kernel 4.4.0-130-generic - packet loss with ip forward

[Kseniya Blashchuk]

Reproduced with 16.04.4 LTS and Citrix Xenserver 7.0, 7.1, 7.4.
Some packet loss is observed after upgrading to 4.4.0-130-generic when the traffic is routed via VM.

Steps to reproduce:
1) Using Citrix Xenserver, set up Ubuntu server VM, upgrade to 4.4.0-130-generic
2) Enable IP forwarding
3) Send any traffic via this VM (for ex. icmp ping)
4) Packets leaving the VM may not reach the second VM on the same physical host or not leave the physical host machine
5) Packets coming to a physical host machine interface may not reach the virtual machine

Rollback to 4.4.0-128-generic helps.

A file with tcpdump results and a brief explanation is attached.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-130-generic 4.4.0-130.156
ProcVersionSignature: Ubuntu 4.4.0-130.156-generic 4.4.134
Uname: Linux 4.4.0-130-generic x86_64
AlsaDevices:
 total 0
 crw-rw---- 1 root audio 116, 1 Jul 9 11:24 seq
 crw-rw---- 1 root audio 116, 33 Jul 9 11:24 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Date: Mon Jul 9 13:18:47 2018
InstallationDate: Installed on 2018-06-04 (34 days ago)
InstallationMedia: Ubuntu-Server 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215.8)
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
Lsusb:
 Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd
 Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
MachineType: Xen HVM domU
PciMultimedia:

ProcEnviron:
 LANGUAGE=en_US:en
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB: 0 EFI VGA
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-130-generic root=UUID=46979d34-98b0-470f-9f1f-29147de9f253 ro ipv6.disable=1 net.ifnames=0 biosdevname=0
RelatedPackageVersions:
 linux-restricted-modules-4.4.0-130-generic N/A
 linux-backports-modules-4.4.0-130-generic N/A
 linux-firmware 1.157.19
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 06/14/2018
dmi.bios.vendor: Xen
dmi.bios.version: 4.7.5-4.4
dmi.chassis.type: 1
dmi.chassis.vendor: Xen
dmi.modalias: dmi:bvnXen:bvr4.7.5-4.4:bd06/14/2018:svnXen:pnHVMdomU:pvr4.7.5-4.4:cvnXen:ct1:cvr:
dmi.product.name: HVM domU
dmi.product.version: 4.7.5-4.4
dmi.sys.vendor: Xen

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

This change was made by a bot.

[Kseniya Blashchuk (ksyblast)]

We have performed kernel bisect, git bisect log is attached.
The results show:

2e118dcfc70978d2c8b7d55ce6d2decc6588ee62 is the first bad commit
commit 2e118dcfc70978d2c8b7d55ce6d2decc6588ee62
Author: Ross Lagerwall <email address hidden>
Date: Thu Jan 11 09:36:38 2018 +0000

xen-netfront: Fix race between device setup and open

[Kseniya Blashchuk (ksyblast)]

Installed and tested kernel 4.15.0-24: also affected

[Joseph Salisbury (jsalisbury)]

This bug may be fixed by the following commit, which is in Xenial -proposed:
758c626 xen-netfront: Fix mismatched rtnl_unlock

Would it be possible for you to test the proposed kernel and post back if it resolves this bug?
See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed.

Thank you in advance!

[Kseniya Blashchuk (ksyblast)]

Thank you. Tested on 4.4.0-131-generic from xenial-proposed. I can confirm that it resolves the bug.