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          ovs-vlan-bug-workaround(8)    Open vSwitch Manual   ovs-vlan-bug-workaround(8)
                 ovs-vlan-bug-workaround - utility for configuring Linux VLAN driver bug
                 ovs-vlan-bug-workaround netdev on
                 ovs-vlan-bug-workaround netdev off
                 ovs-vlan-bug-workaround --help
                 ovs-vlan-bug-workaround --version
                 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
                 device associated with a particular VLAN, e.g. eth0.9  for  VLAN  9  on
                 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
                 ·      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.
                 The       following       drivers        in        Linux        version
         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:
                        Not used with Open vSwitch on XenServer.
                        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.
                        Not shipped with XenServer.  For use inside VMware VMs only.
                 --help Prints a brief help message to the console.
                        Prints version information to the console.
          SEE ALSO
          Open vSwitch                        2.5.90          ovs-vlan-bug-workaround(8)