this is awful, but also it's about 20% better

overlay/tun.go

@@ -2,6 +2,7 @@ package overlay
 
 import (
 	"fmt"
+	"io"
 	"net"
 	"net/netip"
 
@@ -12,6 +13,11 @@ import (
 
 const DefaultMTU = 1300
 
+type TunDev interface {
+	io.ReadWriteCloser
+	WriteMany([][]byte) (int, error)
+}
+
 // TODO: We may be able to remove routines
 type DeviceFactory func(c *config.C, l *logrus.Logger, vpnNetworks []netip.Prefix, routines int) (Device, error)