LAN connection keeps connecting and disconnecting in an infinite loop

[Markus Baumann]

With Xubuntu 17.10 the following problem occurs on a Lenovo X230 Laptop:
- Boot from live-ISO
- Click on network icon in title bar and edit LAN-connection
- Change MTU from Auto to 1492
- Connect LAN cable
=> LAN network keeps connecting and disconnecting in an infinite loop

(No wireless network is configured.)

The error did not occur on Xubuntu 16.04. The same situation occurs with Xubuntu installed on the SSD. I took the ISO for this bug report, in order to exclude wrong settings on the installed system.

WORKAROUND: Don't adjust the MTU.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: network-manager 1.8.4-1ubuntu3
ProcVersionSignature: Ubuntu 4.13.0-21.24-generic 4.13.13
Uname: Linux 4.13.0-21-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.7
Architecture: amd64
CasperVersion: 1.387
CurrentDesktop: XFCE
Date: Fri Mar 9 20:26:21 2018
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
IpRoute:
 default via 10.110.120.1 dev enp0s25 proto static metric 100
 10.110.120.0/24 dev enp0s25 proto kernel scope link src 10.110.120.57 metric 100
 169.254.0.0/16 dev enp0s25 scope link metric 1000
LiveMediaBuild: Xubuntu 17.10 "Artful Aardvark" - Release amd64 (20180105)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: network-manager
UpgradeStatus: No upgrade log present (probably fresh install)
nmcli-con:
 NAME UUID TYPE TIMESTAMP TIMESTAMP-REAL AUTOCONNECT AUTOCONNECT-PRIORITY READONLY DBUS-PATH ACTIVE DEVICE STATE ACTIVE-PATH SLAVE
 Wired connection 1 db135360-f229-3472-bd3a-eb8d6bc8b601 802-3-ethernet 1520627169 Fr 09 Mär 2018 20:26:09 UTC yes 4294966297 no /org/freedesktop/NetworkManager/Settings/1 yes enp0s25 activated /org/freedesktop/NetworkManager/ActiveConnection/32 --
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH CONNECTION CON-UUID CON-PATH
 enp0s25 ethernet connected /org/freedesktop/NetworkManager/Devices/2 Wired connection 1 db135360-f229-3472-bd3a-eb8d6bc8b601 /org/freedesktop/NetworkManager/ActiveConnection/32
 wlp3s0 wifi disconnected /org/freedesktop/NetworkManager/Devices/3 -- -- --
 lo loopback unmanaged /org/freedesktop/NetworkManager/Devices/1 -- -- --
nmcli-nm:
 RUNNING VERSION STATE STARTUP CONNECTIVITY NETWORKING WIFI-HW WIFI WWAN-HW WWAN
 running 1.8.4 connected started full enabled enabled enabled enabled enabled
---
ApportVersion: 2.20.7-0ubuntu3.7
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: xubuntu 3822 F.... pulseaudio
CasperVersion: 1.387
DistroRelease: Ubuntu 17.10
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
IpRoute:
 default via 10.110.120.1 dev enp0s25 proto static metric 100
 10.110.120.0/24 dev enp0s25 proto kernel scope link src 10.110.120.57 metric 100
 169.254.0.0/16 dev enp0s25 scope link metric 1000
LiveMediaBuild: Xubuntu 17.10 "Artful Aardvark" - Release amd64 (20180105)
MachineType: LENOVO 2333B15
Package: network-manager 1.8.4-1ubuntu3
PackageArchitecture: amd64
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: file=/cdrom/preseed/hostname.seed boot=casper initrd=/casper/initrd.lz quiet splash --- maybe-ubiquity
ProcVersionSignature: Ubuntu 4.13.0-21.24-generic 4.13.13
PulseList:
 Error: command ['pacmd', 'list'] failed with exit code 1: Home directory not accessible: Permission denied
 No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
 linux-restricted-modules-4.13.0-21-generic N/A
 linux-backports-modules-4.13.0-21-generic N/A
 linux-firmware 1.169.1
Tags: artful
Uname: Linux 4.13.0-21-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

