Give up if DNS flush takes too long

1 files changed, 22 insertions, 1 deletions

diff --git a/talpid-core/src/dns/windows/dnsapi.rs b/talpid-core/src/dns/windows/dnsapi.rs
index 1c6b2c4fbc..4a0cf636e5 100644
--- a/talpid-core/src/dns/windows/dnsapi.rs
+++ b/talpid-core/src/dns/windows/dnsapi.rs
@@ -1,5 +1,5 @@
 use once_cell::sync::OnceCell;
-use std::{io, ptr};
+use std::{io, ptr, sync::mpsc, time::Duration};
 use winapi::{
     shared::minwindef::{BOOL, FALSE},
     um::libloaderapi::{FreeLibrary, GetProcAddress, LoadLibraryExW, LOAD_LIBRARY_SEARCH_SYSTEM32},
@@ -8,6 +8,7 @@ use winapi::{
 type FlushResolverCacheFn = unsafe extern "stdcall" fn() -> BOOL;
 
 static FLUSH_RESOLVER_CACHE: OnceCell<FlushResolverCacheFn> = OnceCell::new();
+static FLUSH_TIMEOUT: Duration = Duration::from_secs(5);
 
 /// Errors that can happen when configuring DNS on Windows.
 #[derive(err_derive::Error, Debug)]
@@ -24,9 +25,29 @@ pub enum Error {
     /// Failed to flush the DNS cache.
     #[error(display = "Call to flush DNS cache failed")]
     FlushCache,
+
+    /// Flushing the DNS cache timed out.
+    #[error(display = "Timeout while flushing DNS cache")]
+    Timeout,
 }
 
 pub fn flush_resolver_cache() -> Result<(), Error> {
+    let (tx, rx) = mpsc::channel();
+
+    std::thread::spawn(move || {
+        if tx.send(flush_resolver_cache_inner()).is_err() {
+            log::warn!("Flushing DNS cache completed (delayed)");
+        }
+    });
+
+    match rx.recv_timeout(FLUSH_TIMEOUT) {
+        Ok(result) => result,
+        // TODO: Can this be a cancelled safely?
+        Err(_timeout_err) => Err(Error::Timeout),
+    }
+}
+
+fn flush_resolver_cache_inner() -> Result<(), Error> {
     let flush_cache = FLUSH_RESOLVER_CACHE.get_or_try_init(|| {
         let handle = unsafe {
             LoadLibraryExW(