[glibc/release/2.34/master] nss: Use "files dns" as the default for the hosts database (bug 28700)

[glibc/release/2.34/master] nss: Use "files dns" as the default for the hosts database (bug 28700)

[Florian Weimer]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=dc9b69d5331dcdca4547c0490cb9fefbd89e40f6

commit dc9b69d5331dcdca4547c0490cb9fefbd89e40f6
Author: Florian Weimer <fweimer@redhat.com>
Date:   Fri Dec 17 12:01:20 2021 +0100

    nss: Use "files dns" as the default for the hosts database (bug 28700)
    
    This matches what is currently in nss/nsswitch.conf.  The new ordering
    matches what most distributions use in their installed configuration
    files.
    
    It is common to add localhost to /etc/hosts because the name does not
    exist in the DNS, but is commonly used as a host name.
    
    With the built-in "dns [!UNAVAIL=return] files" default, dns is
    searched first and provides an answer for "localhost" (NXDOMAIN).
    We never look at the files database as a result, so the contents of
    /etc/hosts is ignored.  This means that "getent hosts localhost"
    fail without a /etc/nsswitch.conf file, even though the host name
    is listed in /etc/hosts.
    
    Reviewed-by: Carlos O'Donell <carlos@redhat.com>
    (cherry picked from commit b99b0f93ee8762fe53ff65802deb6f00700b9924)

Diff:
---
 NEWS               | 1 +
 manual/nss.texi    | 5 ++---
 nss/XXX-lookup.c   | 2 +-
 nss/nss_database.c | 4 ++--
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/NEWS b/NEWS
index 693ac78229..6864af471c 100644
--- a/NEWS
+++ b/NEWS
@@ -23,6 +23,7 @@ The following bugs are resolved with this release:
   [28607] Masked signals are delivered on thread exit
   [28532] powerpc64[le]: CFI for assembly templated syscalls is incorrect
   [28678] nptl/tst-create1 hangs sporadically
+  [28700] "dns [!UNAVAIL=return] files" NSS default for hosts is not useful
 
 \f
 Version 2.34
diff --git a/manual/nss.texi b/manual/nss.texi
index 3aaa7786f8..524d22ad1e 100644
--- a/manual/nss.texi
+++ b/manual/nss.texi
@@ -324,9 +324,8 @@ missing.
 
 @cindex default value, and NSS
 For the @code{hosts} and @code{networks} databases the default value is
-@code{dns [!UNAVAIL=return] files}.  I.e., the system is prepared for
-the DNS service not to be available but if it is available the answer it
-returns is definitive.
+@code{files dns}.  I.e., local configuration will override the contents
+of the domain name system (DNS).
 
 The @code{passwd}, @code{group}, and @code{shadow} databases was
 traditionally handled in a special way.  The appropriate files in the
diff --git a/nss/XXX-lookup.c b/nss/XXX-lookup.c
index f1c97f7c8e..dbc87868dd 100644
--- a/nss/XXX-lookup.c
+++ b/nss/XXX-lookup.c
@@ -29,7 +29,7 @@
 |* ALTERNATE_NAME - name of another service which is examined in   *|
 |*                  case DATABASE_NAME is not found                *|
 |* 								   *|
-|* DEFAULT_CONFIG - string for default conf (e.g. "dns files")	   *|
+|* DEFAULT_CONFIG - string for default conf (e.g. "files dns")	   *|
 |* 								   *|
 \*******************************************************************/
 
diff --git a/nss/nss_database.c b/nss/nss_database.c
index ab121cb371..54561f0328 100644
--- a/nss/nss_database.c
+++ b/nss/nss_database.c
@@ -80,7 +80,7 @@ enum nss_database_default
 {
  nss_database_default_defconfig = 0, /* "nis [NOTFOUND=return] files".  */
  nss_database_default_compat, /* "compat [NOTFOUND=return] files".  */
- nss_database_default_dns,    /* "dns [!UNAVAIL=return] files".  */
+ nss_database_default_dns,    /* "files dns".  */
  nss_database_default_files,    /* "files".  */
  nss_database_default_nis,    /* "nis".  */
  nss_database_default_nis_nisplus,    /* "nis nisplus".  */
@@ -133,7 +133,7 @@ nss_database_select_default (struct nss_database_default_cache *cache,
 #endif
 
     case nss_database_default_dns:
-      line = "dns [!UNAVAIL=return] files";
+      line = "files dns";
       break;
 
     case nss_database_default_files: