glibc/resolv
Florian Weimer 868ab8923a resolv: Track single-request fallback via _res._flags (bug 31476)
This avoids changing _res.options, which inteferes with change
detection as part of automatic reloading of /etc/resolv.conf.

Reviewed-by: DJ Delorie <dj@redhat.com>
2024-06-13 18:56:30 +02:00
..
arpa Fix all the remaining misspellings -- BZ 25337 2023-06-02 01:39:48 +00:00
bits/types Fix all the remaining misspellings -- BZ 25337 2023-06-02 01:39:48 +00:00
nss_dns Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
sys initial import 1995-02-18 01:27:10 +00:00
tst-leaks2.root/etc Use libnss_files.so for tests posix/bug-ga2 and resolv/tst-leaks2 [BZ #26821] 2020-11-23 10:51:24 +01:00
base64.c Relicense IBM portions of resolv/base64.c resolv/res_debug.c. 2024-01-26 13:33:36 -05:00
compat-gethnamaddr.c resolv: Move dn_expand to its own file and into libc 2021-07-19 07:56:21 +02:00
compat-hooks.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
Depend hurd: Add hurd thread library 2018-04-02 01:44:14 +02:00
dn_comp.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
dn_expand.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
dn_skipname.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
gai_cancel.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
gai_error.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
gai_misc.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
gai_misc.h Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
gai_notify.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
gai_sigqueue.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
gai_suspend.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
getaddrinfo_a.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
herror.c Consolidate non cancellable writev call 2017-08-21 15:37:45 -03:00
inet_addr.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
inet_net_ntop.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
inet_net_pton.c Fix all the remaining misspellings -- BZ 25337 2023-06-02 01:39:48 +00:00
inet_neta.c Consistently use uintN_t not u_intN_t everywhere. 2017-08-07 19:55:34 +00:00
inet_ntop.c resolv: Remove internal_function attribute 2017-08-31 16:07:52 +02:00
inet_pton.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
libanl-compat.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
Makefile Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
mapv4v6addr.h Restore lookup of IPv4 mapped addresses in files database (bug 25457) 2023-07-24 13:16:24 +02:00
netdb.h Always define __USE_TIME_BITS64 when 64 bit time_t is used 2024-04-02 15:28:36 -03:00
ns_date.c Consistently use uintN_t not u_intN_t everywhere. 2017-08-07 19:55:34 +00:00
ns_makecanon.c resolv: Move ns_makecanon into its own file, and into libc 2021-07-19 07:56:21 +02:00
ns_name_compress.c resolv: Move ns_name_compress into its own file and into libc 2021-07-19 07:56:21 +02:00
ns_name_length_uncompressed.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
ns_name_ntop.c resolv: Move ns_name_ntop to its own file and into libc 2021-07-15 08:39:31 +02:00
ns_name_pack.c resolv: Move ns_name_pack into its own file and into libc 2021-07-19 07:56:21 +02:00
ns_name_pton.c resolv: Move ns_name_pton into its own file and into libc 2021-07-19 07:56:21 +02:00
ns_name_skip.c resolv: Move ns_name_skip to its own file and into libc (bug 28091) 2021-07-19 07:56:13 +02:00
ns_name_uncompress.c resolv: Move ns_name_uncompress into its own file and into libc 2021-07-19 07:56:21 +02:00
ns_name_unpack.c resolv: Move ns_name_unpack to its own file and into libc 2021-07-15 09:00:27 +02:00
ns_name.c resolv: Move ns_name_compress into its own file and into libc 2021-07-19 07:56:21 +02:00
ns_netint.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
ns_parse.c resolv: Move dn_expand to its own file and into libc 2021-07-19 07:56:21 +02:00
ns_print.c Fix all the remaining misspellings -- BZ 25337 2023-06-02 01:39:48 +00:00
ns_rr_cursor_init.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
ns_rr_cursor_next.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
ns_samebinaryname.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
ns_samedomain.c resolv: Move ns_samename into its own file, and into libc 2021-07-19 07:56:21 +02:00
ns_samename.c resolv: Move ns_samename into its own file, and into libc 2021-07-19 07:56:21 +02:00
ns_ttl.c Add fall-through comments. 2019-02-12 10:30:34 +00:00
nsap_addr.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
nss_dns_functions.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
README nss_dns: Remove remnants of IPv6 address mapping 2022-08-30 10:02:49 +02:00
res_context_hostalias.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_data.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_debug.c resolv: Make _res_opcodes a compat symbol [BZ #31764] 2024-05-20 19:35:25 -07:00
res_enable_icmp.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_get_nsaddr.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_hconf.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_hconf.h Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_hostalias.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_init.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_isourserver.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_libc.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_mkquery.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_nameinquery.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_queriesmatch.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_query.c resolv: Fix endless loop in __res_context_query 2024-01-11 16:38:25 +01:00
res_randomid.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res_send.c resolv: Track single-request fallback via _res._flags (bug 31476) 2024-06-13 18:56:30 +02:00
res-close.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res-name-checking.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res-noaaaa.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res-putget.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
res-state.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
resolv_conf.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
resolv_conf.h Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
resolv_context.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
resolv_context.h Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
resolv-deprecated.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
resolv-internal.h resolv: Track single-request fallback via _res._flags (bug 31476) 2024-06-13 18:56:30 +02:00
resolv.h Fix all the remaining misspellings -- BZ 25337 2023-06-02 01:39:48 +00:00
tst-aton.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-bug18665-tcp.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-bug18665.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-inet_addr-binary.c Refer to C23 in place of C2X in glibc 2024-02-01 11:02:01 +00:00
tst-inet_aton_exact.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-inet_ntop.c Modify several tests to use test-skeleton.c 2014-11-05 15:24:08 +05:30
tst-inet_pton.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-leaks2.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-leaks.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-no-libidn2.c Switch IDNA implementation to libidn2 [BZ #19728] [BZ #19729] [BZ #22247] 2018-05-23 15:27:24 +02:00
tst-ns_name_compress.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-ns_name_length_uncompressed.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-ns_name_pton.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-ns_name.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-ns_name.data Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-ns_rr_cursor.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-ns_samebinaryname.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-p_secstodate.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-res_hconf_reorder.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-res_hnok.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-ai_idn-common.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-ai_idn-latin1.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-ai_idn-nolibidn2.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-ai_idn.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-aliases.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-basic.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-binary.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-byaddr.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-canonname.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-edns.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-invalid-cname.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-maybe_insert_sig.h Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-network.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-noaaaa-vc.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-noaaaa.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-nondecimal.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-qtypes.c resolv: Fix endless loop in __res_context_query 2024-01-11 16:38:25 +01:00
tst-resolv-res_init-multi.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-res_init-skeleton.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-res_init-thread.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-res_init.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-res_ninit.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-rotate.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-search.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-threads.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-trailing.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-trustad.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
tst-resolv-txnid-collision.c Update copyright dates with scripts/update-copyrights 2024-01-01 10:53:40 -08:00
Versions resolv: Move nss_dns into libc 2021-07-19 07:56:57 +02:00

