Implement ability to disable trust-dns in ClientBuilder.

src/async_impl/client.rs

@@ -31,7 +31,7 @@ use log::debug;
 use super::request::{Request, RequestBuilder};
 use super::response::Response;
 use super::Body;
-use crate::connect::Connector;
+use crate::connect::{Connector, HttpConnector};
 #[cfg(feature = "cookies")]
 use crate::cookie;
 use crate::into_url::{expect_uri, try_uri};
@@ -91,6 +91,7 @@ struct Config {
     nodelay: bool,
     #[cfg(feature = "cookies")]
     cookie_store: Option<cookie::CookieStore>,
+    trust_dns: bool,
     error: Option<crate::Error>,
 }
 
@@ -138,6 +139,7 @@ impl ClientBuilder {
                 http2_initial_connection_window_size: None,
                 local_address: None,
                 nodelay: false,
+                trust_dns: cfg!(feature = "trust-dns"),
                 #[cfg(feature = "cookies")]
                 cookie_store: None,
             },
@@ -169,6 +171,14 @@ impl ClientBuilder {
                 headers.get(USER_AGENT).cloned()
             }
 
+            let http = match config.trust_dns {
+                false => HttpConnector::new_gai(),
+                #[cfg(feature = "trust-dns")]
+                true => HttpConnector::new_trust_dns()?,
+                #[cfg(not(feature = "trust-dns"))]
+                true => unreachable!("trust-dns shouldn't be enabled unless the feature is"),
+            };
+
             #[cfg(feature = "__tls")]
             match config.tls {
                 #[cfg(feature = "default-tls")]
@@ -195,6 +205,7 @@ impl ClientBuilder {
 
 
                     Connector::new_default_tls(
+                        http,
                         tls,
                         proxies.clone(),
                         user_agent(&config.headers),
@@ -205,6 +216,7 @@ impl ClientBuilder {
                 #[cfg(feature = "native-tls")]
                 TlsBackend::BuiltNativeTls(conn) => {
                     Connector::from_built_default_tls(
+                        http,
                         conn,
                         proxies.clone(),
                         user_agent(&config.headers),
@@ -214,6 +226,7 @@ impl ClientBuilder {
                 #[cfg(feature = "rustls-tls")]
                 TlsBackend::BuiltRustls(conn) => {
                     Connector::new_rustls_tls(
+                        http,
                         conn,
                         proxies.clone(),
                         user_agent(&config.headers),
@@ -247,6 +260,7 @@ impl ClientBuilder {
                     }
 
                     Connector::new_rustls_tls(
+                        http,
                         tls,
                         proxies.clone(),
                         user_agent(&config.headers),
@@ -266,7 +280,7 @@ impl ClientBuilder {
             }
 
             #[cfg(not(feature = "__tls"))]
-            Connector::new(proxies.clone(), config.local_address, config.nodelay)?
+            Connector::new(http, proxies.clone(), config.local_address, config.nodelay)?
         };
 
         connector.set_timeout(config.connect_timeout);
@@ -793,6 +807,36 @@ impl ClientBuilder {
         self.config.tls = crate::tls::TlsBackend::UnknownPreconfigured;
         self
     }
+
+    /// Enables the [trust-dns](trust_dns_resolver) async resolver instead of a default threadpool using `getaddrinfo`.
+    ///
+    /// If the `trust-dns` feature is turned on, the default option is enabled.
+    ///
+    /// # Optional
+    ///
+    /// This requires the optional `trust-dns` feature to be enabled
+    #[cfg(feature = "trust-dns")]
+    pub fn trust_dns(mut self, enable: bool) -> ClientBuilder {
+        self.config.trust_dns = enable;
+        self
+    }
+
+    /// Disables the trust-dns async resolver.
+    ///
+    /// This method exists even if the optional `trust-dns` feature is not enabled.
+    /// This can be used to ensure a `Client` doesn't use the trust-dns async resolver
+    /// even if another dependency were to enable the optional `trust-dns` feature.
+    pub fn no_trust_dns(self) -> ClientBuilder {
+        #[cfg(feature = "trust-dns")]
+        {
+            self.trust_dns(false)
+        }
+
+        #[cfg(not(feature = "trust-dns"))]
+        {
+            self
+        }
+    }
 }
 
 type HyperClient = hyper::Client<Connector, super::body::ImplStream>;

src/blocking/client.rs

@@ -481,6 +481,27 @@ impl ClientBuilder {
         self.with_inner(move |inner| inner.use_preconfigured_tls(tls))
     }
 
