make kcp proxy compitible with old version (#585)

* fix kcp not work with smoltcp
* check if dst kcp input is enabled

easytier/src/gateway/tcp_proxy.rs

@@ -700,6 +700,10 @@ impl<C: NatDstConnector> TcpProxy<C> {
         }
     }
 
+    pub fn get_global_ctx(&self) -> &ArcGlobalCtx {
+        &self.global_ctx
+    }
+
     pub fn is_smoltcp_enabled(&self) -> bool {
         self.enable_smoltcp
             .load(std::sync::atomic::Ordering::Relaxed)
@@ -783,4 +787,8 @@ impl<C: NatDstConnector> TcpProxy<C> {
 
         Some(())
     }
+
+    pub fn get_peer_manager(&self) -> &Arc<PeerManager> {
+        &self.peer_manager
+    }
 }