fix(swarm): external address candidate only after address translation

Pull-Request: #4158.

Cargo.lock

@@ -3104,7 +3104,7 @@ dependencies = [
 
 [[package]]
 name = "libp2p-swarm"
-version = "0.43.0"
+version = "0.43.1"
 dependencies = [
  "async-std",
  "either",

Cargo.toml

@@ -87,7 +87,7 @@ libp2p-quic = { version = "0.8.0-alpha", path = "transports/quic" }
 libp2p-relay = { version = "0.16.0", path = "protocols/relay" }
 libp2p-rendezvous = { version = "0.13.0", path = "protocols/rendezvous" }
 libp2p-request-response = { version = "0.25.0", path = "protocols/request-response" }
-libp2p-swarm = { version = "0.43.0", path = "swarm" }
+libp2p-swarm = { version = "0.43.1", path = "swarm" }
 libp2p-swarm-derive = { version = "0.33.0", path = "swarm-derive" }
 libp2p-swarm-test = { version = "0.2.0", path = "swarm-test" }
 libp2p-tcp = { version = "0.40.0", path = "transports/tcp" }

swarm/CHANGELOG.md

@@ -1,4 +1,11 @@
-## 0.43.0 
+## 0.43.1 - unreleased
+
+- Do not announce external address candidate before address translation, unless translation does not apply.
+  This will prevent ephemeral TCP addresses being announced as external address candidates.
+  See [PR 4158].
+
+
+## 0.43.0
 
 - Allow `NetworkBehaviours` to create and remove listeners.
   See [PR 3292].

swarm/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-swarm"
 edition = "2021"
 rust-version = { workspace = true }
 description = "The libp2p swarm"
-version = "0.43.0"
+version = "0.43.1"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"

swarm/src/lib.rs

@@ -1062,14 +1062,8 @@ where
                 self.pending_event = Some((peer_id, handler, event));
             }
             ToSwarm::NewExternalAddrCandidate(addr) => {
-                self.behaviour
-                    .on_swarm_event(FromSwarm::NewExternalAddrCandidate(
-                        NewExternalAddrCandidate { addr: &addr },
-                    ));
-
-                // Generate more candidates based on address translation.
+                // Apply address translation to the candidate address.
                 // For TCP without port-reuse, the observed address contains an ephemeral port which needs to be replaced by the port of a listen address.
-
                 let translated_addresses = {
                     let mut addrs: Vec<_> = self
                         .listened_addrs
@@ -1083,11 +1077,20 @@ where
                     addrs.dedup();
                     addrs
                 };
-                for addr in translated_addresses {
+
+                // If address translation yielded nothing, broacast the original candidate address.
+                if translated_addresses.is_empty() {
                     self.behaviour
                         .on_swarm_event(FromSwarm::NewExternalAddrCandidate(
                             NewExternalAddrCandidate { addr: &addr },
                         ));
+                } else {
+                    for addr in translated_addresses {
+                        self.behaviour
+                            .on_swarm_event(FromSwarm::NewExternalAddrCandidate(
+                                NewExternalAddrCandidate { addr: &addr },
+                            ));
+                    }
                 }
             }
             ToSwarm::ExternalAddrConfirmed(addr) => {