feat(iroh-net): DNS queries: lookup ipv6 & ipv4 in parallel

Closes #2006

iroh-net/src/dns.rs

@@ -1,6 +1,6 @@
 use anyhow::Result;
 use once_cell::sync::Lazy;
-use trust_dns_resolver::{config, AsyncResolver, TokioAsyncResolver};
+use trust_dns_resolver::{AsyncResolver, TokioAsyncResolver};
 
 pub static DNS_RESOLVER: Lazy<TokioAsyncResolver> =
     Lazy::new(|| get_resolver().expect("unable to create DNS resolver"));
@@ -11,13 +11,11 @@ pub static DNS_RESOLVER: Lazy<TokioAsyncResolver> =
 /// This does not work at least on some Androids, therefore we fallback
 /// to the default `ResolverConfig` which uses eg. to google's `8.8.8.8` or `8.8.4.4`.
 fn get_resolver() -> Result<TokioAsyncResolver> {
-    if let Ok(resolver) = AsyncResolver::tokio_from_system_conf() {
-        return Ok(resolver);
-    }
-    let resolver = AsyncResolver::tokio(
-        config::ResolverConfig::default(),
-        config::ResolverOpts::default(),
-    );
+    let (config, mut options) = trust_dns_resolver::system_conf::read_system_conf().unwrap_or_default();
+    // lookup IPv4 and IPv6 in parallel
+    options.ip_strategy = trust_dns_resolver::config::LookupIpStrategy::Ipv4AndIpv6;
+
+    let resolver = AsyncResolver::tokio(config, options);
     Ok(resolver)
 }