BIND 9.3.2 Release Notes (5900-2140, December 2011)

New option to configure the ordering of records
The new rrset-order option in the options statement enables you to configure the ordering
of the records in a multiple-record response. When the name server returns multiple records in a
response, it is useful to configure the order of the records placed into the response.
The following is the syntax of the rrset-order option:
rrset-order {order_spec};
Where, an order_spec can be defined as follows:
[class class_name]
[ type type_name ]
[ name domain_name]
order ordering
The default value for class and type is ANY, and for name is *.
The valid values for ordering are:
fixed Records are returned in the order they are defined in the zone file
random Records are returned in a random order
cyclic Records are returned in a round-robin order
The following is an example of the rrset-order option:
rrset-order {
class IN type A name "host.example.com" order random;
order cyclic;
};
This rrset-order option causes responses for type A records in class IN that have
host.example.com as a suffix, to be returned in random order. Other types of records are
returned in cyclic order.
If the options statement contains multiple rrset-order options, they are not combined but
only the last rrset-order option is used.
New option to set the advertized EDNS UDP buffer size
The edns-udp-size option in the options statement sets the advertised Extended DNS (EDNS)
User Datagram Protocol (UDP) buffer size to enable UDP answers to pass through broken firewalls
that block fragmented packets greater than 512 bytes. The valid range of values is 512 to 4096
bytes (values not in this range are adjusted appropriately). The default value of this option is 4096
bytes.
New option to restrict the character set of domain names
This check-names option in the options statement restricts the character set and syntax of
certain domain names in the master files and DNS responses. The rules for valid host names or
mail domains are derived from RFC 952 (DoD Internet Host Table Specification) and RFC 821
(Simple Mail Transfer Protocol) as modified by RFC 1123 (Requirements for Internet Hosts -
Application and Support). The check-names option checks the names of the owner names of A,
AAAA, and MX records and also checks domain names in the RDATA of NS, SOA, and MX records.
It also applies to the RDATA of PTR records where the owner name indicates that it is a reverse
lookup of a hostname (the owner name ends with in-addr.arpa, ip6.arpa, or ip6.int).
The default value of the check-names option depends on the usage area. For master zones, the
default value is fail. For slave zones, the default value is warn. For an answer (response) received
from the network, the default value is ignore.
8 BIND 9.3.2 Release Notes