code: func ValidateNetworking(c *kubeadm.Networking, fldPath *field.Path) field.ErrorList {
  	allErrs := field.ErrorList{}
  	allErrs = append(allErrs, apivalidation.ValidateDNS1123Subdomain(c.DNSDomain, field.NewPath("dnsDomain"))...)
  	allErrs = append(allErrs, ValidateIPNetFromString(c.ServiceSubnet, constants.MinimumAddressesInServiceSubnet, field.NewPath("serviceSubnet"))...)
  	if len(c.PodSubnet) != 0 {
  		allErrs = append(allErrs, ValidateIPNetFromString(c.PodSubnet, constants.MinimumAddressesInServiceSubnet, field.NewPath("podSubnet"))...)
  	}
  	return allErrs
  }
docs: // ValidateNetworking validates networking configuration