fix(gui-client): allow disabling telemetry (#9785)

Resolves: #9778

rust/gui-client/src-tauri/src/bin/firezone-gui-client.rs

@@ -81,12 +81,14 @@ fn try_main(
     // Technically this means we can fail to get the device ID on a newly-installed system, since the Tunnel service may not have fully started up when the GUI process reaches this point, but in practice it's unlikely.
     let id = firezone_bin_shared::device_id::get().context("Failed to get device ID")?;
 
-    rt.block_on(telemetry.start(
-        &api_url,
-        firezone_gui_client::RELEASE,
-        firezone_telemetry::GUI_DSN,
-        id.id,
-    ));
+    if cli.is_telemetry_allowed() {
+        rt.block_on(telemetry.start(
+            &api_url,
+            firezone_gui_client::RELEASE,
+            firezone_telemetry::GUI_DSN,
+            id.id,
+        ));
+    }
 
     // Don't fix the log filter for smoke tests because we can't show a dialog there.
     if !config.smoke_test {
@@ -277,6 +279,15 @@ struct Cli {
     /// For headless CI, disable the elevation check.
     #[arg(long, hide = true)]
     no_elevation_check: bool,
+
+    /// Disable sentry.io crash-reporting agent.
+    #[arg(
+        long,
+        env = "FIREZONE_NO_TELEMETRY",
+        default_value_t = false,
+        hide = true
+    )]
+    no_telemetry: bool,
 }
 
 impl Cli {
@@ -295,6 +306,10 @@ impl Cli {
     fn check_elevation(&self) -> bool {
         !self.no_elevation_check
     }
+
+    fn is_telemetry_allowed(&self) -> bool {
+        !self.no_telemetry
+    }
 }
 
 #[derive(clap::Subcommand)]

rust/gui-client/src-tauri/src/service.rs

@@ -576,14 +576,25 @@ impl<'a> Handler<'a> {
                 release,
                 account_slug,
             } => {
-                self.telemetry
-                    .start(
-                        &environment,
-                        &release,
-                        firezone_telemetry::GUI_DSN,
-                        self.device_id.id.clone(),
-                    )
-                    .await;
+                // This is a bit hacky.
+                // It would be cleaner to pass it down from the `Cli` struct.
+                // However, the service can be run in many different ways and adapting all of those
+                // is cumbersome.
+                // Disabling telemetry for the service is mostly useful for our own testing and therefore
+                // doesn't need to be exposed publicly anyway.
+                let no_telemetry =
+                    std::env::var("FIREZONE_NO_TELEMETRY").is_ok_and(|s| s == "true");
+
+                if !no_telemetry {
+                    self.telemetry
+                        .start(
+                            &environment,
+                            &release,
+                            firezone_telemetry::GUI_DSN,
+                            self.device_id.id.clone(),
+                        )
+                        .await
+                }
 
                 if let Some(account_slug) = account_slug {
                     Telemetry::set_account_slug(account_slug.clone());