feat(proxy): Add socks4a proxy protocol support (#416)

Cargo.toml

@@ -82,10 +82,7 @@ url = "2.5"
 bytes = "1.0"
 serde = { version = "1.0", features = ["derive"] }
 serde_urlencoded = "0.7.1"
-tower = { version = "0.5.2", default-features = false, features = [
-    "timeout",
-    "util",
-] }
+tower = { version = "0.5.2", default-features = false, features = ["timeout","util"] }
 tower-service = "0.3"
 futures-util = { version = "0.3.0", default-features = false }
 sync_wrapper = { version = "1.0", features = ["futures"] }
@@ -104,6 +101,8 @@ encoding_rs = { version = "0.8", optional = true }
 http-body = "1"
 http-body-util = "0.1"
 hyper2 = { version = "1.5.0", features = ["http1", "http2", "client"] }
+socket2 = { version = "0.5", features = ["all"] }
+lru = { version = "0.13", default-features = false }
 log = "0.4"
 mime = "0.3.17"
 percent-encoding = "2.3"
@@ -112,10 +111,6 @@ pin-project-lite = "0.2.0"
 ipnet = "2.11.0"
 arc-swap = "1.7.0"
 
-## util
-socket2 = { version = "0.5", features = ["all"] }
-lru = { version = "0.13", default-features = false }
-
 ## boring-tls
 boring2 = { version = "4.15.2", features = ["pq-experimental", "cert-compression"] }
 tokio-boring2 = { version = "4.15.2", features = ["pq-experimental"] }

src/connect.rs

@@ -223,7 +223,12 @@ impl ConnectorService {
     #[cfg(feature = "socks")]
     async fn connect_socks(&self, mut dst: Dst, proxy: ProxyScheme) -> Result<Conn, BoxError> {
         let dns = match proxy {
-            ProxyScheme::Socks4 { .. } => socks::DnsResolve::Local,
+            ProxyScheme::Socks4 {
+                remote_dns: false, ..
+            } => socks::DnsResolve::Local,
+            ProxyScheme::Socks4 {
+                remote_dns: true, ..
+            } => socks::DnsResolve::Proxy,
             ProxyScheme::Socks5 {
                 remote_dns: false, ..
             } => socks::DnsResolve::Local,
@@ -777,7 +782,7 @@ mod socks {
         }
 
         match proxy {
-            ProxyScheme::Socks4 { addr } => {
+            ProxyScheme::Socks4 { addr, .. } => {
                 let stream = Socks4Stream::connect(addr, (host.as_str(), port))
                     .await
                     .map_err(|e| format!("socks connect error: {e}"))?;

src/proxy.rs

@@ -106,7 +106,7 @@ pub enum ProxyScheme {
         host: http::uri::Authority,
     },
     #[cfg(feature = "socks")]
-    Socks4 { addr: SocketAddr },
+    Socks4 { addr: SocketAddr, remote_dns: bool },
     #[cfg(feature = "socks")]
     Socks5 {
         addr: SocketAddr,
@@ -586,7 +586,25 @@ impl ProxyScheme {
     /// Current SOCKS4 support is provided via blocking IO.
     #[cfg(feature = "socks")]
     fn socks4(addr: SocketAddr) -> crate::Result<Self> {
-        Ok(ProxyScheme::Socks4 { addr })
+        Ok(ProxyScheme::Socks4 {
+            addr,
+            remote_dns: false,
+        })
+    }
+
+    /// Proxy traffic via the specified socket address over SOCKS4A
+    ///
+    /// This differs from SOCKS4 in that DNS resolution is also performed via the proxy.
+    ///
+    /// # Note
+    ///
+    /// Current SOCKS4 support is provided via blocking IO.
+    #[cfg(feature = "socks")]
+    fn socks4a(addr: SocketAddr) -> crate::Result<Self> {
+        Ok(ProxyScheme::Socks4 {
+            addr,
+            remote_dns: true,
+        })
     }
 
     /// Proxy traffic via the specified socket address over SOCKS5
@@ -702,7 +720,7 @@ impl ProxyScheme {
         let to_addr = || {
             let addrs = url
                 .socket_addrs(|| match url.scheme() {
-                    "socks4" | "socks5" | "socks5h" => Some(1080),
+                    "socks4" | "socks4a" | "socks5" | "socks5h" => Some(1080),
                     _ => None,
                 })
                 .map_err(crate::error::builder)?;
@@ -718,6 +736,8 @@ impl ProxyScheme {
             #[cfg(feature = "socks")]
             "socks4" => Self::socks4(to_addr()?)?,
             #[cfg(feature = "socks")]
+            "socks4a" => Self::socks4a(to_addr()?)?,
+            #[cfg(feature = "socks")]
             "socks5" => Self::socks5(to_addr()?)?,
             #[cfg(feature = "socks")]
             "socks5h" => Self::socks5h(to_addr()?)?,
@@ -740,8 +760,9 @@ impl fmt::Debug for ProxyScheme {
             ProxyScheme::Http { auth: _auth, host } => write!(f, "http://{}", host),
             ProxyScheme::Https { auth: _auth, host } => write!(f, "https://{}", host),
             #[cfg(feature = "socks")]
-            ProxyScheme::Socks4 { addr } => {
-                write!(f, "socks4://{addr}")
+            ProxyScheme::Socks4 { addr, remote_dns } => {
+                let h = if *remote_dns { "a" } else { "" };
+                write!(f, "socks4{}://{}", h, addr)
             }
             #[cfg(feature = "socks")]
             ProxyScheme::Socks5 {