Bug#990278: /etc/hosts: Reverse lookup on 127.0.0.1 returns hostname instead of localhost

[Ariel D'Alessandro]

Package: obs-build
Version: 20190710-1
Severity: normal
Tags: patch upstream

Dear Maintainer,

Building spymemcached Debian package in an OBS instance, FTBFS because a
test expects a reverse lookup on 127.0.0.1 to be localhost. See:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=990196

OBS configuration sets first entry in /etc/hosts to 127.0.0.1 $hostname.
See upstream configuration:
https://github.com/openSUSE/obs-build/blob/master/init_buildsystem#L1236

Although spymemcached test seems to be adding an unreasonable constraint
to the building host in this case, it's not clear why OBS is configured
this way, even having this note on it:

# this makes a reverse lookup on 127.0.0.1 return the host name,
# which is bad, but 127.0.0.2 does not work on all unix systems

Is there any reason to have this hosts configuration?

If there's not, please find a follow up patch e-mail in this bug report.

Regards,
Ariel D'Alessandro

-- System Information:
Debian Release: 11.0
APT prefers testing-security
APT policy: (500, 'testing-security'), (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 5.10.0-7-amd64 (SMP w/8 CPU threads)
Kernel taint flags: TAINT_FIRMWARE_WORKAROUND, TAINT_OOT_MODULE,
TAINT_UNSIGNED_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE
not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages obs-build depends on:
ii debootstrap 1.0.123
ii libarchive-tools 3.4.3-2+b1
ii perl 5.32.1-4
ii python3 3.9.2-3
ii python3-websocket 0.57.0-1
ii rpm 4.16.1.2+dfsg1-0.4
ii sudo 1.9.5p2-3

Versions of packages obs-build recommends:
ii e2fsprogs 1.46.2-1
ii libcrypt-ssleay-perl 0.73.06-1+b3
ii osc 0.169.1-1
ii rpm2cpio 4.16.1.2+dfsg1-0.4
ii xzdec 5.2.5-2

Versions of packages obs-build suggests:
pn btrfs-progs <none>
pn xfsprogs <none>

-- no debconf information

[Ariel D'Alessandro]

spymemcached package is FTBFS because a test expects a reverse lookup of
127.0.0.1 to return localhost, but current /etc/hosts configuration
returns the hostname instead.

Let's move this `hostname/ip` entry to the end of /etc/hosts so the
reverse lookup of 127.0.0.1 returns localhost, which makes sense to be
the default case usually.

Signed-off-by: Ariel D'Alessandro <ariel.da...@collabora.com>
---
init_buildsystem | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/init_buildsystem b/init_buildsystem
index 23e1c40..62b7966 100755
--- a/init_buildsystem
+++ b/init_buildsystem
@@ -1077,11 +1077,7 @@ fi
test -e $BUILD_ROOT/.build/init_buildsystem.data || HOST=`hostname`
test -e $BUILD_ROOT/etc/hosts || echo "127.0.0.1 localhost" > $BUILD_ROOT/etc/hosts
if ! grep -F "127.0.0.1 $HOST" $BUILD_ROOT/etc/hosts > /dev/null ; then
- # this makes a reverse lookup on 127.0.0.1 return the host name,
- # which is bad, but 127.0.0.2 does not work on all unix systems
- echo "127.0.0.1 $HOST" > $BUILD_ROOT/etc/hosts.new
- test -f $BUILD_ROOT/etc/hosts && cat $BUILD_ROOT/etc/hosts >> $BUILD_ROOT/etc/hosts.new
- mv $BUILD_ROOT/etc/hosts.new $BUILD_ROOT/etc/hosts
+ echo "127.0.0.1 $HOST" >> $BUILD_ROOT/etc/hosts
fi

# XXX: still needed?
--
2.30.2