fix(examples): call Swarm::add_external_address in dcutr and relay

> Observed addresses (aka. external address candidates) of the local node, reported by a remote node
> via `libp2p-identify`, are no longer automatically considered confirmed external addresses, in
> other words they are no longer trusted by default. Instead users need to confirm the reported
> observed address either manually, or by using `libp2p-autonat`. In trusted environments users can
> simply extract observed addresses from a `libp2p-identify::Event::Received { info:
> libp2p_identify::Info { observed_addr }}` and confirm them via `Swarm::add_external_address`.

Follow-up to libp2p#3954.

examples/dcutr/src/main.rs

@@ -214,6 +214,7 @@ fn main() -> Result<(), Box<dyn Error>> {
                     ..
                 })) => {
                     info!("Relay told us our public address: {:?}", observed_addr);
+                    swarm.add_external_address(observed_addr);
                     learned_observed_addr = true;
                 }
                 event => panic!("{event:?}"),

examples/relay-server/src/main.rs

@@ -82,6 +82,14 @@ fn main() -> Result<(), Box<dyn Error>> {
         loop {
             match swarm.next().await.expect("Infinite Stream.") {
                 SwarmEvent::Behaviour(event) => {
+                    if let BehaviourEvent::Identify(identify::Event::Received {
+                        info: identify::Info { observed_addr, .. },
+                        ..
+                    }) = &event
+                    {
+                        swarm.add_external_address(observed_addr.clone());
+                    }
+
                     println!("{event:?}")
                 }
                 SwarmEvent::NewListenAddr { address, .. } => {

protocols/identify/CHANGELOG.md

@@ -1,5 +1,10 @@
 ## 0.43.0 - unreleased
 
+- Observed addresses (aka. external address candidates) of the local node, reported by a remote node via `libp2p-identify`, are no longer automatically considered confirmed external addresses, in other words they are no longer trusted by default.
+  Instead users need to confirm the reported observed address either manually, or by using `libp2p-autonat`.
+  In trusted environments users can simply extract observed addresses from a `libp2p-identify::Event::Received { info: libp2p_identify::Info { observed_addr }}` and confirm them via `Swarm::add_external_address`.
+  See [PR 3954] and [PR XXX].
+
 - Remove deprecated `Identify` prefixed symbols. See [PR 3698].
 - Raise MSRV to 1.65.
   See [PR 3715].
@@ -17,7 +22,9 @@
 [PR 3698]: https://github.com/libp2p/rust-libp2p/pull/3698
 [PR 3715]: https://github.com/libp2p/rust-libp2p/pull/3715
 [PR 3876]: https://github.com/libp2p/rust-libp2p/pull/3876
+[PR 3954]: https://github.com/libp2p/rust-libp2p/pull/3954
 [PR 3980]: https://github.com/libp2p/rust-libp2p/pull/3980
+[PR XXX]: https://github.com/libp2p/rust-libp2p/pull/XXX
 
 ## 0.42.2