The resolver in the GNU C Library
*********************************

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 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 initialising 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.

* The resolver in glibc can connect to a nameserver over IPv6.  Just
  specify the IPv6 address in /etc/resolv.conf.  You cannot change the
  address of an IPv6 nameserver dynamically in your program though.


Using the resolver in multi-threaded code
=========================================

The traditional resolver interfaces `res_query', `res_search',
`res_mkquery', `res_send' and `res_init', used a static (global)
resolver state stored in the `_res' structure.  Therefore, these
interfaces are not thread-safe.  Therefore, BIND 8.2 introduced a set
of "new" interfaces `res_nquery', `res_nsearch', `res_nmkquery',
`res_nsend' and `res_ninit' that take a `res_state' as their first
argument, so you can use a per-thread resolver state.  In glibc, when
you link with -lpthread, such a per-thread resolver state is already
present.  It can be accessed using `_res', which has been redefined as
a macro, in a similar way to what has been done for the `errno' and
`h_errno' variables.  This per-thread resolver state is also used for
the `gethostby*' family of functions, which means that for example
`gethostbyname_r' is now fully thread-safe and re-entrant.  The
traditional resolver interfaces however, continue to use a single
resolver state and are therefore still thread-unsafe.  The resolver
state is the same resolver state that is used for the initial ("main")
thread.

This has the following consequences for existing binaries and source
code:

* Single-threaded programs will continue to work.  There should be no
  user-visible changes when you recompile them.

* Multi-threaded programs that use the traditional resolver interfaces
  in the "main" thread should continue to work, except that they no
  longer see any changes in the global resolver state caused by calls
  to, for example, `gethostbyname' in other threads.  Again there
  should be no user-visible changes when you recompile these programs.

* Multi-threaded programs that use the traditional resolver interfaces
  in more than one thread should be just as buggy as before (there are
  no problems if you use proper locking of course).  If you recompile
  these programs, manipulating the _res structure in threads other
  than the "main" thread will seem to have no effect though.

* In Multi-threaded that manipulate the _res structure, calls to
  functions like `gethostbyname' in threads other than the "main"
  thread won't be influenced by the those changes anymore.

We recommend to use the new thread-safe interfaces in new code, since
the traditional interfaces have been deprecated by the BIND folks.
For compatibility with other (older) systems you might want to
continue to use those interfaces though.


Using the resolver in C++ code
==============================

There resolver contains some hooks which will allow the user to
install some callback functions that make it possible to filter DNS
requests and responses.  Although we do not encourage you to make use
of this facility at all, C++ developers should realise that it isn't
safe to throw exceptions from such callback functions.


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_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 optimised a bit, and adaptations have
been made to make them fit in with the rest of glibc.

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.