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.
438e82396b