glibc/resolv
Joseph Myers 176804300b Fix network headers stdint.h namespace (bug 21455).
conform/ namespace tests of arpa/inet.h, netdb.h and netinet/in.h fail
for UNIX98 and XPG42 because of inclusion of stdint.h, which defines
macros not permitted in those headers for those standards.  UNIX98
allows them to include inttypes.h, but (predating C99) has restricted
inttypes.h contents (not yet tested in the conform/ tests) not
including those macros; XPG4.2 has no such permission and no
inttypes.h / stdint.h at all.

This patch rearranges the headers to avoid this issue.  intN_t
definitions move to bits/stdint-intn.h, and uintN_t definitions to
bits/stdint-uintn.h.  (These are not bits/types/ headers because they
each define four types.  They are separate rather than just a single
header because sys/types.h defines intN_t but u_intN_t rather than
uintN_t - and while sys/types.h could define uintN_t because of the
POSIX reservation of *_t, existing practice there is largely to
condition types on appropriate feature test macros, and indeed there
is at least one open bug report (14553) about a type that's not
so-conditioned, so maybe types there should actually have conditions
added where appropriate.)  The affected network headers are then made
to include bits/stdint-uintn.h instead of stdint.h.  This allows six
XFAILs to be removed.

This doesn't do anything about inttypes.h defining more than it should
for UNIX98, but we don't have conformtest expectations for that case
at present (and my inclination is that a fix for that should be as
local as possible - affecting only inttypes.h, not stdint.h, only for
the case of __USE_UNIX98 && !__USE_ISOC99).

Tested for x86_64.

