Add ability to specify multiple IP addresses for resolver overrides (#1622)

This change allows the `ClientBuilder::resolve_to_addrs` method to accept a
slice of `SocketAddr`s for overriding resolution for a single domain.
Allowing multiple IPs more accurately reflects behavior of `getaddrinfo`
and allows users to rely on hyper's happy eyeballs algorithm to connect
to a host that can accept traffic on IPv4 and IPv6.

src/async_impl/client.rs

@@ -120,7 +120,7 @@ struct Config {
     trust_dns: bool,
     error: Option<crate::Error>,
     https_only: bool,
-    dns_overrides: HashMap<String, SocketAddr>,
+    dns_overrides: HashMap<String, Vec<SocketAddr>>,
 }
 
 impl Default for ClientBuilder {
@@ -1314,7 +1314,7 @@ impl ClientBuilder {
         self
     }
 
-    /// Override DNS resolution for specific domains to particular IP addresses.
+    /// Override DNS resolution for specific domains to a particular IP address.
     ///
     /// Warning
     ///
@@ -1322,8 +1322,22 @@ impl ClientBuilder {
     /// traffic to a particular port you must include this port in the URL
     /// itself, any port in the overridden addr will be ignored and traffic sent
     /// to the conventional port for the given scheme (e.g. 80 for http).
-    pub fn resolve(mut self, domain: &str, addr: SocketAddr) -> ClientBuilder {
-        self.config.dns_overrides.insert(domain.to_string(), addr);
+    pub fn resolve(self, domain: &str, addr: SocketAddr) -> ClientBuilder {
+        self.resolve_to_addrs(domain, &[addr])
+    }
+
+    /// Override DNS resolution for specific domains to particular IP addresses.
+    ///
+    /// Warning
+    ///
+    /// Since the DNS protocol has no notion of ports, if you wish to send
+    /// traffic to a particular port you must include this port in the URL
+    /// itself, any port in the overridden addresses will be ignored and traffic sent
+    /// to the conventional port for the given scheme (e.g. 80 for http).
+    pub fn resolve_to_addrs(mut self, domain: &str, addrs: &[SocketAddr]) -> ClientBuilder {
+        self.config
+            .dns_overrides
+            .insert(domain.to_string(), addrs.to_vec());
         self
     }
 }

src/blocking/client.rs

@@ -757,7 +757,7 @@ impl ClientBuilder {
         self.with_inner(|inner| inner.https_only(enabled))
     }
 
-    /// Override DNS resolution for specific domains to particular IP addresses.
+    /// Override DNS resolution for specific domains to a particular IP address.
     ///
     /// Warning
     ///
@@ -766,7 +766,19 @@ impl ClientBuilder {
     /// itself, any port in the overridden addr will be ignored and traffic sent
     /// to the conventional port for the given scheme (e.g. 80 for http).
     pub fn resolve(self, domain: &str, addr: SocketAddr) -> ClientBuilder {
-        self.with_inner(|inner| inner.resolve(domain, addr))
+        self.resolve_to_addrs(domain, &[addr])
+    }
+
+    /// Override DNS resolution for specific domains to particular IP addresses.
+    ///
+    /// Warning
+    ///
+    /// Since the DNS protocol has no notion of ports, if you wish to send
+    /// traffic to a particular port you must include this port in the URL
+    /// itself, any port in the overridden addresses will be ignored and traffic sent
+    /// to the conventional port for the given scheme (e.g. 80 for http).
+    pub fn resolve_to_addrs(self, domain: &str, addrs: &[SocketAddr]) -> ClientBuilder {
+        self.with_inner(|inner| inner.resolve_to_addrs(domain, addrs))
     }
 
     // private

src/connect.rs

@@ -46,7 +46,7 @@ impl HttpConnector {
         Self::Gai(hyper::client::HttpConnector::new())
     }
 
-    pub(crate) fn new_gai_with_overrides(overrides: HashMap<String, SocketAddr>) -> Self {
+    pub(crate) fn new_gai_with_overrides(overrides: HashMap<String, Vec<SocketAddr>>) -> Self {
         let gai = hyper::client::connect::dns::GaiResolver::new();
         let overridden_resolver = DnsResolverWithOverrides::new(gai, overrides);
         Self::GaiWithDnsOverrides(hyper::client::HttpConnector::new_with_resolver(
@@ -64,7 +64,7 @@ impl HttpConnector {
 
