Public bug reported:
Issue found in a test harness for some code running on Ubuntu 16.04.4
LTS where we use a veth device to play in packets to the code under
test. Essentially we see an extra 14 bytes being transmitted at the end
of every packet that is just random garbage. Problem came in with the
4.4.0-130 kernel; if I revert to the 4.4.0-128 kernel the issue goes
away. I have verified the issue on several different boxes running 16.04
The following steps reproduce the problem:
1) Veth setup
sudo ip link add name nic1 type veth peer name nic2
sudo sysctl -q -w net.ipv6.conf.nic1.disable_ipv6=1
sudo sysctl -q -w net.ipv6.conf.nic2.disable_ipv6=1
sudo ip link set nic1 up
sudo ip link set nic2 up
2) Configure tcpdump to collect packets on one interface:
sudo tcpdump -i nic1 -w outPkts.pcap
3) Play in packets on the other (Any pcap will do):
sudo tcpreplay -q -i nic2 inPkts.pcap
When I check ifconfig I can see nic2/nic1 transmitting/receiving more
bytes than expected. Opening the capture seen by tcpdump shows an extra
14 bytes received for every packet when compared to the input.
tcpreplay version info:
tcpreplay version: 3.4.4 (build 2450) (debug)
Copyright 2000-2010 by Aaron Turner <aturner at synfin dot net>
Cache file supported: 04
Not compiled with libdnet.
Compiled against libpcap: 1.7.4
64 bit packet counters: enabled
Verbose printing via tcpdump: enabled
Packet editing: disabled
Fragroute engine: disabled
Injection method: PF_PACKET send()
tcpdump version info
tcpdump version 4.9.2
libpcap version 1.7.4
OpenSSL 1.0.2g 1 Mar 2016
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
NonfreeKernelModules: nvidia_uvm nvidia
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC1: spw 3336 F.... pulseaudio
/dev/snd/controlC0: spw 3336 F.... pulseaudio
CurrentDesktop: Unity
Date: Thu Jul 19 10:30:07 2018
HibernationDevice: RESUME=UUID=032369ab-18b8-41c3-a386-4ed08706f461
InstallationDate: Installed on 2016-11-03 (622 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
MachineType: Dell Inc. OptiPlex 7010
ProcFB:
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-130-generic
root=UUID=7b20f97c-4edc-4af1-bdbb-72ccb26cfbec ro quiet splash intel_iommu=on
RelatedPackageVersions:
linux-restricted-modules-4.4.0-130-generic N/A
linux-backports-modules-4.4.0-130-generic N/A
linux-firmware 1.157.20
RfKill:
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/12/2013
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A15
dmi.board.name: 0KRC95
dmi.board.vendor: Dell Inc.
dmi.board.version: A02
dmi.chassis.type: 6
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvrA15:bd08/12/2013:svnDellInc.:pnOptiPlex7010:pvr01:rvnDellInc.:rn0KRC95:rvrA02:cvnDellInc.:ct6:cvr:
dmi.product.name: OptiPlex 7010
dmi.product.version: 01
dmi.sys.vendor: Dell Inc.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Confirmed
** Tags: amd64 apport-bug xenial
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https://bugs.launchpad.net/bugs/1782544
Title:
tcpreplay and veth device; extra transmit bytes on 4.4.0-130-generic
kernel
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