ISC's libbind provides the standard resolver library,
along with header files and documentation, for communicating
with domain name servers, retrieving network host entries
from /etc/hosts or via DNS, converting CIDR network addresses,
perform Hesiod information lookups, retrieve network entries
from /etc/networks, implement TSIG transaction/request
security of DNS messages, perform name-to-address and
address-to-name translations, utilize /etc/resolv.conf
for resolver configuration.
It contains many of the same historical functions and headers
included with many Unix operating systems.
Originally written for BIND 8, it was included in BIND 9 as
optionally-compiled code through release 9.5. It has been
removed from subsequent releases of BIND 9 and is now
provided as a separate package.
