** Description changed:
[Impact]
sssd can switch to an offline mode of operation when it cannot reach the
authentication or id backend. It uses several methods to assess the situation,
and one of them is monitoring the /etc/resolv.conf file for changes.
In ubuntu that file is a symlink to /run/systemd/resolve/stub-
resolv.conf, but the target doesn't exist at all times during boot. It's
expected that symlink to be broken for a while during boot.
Turns out that the monitoring that sssd was doing on /etc/resolv.conf
didn't take into consideration that what could change was the *target*
of the symlink. it completely ignored that fact, and didn't notice when
the resolv.conf contents actually changed in this scenario, which
resulted in sssd staying in the offline mode when it shouldn't.
There are two fixes being pulled in for this SRU:
a) fix the monitoring of the target of the /etc/resolv.conf symlink
b) change the fallback polling code to keep trying, instead of giving up
right away
[Test Case]
It's recommended to test this in a lxd container, or a vm.
Preparation steps. When prompted for an openldap/slapd password, chose any
password you want. It won't be needed again:
$ sudo apt update && sudo apt dist-upgrade
$ sudo apt install sssd-ldap sssd-tools sssd-dbus slapd dnsmasq
Become root:
$ sudo su -
Detect your ip:
# export interface=$(ip route | grep default | sed -r 's,^default via .* dev
([a-z0-9]+) .*,\1,')
# export ip=$(ip addr show dev $interface | grep "inet [0-9]" | awk '{print
$2}' | cut -d / -f 1)
Confirm the $ip variable is correct for your case:
# echo $ip
Create /etc/dnsmasq.d/sssd-test.conf using your real ip:
# cat > /etc/dnsmasq.d/sssd-test.conf <<EOF
host-record=ldap01.example.com,$ip
listen-address=$ip
interface=$interface
except-interface=lo
- bind-interface
+ bind-interfaces
EOF
restart dnsmasq
# systemctl restart dnsmasq
a) inotify test
Create /etc/sssd/sssd.conf:
# cat > /etc/sssd/sssd.conf <<EOF
[sssd]
config_file_version = 2
services = nss, pam, ifp
domains = LDAP
debug_level = 6
[domain/LDAP]
id_provider = ldap
ldap_uri = ldap://ldap01.example.com
cache_credentials = True
ldap_search_base = dc=example,dc=com
EOF
# chmod 0600 /etc/sssd/sssd.conf
# rm /etc/resolv.conf
# ln -s /etc/resolv.conf.target /etc/resolv.conf
create good resolv.conf:
# echo "nameserver $ip" > /etc/resolv.conf.good
Confirm /etc/resolv.conf is a broken symlink:
# ll /etc/resolv.conf*
lrwxrwxrwx 1 root root 23 May 13 20:48 /etc/resolv.conf ->
/etc/resolv.conf.target
-rw-r--r-- 1 root root 24 May 13 20:48 /etc/resolv.conf.good
Open another terminal/screen and tail the sssd logs with a grep:
# tail -F /var/log/sssd/sssd.log | grep -i resolv
Start sssd
# systemctl restart sssd
The tail output from that other terminal should say sssd is monitoring
/etc/resolv.conf (that's the broken symlink):
(Mon May 18 17:32:34 2020) [sssd] [_snotify_create] (0x0400): Added a watch
for /etc/resolv.conf with inotify flags 0x8D88 internal flags 0x1 using
function resolv_conf_inotify_cb after delay 1.0
Repeat this sssctl call until it shows the offline mode persistently:
# sssctl domain-status LDAP
Online status: Offline
Active servers:
LDAP: not connected
Discovered LDAP servers:
- ldap01.example.com
"Unbreak" the symlink:
# cp /etc/resolv.conf.good /etc/resolv.conf.target
The log should now say:
(Mon May 18 17:33:30 2020) [sssd] [process_dir_event] (0x0400): Not
interested in resolv.conf.target
This shows that sssd didn't pick up that resolv.conf changed, via the
target of the symlink.
Run sssctl again, and the online status will remain offline.