     #[cfg(feature = "trust-dns")]
     pub(crate) fn new_trust_dns_with_overrides(
-        overrides: HashMap<String, SocketAddr>,
+        overrides: HashMap<String, Vec<SocketAddr>>,
     ) -> crate::Result<HttpConnector> {
         TrustDnsResolver::new()
             .map(|resolver| DnsResolverWithOverrides::new(resolver, overrides))
@@ -994,7 +994,7 @@ where
     Fut: std::future::Future<Output = Result<FutOutput, FutError>>,
     FutOutput: Iterator<Item = SocketAddr>,
 {
-    type Output = Result<itertools::Either<FutOutput, std::iter::Once<SocketAddr>>, FutError>;
+    type Output = Result<itertools::Either<FutOutput, std::vec::IntoIter<SocketAddr>>, FutError>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         let this = self.project();
@@ -1010,11 +1010,11 @@ where
     Resolver: Clone,
 {
     dns_resolver: Resolver,
-    overrides: Arc<HashMap<String, SocketAddr>>,
+    overrides: Arc<HashMap<String, Vec<SocketAddr>>>,
 }
 
 impl<Resolver: Clone> DnsResolverWithOverrides<Resolver> {
-    fn new(dns_resolver: Resolver, overrides: HashMap<String, SocketAddr>) -> Self {
+    fn new(dns_resolver: Resolver, overrides: HashMap<String, Vec<SocketAddr>>) -> Self {
         DnsResolverWithOverrides {
             dns_resolver,
             overrides: Arc::new(overrides),
@@ -1027,12 +1027,12 @@ where
     Resolver: Service<Name, Response = Iter> + Clone,
     Iter: Iterator<Item = SocketAddr>,
 {
-    type Response = itertools::Either<Iter, std::iter::Once<SocketAddr>>;
+    type Response = itertools::Either<Iter, std::vec::IntoIter<SocketAddr>>;
     type Error = <Resolver as Service<Name>>::Error;
     type Future = Either<
         WrappedResolverFuture<<Resolver as Service<Name>>::Future>,
         futures_util::future::Ready<
-            Result<itertools::Either<Iter, std::iter::Once<SocketAddr>>, Self::Error>,
+            Result<itertools::Either<Iter, std::vec::IntoIter<SocketAddr>>, Self::Error>,
         >,
     >;
 
@@ -1044,7 +1044,7 @@ where
         match self.overrides.get(name.as_str()) {
             Some(dest) => {
                 let fut = futures_util::future::ready(Ok(itertools::Either::Right(
-                    std::iter::once(dest.to_owned()),
+                    dest.clone().into_iter(),
                 )));
                 Either::Right(fut)
             }

tests/client.rs

@@ -190,6 +190,40 @@ async fn overridden_dns_resolution_with_gai() {
     assert_eq!("Hello", text);
 }
 
+#[tokio::test]
+async fn overridden_dns_resolution_with_gai_multiple() {
+    let _ = env_logger::builder().is_test(true).try_init();
+    let server = server::http(move |_req| async { http::Response::new("Hello".into()) });
+
+    let overridden_domain = "rust-lang.org";
+    let url = format!(
+        "http://{}:{}/domain_override",
+        overridden_domain,
+        server.addr().port()
+    );
+    // the server runs on IPv4 localhost, so provide both IPv4 and IPv6 and let the happy eyeballs
+    // algorithm decide which address to use.
+    let client = reqwest::Client::builder()
+        .resolve_to_addrs(
+            overridden_domain,
+            &[
+                std::net::SocketAddr::new(
+                    std::net::IpAddr::V6(std::net::Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1)),
+                    server.addr().port(),
+                ),
+                server.addr(),
+            ],
+        )
+        .build()
+        .expect("client builder");
+    let req = client.get(&url);
+    let res = req.send().await.expect("request");
+
+    assert_eq!(res.status(), reqwest::StatusCode::OK);
+    let text = res.text().await.expect("Failed to get text");
+    assert_eq!("Hello", text);
+}
+
 #[cfg(feature = "trust-dns")]
 #[tokio::test]
 async fn overridden_dns_resolution_with_trust_dns() {
@@ -215,6 +249,42 @@ async fn overridden_dns_resolution_with_trust_dns() {
     assert_eq!("Hello", text);
 }
 
+#[cfg(feature = "trust-dns")]
+#[tokio::test]
+async fn overridden_dns_resolution_with_trust_dns_multiple() {
+    let _ = env_logger::builder().is_test(true).try_init();
+    let server = server::http(move |_req| async { http::Response::new("Hello".into()) });
+
+    let overridden_domain = "rust-lang.org";
+    let url = format!(
+        "http://{}:{}/domain_override",
+        overridden_domain,
+        server.addr().port()
+    );
+    // the server runs on IPv4 localhost, so provide both IPv4 and IPv6 and let the happy eyeballs
+    // algorithm decide which address to use.
+    let client = reqwest::Client::builder()
+        .resolve_to_addrs(
+            overridden_domain,
+            &[
+                std::net::SocketAddr::new(
+                    std::net::IpAddr::V6(std::net::Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1)),
+                    server.addr().port(),
+                ),
+                server.addr(),
+            ],
+        )
+        .trust_dns(true)
+        .build()
+        .expect("client builder");
+    let req = client.get(&url);
+    let res = req.send().await.expect("request");
+
+    assert_eq!(res.status(), reqwest::StatusCode::OK);
+    let text = res.text().await.expect("Failed to get text");
+    assert_eq!("Hello", text);
+}
+
 #[cfg(any(feature = "native-tls", feature = "__rustls",))]
 #[test]
 fn use_preconfigured_tls_with_bogus_backend() {