protocols/mdns: Update to if-watch v2.0.0 (#2978)

examples/chat-tokio.rs

@@ -105,7 +105,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
 
     // Create a Swarm to manage peers and events.
     let mut swarm = {
-        let mdns = TokioMdns::new(Default::default()).await?;
+        let mdns = TokioMdns::new(Default::default())?;
         let mut behaviour = MyBehaviour {
             floodsub: Floodsub::new(peer_id),
             mdns,

examples/chat.rs

@@ -49,7 +49,7 @@
 //!
 //! The two nodes then connect.
 
-use async_std::{io, task};
+use async_std::io;
 use futures::{
     prelude::{stream::StreamExt, *},
     select,
@@ -108,7 +108,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
 
     // Create a Swarm to manage peers and events
     let mut swarm = {
-        let mdns = task::block_on(Mdns::new(MdnsConfig::default()))?;
+        let mdns = Mdns::new(MdnsConfig::default())?;
         let mut behaviour = MyBehaviour {
             floodsub: Floodsub::new(local_peer_id),
             mdns,

examples/distributed-key-value-store.rs

@@ -40,7 +40,7 @@
 //!
 //! 4. Close with Ctrl-c.
 
-use async_std::{io, task};
+use async_std::io;
 use futures::{prelude::*, select};
 use libp2p::kad::record::store::MemoryStore;
 use libp2p::kad::{
@@ -96,7 +96,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
         // Create a Kademlia behaviour.
         let store = MemoryStore::new(local_peer_id);
         let kademlia = Kademlia::new(local_peer_id, store);
-        let mdns = task::block_on(Mdns::new(MdnsConfig::default()))?;
+        let mdns = Mdns::new(MdnsConfig::default())?;
         let behaviour = MyBehaviour { kademlia, mdns };
         Swarm::new(transport, behaviour, local_peer_id)
     };

examples/mdns-passive-discovery.rs

@@ -40,7 +40,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
     let transport = libp2p::development_transport(id_keys).await?;
 
     // Create an MDNS network behaviour.
-    let behaviour = Mdns::new(MdnsConfig::default()).await?;
+    let behaviour = Mdns::new(MdnsConfig::default())?;
 
     // Create a Swarm that establishes connections through the given transport.
     // Note that the MDNS behaviour itself will not actually inititiate any connections,

protocols/mdns/CHANGELOG.md

@@ -10,9 +10,12 @@
 
 - Removed the `lazy_static` dependency. See [PR 2977].
 
+- Update to `if-watch` `v2.0.0` and thus the `async` method `Mdns::new` and `TokioMdns::new` becomes synchronous. See [PR 2978].
+
 [PR 2918]: https://github.com/libp2p/rust-libp2p/pull/2918
 [PR 2939]: https://github.com/libp2p/rust-libp2p/pull/2939
 [PR 2977]: https://github.com/libp2p/rust-libp2p/pull/2977
+[PR 2978]: https://github.com/libp2p/rust-libp2p/pull/2978
 
 # 0.40.0
 

protocols/mdns/Cargo.toml

@@ -14,7 +14,7 @@ categories = ["network-programming", "asynchronous"]
 data-encoding = "2.3.2"
 dns-parser = "0.8.0"
 futures = "0.3.13"
-if-watch = "1.1.1"
+if-watch = "2.0.0"
 libp2p-core = { version = "0.37.0", path = "../../core" }
 libp2p-swarm = { version = "0.40.0", path = "../../swarm" }
 log = "0.4.14"

protocols/mdns/src/behaviour.rs

@@ -25,7 +25,6 @@ mod timer;
 use self::iface::InterfaceState;
 use crate::behaviour::{socket::AsyncSocket, timer::Builder};
 use crate::MdnsConfig;
-use futures::prelude::*;
 use futures::Stream;
 use if_watch::{IfEvent, IfWatcher};
 use libp2p_core::transport::ListenerId;
@@ -81,8 +80,8 @@ where
     T: Builder,
 {
     /// Builds a new `Mdns` behaviour.
-    pub async fn new(config: MdnsConfig) -> io::Result<Self> {
-        let if_watch = if_watch::IfWatcher::new().await?;
+    pub fn new(config: MdnsConfig) -> io::Result<Self> {
+        let if_watch = if_watch::IfWatcher::new()?;
         Ok(Self {
             config,
             if_watch,
@@ -169,7 +168,7 @@ where
         params: &mut impl PollParameters,
     ) -> Poll<NetworkBehaviourAction<Self::OutEvent, dummy::ConnectionHandler>> {
         // Poll ifwatch.
-        while let Poll::Ready(event) = Pin::new(&mut self.if_watch).poll(cx) {
+        while let Poll::Ready(Some(event)) = Pin::new(&mut self.if_watch).poll_next(cx) {
             match event {
                 Ok(IfEvent::Up(inet)) => {
                     let addr = inet.addr();

protocols/mdns/tests/use-async-std.rs

@@ -61,7 +61,7 @@ async fn create_swarm(config: MdnsConfig) -> Result<Swarm<Mdns>, Box<dyn Error>>
     let id_keys = identity::Keypair::generate_ed25519();
     let peer_id = PeerId::from(id_keys.public());
     let transport = libp2p::development_transport(id_keys).await?;
-    let behaviour = Mdns::new(config).await?;
+    let behaviour = Mdns::new(config)?;
     let mut swarm = Swarm::new(transport, behaviour, peer_id);
     swarm.listen_on("/ip4/0.0.0.0/tcp/0".parse()?)?;
     Ok(swarm)

protocols/mdns/tests/use-tokio.rs

@@ -57,7 +57,7 @@ async fn create_swarm(config: MdnsConfig) -> Result<Swarm<TokioMdns>, Box<dyn Er
     let id_keys = identity::Keypair::generate_ed25519();
     let peer_id = PeerId::from(id_keys.public());
     let transport = libp2p::tokio_development_transport(id_keys)?;
-    let behaviour = TokioMdns::new(config).await?;
+    let behaviour = TokioMdns::new(config)?;
     let mut swarm = Swarm::new(transport, behaviour, peer_id);
     swarm.listen_on("/ip4/0.0.0.0/tcp/0".parse()?)?;
     Ok(swarm)