+extern const NetDevVTable ip6tnl_vtable;
+
+const char *ip6tnl_mode_to_string(Ip6TnlMode d) _const_;
+Ip6TnlMode ip6tnl_mode_from_string(const char *d) _pure_;
+
+int config_parse_ip6tnl_mode(const char *unit, const char *filename,
+ unsigned line, const char *section,
+ unsigned section_line, const char *lvalue,
+ int ltype, const char *rvalue, void *data,
+ void *userdata);