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Bug 2207878 - NetworkManager should not enable loopback IPv6 without explicit configuration
Summary: NetworkManager should not enable loopback IPv6 without explicit configuration
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 9
Classification: Red Hat
Component: NetworkManager
Version: 9.2
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Wen Liang
QA Contact: Filip Pokryvka
URL:
Whiteboard:
Depends On:
Blocks: 2229671
TreeView+ depends on / blocked
 
Reported: 2023-05-17 07:55 UTC by Marko Myllynen
Modified: 2023-11-07 10:14 UTC (History)
10 users (show)

Fixed In Version: NetworkManager-1.43.90-1.el9
Doc Type: No Doc Update
Doc Text:
Clone Of:
: 2229671 (view as bug list)
Environment:
Last Closed: 2023-11-07 08:38:04 UTC
Type: Bug
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
boot-journal.txt (289.94 KB, text/plain)
2023-05-23 07:57 UTC, Marko Myllynen 		no flags Details
View All


Links
System ID Private Priority Status Summary Last Updated
Red Hat Issue Tracker NMT-555 0 None None None 2023-05-17 07:56:40 UTC
Red Hat Issue Tracker RHELPLAN-157456 0 None None None 2023-05-17 07:56:46 UTC
Red Hat Product Errata RHBA-2023:6585 0 None None None 2023-11-07 08:38:44 UTC
freedesktop.org Gitlab NetworkManager NetworkManager-ci merge_requests 1462 0 None merged ipv6: do not enable IPv6 on externally connected device 2023-08-07 09:00:53 UTC
freedesktop.org Gitlab NetworkManager NetworkManager merge_requests 1694 0 None opened device: do not set disable_ipv6 on external 2023-07-18 19:07:41 UTC

Description Marko Myllynen 2023-05-17 07:55:06 UTC 
Description of problem:
Installing RHEL 9.1, configuring the following sysctls, updating initramfs, and rebooting shows IPv6 being disabled on all interfaces after boot and the sysctl values in use as configured:

# cat /etc/sysctl.d/50-ipv6.conf
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

On the same system upgrading kernel to the latest (currently ~ RHEL 9.2) and rebooting still shows the same results.

However, after upgrading NetworkManager to the latest on the same system or doing a fresh RHEL 9.2 installation with the same configuration we see the loopback having IPv6 enabled and the related sysctl changed even when the configuration file sets it to 1:

# cat /proc/sys/net/ipv6/conf/lo/disable_ipv6
0
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever

This procedure of disabling IPv6 is documented in the RHKB article and works on RHEL 7, RHEL 8, and RHEL 9.0-9.1. It would be preferable if RHEL 9.2 would continue working in the same manner. Perhaps NM managing the loopback device should be only opt-in without the need for opt-out anything. Thanks.
Comment 1 Thomas Haller 2023-05-18 11:30:04 UTC 
unless you configure a loopback profile in NetworkManager, NM shouldn't do anything with lo.

Please attach the complete journal from the boot, with `level=TRACE` enabled (see DEBUGGING in `man NetworkManager`).
Comment 2 Marko Myllynen 2023-05-23 07:57:30 UTC 
Created attachment 1966388 [details]
boot-journal.txt

I'm attaching the output of "/usr/bin/journalctl -b -n 50000 > boot-journal.txt" after booting up a test VM with:

# cat /etc/sysctl.d/50-ipv6.conf 
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
# cat /proc/sys/net/ipv6/conf/lo/disable_ipv6
0

Let me know if any additional information is needed. Thanks.
Comment 3 Thomas Haller 2023-05-23 08:21:49 UTC 
> <info>  [1684828385.5587] device (lo): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'external')
...
> <debug> [1684828385.5590] platform-linux: sysctl: setting '/proc/sys/net/ipv6/conf/lo/disable_ipv6' to '0' (current value is '1')


That's a bug that needs fixing.
Comment 12 errata-xmlrpc 2023-11-07 08:38:04 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 (NetworkManager 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/RHBA-2023:6585
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