From 43437abae73898da7971d168e8307cdb0fda9661 Mon Sep 17 00:00:00 2001
From: Gregory Schier <gschier1990@gmail.com>
Date: Fri, 24 Oct 2025 08:01:12 -0700
Subject: [PATCH] Add custom DNS resolver for *.localhost (#280)

---
 src-tauri/Cargo.lock          | 10 ++++---
 src-tauri/Cargo.toml          |  2 ++
 src-tauri/src/dns.rs          | 54 +++++++++++++++++++++++++++++++++++
 src-tauri/src/http_request.rs |  2 ++
 src-tauri/src/lib.rs          |  1 +
 5 files changed, 65 insertions(+), 4 deletions(-)
 create mode 100644 src-tauri/src/dns.rs

diff --git a/src-tauri/Cargo.lock b/src-tauri/Cargo.lock
index 1339cfdd..35246708 100644
--- a/src-tauri/Cargo.lock
+++ b/src-tauri/Cargo.lock
@@ -1259,7 +1259,7 @@ dependencies = [
  "libc",
  "option-ext",
  "redox_users",
- "windows-sys 0.60.2",
+ "windows-sys 0.61.2",
 ]
 
 [[package]]
@@ -2352,9 +2352,9 @@ dependencies = [
 
 [[package]]
 name = "hyper-util"
-version = "0.1.14"
+version = "0.1.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dc2fdfdbff08affe55bb779f33b053aa1fe5dd5b54c257343c17edfa55711bdb"
+checksum = "3c6995591a8f1380fcb4ba966a252a4b29188d51d2b89e3a252f5305be65aea8"
 dependencies = [
  "base64 0.22.1",
  "bytes",
@@ -2368,7 +2368,7 @@ dependencies = [
  "libc",
  "percent-encoding",
  "pin-project-lite",
- "socket2 0.5.10",
+ "socket2 0.6.1",
  "system-configuration",
  "tokio",
  "tower-service",
@@ -7816,6 +7816,7 @@ dependencies = [
  "cookie",
  "eventsource-client",
  "http",
+ "hyper-util",
  "log",
  "md5 0.8.0",
  "mime_guess",
@@ -7841,6 +7842,7 @@ dependencies = [
  "thiserror 2.0.17",
  "tokio",
  "tokio-stream",
+ "tower-service",
  "ts-rs",
  "uuid",
  "yaak-common",
diff --git a/src-tauri/Cargo.toml b/src-tauri/Cargo.toml
index 58a275e4..0c3b9086 100644
--- a/src-tauri/Cargo.toml
+++ b/src-tauri/Cargo.toml
@@ -68,6 +68,8 @@ tauri-plugin-shell = { workspace = true }
 tauri-plugin-single-instance = { version = "2.3.4", features = ["deep-link"] }
 tauri-plugin-updater = "2.9.0"
 tauri-plugin-window-state = "2.4.0"
+hyper-util = { version = "0.1.17", default-features = false, features = ["client-legacy"] }
+tower-service = "0.3.3"
 thiserror = { workspace = true }
 tokio = { workspace = true, features = ["sync"] }
 tokio-stream = "0.1.17"
diff --git a/src-tauri/src/dns.rs b/src-tauri/src/dns.rs
new file mode 100644
index 00000000..ef65d058
--- /dev/null
+++ b/src-tauri/src/dns.rs
@@ -0,0 +1,54 @@
+use hyper_util::client::legacy::connect::dns::{
+    GaiResolver as HyperGaiResolver, Name as HyperName,
+};
+use reqwest::dns::{Addrs, Name, Resolve, Resolving};
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
+use std::str::FromStr;
+use std::sync::Arc;
+use tower_service::Service;
+
+#[derive(Clone)]
+pub(crate) struct LocalhostResolver {
+    fallback: HyperGaiResolver,
+}
+
+impl LocalhostResolver {
+    pub fn new() -> Arc<Self> {
+        let resolver = HyperGaiResolver::new();
+        Arc::new(Self { fallback: resolver })
+    }
+}
+
+impl Resolve for LocalhostResolver {
+    fn resolve(&self, name: Name) -> Resolving {
+        let host = name.as_str().to_lowercase();
+
+        let is_localhost = host.ends_with(".localhost");
+        if is_localhost {
+            // Port 0 is fine; reqwest replaces it with the URL's explicit
+            // port or the scheme’s default (80/443, etc.).
+            // (See docs note below.)
+            let addrs: Vec<SocketAddr> = vec![
+                SocketAddr::new(IpAddr::V4(Ipv4Addr::LOCALHOST), 0),
+                SocketAddr::new(IpAddr::V6(Ipv6Addr::LOCALHOST), 0),
+            ];
+
+            return Box::pin(async move {
+                Ok::<Addrs, Box<dyn std::error::Error + Send + Sync>>(Box::new(addrs.into_iter()))
+            });
+        }
+
+        let mut fallback = self.fallback.clone();
+        let name_str = name.as_str().to_string();
+        Box::pin(async move {
+            match HyperName::from_str(&name_str) {
+                Ok(n) => fallback
+                    .call(n)
+                    .await
+                    .map(|addrs| Box::new(addrs) as Addrs)
+                    .map_err(|err| Box::new(err) as Box<dyn std::error::Error + Send + Sync>),
+                Err(e) => Err(Box::new(e) as Box<dyn std::error::Error + Send + Sync>),
+            }
+        })
+    }
+}
diff --git a/src-tauri/src/http_request.rs b/src-tauri/src/http_request.rs
index 959596e0..35b23567 100644
--- a/src-tauri/src/http_request.rs
+++ b/src-tauri/src/http_request.rs
@@ -33,6 +33,7 @@ use yaak_plugins::events::{
 use yaak_plugins::manager::PluginManager;
 use yaak_plugins::template_callback::PluginTemplateCallback;
 use yaak_templates::{RenderErrorBehavior, RenderOptions};
+use crate::dns::LocalhostResolver;
 
 pub async fn send_http_request<R: Runtime>(
     window: &WebviewWindow<R>,
@@ -110,6 +111,7 @@ pub async fn send_http_request<R: Runtime>(
         .gzip(true)
         .brotli(true)
         .deflate(true)
+        .dns_resolver(LocalhostResolver::new())
         .referer(false)
         .tls_info(true);
 
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index f422d2bb..8d1e67d2 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -60,6 +60,7 @@ mod updates;
 mod uri_scheme;
 mod window;
 mod window_menu;
+mod dns;
 
 #[derive(serde::Serialize)]
 #[serde(default, rename_all = "camelCase")]