From a799bf88e0e26763f8cb072500b10f3cc3102e87 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Sun, 1 Nov 2026 19:51:08 +0100
Subject: libp2p: remember wrong addresses

---
 src/transport/libp2p/book.rs | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

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

diff --git a/src/transport/libp2p/book.rs b/src/transport/libp2p/book.rs
index c5a73c4..8620895 100644
--- a/src/transport/libp2p/book.rs
+++ b/src/transport/libp2p/book.rs
@@ -44,6 +44,11 @@ pub(super) struct Book {
     /// 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>>,
+    /// Addresses where a dial for a peer reached another (`wrongPeerId`), say a NATed
+    /// peer's LAN address in a range our LAN uses too: not that peer's, whatever
+    /// identify or the member list say, so not kept, dialled or explored again. As long
+    /// as the peer is known (`prune`), `WRONG_PER_PEER` each.
+    pub(super) wrong: 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>,
@@ -224,6 +229,7 @@ impl Book {
             self.addresses.remove(peer);
             self.identified.remove(peer);
             self.explored.remove(peer);
+            self.wrong.remove(peer);
             self.relays.remove(peer);
             self.public_relays.remove(peer);
             self.continuum.remove(peer);
@@ -467,6 +473,19 @@ impl Book {
     /// one it doesn't publish (`Libp2pConfig::ignore`). Nor one in a range this node
     /// leaves out, directly or through a relay there (`left_out`): never dialled, it
     /// would only take a place, and be passed on.
+    /// A dial for `peer` at `address` reached another peer: `address` isn't `peer`'s.
+    /// Forgotten, and not taken again (`wrong`).
+    pub(super) fn not_theirs(&mut self, peer: PeerId, address: Multiaddr) {
+        let address = without_peer(address);
+        if let Some(known) = self.addresses.get_mut(&peer) {
+            known.retain(|known| *known != address);
+        }
+        let wrong = self.wrong.entry(peer).or_default();
+        if wrong.len() < WRONG_PER_PEER {
+            wrong.insert(address);
+        }
+    }
+
     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 {
@@ -475,6 +494,13 @@ impl Book {
         if self.left_out(&address) {
             return;
         }
+        if self
+            .wrong
+            .get(&peer)
+            .is_some_and(|wrong| wrong.contains(&address))
+        {
+            return;
+        }
         if self
             .identified
             .get(&peer)
-- 
cgit v1.3.1