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Bug 1820770 - Keepalived assignment of a deprecated IPv6 Virtual IP triggers "set hostname"
Summary: Keepalived assignment of a deprecated IPv6 Virtual IP triggers "set hostname"
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: NetworkManager
Version: 8.1
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: rc
: 8.1
Assignee: Beniamino Galvani
QA Contact: Matej Berezny
URL:
Whiteboard:
: 2052098 (view as bug list)
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2020-04-03 20:24 UTC by Ben Nemec
Modified: 2022-02-23 17:58 UTC (History)
14 users (show)

Fixed In Version: NetworkManager-1.32.2-1.el8
Doc Type: No Doc Update
Doc Text:
Clone Of:
Environment:
Last Closed: 2021-11-09 19:28:54 UTC
Type: Bug
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2021:4361 0 None None None 2021-11-09 19:29:30 UTC
freedesktop.org Gitlab NetworkManager NetworkManager-ci merge_requests 807 0 None None None 2021-08-10 12:22:37 UTC
freedesktop.org Gitlab NetworkManager NetworkManager merge_requests 889 0 None merged device: prefer IPv6 not-deprecated addresses for hostname lookup 2021-06-22 14:10:27 UTC

Description Ben Nemec 2020-04-03 20:24:40 UTC 
Description of problem:
On an Red Hat Enterprise Linux CoreOS release 4.5 node. With a pre-existing hostname "master-0.ostest.test.metalkube.org", when Keepalived configures a Virtual IP to an interface, it triggers a "set hostname" operation which does an address lookup and changes the hostname to the DNS record that matches the VIP, i.e., "ns1.ostest.test.metalkube.org". Being that Keepalived addresses are correctly marked as deprecated:

3: enp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
    inet6 fd2e:6f44:5dd8:c956::5/128 scope global nodad deprecated noprefixroute 
       valid_lft forever preferred_lft 0sec
    inet6 fd2e:6f44:5dd8:c956::2/128 scope global nodad deprecated noprefixroute 
       valid_lft forever preferred_lft 0sec
    inet6 fd2e:6f44:5dd8:c956::14/128 scope global dynamic noprefixroute 
       valid_lft 3121sec preferred_lft 3121sec

I find that this behavior is incorrect due to substituting the already configured non "localhost" hostname of a live address in the same interface with a new lookup for an address that is deprecated and not meant to be used for much else than receiving traffic.

Version-Release number of selected component (if applicable):
NetworkManager-1.20.0-5.el8_1.x86_64

Steps to Reproduce:
1. Set up Keepalived to configure VIPs on the same subnet and iface that gets configured by DHCPv6
2. Wait for the VIPs to get configured
3. sudo journalctl -b | cut -f 3,4 -d' ' | uniq -f 1

Actual results:
begin at
17:19:12 localhost
17:19:21 master-0.ostest.test.metalkube.org
17:26:33 ns1.ostest.test.metalkube.org
17:48:15 master-0.ostest.test.metalkube.org
[core@master-0 ~]$ 

Expected results:
begin at
17:19:12 localhost
17:19:21 master-0.ostest.test.metalkube.org
[core@master-0 ~]$ 

Additional info:
This happened on a https://github.com/openshift-metal3/dev-scripts deployment
Comment 1 Beniamino Galvani 2020-04-07 16:22:17 UTC 
Hi,

NetworkManager doesn't update the kernel hostname when there is already a
static hostname configured on the machine. The static hostname is what
is set in /etc/hostname and is visible with:

 $ hostnamectl
 Static hostname: fedora

If somebody else sets the hostname only in kernel (using the
equivalent of 'hostname foo'), it is setting the *transient*
hostname. NM doesn't honor an already configured transient hostname
because it assumes to be only the entity managing it. It would be racy
to let NM and other tools manage the transient hostname at the same
time.

So, from this point of view, I think NM is doing the right thing.

Talking about the deprecated address issue, NM simply takes the first
address configured without considering the deprecation. Probably it
should consider it; this would be easy to fix.

In your case, if we modify NM to take the first non deprecated address
(fd2e:6f44:5dd8:c956::14/128), would it get the right hostname
(master-0.ostest.test.metalkube.org) via reverse lookup?

To avoid the reverse lookup you could also set 'hostname-mode=dhcp' or
even 'hostname-mode=none' in the [main] section of a new configuration
file /etc/NetworkManager/conf.d/.  See 'man NetworkManager.conf' for
an explanation of the setting.
Comment 2 Ben Nemec 2020-04-09 22:30:39 UTC 
Oops, I missed your response. Thanks for the update. Some comments inline.

(In reply to Beniamino Galvani from comment #1)
> In your case, if we modify NM to take the first non deprecated address
> (fd2e:6f44:5dd8:c956::14/128), would it get the right hostname
> (master-0.ostest.test.metalkube.org) via reverse lookup?

Yes, that's the behavior we want.

> 
> To avoid the reverse lookup you could also set 'hostname-mode=dhcp' or
> even 'hostname-mode=none' in the [main] section of a new configuration
> file /etc/NetworkManager/conf.d/.  See 'man NetworkManager.conf' for
> an explanation of the setting.

I'm not sure we can do that. We have users who are not sending the hostname via DHCP and need to do the reverse lookup in order to get the hostname set at all. We have a workaround for the DHCP case, but anyone relying on the reverse DNS is likely broken.
Comment 8 Beniamino Galvani 2021-07-23 08:48:21 UTC 
Created attachment 1804797 [details]
Reproducer
Comment 10 errata-xmlrpc 2021-11-09 19:28:54 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: NetworkManager security, bug fix, and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2021:4361
Comment 11 Ben Nemec 2022-02-23 17:58:35 UTC 
*** Bug 2052098 has been marked as a duplicate of this bug. ***
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