From 8124270037d2949fb455f704f6bc45716179767e Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Sat, 31 Oct 2026 20:51:53 +0100
Subject: libp2p: identify replaces addresses

---
 src/transport/libp2p/book.rs | 40 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 39 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 6706512..ceb9d27 100644
--- a/src/transport/libp2p/book.rs
+++ b/src/transport/libp2p/book.rs
@@ -36,6 +36,11 @@ pub(super) struct NamedRelay {
 #[derive(Default)]
 pub(super) struct Book {
     pub(super) addresses: HashMap<PeerId, Vec<Multiaddr>>,
+    /// Where connected peers say they are, by their last identify (`identified`): while
+    /// connected, the only direct addresses of theirs kept. Forgotten when the last
+    /// connection to the peer closes, as a peer restarted elsewhere is found by what
+    /// the others say.
+    pub(super) identified: HashMap<PeerId, Vec<Multiaddr>>,
     pub(super) listening: Vec<Multiaddr>,
     /// Where the router forwards to our listen addresses (UPnP, `Libp2pConfig::upnp`).
     pub(super) mapped: Vec<Multiaddr>,
@@ -205,6 +210,7 @@ impl Book {
             .collect();
         for peer in &stale {
             self.addresses.remove(peer);
+            self.identified.remove(peer);
             self.relays.remove(peer);
             self.public_relays.remove(peer);
             self.continuum.remove(peer);
@@ -439,18 +445,50 @@ impl Book {
             .all(|address| known.contains(&without_peer(address.clone())))
     }
 
-    /// `peer` is at `address` (without its `/p2p` part): kept first.
+    /// `peer` is at `address` (without its `/p2p` part): kept first. Not a direct
+    /// address the peer's identify left out (`identified`): one it no longer has, or
+    /// one it doesn't publish (`Libp2pConfig::ignore`).
     pub(super) fn remember(&mut self, peer: PeerId, address: Multiaddr) {
         let address = without_peer(address);
         if !self.addresses.contains_key(&peer) && self.addresses.len() >= MAX_PEERS {
             return;
         }
+        if self
+            .identified
+            .get(&peer)
+            .is_some_and(|said| is_ip(&address) && !said.contains(&address))
+        {
+            return;
+        }
         self.touch(peer);
         let addresses = self.addresses.entry(peer).or_default();
         addresses.retain(|known| *known != address);
         addresses.insert(0, address);
         addresses.truncate(ADDRESSES_PER_PEER);
     }
+
+    /// `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.
+    pub(super) fn identified(&mut self, peer: PeerId, listen: Vec<Multiaddr>) {
+        let listen: Vec<Multiaddr> = listen.into_iter().map(without_peer).collect();
+        if let Some(known) = self.addresses.get_mut(&peer) {
+            known.retain(|address| !is_ip(address) || listen.contains(address));
+        }
+        self.identified.insert(peer, listen.clone());
+        // Last first: `remember` puts each in front.
+        for address in listen.into_iter().rev() {
+            self.remember(peer, address);
+        }
+    }
+}
+
+/// Whether `address` is a direct one at an IP address (not through a relay, nor a name).
+pub(super) fn is_ip(address: &Multiaddr) -> bool {
+    matches!(
+        address.iter().next(),
+        Some(Protocol::Ip4(_) | Protocol::Ip6(_))
+    ) && !is_relayed(address)
 }
 
 /// Whether `address` goes through a relay.
-- 
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