Detect whether the Hyper-V firewall is available

2 files changed, 23 insertions, 10 deletions

diff --git a/talpid-core/src/firewall/windows/hyperv.rs b/talpid-core/src/firewall/windows/hyperv.rs
index c78d690e72..1fc8bb2578 100644
--- a/talpid-core/src/firewall/windows/hyperv.rs
+++ b/talpid-core/src/firewall/windows/hyperv.rs
@@ -40,11 +40,18 @@ pub enum Error {
 /// Initialize WMI connection to the ROOT\StandardCIMV2 namespace, which may be used for
 /// interacting with Hyper-V rules.
 pub fn init_wmi() -> Result<wmi::WMIConnection, Error> {
-    wmi::WMIConnection::with_namespace_path(
+    let con = wmi::WMIConnection::with_namespace_path(
         WMI_NAMESPACE,
         wmi::COMLibrary::new().map_err(Error::InitializeCom)?,
     )
-    .map_err(Error::ConnectWmi)
+    .map_err(Error::ConnectWmi)?;
+
+    // Test whether the class is available
+    let _ = con
+        .get_raw_by_path("MSFT_NetFirewallHyperVRule")
+        .map_err(Error::ObtainHyperVClass)?;
+
+    Ok(con)
 }
 
 /// Add a Hyper-V rule that blocks all traffic using WMI (Windows Management Instrumentation).
diff --git a/talpid-core/src/firewall/windows/mod.rs b/talpid-core/src/firewall/windows/mod.rs
index 62701c6d82..d4b0b883d4 100644
--- a/talpid-core/src/firewall/windows/mod.rs
+++ b/talpid-core/src/firewall/windows/mod.rs
@@ -14,12 +14,21 @@ use windows_sys::Win32::Globalization::{MultiByteToWideChar, CP_ACP};
 
 mod hyperv;
 
+const HYPERV_LEAK_WARNING_MSG: &str = "Hyper-V (e.g. WSL machines) may leak in blocked states.";
+
 // `COMLibrary` must be initialized for per thread, so use TLS
 thread_local! {
-    static WMI: Option<wmi::WMIConnection> = consume_and_log_hyperv_err(
-        "Initialize COM and WMI",
-        hyperv::init_wmi(),
-    );
+    static WMI: Option<wmi::WMIConnection> = {
+        let result = hyperv::init_wmi();
+        if matches!(&result, Err(hyperv::Error::ObtainHyperVClass(_))) {
+            log::warn!("The Hyper-V firewall is not available. {HYPERV_LEAK_WARNING_MSG}");
+            return None;
+        }
+        consume_and_log_hyperv_err(
+            "Initialize COM and WMI",
+            result,
+        )
+    };
 }
 
 /// Enable or disable blocking Hyper-V rule
@@ -497,10 +506,7 @@ fn consume_and_log_hyperv_err<T>(
         .inspect_err(|error| {
             log::error!(
                 "{}",
-                error.display_chain_with_msg(&format!(
-                    "Failed: {action}. \
-                     Hyper-V (e.g. WSL machines) may leak in blocked states."
-                ))
+                error.display_chain_with_msg(&format!("{action}. {HYPERV_LEAK_WARNING_MSG}"))
             );
         })
         .ok()