Merge branch 'ipv6' into 'main'

tokio-xmpp: set resolve ip_strategy to Ipv4AndIpv6, let connect happy_eyeballs in parallel

See merge request xmpp-rs/xmpp-rs!308

tokio-xmpp/src/starttls/happy_eyeballs.rs

@@ -1,5 +1,11 @@
 use super::error::{ConnectorError, Error};
-use hickory_resolver::{IntoName, TokioAsyncResolver};
+use futures::{future, FutureExt};
+use hickory_resolver::{
+    IntoName,
+    config::LookupIpStrategy,
+    TokioAsyncResolver,
+    name_server::TokioConnectionProvider,
+};
 use log::debug;
 use std::net::SocketAddr;
 use tokio::net::TcpStream;
@@ -13,17 +19,29 @@ pub async fn connect_to_host(domain: &str, port: u16) -> Result<TcpStream, Error
             .map_err(|e| Error::from(crate::Error::Io(e)))?);
     }
 
-    let resolver = TokioAsyncResolver::tokio_from_system_conf().map_err(ConnectorError::Resolve)?;
+    let (config, mut options) = hickory_resolver::system_conf::read_system_conf()
+        .map_err(ConnectorError::Resolve)?;
+    options.ip_strategy = LookupIpStrategy::Ipv4AndIpv6;
+    let resolver = TokioAsyncResolver::new(
+        config, options,
+        TokioConnectionProvider::default()
+    );
 
     let ips = resolver
         .lookup_ip(ascii_domain)
         .await
         .map_err(ConnectorError::Resolve)?;
-    for ip in ips.iter() {
-        match TcpStream::connect(&SocketAddr::new(ip, port)).await {
-            Ok(stream) => return Ok(stream),
-            Err(_) => {}
+    // Happy Eyeballs: connect to all records in parallel
+    let mut connects = ips.into_iter()
+        .map(|ip| TcpStream::connect(SocketAddr::new(ip, port)).boxed())
+        .collect::<Vec<_>>();
+    while connects.len() > 0 {
+        let (result, _, remaining) = future::select_all(connects.into_iter()).await;
+        if let Ok(stream) = result {
+            // Use the first to connect successfully
+            return Ok(stream);
         }
+        connects = remaining;
     }
     Err(crate::Error::Disconnected.into())
 }