support overriding DNS items for connect

src/client.rs

@@ -1,6 +1,7 @@
 //! Methods to connect to a WebSocket as a client.
 
 use std::{
+    collections::HashMap,
     io::{Read, Write},
     net::{SocketAddr, TcpStream, ToSocketAddrs},
     result::Result as StdResult,
@@ -43,10 +44,35 @@ pub fn connect_with_config<Req: IntoClientRequest>(
     request: Req,
     config: Option<WebSocketConfig>,
     max_redirects: u8,
+) -> Result<(WebSocket<MaybeTlsStream<TcpStream>>, Response)> {
+    connect_with_config_overrides_dns(request, config, HashMap::new(), max_redirects)
+}
+
+/// Connect to the given WebSocket in blocking mode, overrides DNS items.
+///
+/// Uses a websocket configuration passed as an argument to the function. Calling it with `None` is
+/// equal to calling `connect()` function.
+///
+/// The URL may be either ws:// or wss://.
+/// To support wss:// URLs, feature `native-tls` or `rustls-tls` must be turned on.
+///
+/// This function "just works" for those who wants a simple blocking solution
+/// similar to `std::net::TcpStream`. If you want a non-blocking or other
+/// custom stream, call `client` instead.
+///
+/// This function uses `native_tls` or `rustls` to do TLS depending on the feature flags enabled. If
+/// you want to use other TLS libraries, use `client` instead. There is no need to enable any of
+/// the `*-tls` features if you don't call `connect` since it's the only function that uses them.
+pub fn connect_with_config_overrides_dns<Req: IntoClientRequest>(
+    request: Req,
+    config: Option<WebSocketConfig>,
+    dns_overrides: HashMap<String, SocketAddr>,
+    max_redirects: u8,
 ) -> Result<(WebSocket<MaybeTlsStream<TcpStream>>, Response)> {
     fn try_client_handshake(
         request: Request,
         config: Option<WebSocketConfig>,
+        dns_overrides: &HashMap<String, SocketAddr>,
     ) -> Result<(WebSocket<MaybeTlsStream<TcpStream>>, Response)> {
         let uri = request.uri();
         let mode = uri_mode(uri)?;
@@ -55,7 +81,11 @@ pub fn connect_with_config<Req: IntoClientRequest>(
             Mode::Plain => 80,
             Mode::Tls => 443,
         });
-        let addrs = (host, port).to_socket_addrs()?;
+        let addrs = if dns_overrides.contains_key(host) {
+            vec![dns_overrides.get(host).unwrap().clone()].into_iter()
+        } else {
+            (host, port).to_socket_addrs()?
+        };
         let mut stream = connect_to_some(addrs.as_slice(), &request.uri())?;
         NoDelay::set_nodelay(&mut stream, true)?;
 
@@ -83,7 +113,7 @@ pub fn connect_with_config<Req: IntoClientRequest>(
     for attempt in 0..(max_redirects + 1) {
         let request = create_request(&parts, &uri);
 
-        match try_client_handshake(request, config) {
+        match try_client_handshake(request, config, &dns_overrides) {
             Err(Error::Http(res)) if res.status().is_redirection() && attempt < max_redirects => {
                 if let Some(location) = res.headers().get("Location") {
                     uri = location.to_str()?.parse::<Uri>()?;
@@ -119,6 +149,25 @@ pub fn connect<Req: IntoClientRequest>(
     connect_with_config(request, None, 3)
 }
 
+/// Connect to the given WebSocket in blocking mode, overrides DNS items.
+///
+/// The URL may be either ws:// or wss://.
+/// To support wss:// URLs, feature `native-tls` or `rustls-tls` must be turned on.
+///
+/// This function "just works" for those who wants a simple blocking solution
+/// similar to `std::net::TcpStream`. If you want a non-blocking or other
+/// custom stream, call `client` instead.
+///
+/// This function uses `native_tls` or `rustls` to do TLS depending on the feature flags enabled. If
+/// you want to use other TLS libraries, use `client` instead. There is no need to enable any of
+/// the `*-tls` features if you don't call `connect` since it's the only function that uses them.
+pub fn connect_overrides_dns<Req: IntoClientRequest>(
+    request: Req,
+    dns_overrides: HashMap<String, SocketAddr>,
+) -> Result<(WebSocket<MaybeTlsStream<TcpStream>>, Response)> {
+    connect_with_config_overrides_dns(request, None, dns_overrides, 3)
+}
+
 fn connect_to_some(addrs: &[SocketAddr], uri: &Uri) -> Result<TcpStream> {
     for addr in addrs {
         debug!("Trying to contact {} at {}...", uri, addr);