fix(iroh-net): race ipv4 and ipv6 dns resolution (n0-computer#2026)

This now races the resolution, with a fixed timeout on each, returning
as many results as found during that time.

Ref n0-computer#2006

iroh-net/src/derp/http/client.rs

@@ -29,7 +29,7 @@ use crate::derp::{
     client::ClientReceiver as DerpClientReceiver, metrics::Metrics, server::PacketForwarderHandler,
     MeshKey, PacketForwarder, ReceivedMessage,
 };
-use crate::dns::DNS_RESOLVER;
+use crate::dns::lookup_ipv4_ipv6;
 use crate::key::{PublicKey, SecretKey};
 use crate::util::AbortingJoinHandle;
 
@@ -104,7 +104,7 @@ pub enum ClientError {
     InvalidUrl(String),
     /// There was an error with DNS resolution
     #[error("dns: {0:?}")]
-    Dns(Option<trust_dns_resolver::error::ResolveError>),
+    Dns(Option<anyhow::Error>),
     /// There was a timeout resolving DNS.
     #[error("dns timeout")]
     DnsTimeout,
@@ -1019,14 +1019,13 @@ async fn resolve_host(url: &Url, prefer_ipv6: bool) -> Result<IpAddr, ClientErro
     match host {
         url::Host::Domain(domain) => {
             // Need to do a DNS lookup
-            let addrs = tokio::time::timeout(DNS_TIMEOUT, DNS_RESOLVER.lookup_ip(domain))
+            let addrs = lookup_ipv4_ipv6(domain, DNS_TIMEOUT)
                 .await
-                .map_err(|_| ClientError::DnsTimeout)?
                 .map_err(|e| ClientError::Dns(Some(e)))?;
 
             if prefer_ipv6 {
                 if let Some(addr) = addrs.iter().find(|addr| addr.is_ipv6()) {
-                    return Ok(addr);
+                    return Ok(*addr);
                 }
             }
             addrs

iroh-net/src/dns.rs

@@ -1,6 +1,9 @@
+use std::net::IpAddr;
+use std::time::Duration;
+
 use anyhow::Result;
 use once_cell::sync::Lazy;
-use trust_dns_resolver::{AsyncResolver, TokioAsyncResolver};
+use trust_dns_resolver::{AsyncResolver, IntoName, TokioAsyncResolver, TryParseIp};
 
 pub static DNS_RESOLVER: Lazy<TokioAsyncResolver> =
     Lazy::new(|| get_resolver().expect("unable to create DNS resolver"));
@@ -14,23 +17,87 @@ fn get_resolver() -> Result<TokioAsyncResolver> {
     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;
+    options.ip_strategy = trust_dns_resolver::config::LookupIpStrategy::Ipv4thenIpv6;
 
