hv_set_ifconfig script don't check dns is empty when add this information to network interface.

[Truc Nguyen Van]

When trying to configure a virtual NIC using Hyper-V's integration services with no dns entries.
The script will add a line "dns-nameservers" with no arguments (you can see that in attachment file) into network/interface.

So when we restart network the new configure of virtual NIC can't apply.
---
AlsaDevices:
 total 0
 crw-rw----+ 1 root audio 116, 1 Apr 20 04:09 seq
 crw-rw----+ 1 root audio 116, 33 Apr 20 04:09 timer
AplayDevices: Error: [Errno 2] No such file or directory
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
DistroRelease: Ubuntu 16.04
HibernationDevice: RESUME=/dev/mapper/ubuntu--vg-swap_1
InstallationDate: Installed on 2017-09-21 (210 days ago)
InstallationMedia: Ubuntu-Server 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
IwConfig: Error: [Errno 2] No such file or directory
Lsusb: Error: command ['lsusb'] failed with exit code 1:
MachineType: Microsoft Corporation Virtual Machine
Package: linux (not installed)
PciMultimedia:

ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB: 0 hyperv_fb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-119-generic root=/dev/mapper/hostname--vg-root ro
ProcVersionSignature: Ubuntu 4.4.0-119.143-generic 4.4.114
RelatedPackageVersions:
 linux-restricted-modules-4.4.0-119-generic N/A
 linux-backports-modules-4.4.0-119-generic N/A
 linux-firmware 1.157.11
RfKill: Error: [Errno 2] No such file or directory
Tags: xenial
Uname: Linux 4.4.0-119-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

_MarkForUpload: True
dmi.bios.date: 04/28/2016
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 090006
dmi.board.name: Virtual Machine
dmi.board.vendor: Microsoft Corporation
dmi.board.version: 7.0
dmi.chassis.asset.tag: 5080-1511-9585-7780-7149-7192-64
dmi.chassis.type: 3
dmi.chassis.vendor: Microsoft Corporation
dmi.chassis.version: 7.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr090006:bd04/28/2016:svnMicrosoftCorporation:pnVirtualMachine:pvr7.0:rvnMicrosoftCorporation:rnVirtualMachine:rvr7.0:cvnMicrosoftCorporation:ct3:cvr7.0:
dmi.product.name: Virtual Machine
dmi.product.version: 7.0
dmi.sys.vendor: Microsoft Corporation

[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 1765621

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.

[Truc Nguyen Van (vantruc1602)]

apport information

[Truc Nguyen Van (vantruc1602)]

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[Truc Nguyen Van (vantruc1602)]

apport information

[Truc Nguyen Van (vantruc1602)]

apport information

[Truc Nguyen Van (vantruc1602)]

apport information

[Truc Nguyen Van (vantruc1602)]

apport information

[Truc Nguyen Van (vantruc1602)]

apport information

[Truc Nguyen Van (vantruc1602)]

apport information

[Truc Nguyen Van (vantruc1602)]

apport information

[Truc Nguyen Van (vantruc1602)]

apport information

[Joseph Salisbury (jsalisbury)]

Did this issue start happening after an update/upgrade? Was there a kernel version where you were not having this particular problem? This will help determine if the problem you are seeing is the result of a regression, and when this regression was introduced. If this is a regression, we can perform a kernel bisect to identify the commit that introduced the problem.

[Truc Nguyen Van (vantruc1602)]

1. I don't update anything on ubuntu VM.
2. I just seen this happen on ubuntu 16.04 LTS and don't test on other version.

Please see the attach file about hv_set_ifconfig in my ubuntu.