Ethernet connection, Ubuntu 16.04.2 LTS (MATE), persistent name resolution failures

[windsnow]

I moved to Ubuntu MATE 16.04 from Linux Mint 17.2 about 2-3 weeks ago. I did not experience the problem under consideration under Linux Mint.

I am now experiencing random drops of internet access. When such drops occur, I can no longer access new websites or new webpages, I cannot refresh webpages that are already open and I cannot launch new applications accessing the internet. However, existing connections, such as live streams, live chats, downloads or applications, usually remain operational after the drops, even though they may also break from time to time along with the drop.

After a drop, when I am trying to access a new webpage or refresh an existing one, I receive the following browser message:

“This site can’t be reached
The webpage at https://www.youtube.com/ might be temporarily down or it may have moved permanently to a new web address.
ERR_NAME_RESOLUTION_FAILED”

(This message is different from the one that I receive when I intentionally turn the internet off:

“There is no Internet connection
Try:
Checking the network cables, modem, and router
Reconnecting to Wi-Fi
ERR_INTERNET_DISCONNECTED”)

Also, after a drop, the Network Manager continues to show that the internet/Ethernet connection is up, and the modem indicators also show that intenet connection is OK. I have an ADSL modem.

The problem can be resolved by turning the modem off and then on. After this, the internet connection is working as normal until the next drop.

I have changed my Ethernet driver from r8169 to r8168, and this reduced the frequency of the drops. However, the drops still occur even though at a smaller frequency.

The output of $ dmesg | grep r816 immediately after a reboot is as follows:

[ 1.588495] r8168: module verification failed: signature and/or required key missing - tainting kernel
[ 1.588839] r8168 Gigabit Ethernet driver 8.041.00-NAPI loaded
[ 1.589735] r8168: This product is covered by one or more of the following patents: US6,570,884, US6,115,776, and US6,327,625.
[ 1.589741] r8168 Copyright (C) 2015 Realtek NIC software team <[email protected]> 
[ 1.589878] r8168 Gigabit Ethernet driver 8.041.00-NAPI loaded
[ 1.590692] r8168: This product is covered by one or more of the following patents: US6,570,884, US6,115,776, and US6,327,625.
[ 1.590695] r8168 Copyright (C) 2015 Realtek NIC software team <[email protected]> 
[ 1.648874] r8168 0000:06:00.0 enp6s0: renamed from eth1
[ 1.660233] r8168 0000:05:00.0 enp5s0: renamed from eth0
[ 34.452482] r8168: enp5s0: link up

However, after the first drop the output of $ dmesg | grep r816 changes to:

[ 1.589145] r8168: module verification failed: signature and/or required key missing - tainting kernel
[ 1.589456] r8168 Gigabit Ethernet driver 8.041.00-NAPI loaded
[ 1.590311] r8168: This product is covered by one or more of the following patents: US6,570,884, US6,115,776, and US6,327,625.
[ 1.590317] r8168 Copyright (C) 2015 Realtek NIC software team <[email protected]> 
[ 1.590332] r8168 Gigabit Ethernet driver 8.041.00-NAPI loaded
[ 1.591136] r8168: This product is covered by one or more of the following patents: US6,570,884, US6,115,776, and US6,327,625.
[ 1.591139] r8168 Copyright (C) 2015 Realtek NIC software team <[email protected]> 
[ 1.640349] r8168 0000:05:00.0 enp5s0: renamed from eth0
[ 1.664192] r8168 0000:06:00.0 enp6s0: renamed from eth1
[ 34.388479] r8168: enp5s0: link up
[ 4949.392006] r8168: enp5s0: link down
[ 4952.412478] r8168: enp5s0: link up
[ 4966.412007] r8168: enp5s0: link down
[ 4969.432481] r8168: enp5s0: link up
[13409.440008] r8168: enp5s0: link down
[13412.460476] r8168: enp5s0: link up
[13425.460006] r8168: enp5s0: link down
[13428.480476] r8168: enp5s0: link up

