Starting with version 2.2, the resolver in the GNU C Library comes
from BIND 8.  Only a subset of the src/lib/resolv part of libbind is
included here; basically the parts that are needed to provide the
functionality present in the resolver from BIND 4.9.7 that was
included in the previous release of the GNU C Library, augmented by
the parts needed to provide thread-safety.  This means that support
for things as dynamic DNS updates and TSIG keys isn't included.  If
you need those facilities, please take a look at the full BIND
distribution.


Differences
===========

The resolver in the GNU C Library still differs from what's in BIND
8.2.3-T5B:

* The resolver in glibc strictly adheres to the recommendations in RFC
  1535.  BIND 8.2.3-T5B seems to relax those rules a bit (see the code
  that's wrapped in `#ifndef RFC1535').

* The RES_DEBUG option (`options debug' in /etc/resolv.conf) has been
  disabled.

* The resolver in glibc allows underscores in domain names.

* The <resolv.h> header in glibc includes <netinet/in.h> and
  <arpa/nameser.h> to make it self-contained.

* The `res_close' function in glibc only tries to close open files
  referenced through `_res' if the RES_INIT bit is set in
  `_res.options'.  This fixes a potential security bug with programs
  that bogusly call `res_close' without initializing the resolver
  state first.  Note that the thread-safe `res_nclose' still doesn't
  check the RES_INIT bit.  By the way, you're not really supposed to
  call `res_close/res_nclose' directly.


Source code
===========

The following files come from the BIND distribution (currently version
8.2.3-T5B):

src/include/
  arpa/nameser.h
  arpa/nameser_compat.h
  resolv.h

src/lib/resolv/
  herror.c
  res_comp.c
  res_data.c
  res_debug.c
  res_debug.h
  res_init.c
  res_mkquery.c
  res_query.c
  res_send.c

src/lib/nameser/
  ns_name.c
  ns_netint.c
  ns_parse.c
  ns_print.c
  ns_samedomain.c
  ns_ttl.c

src/lib/inet/
  inet_addr.c
  inet_net_ntop.c
  inet_net_pton.c
  inet_neta.c
  inet_ntop.c
  inet_pton.c
  nsap_addr.c

src/lib/isc/
  base64.c

Some of these files have been optimized a bit, and adaptations have
been made to make them fit in with the rest of glibc.  The more
non-obvious changes are wrapped in something like `#ifdef _LIBC'.

res_libc.c is home-brewn, although parts of it are taken from res_data.c.

res_hconf.c and res_hconf.h were contributed by David Mosberger, and
do not come from BIND.

The files gethnamaddr.c, mapv4v6addr.h and mapv4v6hostent.h are
leftovers from BIND 4.9.7.