The async resolver only tries the first nameserver in /etc/resolv.conf

[sssd-bot]

Cloned from Pagure issue: https://pagure.io/SSSD/sssd/issue/867

• Created at 2011-05-11 22:20:14 by sgallagh
• Closed as Fixed
• Assigned to jhrozek

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We're not properly failing over to secondary DNS servers if the first server in the list is broken.

Steps to reproduce:

1. Set up a valid /etc/resolv.conf with a working primary DNS server
2. Add {{{nameserver 127.0.0.2}}} to the above the working DNS entries (simulates having an unreachable DNS server in the list)
3. Enable debug logs and restart SSSD

The debug log will contain

(Wed May 11 16:08:52 2011) [sssd[be[example.com]]] [fo_resolve_service_done] (1): Failed to resolve server 'ldap.example.com': Could not contact DNS servers

and SSSD will operate permanently in offline mode because it can never resolve the SRV records.

It's unclear right now whether the bug is in SSSD's async resolver or internal to the c-ares library.

Comments

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Comment from sgallagh at 2011-05-11 22:22:35

Fields changed

description: We're not properly failing over to secondary DNS servers if the first server in the list is broken.

Steps to reproduce:

1. Set up a valid /etc/resolv.conf with a working primary DNS server
2. Add {{{nameserver 127.0.0.2}}} to the above the working DNS entries
3. Enable debug logs and restart SSSD

The debug log will contain
{{{
(Wed May 11 16:08:52 2011) [sssd[be[example.com]]] [fo_resolve_service_done] (1): Failed to resolve server 'ldap.example.com': Could not contact DNS servers
}}}
and SSSD will operate permanently in offline mode because it can never resolve the SRV records.

It's unclear right now whether the bug is in SSSD's async resolver or internal to the c-ares library. => We're not properly failing over to secondary DNS servers if the first server in the list is broken.

Steps to reproduce:

1. Set up a valid /etc/resolv.conf with a working primary DNS server
2. Add {{{nameserver 127.0.0.2}}} to the above the working DNS entries (simulates having an unreachable DNS server in the list)
3. Enable debug logs and restart SSSD

The debug log will contain
{{{
(Wed May 11 16:08:52 2011) [sssd[be[example.com]]] [fo_resolve_service_done] (1): Failed to resolve server 'ldap.example.com': Could not contact DNS servers
}}}
and SSSD will operate permanently in offline mode because it can never resolve the SRV records.

It's unclear right now whether the bug is in SSSD's async resolver or internal to the c-ares library.

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Comment from jhrozek at 2011-05-12 13:36:55

Fields changed

patch: 0 => 1
status: new => assigned

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Comment from sgallagh at 2011-05-12 21:47:21

Fixed by
- 4ebd399 (master)
- a5c7d86 (sssd-1-5)

resolution: => fixed
status: assigned => closed

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Comment from dpal at 2012-01-19 03:10:32

Fields changed

rhbz: => 0

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Comment from sgallagh at 2017-02-24 14:48:43

Metadata Update from @sgallagh:

• Issue assigned to jhrozek
• Issue set to the milestone: SSSD 1.5.8