+    /// Enables the [trust-dns](trust_dns_resolver) async resolver instead of a default threadpool using `getaddrinfo`.
+    ///
+    /// If the `trust-dns` feature is turned on, the default option is enabled.
+    ///
+    /// # Optional
+    ///
+    /// This requires the optional `trust-dns` feature to be enabled
+    #[cfg(feature = "trust-dns")]
+    pub fn trust_dns(self, enable: bool) -> ClientBuilder {
+        self.with_inner(|inner| inner.trust_dns(enable))
+    }
+
+    /// Disables the trust-dns async resolver.
+    ///
+    /// This method exists even if the optional `trust-dns` feature is not enabled.
+    /// This can be used to ensure a `Client` doesn't use the trust-dns async resolver
+    /// even if another dependency were to enable the optional `trust-dns` feature.
+    pub fn no_trust_dns(self) -> ClientBuilder {
+        self.with_inner(|inner| inner.no_trust_dns())
+    }
+
     // private
 
     fn with_inner<F>(mut self, func: F) -> ClientBuilder

src/connect.rs

@@ -7,6 +7,7 @@ use tokio::io::{AsyncRead, AsyncWrite};
 use native_tls_crate::{TlsConnector, TlsConnectorBuilder};
 #[cfg(feature = "__tls")]
 use http::header::HeaderValue;
+use futures_util::future::Either;
 use bytes::{Buf, BufMut};
 
 use std::future::Future;
@@ -28,10 +29,80 @@ use self::native_tls_conn::NativeTlsConn;
 #[cfg(feature = "rustls-tls")]
 use self::rustls_tls_conn::RustlsTlsConn;
 
+#[derive(Clone)]
+pub(crate) enum HttpConnector {
+    Gai(hyper::client::HttpConnector),
     #[cfg(feature = "trust-dns")]
-type HttpConnector = hyper::client::HttpConnector<TrustDnsResolver>;
+    TrustDns(hyper::client::HttpConnector<TrustDnsResolver>),
+}
+
+impl HttpConnector {
+    pub(crate) fn new_gai() -> Self {
+        Self::Gai(hyper::client::HttpConnector::new())
+    }
+
+    #[cfg(feature = "trust-dns")]
+    pub(crate) fn new_trust_dns() -> crate::Result<HttpConnector> {
+        TrustDnsResolver::new()
+            .map(hyper::client::HttpConnector::new_with_resolver)
+            .map(Self::TrustDns)
+            .map_err(crate::error::builder)
+    }
+}
+
+macro_rules! impl_http_connector {
+    ($(fn $name:ident(&mut self, $($par_name:ident: $par_type:ty),*)$( -> $return:ty)?;)+) => {
+        #[allow(dead_code)]
+        impl HttpConnector {
+            $(
+                fn $name(&mut self, $($par_name: $par_type),*)$( -> $return)? {
+                    match self {
+                        Self::Gai(resolver) => resolver.$name($($par_name),*),
+                        #[cfg(feature = "trust-dns")]
+                        Self::TrustDns(resolver) => resolver.$name($($par_name),*),
+                    }
+                }
+            )+
+        }
+    };
+}
+
+impl_http_connector! {
+    fn set_local_address(&mut self, addr: Option<IpAddr>);
+    fn enforce_http(&mut self, is_enforced: bool);
+    fn set_nodelay(&mut self, nodelay: bool);
+}
+
+impl Service<Uri> for HttpConnector {
+    type Response = <hyper::client::HttpConnector as Service<Uri>>::Response;
+    type Error = <hyper::client::HttpConnector as Service<Uri>>::Error;
+    #[cfg(feature = "trust-dns")]
+    type Future = Either<
+        <hyper::client::HttpConnector as Service<Uri>>::Future,
+        <hyper::client::HttpConnector<TrustDnsResolver> as Service<Uri>>::Future,
+    >;
     #[cfg(not(feature = "trust-dns"))]
-type HttpConnector = hyper::client::HttpConnector;
+    type Future = Either<
+        <hyper::client::HttpConnector as Service<Uri>>::Future,
+        <hyper::client::HttpConnector as Service<Uri>>::Future,
+    >;
+
+    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+        match self {
+            Self::Gai(resolver) => resolver.poll_ready(cx),
+            #[cfg(feature = "trust-dns")]
+            Self::TrustDns(resolver) => resolver.poll_ready(cx),
+        }
+    }
+
+    fn call(&mut self, dst: Uri) -> Self::Future {
+        match self {
+            Self::Gai(resolver) => Either::Left(resolver.call(dst)),
+            #[cfg(feature = "trust-dns")]
+            Self::TrustDns(resolver) => Either::Right(resolver.call(dst)),
+        }
+    }
+}
 
