improve experience of subnet/kcp proxy

1. add self to windows firewall on windows
2. android always use smoltcp

easytier/src/instance/virtual_nic.rs

@@ -349,6 +349,15 @@ impl VirtualNic {
         {
             let dev_name = self.global_ctx.get_flags().dev_name;
 
+            match crate::arch::windows::add_self_to_firewall_allowlist() {
+                Ok(_) => tracing::info!("add_self_to_firewall_allowlist successful!"),
+                Err(e) => {
+                    println!("Failed to add Easytier to firewall allowlist, Subnet proxy and KCP proxy may not work properly. error: {}", e);
+                    println!("You can add firewall rules manually, or use --use-smoltcp to run with user-space TCP/IP stack.");
+                    println!("");
+                }
+            }
+
             match checkreg(&dev_name) {
                 Ok(_) => tracing::trace!("delete successful!"),
                 Err(e) => tracing::error!("An error occurred: {}", e),