relays.remove(peer);
             self.public_relays.remove(peer);
             self.continuum.remove(peer);
@@ -475,6 +479,38 @@ impl Book {
         addresses.truncate(ADDRESSES_PER_PEER);
     }
 
+    /// The addresses `explore` dials `peer` at, noted as dialled: a node of the swarm
+    /// connected directly, at addresses of its not dialled so yet, and with `again`
+    /// not only those at an IP it isn't connected at (an inbound connection's remote
+    /// port isn't where the peer listens).
+    pub(super) fn to_explore(&mut self, peer: PeerId, again: bool) -> Vec<Multiaddr> {
+        if !self.continuum.contains(&peer)
+            || book_connection(&self.connections, &peer) != Some(Connection::Direct)
+        {
+            return Vec::new();
+        }
+        let used: Vec<Option<std::net::IpAddr>> = self
+            .connections
+            .values()
+            .filter(|(connected, relayed, _)| *connected == peer && !relayed)
+            .map(|(_, _, address)| ip_of(address))
+            .collect();
+        let tried = self.explored.entry(peer).or_default();
+        let candidates: Vec<Multiaddr> = self
+            .addresses
+            .get(&peer)
+            .into_iter()
+            .flatten()
+            .filter(|address| is_ip(address) && !left_out(&self.ignored, address))
+            .filter(|address| again || !used.contains(&ip_of(address)))
+            .filter(|address| !tried.contains(*address))
+            .take(EXPLORED_AT_ONCE)
+            .cloned()
+            .collect();
+        tried.extend(candidates.iter().cloned());
+        candidates
+    }
+
     /// `peer`, connected, identified itself at `listen` (`published`): its direct
     /// addresses are those from now on, while connected (`remember`); those through
     /// relays and by name stay. Kept in order of `preference`: of a peer with many,
@@ -520,7 +556,7 @@ impl Book {
 }
 
 /// The IP address `address` starts with, if any.
-fn ip_of(address: &Multiaddr) -> Option<std::net::IpAddr> {
+pub(super) fn ip_of(address: &Multiaddr) -> Option<std::net::IpAddr> {
     match address.iter().next() {
         Some(Protocol::Ip4(ip)) => Some(ip.into()),
         Some(Protocol::Ip6(ip)) => Some(ip.into()),
-- 
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