cli: use win32 app mutex to detect running tunnels and tunnel sevices (#179622)

* cli: fix distro mixin

* cli: use win32 app mutex to detect running tunnels and tunnel sevices

Fixes #179265

* cli: fix distro mixin more

* fix

* fix build

cli/src/util/app_lock.rs

@@ -0,0 +1,58 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+#[cfg(windows)]
+use std::{io, ptr};
+
+#[cfg(windows)]
+use winapi::{
+	shared::winerror::ERROR_ALREADY_EXISTS,
+	um::{handleapi::CloseHandle, synchapi::CreateMutexA, winnt::HANDLE},
+};
+
+use super::errors::CodeError;
+
+pub struct AppMutex {
+	#[cfg(windows)]
+	handle: HANDLE,
+}
+
+#[cfg(windows)] // handle is thread-safe, mark it so with this
+unsafe impl Send for AppMutex {}
+
+impl AppMutex {
+	#[cfg(unix)]
+	pub fn new(_name: &str) -> Result<Self, CodeError> {
+		Ok(Self {})
+	}
+
+	#[cfg(windows)]
+	pub fn new(name: &str) -> Result<Self, CodeError> {
+		let handle = unsafe { CreateMutexA(ptr::null_mut(), 0, name.as_ptr() as _) };
+
+		if !handle.is_null() {
+			return Ok(Self { handle });
+		}
+
+		let err = io::Error::last_os_error();
+		let raw = err.raw_os_error();
+		// docs report it should return ERROR_IO_PENDING, but in my testing it actually
+		// returns ERROR_LOCK_VIOLATION. Or maybe winapi is wrong?
+		if raw == Some(ERROR_ALREADY_EXISTS as i32) {
+			return Err(CodeError::AppAlreadyLocked(name.to_string()));
+		}
+
+		Err(CodeError::AppLockFailed(err))
+	}
+}
+
+impl Drop for AppMutex {
+	fn drop(&mut self) {
+		#[cfg(windows)]
+		unsafe {
+			CloseHandle(self.handle)
+		};
+	}
+}

cli/src/util/errors.rs

@@ -494,6 +494,12 @@ pub enum CodeError {
 	NoRunningTunnel,
 	#[error("rpc call failed: {0:?}")]
 	TunnelRpcCallFailed(ResponseError),
+	#[cfg(windows)]
+	#[error("the windows app lock {0} already exists")]
+	AppAlreadyLocked(String),
+	#[cfg(windows)]
+	#[error("could not get windows app lock: {0:?}")]
+	AppLockFailed(std::io::Error),
 }
 
 makeAnyError!(