 #[derive(Clone)]
 pub(crate) struct Connector {
@@ -62,6 +133,7 @@ enum Inner {
 impl Connector {
     #[cfg(not(feature = "__tls"))]
     pub(crate) fn new<T>(
+        mut http: HttpConnector,
         proxies: Arc<Vec<Proxy>>,
         local_addr: T,
         nodelay: bool,
@@ -69,7 +141,6 @@ impl Connector {
     where
         T: Into<Option<IpAddr>>,
     {
-        let mut http = http_connector()?;
         http.set_local_address(local_addr.into());
         http.set_nodelay(nodelay);
         Ok(Connector {
@@ -82,6 +153,7 @@ impl Connector {
 
     #[cfg(feature = "default-tls")]
     pub(crate) fn new_default_tls<T>(
+        http: HttpConnector,
         tls: TlsConnectorBuilder,
         proxies: Arc<Vec<Proxy>>,
         user_agent: Option<HeaderValue>,
@@ -93,6 +165,7 @@ impl Connector {
     {
         let tls = tls.build().map_err(crate::error::builder)?;
         Self::from_built_default_tls(
+            http,
             tls,
             proxies,
             user_agent,
@@ -103,6 +176,7 @@ impl Connector {
 
     #[cfg(feature = "default-tls")]
     pub(crate) fn from_built_default_tls<T> (
+        mut http: HttpConnector,
         tls: TlsConnector,
         proxies: Arc<Vec<Proxy>>,
         user_agent: Option<HeaderValue>,
@@ -111,7 +185,6 @@ impl Connector {
         where
             T: Into<Option<IpAddr>>,
     {
-        let mut http = http_connector()?;
         http.set_local_address(local_addr.into());
         http.enforce_http(false);
 
@@ -127,6 +200,7 @@ impl Connector {
 
     #[cfg(feature = "rustls-tls")]
     pub(crate) fn new_rustls_tls<T>(
+        mut http: HttpConnector,
         tls: rustls::ClientConfig,
         proxies: Arc<Vec<Proxy>>,
         user_agent: Option<HeaderValue>,
@@ -136,7 +210,6 @@ impl Connector {
     where
         T: Into<Option<IpAddr>>,
     {
-        let mut http = http_connector()?;
         http.set_local_address(local_addr.into());
         http.enforce_http(false);
 
@@ -413,19 +486,6 @@ fn into_uri(scheme: Scheme, host: Authority) -> Uri {
         .expect("scheme and authority is valid Uri")
 }
 
-#[cfg(feature = "trust-dns")]
-fn http_connector() -> crate::Result<HttpConnector> {
-    TrustDnsResolver::new()
-        .map(HttpConnector::new_with_resolver)
-        .map_err(crate::error::builder)
-}
-
-#[cfg(not(feature = "trust-dns"))]
-fn http_connector() -> crate::Result<HttpConnector> {
-    Ok(HttpConnector::new())
-}
-
-
 async fn with_timeout<T, F>(f: F, timeout: Option<Duration>) -> Result<T, BoxError>
 where
     F: Future<Output = Result<T, BoxError>>,