getaddrinfo() not return (or return incorrect) IPv6 address for hostname lookup using /etc/hosts file if IPv4 address exists for that hostname this make hostname lookup using host file that has both IPv4 and IPv6 address on same hostname with IPv6 only application (use AF_INET6 or IPV6_V6ONLY socket) failed to work. For example: coresv01 / # ping6 localhost unknown host coresv01 / # ssh -6 localhost ssh: Could not resolve hostname localhost: No address associated with hostname Seems that for AF_INET6 IPv4 mapped IPv6 address returned instead of actual IPv6 address In case AF_UNSPEC, only IPv4 returned Affected both current hardened and default profiles Reproducible: Always Steps to Reproduce: Create hosts file with host listed both IPv4 and IPv6 addresses default installation of localhost in /etc/hosts also has problems 127.0.0.1 localhost ::1 localhost Actual Results: coresv01 / # ping6 localhost unknown host coresv01 / # getent ahosts localhost 127.0.0.1 STREAM localhost 127.0.0.1 DGRAM 127.0.0.1 RAW coresv01 / # getent ahostsv4 localhost 127.0.0.1 STREAM localhost 127.0.0.1 DGRAM 127.0.0.1 RAW coresv01 / # getent ahostsv6 localhost ::ffff:127.0.0.1 STREAM localhost ::ffff:127.0.0.1 DGRAM ::ffff:127.0.0.1 RAW Expected Results: This output taken from CentOS/RHEL 6 (glibc 2.12) [root@vpsserv01 etc]# ping6 localhost PING localhost(localhost) 56 data bytes 64 bytes from localhost: icmp_seq=1 ttl=64 time=0.025 ms [root@vpsserv01 ~]# getent ahosts localhost ::1 STREAM localhost ::1 DGRAM ::1 RAW 127.0.0.1 STREAM 127.0.0.1 DGRAM 127.0.0.1 RAW [root@vpsserv01 ~]# getent ahostsv4 localhost 127.0.0.1 STREAM localhost 127.0.0.1 DGRAM 127.0.0.1 RAW [root@vpsserv01 ~]# getent ahostsv6 localhost ::1 STREAM localhost ::1 DGRAM ::1 RAW ### emerge --info Portage 2.1.10.49 (default/linux/amd64/10.0, gcc-4.5.3, glibc-2.14.1-r3, 3.2.12-gentoo x86_64) ================================================================= System uname: Linux-3.2.12-gentoo-x86_64-Intel-R-_Xeon-R-_CPU_X3220_@_2.40GHz-with-gentoo-2.1 Timestamp of tree: Mon, 04 Jun 2012 10:00:01 +0000 app-shells/bash: 4.2_p20 dev-lang/python: 2.7.3-r1, 3.2.3 dev-util/pkgconfig: 0.26 sys-apps/baselayout: 2.1-r1 sys-apps/openrc: 0.9.8.4 sys-apps/sandbox: 2.5 sys-devel/autoconf: 2.68 sys-devel/automake: 1.11.1 sys-devel/binutils: 2.21.1-r1 sys-devel/gcc: 4.5.3-r2 sys-devel/gcc-config: 1.6 sys-devel/libtool: 2.4-r1 sys-devel/make: 3.82-r1 sys-kernel/linux-headers: 3.1 (virtual/os-headers) sys-libs/glibc: 2.14.1-r3 Repositories: gentoo ACCEPT_KEYWORDS="amd64" ACCEPT_LICENSE="* -@EULA" CBUILD="x86_64-pc-linux-gnu" CFLAGS="-O2 -pipe" CHOST="x86_64-pc-linux-gnu" CONFIG_PROTECT="/etc /usr/share/openvpn/easy-rsa /var/bind" CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/env.d /etc/gconf /etc/gentoo-release /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo" CXXFLAGS="-O2 -pipe" DISTDIR="/usr/portage/distfiles" FEATURES="assume-digests binpkg-logs distlocks ebuild-locks fixlafiles news parallel-fetch protect-owned sandbox sfperms strict unknown-features-warn unmerge-logs unmerge-orphans userfetch" FFLAGS="" GENTOO_MIRRORS="http://mirror.nettree.co.th/gentoo http://gentoo.osuosl.org" LDFLAGS="-Wl,-O1 -Wl,--as-needed" MAKEOPTS="-j4" PKGDIR="/sharedata/cshost/usr/portage/packages" PORTAGE_CONFIGROOT="/" PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress --force --whole-file --delete --stats --human-readable --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages" PORTAGE_TMPDIR="/var/tmp" PORTDIR="/usr/portage" PORTDIR_OVERLAY="" SYNC="rsync://202.162.76.90/gentoo-portage" USE="acl amd64 berkdb bzip2 cli cracklib crypt cups cxx dri fortran gdbm gpm iconv ipv6 mmx modules mudflap multilib ncurses nls nptl openmp pam pcre pppd readline session sse sse2 ssl tcpd unicode xorg zlib" ALSA_CARDS="ali5451 als4000 atiixp atiixp-modem bt87x ca0106 cmipci emu10k1x ens1370 ens1371 es1938 es1968 fm801 hda-intel intel8x0 intel8x0m maestro3 trident usb-audio via82xx via82xx-modem ymfpci" ALSA_PCM_PLUGINS="adpcm alaw asym copy dmix dshare dsnoop empty extplug file hooks iec958 ioplug ladspa lfloat linear meter mmap_emul mulaw multi null plug rate route share shm softvol" APACHE2_MODULES="actions alias auth_basic authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter file_cache filter headers include info log_config logio mem_cache mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" CALLIGRA_FEATURES="kexi words flow plan sheets stage tables krita karbon braindump" CAMERAS="ptp2" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf superstar2 timing tsip tripmate tnt ubx" INPUT_DEVICES="keyboard mouse evdev" KERNEL="linux" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" PHP_TARGETS="php5-3" PYTHON_TARGETS="python3_2 python2_7" QEMU_SOFTMMU_TARGETS="i386 x86_64" QEMU_USER_TARGETS="i386 x86_64" RUBY_TARGETS="ruby18 ruby19" USERLAND="GNU" VIDEO_CARDS="fbdev glint intel mach64 mga neomagic nouveau nv r128 radeon savage sis tdfx trident vesa via vmware dummy v4l" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq steal rawnat logmark ipmark dhcpmac delude chaos account" Unset: CPPFLAGS, CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LANG, LC_ALL, LINGUAS, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS, USE_PYTHON
I found the solution. Seems it need 'multi on' in /etc/host.conf file to allow glibc return multiple (both IPv4 and IPv6) address in /etc/hosts. Not quite a bug, but default /etc/host.conf need to be update to fix this. But output from Gentoo GLIBC is still differnet from Redhat here on getent ahostsv4 if only this 2 lines exists #cat /etc/hosts 127.0.0.1 localhost ::1 localhost Gentoo #getent ahostsv4 localhost 127.0.0.1 STREAM localhost 127.0.0.1 DGRAM 127.0.0.1 RAW 127.0.0.1 STREAM 127.0.0.1 DGRAM 127.0.0.1 RAW RHEL6 # getent ahostsv4 localhost 127.0.0.1 STREAM localhost 127.0.0.1 DGRAM 127.0.0.1 RAW
returning an ipv4-mapped ipv6 address is a valid ipv6 address, so i wouldn't say that is a bug if you want the system to prefer ipv6 over ipv4 with resolving, then you could change the ordering of your /etc/hosts file as for the getent output, it works fine for me with glibc-2.15: $ getent ahostsv4 localhost 127.0.0.1 STREAM localhost 127.0.0.1 DGRAM 127.0.0.1 RAW
By the way, I suggested we should add comment to shipped /etc/hosts for people to beware order of IPv6 addresses. It may not a bug to glibc but Gentoo system because any IPv6 only application (which use IPv6_V6ONLY) will fail to work because IPv4 mapped IPv6 address found first and not valid IPv6 Only address. (Or do like other distro, shipped glibc with 'multi on' in host.conf) I spend a couple of hours for debug what cause my application not working because this problem of /etc/hosts.
the `ping6 localhost` behavior is just wrong i think regardless of multi in /etc/host.conf. but i've filed that upstream if you want to follow along.