_MarkForUpload: True
dmi.bios.date: 04/19/2017
dmi.bios.vendor: LENOVO
dmi.bios.version: G2ETA8WW (2.68 )
dmi.board.asset.tag: Not Available
dmi.board.name: 2333B15
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: R9YFLET
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvrG2ETA8WW(2.68):bd04/19/2017:svnLENOVO:pn2333B15:pvrThinkPadX230:rvnLENOVO:rn2333B15:rvrNotDefined:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.family: ThinkPad X230
dmi.product.name: 2333B15
dmi.product.version: ThinkPad X230
dmi.sys.vendor: LENOVO
nmcli-con:
 NAME UUID TYPE TIMESTAMP TIMESTAMP-REAL AUTOCONNECT AUTOCONNECT-PRIORITY READONLY DBUS-PATH ACTIVE DEVICE STATE ACTIVE-PATH SLAVE
 Wired connection 1 fbb05466-4739-330d-ba0a-109a6e5b3cfe 802-3-ethernet 1520971267 Di 13 Mär 2018 20:01:07 UTC yes 4294966297 no /org/freedesktop/NetworkManager/Settings/1 yes enp0s25 activated /org/freedesktop/NetworkManager/ActiveConnection/5 --
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH CONNECTION CON-UUID CON-PATH
 enp0s25 ethernet connected /org/freedesktop/NetworkManager/Devices/2 Wired connection 1 fbb05466-4739-330d-ba0a-109a6e5b3cfe /org/freedesktop/NetworkManager/ActiveConnection/5
 wlp3s0 wifi disconnected /org/freedesktop/NetworkManager/Devices/3 -- -- --
 lo loopback unmanaged /org/freedesktop/NetworkManager/Devices/1 -- -- --
nmcli-nm:
 RUNNING VERSION STATE STARTUP CONNECTIVITY NETWORKING WIFI-HW WIFI WWAN-HW WWAN
 running 1.8.4 connected started full enabled enabled enabled enabled enabled

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1754759

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Markus Baumann (mark.us)]

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[penalvch (penalvch)]

Markus Baumann, thank you for reporting this and helping make Ubuntu better.

1) To clarify, if you don't adjust the MTU does the LAN network still connection cycle?

2) To see if this is already resolved in Ubuntu, could you please test http://cdimage.ubuntu.com/daily-live/current/ and advise to the results?

[Markus Baumann (mark.us)]

Hello Christopher,

thank you for triaging.

1) No. LAN only cycles the connection when setting the MTU. Setting MTU to "automatic" (= the default) works fine.

2) I tested with the daily-live-ISO (downloaded at 06/16/2018). With this version the LAN interface worked without connection cycles - even if I changed the MTU. For further review, I have also tested with Xubuntu 18.04. Again, the LAN interface showed no connection cycles after changing the MTU.

Additional information: My currently installed and fully updated version 17.10 still shows the problem. It looks like the bug is fixed from version 18.04 on, so I will update to Xubuntu 18.04.1 soon.

Thank you for your efforts
Markus

[penalvch (penalvch)]

Markus Baumann, this bug report is being closed due to your last comment https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1754759/comments/24 regarding this being fixed with an update. For future reference you can manage the status of your own bugs by clicking on the current status in the yellow line and then choosing a new status in the revealed drop down box. You can learn more about bug statuses at https://wiki.ubuntu.com/Bugs/Status. Thank you again for taking the time to report this bug and helping to make Ubuntu better. Please submit any future bugs you may find.

[Kai-Heng Feng (kaihengfeng)]

Please try latest mainline kernel (v4.18-rc1).

[Markus Baumann (mark.us)]

Does it make sense to try the mainline kernel, since the error is obviously fixed with 18.04? Unfortunately, I also do not know how to try the mainline kernel. Can I test this with a live image (I do not want to destroy my production machine)? Is the mainline kernel compatible with 17.10?

[penalvch (penalvch)]

Markus Baumann:

>"Does it make sense to try the mainline kernel, since the error is obviously fixed with 18.04?"

No, it doesn't. Given you reproduced this in 17.10 (which is EOL July 2018 as per https://wiki.ubuntu.com/Releases ), when you upgrade soon to 18.04, the issue would be gone.