With the fixed packages, the sssd startup log will say:
(Mon May 18 17:17:06 2020) [sssd] [_snotify_create] (0x0400): Added a watch
for /etc/resolv.conf.target with inotify flags 0x8D88 internal flags 0x1 using
function resolv_conf_inotify_cb after delay 1.0
Showing that it's monitoring the symlink target.
And after fixing the broken symlink, it will say:
(Mon May 18 17:18:06 2020) [sssd] [process_dir_event] (0x0400): received
notification for watched file [resolv.conf.target] under /etc
Run sssctl again, it should almost immediately switch to online:
# sssctl domain-status LDAP
Online status: Online
Active servers:
LDAP: ldap01.example.com
Discovered LDAP servers:
- ldap01.example.com
b) polling test
Repeat the previous test, but with "try_inotify = false" in sssd.conf, like
this:
# cat > /etc/sssd/sssd.conf <<EOF
[sssd]
config_file_version = 2
services = nss, pam, ifp
domains = LDAP
debug_level = 6
try_inotify = false
[domain/LDAP]
id_provider = ldap
ldap_uri = ldap://ldap01.example.com
cache_credentials = True
ldap_search_base = dc=example,dc=com
EOF
Then follow the other steps of test case (a).
Upon startup, the sssd log will show:
(Mon May 18 17:57:04 2020) [sssd] [monitor_config_file_fallback] (0x0080):
file [/etc/resolv.conf] is missing. Will not update online status based on
watching the file
Note how it says it will not watch it for updates.
With the fixed package, the log will show this instead:
(Mon May 18 18:02:56 2020) [sssd] [monitor_config_file_fallback] (0x0020):
file [/etc/resolv.conf] is missing. Will try again later.
Notice how it says it will try again, and multiple times if you keep
watching it (once every 10s).
"Unbreak" the symlink:
# cp /etc/resolv.conf.good /etc/resolv.conf.target
And the log output will eventually show this:
(Mon May 18 18:04:06 2020) [sssd] [monitor_config_file_fallback] (0x0020):
file [/etc/resolv.conf] is missing. Will try again later.
(Mon May 18 18:04:17 2020) [sssd] [signal_res_init] (0x0040): Reloading
Resolv.conf.
And sssctl will show the now online status:
# sssctl domain-status LDAP
Online status: Online
Active servers:
LDAP: ldap01.example.com
Discovered LDAP servers:
- ldap01.example.com
[Regression Potential]
Breaking sssd can mean preventing logins of network remote users on a system,
but should still allow local users (and root) to login. Another possible source
of regressions, but not related to the code changes in this update, if there
are pre-existing incorrect changes to sssd.conf, they might prevent the service
from restarting when this update is applied.
[Other Info]
Not at this time.
[Original Description]
SSSD 1.15.3-2ubuntu1 on 17.10/artful (previous versions on artful were
also affected) is offline on boot and seems to stay offline forever (I
waited over 20 minutes).
sssd_nss.log:
(Fri Oct 13 09:49:50 2017) [sssd[nss]] [sss_dp_get_reply] (0x0010): The Data
Provider returned an error [org.freedesktop.sssd.Error.DataProvider.Offline]
(Fri Oct 13 09:49:51 2017) [sssd[nss]] [sss_dp_get_reply] (0x0010): The Data
Provider returned an error [org.freedesktop.sssd.Error.DataProvider.Offline]
(Fri Oct 13 09:49:51 2017) [sssd[nss]] [sss_dp_get_reply] (0x0010): The Data
Provider returned an error [org.freedesktop.sssd.Error.DataProvider.Offline]
(Fri Oct 13 09:49:51 2017) [sssd[nss]] [sss_dp_get_reply] (0x0010): The Data
Provider returned an error [org.freedesktop.sssd.Error.DataProvider.Offline]
...
SSSD immediately returns to normal operation after restarting it or
after sending SIGUSR2.
A workaround for the problem is creating the file
/etc/systemd/system/sssd.service.d/override.conf with contents
[Unit]
Requires=network-online.target
After=network-online.target
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/1723350
Title:
sssd offline on boot, stays offline forever
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/sssd/+bug/1723350/+subscriptions
--
ubuntu-bugs mailing list
ubuntu-bugs@lists.ubuntu.com
https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
