int sd_rtnl_open(sd_rtnl **nl, unsigned n_groups, ...);
int sd_rtnl_open_fd(sd_rtnl **nl, int fd, unsigned n_groups, ...);
int sd_rtnl_inc_rcvbuf(const sd_rtnl *const rtnl, const int size);
int sd_rtnl_open(sd_rtnl **nl, unsigned n_groups, ...);
int sd_rtnl_open_fd(sd_rtnl **nl, int fd, unsigned n_groups, ...);
int sd_rtnl_inc_rcvbuf(const sd_rtnl *const rtnl, const int size);