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          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)
          
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