The output of $ ping 8.8.8.8 after a drop is as follows:

PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=57 time=19.1 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=57 time=18.4 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=57 time=19.2 ms
64 bytes from 8.8.8.8: icmp_seq=4 ttl=57 time=18.7 ms
64 bytes from 8.8.8.8: icmp_seq=5 ttl=57 time=17.7 ms
64 bytes from 8.8.8.8: icmp_seq=6 ttl=57 time=17.6 ms

and so on

I would appreciate if anyone could advise what needs to be done to get rid of this annoying problem, as apart from this issue the performance of the system has been fantastic.

[wolfman]

@windsnow

[ 1.588495] r8168: module verification failed: signature and/or required key missing - tainting kernel

Hi @windsnow,

I try first try running a full system update to see if it can fix the issue for you, the quote above highlights what your problem might be?:

Ubuntu Mate Update Guide

These are my own setting preferences, use at your own risk!. AN IMPORTANT NOTE FOR LINUX BEGINNERS. WHEN YOU ARE IN RECOVERY MODE, THE KEYBOARD DEFAULTS TO US ENGLISH, IF YOU HAVE ANY OTHER LANGUAGE KEYBOARD OTHER THAN US ENGLISH, WHEN YOU TYPE "Y" (FOR "YES"), IT MIGHT SHOW UP AS A DIFFERENT LETTER, ON MY KEYBOARD I MUST PRESS THE "Z" KEY WHICH EQUATES TO "Y" AS I HAVE A GERMAN KEYBOARD, JUST PRESS "BACKSPACE" AND HIT A DIFFERENT KEY UNTIL YOU SEE THE "Y" SHOW UP!. Click on "Subscribe…

[windsnow]

Hi wolfman

Thanks a lot for your quick response.

I understand that “tainted kernel” is a normal reaction of the system to the proprietary drivers, you can see a similar record in the posts where people recommend installation of Realtek’s proprietary driver r8168 instead of Linux’s own r8169. Therefore, it should not be the reason for the problem under review. I did change the driver to r8168 when trying to sort out the connectivity issue, and the connection did become more stable, but unfortunately the issue was not solved completely, and the drops still occur, even if rarer.

I have updated the system via the Welcome tool as you suggested. I also updated the system via the terminal’s update and dist-upgrade instructions. I also updated the system via the System Update tool in the general menu. None of those solved the problem.

I have tried a number of different fixes, including installation of the WICD manager and removal of resolveconf service. None of them totally resolved the issue, even though some tested configurations demonstrated improvement in the connection’s stability.

I am now back to the default configuration with the only exception that I commented line “dns=dnsmasq” with # and set “manage=true” in /etc/NetworkManager/NetworkManager.conf. The problem still persists, but now I don’t have to turn the modem off and on manually to restore the connection; I can do it by disabling and re-enabling the connection in the Network Manager.

What I noticed, however, is that when I disable the default active connection, the Network Manager generates a new active connection naming it enp5s0, and that this new connection has “enp5s0([set of digits constituting HWaddr])” as its Device under the Ethernet tab of the Edit connection menu, and “Link-Local only” as its Method under the IPv6 Settings tab of this menu. This new connection is apparently used to channel the data for the existing data streams from the internet (chats, videos, downloads, program exchanges) that remain operational even after I disable the default active connection. The default active connection has the “[set of digits constituting HWaddr]” as its Device and “Automatic” as its Method, while other parameters of the default connection and the newly generated connection are identical. Does it give any clue with regard to the changes to the configuration that I need to make to sort this issue out?

[wolfman]

Hi @windsnow,

you could try deleting the ethernet connection and reboot then see what happens, it should simply add a new connection, maybe there is something in the connection config file but I really don't know (just a guess!). (There may be multiple entries in "Network Connections"?).