Bug 1753128

Summary: Cannot set MTU lower than 1280
Product: Red Hat Enterprise Linux 8 Reporter: Gris Ge <fge>
Component: NetworkManagerAssignee: Beniamino Galvani <bgalvani>
Status: CLOSED ERRATA QA Contact: Desktop QE <desktop-qa-list>
Severity: medium Docs Contact:
Priority: unspecified    
Version: 8.1CC: atragler, bgalvani, edwardh, fgiudici, lrintel, pasik, rkhan, sukulkar, thaller, toneata, vbenes
Target Milestone: rcKeywords: ZStream
Target Release: 8.2Flags: pm-rhel: mirror+
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: NetworkManager-1.22.0-0.1.el8 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of:
: 1775136 (view as bug list) Environment:
Last Closed: 2020-04-28 16:53:06 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1775136    
Attachments:
Description Flags
System logs with NM trace enabled none

Description Gris Ge 2019-09-18 07:50:56 UTC
Created attachment 1616113 [details]
System logs with NM trace enabled

Description of problem:

Cannot set `802-3-ethernet.mtu` lower than 1280, the network manager
will still activate the profile with 1280 MTU.

Version-Release number of selected component (if applicable):
NetworkManager-1.20.0-3.el8.x86_64

How reproducible:
100%

Steps to Reproduce:

#!/bin/bash
nmcli c del veth1
ip link del veth1
nmcli c del veth1

ip link add veth1 type veth peer name veth1.ep
ip link set veth1 up
ip link set veth1.ep up
nmcli device set veth1 managed yes

nmcli c add  type ethernet ifname veth1 \
    connection.id veth1 \
    ipv4.method disabled \
    802-3-ethernet.mtu 1200 \
    ipv6.method disabled
nmcli c up veth1
ip link show veth1

Actual results:

The MTU of veth1 show as 1280.

Expected results:

The MTU of veth1 show as 1200.

Additional info:

Comment 1 Beniamino Galvani 2019-09-18 09:05:38 UTC
Added a couple of commits to fix this to merge request

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/merge_requests/273

Comment 3 Gris Ge 2019-10-15 12:02:26 UTC
This problem does not exists in NetworkManager-1.12.6-5.fc29.x86_64 of Fedora 29.

Regression it is.

Comment 5 Edward Haas 2019-11-18 14:11:42 UTC
RHV customers have the capability to set the MTU lower than 1280, so it is a regression if we do not fix it for RHEL 8.1.z
Could you please backport it?

Comment 8 sushil kulkarni 2019-11-18 16:09:03 UTC
Per comment c#5, requesting a z stream update for this. Will be required for RHV to pick up this change for their 4.4 release.

Anita, Can you please provide z stream+?

Thanks!
Sushil

Comment 12 errata-xmlrpc 2020-04-28 16:53:06 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, 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-2020:1847