@c gnutls_vdata_types_t
@table @code
@item GNUTLS_@-DT_@-UNKNOWN
Unknown data type.
@item GNUTLS_@-DT_@-DNS_@-HOSTNAME
The data contain a null-terminated DNS hostname; the hostname will be 
matched using the RFC6125 rules. If the data contain a textual IP (v4 or v6) address it will
be marched against the IPAddress Alternative name, unless the verification flag @code{GNUTLS_VERIFY_DO_NOT_ALLOW_IP_MATCHES} 
is specified.
@item GNUTLS_@-DT_@-KEY_@-PURPOSE_@-OID
The data contain a null-terminated key purpose OID. It will be matched
against the certificate's Extended Key Usage extension.
@item GNUTLS_@-DT_@-RFC822NAME
The data contain a null-terminated email address; the email will be
matched against the RFC822Name Alternative name of the certificate, or the EMAIL DN component if the
former isn't available. Prior to matching the email address will be converted to ACE
(ASCII-compatible-encoding).
@item GNUTLS_@-DT_@-IP_@-ADDRESS
The data contain a raw IP address (4 or 16 bytes). If will be matched
against the IPAddress Alternative name; option available since 3.6.0.
@end table