     let resolver = AsyncResolver::tokio(config, options);
     Ok(resolver)
 }
 
+/// Resolve IPv4 and IPv6 in parallel.
+///
+/// `LookupIpStrategy::Ipv4AndIpv6` will wait for ipv6 resolution timeout, even if it is
+/// not usable on the stack, so we manually query both lookups concurrently and time them out
+/// individually.
+pub(crate) async fn lookup_ipv4_ipv6<N: IntoName + TryParseIp + Clone>(
+    host: N,
+    timeout: Duration,
+) -> Result<Vec<IpAddr>> {
+    let ipv4 = DNS_RESOLVER.ipv4_lookup(host.clone());
+    let ipv6 = DNS_RESOLVER.ipv6_lookup(host);
+    let ipv4 = tokio::time::timeout(timeout, ipv4);
+    let ipv6 = tokio::time::timeout(timeout, ipv6);
+
+    let res = futures::future::join(ipv4, ipv6).await;
+    match res {
+        (Ok(Ok(ipv4)), Ok(Ok(ipv6))) => {
+            let res = ipv4
+                .into_iter()
+                .map(|ip| IpAddr::V4(ip.0))
+                .chain(ipv6.into_iter().map(|ip| IpAddr::V6(ip.0)))
+                .collect();
+            Ok(res)
+        }
+        (Ok(Ok(ipv4)), Err(_timeout)) => {
+            let res = ipv4.into_iter().map(|ip| IpAddr::V4(ip.0)).collect();
+            Ok(res)
+        }
+        (Ok(Ok(ipv4)), Ok(Err(_err))) => {
+            let res = ipv4.into_iter().map(|ip| IpAddr::V4(ip.0)).collect();
+            Ok(res)
+        }
+        (Ok(Err(_err)), Ok(Ok(ipv6))) => {
+            let res = ipv6.into_iter().map(|ip| IpAddr::V6(ip.0)).collect();
+            Ok(res)
+        }
+        (Ok(Err(err1)), Ok(Err(err2))) => {
+            anyhow::bail!("Ipv4: {:?}, Ipv6: {:?}", err1, err2);
+        }
+        (Ok(Err(err1)), Err(err2)) => {
+            anyhow::bail!("Ipv4: {:?}, Ipv6: {:?}", err1, err2);
+        }
+        (Err(_timeout), Ok(Ok(ipv6))) => {
+            let res = ipv6.into_iter().map(|ip| IpAddr::V6(ip.0)).collect();
+            Ok(res)
+        }
+        (Err(err1), Ok(Err(err2))) => {
+            anyhow::bail!("Ipv4: {:?}, Ipv6: {:?}", err1, err2);
+        }
+        (Err(timeout1), Err(timeout2)) => {
+            anyhow::bail!("Ipv4: {:?}, Ipv6: {:?}", timeout1, timeout2);
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use crate::defaults::NA_DERP_HOSTNAME;
 
     use super::*;
 
     #[tokio::test]
-    async fn test_dns_lookup() {
+    async fn test_dns_lookup_basic() {
         let res = DNS_RESOLVER.lookup_ip(NA_DERP_HOSTNAME).await.unwrap();
         let res: Vec<_> = res.iter().collect();
         assert!(!res.is_empty());
         dbg!(res);
     }
+
+    #[tokio::test]
+    async fn test_dns_lookup_ipv4_ipv6() {
+        let res = lookup_ipv4_ipv6(NA_DERP_HOSTNAME, Duration::from_secs(1))
+            .await
+            .unwrap();
+        assert!(!res.is_empty());
+        dbg!(res);
+    }
 }

iroh-net/src/netcheck/reportgen.rs

@@ -33,7 +33,7 @@ use tracing::{debug, debug_span, error, info_span, instrument, trace, warn, Inst
 use super::NetcheckMetrics;
 use crate::defaults::DEFAULT_DERP_STUN_PORT;
 use crate::derp::{DerpMap, DerpNode, DerpUrl};
-use crate::dns::DNS_RESOLVER;
+use crate::dns::lookup_ipv4_ipv6;
 use crate::net::interfaces;
 use crate::net::ip;
 use crate::net::UdpSocket;
@@ -65,6 +65,8 @@ const CAPTIVE_PORTAL_TIMEOUT: Duration = Duration::from_secs(2);
 
 const ENOUGH_NODES: usize = 3;
 
+const DNS_TIMEOUT: Duration = Duration::from_secs(1);
+
 /// Holds the state for a single invocation of [`netcheck::Client::get_report`].
 ///
 /// Dropping this will cancel the actor and stop the report generation.
@@ -958,7 +960,7 @@ async fn get_derp_addr(n: &DerpNode, proto: ProbeProto) -> Result<SocketAddr> {
             async move {
                 debug!(?proto, %hostname, "Performing DNS lookup for derp addr");
 
-                if let Ok(addrs) = DNS_RESOLVER.lookup_ip(hostname).await {
+                if let Ok(addrs) = lookup_ipv4_ipv6(hostname, DNS_TIMEOUT).await {
                     for addr in addrs {
                         let addr = ip::to_canonical(addr);
                         if addr.is_ipv4()