mdns discovered node expire too quick

[lynic]

I try to modify this example and handle mdns expired event https://github.com/libp2p/rust-libp2p/blob/master/examples/distributed-key-value-store.rs

            SwarmEvent::Behaviour(MyBehaviourEvent::Mdns(MdnsEvent::Discovered(list))) => {
                for (peer_id, multiaddr) in list {
                    println!("discover {} {}", peer_id, multiaddr);
                    swarm.behaviour_mut().kademlia.add_address(&peer_id, multiaddr);
                }
            }
            SwarmEvent::Behaviour(MyBehaviourEvent::Mdns(MdnsEvent::Expired(list))) => {
                for (peer_id, multiaddr) in list {
                    println!("expire {} {}", peer_id, multiaddr);
                    if !swarm.behaviour().mdns.has_node(&peer_id) {
                        println!("remove {} from kad", peer_id);
                        swarm.behaviour_mut().kademlia.add_address(&peer_id, multiaddr);
                    }
                }
            }

After seconds the new node discovered, the node expired events received.

(base) vagrant@vagrant-PC:~/Documents/source/public/rust-libp2p$ docker run -it --rm -v $(pwd):/opt/p2p ubuntu:20.04 /opt/p2p/target/debug/examples/elynn
Listening in "/ip4/127.0.0.1/tcp/33019"
Listening in "/ip4/172.17.0.2/tcp/33019"

expected GET, GET_PROVIDERS, PUT or PUT_PROVIDER
discover 12D3KooWPuFudGf3ZE4ZXTmH4it7kV5QEp3go4bWC37DKh9ivsBJ /ip4/172.17.0.3/tcp/43257
discover 12D3KooWPuFudGf3ZE4ZXTmH4it7kV5QEp3go4bWC37DKh9ivsBJ /ip4/127.0.0.1/tcp/43257

expected GET, GET_PROVIDERS, PUT or PUT_PROVIDER
PUT b b
Successfully put record "b"
PUT a a
Successfully put record "a"
GET b
Got record "b" "b"
PUT b c
Successfully put record "b"
expire 12D3KooWPuFudGf3ZE4ZXTmH4it7kV5QEp3go4bWC37DKh9ivsBJ /ip4/172.17.0.3/tcp/43257
remove 12D3KooWPuFudGf3ZE4ZXTmH4it7kV5QEp3go4bWC37DKh9ivsBJ from kad
expire 12D3KooWPuFudGf3ZE4ZXTmH4it7kV5QEp3go4bWC37DKh9ivsBJ /ip4/127.0.0.1/tcp/43257
remove 12D3KooWPuFudGf3ZE4ZXTmH4it7kV5QEp3go4bWC37DKh9ivsBJ from kad

Is there anything I'm missing in my code?

[dariusc93]

You might need Ping behaviour to implemented.

[lynic]

Thanks! Add following code helps.

let ping = Ping::new(PingConfig::new().with_keep_alive(true));