Adds support for handling interface changes to mdns behaviour. (#1830)

* mdns: handle address changes.

* Update examples.

* Use async-io.

* Fix tokio-chat.

* Address review comments.

* Update if-watch.

* Poll interfaces correctly.

* Use socket2 and remove wasm-time.

* Update if-watch.

* Update versions and changelogs.

* Further changelog updates.

Co-authored-by: Roman Borschel <romanb@users.noreply.github.com>
Co-authored-by: Roman S. Borschel <roman@parity.io>

examples/chat-tokio.rs

@@ -46,8 +46,7 @@ use libp2p::{
     core::upgrade,
     identity,
     floodsub::{self, Floodsub, FloodsubEvent},
-    // `TokioMdns` is available through the `mdns-tokio` feature.
-    mdns::{TokioMdns, MdnsEvent},
+    mdns::{Mdns, MdnsEvent},
     mplex,
     noise,
     swarm::{NetworkBehaviourEventProcess, SwarmBuilder},
@@ -90,7 +89,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
     #[derive(NetworkBehaviour)]
     struct MyBehaviour {
         floodsub: Floodsub,
-        mdns: TokioMdns,
+        mdns: Mdns,
     }
 
     impl NetworkBehaviourEventProcess<FloodsubEvent> for MyBehaviour {
@@ -122,7 +121,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
 
     // Create a Swarm to manage peers and events.
     let mut swarm = {
-        let mdns = TokioMdns::new()?;
+        let mdns = Mdns::new().await?;
         let mut behaviour = MyBehaviour {
             floodsub: Floodsub::new(peer_id.clone()),
             mdns,
@@ -172,4 +171,4 @@ async fn main() -> Result<(), Box<dyn Error>> {
             }
         }
     }
-}
+}

examples/chat.rs

@@ -121,7 +121,7 @@ fn main() -> Result<(), Box<dyn Error>> {
 
     // Create a Swarm to manage peers and events
     let mut swarm = {
-        let mdns = Mdns::new()?;
+        let mdns = task::block_on(Mdns::new())?;
         let mut behaviour = MyBehaviour {
             floodsub: Floodsub::new(local_peer_id.clone()),
             mdns,

examples/distributed-key-value-store.rs

@@ -151,7 +151,7 @@ fn main() -> Result<(), Box<dyn Error>> {
         // Create a Kademlia behaviour.
         let store = MemoryStore::new(local_peer_id.clone());
         let kademlia = Kademlia::new(local_peer_id.clone(), store);
-        let mdns = Mdns::new()?;
+        let mdns = task::block_on(Mdns::new())?;
         let behaviour = MyBehaviour { kademlia, mdns };
         Swarm::new(transport, behaviour, local_peer_id)
     };

examples/mdns-passive-discovery.rs

@@ -26,7 +26,7 @@ fn main() -> Result<(), Box<dyn Error>> {
     // This example provides passive discovery of the libp2p nodes on the
     // network that send mDNS queries and answers.
     task::block_on(async move {
-        let mut service = MdnsService::new()?;
+        let mut service = MdnsService::new().await?;
         loop {
             let (srv, packet) = service.next().await;
             match packet {