	[BZ #21455]
	* bits/stdint-intn.h: New file.
	* bits/stdint-uintn.h: Likewise.
	* stdlib/Makefile (headers): Add bits/stdint-intn.h and
	bits/stdint-uintn.h.
	* inet/netinet/in.h: Include <bits/stdint-uintn.h> instead of
	<stdint.h>.
	* posix/sys/types.h: Include <bits/stdint-intn.h>.
	(__int8_t_defined): Do not define here.
	(int8_t): Likewise.
	(int16_t): Likewise.
	(int32_t): Likewise.
	(int64_t): Likewise.
	[__GNUC_PREREQ (2, 7)] (__intN_t): Likewise.
	* resolv/netdb.h: Include <bits/stdint-uintn.h> instead of
	<stdint.h>.
	* include/netdb.h [_ISOMAC]: Do not include <stdint.h>.
	* sysdeps/generic/stdint.h: Include <bits/stdint-intn.h> and
	<bits/stdint-uintn.h>.
	(int8_t): Do not define here.
	(int16_t): Likewise.
	(int32_t): Likewise.
	(int64_t): Likewise.
	(uint8_t): Likewise.
	(uint16_t): Likewise.
	(uint32_t): Likewise.
	(uint64_t): Likewise.
	* conform/Makefile (test-xfail-XPG42/arpa/inet.h/conform): Remove
	variable.
	(test-xfail-XPG42/netdb.h/conform): Likewise.
	(test-xfail-XPG42/netinet/in.h/conform): Likewise.
	(test-xfail-UNIX98/arpa/inet.h/conform): Likewise.
	(test-xfail-UNIX98/netdb.h/conform): Likewise.
	(test-xfail-UNIX98/netinet/in.h/conform): Likewise.
2017-05-04 20:36:42 +00:00
..
arpa Update DNS RR type definitions [BZ #20593] 2016-12-31 21:16:27 +01:00
nss_dns nss_dns: Correct parentheses for the __glibc_unlikely argument 2017-04-19 22:19:17 +02:00
rpc Install a dummy <rpc/netdb.h> when not building sunrpc/. 2015-07-08 13:38:50 -07:00
sys
Banner
base64.c Convert 703 function definitions to prototype style. 2015-10-16 20:21:49 +00:00
compat-gethnamaddr.c resolv: Deprecate the "inet6" option and RES_USE_INET6 [BZ #19582] 2016-12-31 18:55:14 +01:00
compat-hooks.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
Depend Don't mention linuxthreads in Depend files. 2014-05-21 16:53:11 +00:00
ga_test.c
gai_cancel.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
gai_error.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
gai_misc.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
gai_misc.h Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
gai_notify.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
gai_sigqueue.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
gai_suspend.c resolv: Replace __builtin_expect with __glibc_unlikely/__glibc_likely 2017-04-19 14:29:24 +02:00
getaddrinfo_a.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
herror.c resolv: Compile without -Wno-write-strings 2016-10-11 15:43:41 +02:00
inet_addr.c resolv: Reindent preprocessor conditionals following cleanups 2016-04-28 16:53:56 +02:00
inet_net_ntop.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
inet_net_pton.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
inet_neta.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
inet_ntop.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
inet_pton.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
Makefile resolv: Reduce EDNS payload size to 1200 bytes [BZ #21361] 2017-04-13 13:09:38 +02:00
mapv4v6addr.h
mapv4v6hostent.h
netdb.h Fix network headers stdint.h namespace (bug 21455). 2017-05-04 20:36:42 +00:00
ns_date.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
ns_name.c resolv: Support an exactly sized buffer in ns_name_pack [BZ #21359] 2017-04-13 11:56:28 +02:00
ns_netint.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
ns_parse.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
ns_print.c Remove obsolete DNSSEC support [BZ #20591] 2016-09-21 16:08:32 +02:00
ns_samedomain.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
ns_ttl.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
nsap_addr.c resolv: Remove SCCS and RCS keywords 2016-04-28 12:53:49 +02:00
README resolv: Deprecate the "inet6" option and RES_USE_INET6 [BZ #19582] 2016-12-31 18:55:14 +01:00
res_comp.c resolv: Remove the BIND_4_COMPAT macro 2016-09-21 16:09:03 +02:00
res_data.c resolv: Remove unsupported hook functions from the API [BZ #20016] 2016-09-21 16:30:27 +02:00
res_debug.c resolv: Remove internal and unused definitions from <resolv.h> 2017-04-13 10:52:42 +02:00
res_debug.h Remove trailing whitespace. 2013-06-05 20:44:03 +00:00
res_hconf.c Create more sockets with SOCK_CLOEXEC [BZ #15722] 2017-04-19 07:45:04 +02:00
res_hconf.h Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
res_init.c resolv: Replace __builtin_expect with __glibc_unlikely/__glibc_likely 2017-04-19 14:29:24 +02:00
res_libc.c resolv: Remove _LIBC conditionals 2016-04-28 12:53:49 +02:00
res_mkquery.c resolv: Reduce EDNS payload size to 1200 bytes [BZ #21361] 2017-04-13 13:09:38 +02:00
res_query.c resolv: Replace __builtin_expect with __glibc_unlikely/__glibc_likely 2017-04-19 14:29:24 +02:00
res_send.c resolv: Replace __builtin_expect with __glibc_unlikely/__glibc_likely 2017-04-19 14:29:24 +02:00
res-state.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
resolv-internal.h resolv: Reduce EDNS payload size to 1200 bytes [BZ #21361] 2017-04-13 13:09:38 +02:00
resolv.h resolv: Remove internal and unused definitions from <resolv.h> 2017-04-13 10:52:42 +02:00
tst-aton.c Modify several tests to use test-skeleton.c 2015-08-06 02:59:04 -04:00
tst-bug18665-tcp.c Add missing header files throughout the testsuite. 2017-02-16 17:33:18 -05:00
tst-bug18665.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
tst-inet_ntop.c Modify several tests to use test-skeleton.c 2014-11-05 15:24:08 +05:30
tst-leaks2.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
tst-leaks.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
tst-ns_name_compress.c A third round of inclusion fixes for _ISOMAC testsuite. 2017-04-19 14:39:04 -04:00
tst-ns_name.c resolv: Support an exactly sized buffer in ns_name_pack [BZ #21359] 2017-04-13 11:56:28 +02:00
tst-ns_name.data resolv: Add test coverage for ns_name_unpack, ns_name_ntop 2017-04-04 20:56:17 +02:00
tst-res_hconf_reorder.c Add missing header files throughout the testsuite. 2017-02-16 17:33:18 -05:00
tst-res_use_inet6.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
tst-resolv-basic.c resolv: Support an exactly sized buffer in ns_name_pack [BZ #21359] 2017-04-13 11:56:28 +02:00
tst-resolv-canonname.c resolv: Add tst-resolv-canonname 2017-04-04 20:56:24 +02:00
tst-resolv-edns.c A third round of inclusion fixes for _ISOMAC testsuite. 2017-04-19 14:39:04 -04:00
tst-resolv-network.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
tst-resolv-qtypes.c Get rid of duplicate const declaration specifier warning in tst-resolv-qtypes.c. 2017-02-24 13:30:13 +01:00
tst-resolv-search.c Add missing header files throughout the testsuite. 2017-02-16 17:33:18 -05:00
Versions Fix h_errno namespace (bug 18520). 2015-06-12 10:10:18 +00:00

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_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 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.

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