allErrs = append(allErrs, ValidateJoinControlPlane(c.ControlPlane, field.NewPath("controlPlane"))...)

	if !isAbs(c.CACertPath) || !strings.HasSuffix(c.CACertPath, ".crt") {
		allErrs = append(allErrs, field.Invalid(field.NewPath("caCertPath"), c.CACertPath, "the ca certificate path must be an absolute path"))
	}
	return allErrs
}