ovs-vlan-bug-workaround(8)    Open vSwitch Manual   ovs-vlan-bug-workaround(8)



NAME
       ovs-vlan-bug-workaround - utility for configuring Linux VLAN driver bug
       workaround

SYNOPSIS
       ovs-vlan-bug-workaround netdev on
       ovs-vlan-bug-workaround netdev off
       ovs-vlan-bug-workaround --help
       ovs-vlan-bug-workaround --version

DESCRIPTION
       Some Linux network drivers support a feature  called  ``VLAN  accelera‐
       tion''.  VLAN acceleration is associated with a data structure called a
       vlan_group that is, abstractly, a dictionary that maps from a  VLAN  ID
       (in the range 0 to 4095) to a VLAN device, that is, a Linux network de‐
       vice associated with a particular VLAN, e.g. eth0.9 for VLAN 9 on eth0.

       Some drivers that support VLAN acceleration have bugs that fall roughly
       into  the categories listed below.  ovs-vlan-test(8) can test for these
       driver bugs.

       •      When NICs use VLAN stripping on receive they must pass a pointer
              to  a vlan_group when reporting the stripped tag to the network‐
              ing core.  If no vlan_group is in use  then  some  drivers  just
              drop  the  extracted  tag.   Drivers are supposed to only enable
              stripping if a vlan_group is registered but not all of  them  do
              that.

       •      On  receive,  some  drivers  handle priority tagged packets spe‐
              cially and don't pass the tag onto the network stack at all,  so
              Open vSwitch never has a chance to see it.

       •      Some  drivers  size  their  receive  buffers  based on whether a
              vlan_group is enabled, meaning that a maximum size packet with a
              VLAN tag will not fit if no vlan_group is configured.

       •      On  transmit, some drivers expect that VLAN acceleration will be
              used if it is available, which can only be done if a  vlan_group
              is configured.  In these cases, the driver may fail to parse the
              packet and correctly setup checksum offloading or TSO.

       The correct long term solution is to fix these driver bugs.

       For now, ovs-vlan-bug-workaround can  enable  a  special-purpose  work‐
       around  for  devices with buggy VLAN acceleration.  A kernel patch must
       be applied for this workaround to work.

       Use the command ovs-vlan-bug-workaround netdev on to  enable  the  VLAN
       driver  bug  workaround  for  network  device  netdev.  Use the command
       ovs-vlan-bug-workaround netdev off to disable the VLAN driver bug work‐
       around for network device netdev.

DRIVER DETAILS
       The        following        drivers        in       Linux       version
       2.6.32.12-0.7.1.xs1.0.0.311.170586 implement VLAN acceleration and  are
       relevant  to Open vSwitch on XenServer.  We have not tested any version
       of most of these drivers, so we do not know whether they  have  a  VLAN
       problem  that  needs  to  be fixed.  The drivers are listed by the name
       that they report in, e.g., ethtool -i output; in a few cases this  dif‐
       fers slightly from the name of the module's .ko file:
       8139cp    acenic    amd8111e  atl1c     ATL1E     atl1
       atl2      be2net    bna       bnx2      bnx2x     cnic
       cxgb      cxgb3     e1000     e1000e    enic      forcedeth
       igb       igbvf     ixgb      ixgbe     jme       ml4x_core
       ns83820   qlge      r8169     S2IO      sky2      starfire
       tehuti    tg3       typhoon   via-velocity        vxge

       The following drivers use vlan_group but are irrelevant to Open vSwitch
       on XenServer:

       bonding
              Not used with Open vSwitch on XenServer.

       gianfar
              Not shipped with XenServer.  A FreeScale CPU-integrated device.

       ehea   Cannot be built on x86.  IBM Power architecture only.

       stmmac Cannot be built on x86.  SH4 architecture only.

       vmxnet3
              Not shipped with XenServer.  For use inside VMware VMs only.

OPTIONS
       -h
       --help Prints a brief help message to the console.

       -V
       --version
              Prints version information to the console.

BUGS
       Obviously.

SEE ALSO
       ovs-vlan-test(8).



Open vSwitch                        2.10.90         ovs-vlan-bug-workaround(8)