ovs-vlan-bug-workaround - utility for configuring Linux VLAN driver bug
ovs-vlan-bug-workaround netdev on
ovs-vlan-bug-workaround netdev off
Some Linux network drivers support a feature called ``VLAN acceleration''. 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 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
- When NICs use VLAN stripping on receive they must pass a
pointer to a vlan_group when reporting the stripped tag to the
networking 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
specially 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 workaround
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
the VLAN driver bug workaround for network device netdev
. Use the
command ovs-vlan-bug-workaround netdev off
to disable the
VLAN driver bug workaround for network device netdev
The following drivers in Linux version 18.104.22.168-0.7.1.xs22.214.171.1241.170586
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 differs slightly from the name of the module's .ko
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
- Not used with Open vSwitch on XenServer.
- Not shipped with XenServer. A FreeScale CPU-integrated
- Cannot be built on x86. IBM Power architecture only.
- Cannot be built on x86. SH4 architecture only.
- Not shipped with XenServer. For use inside VMware VMs
- Prints a brief help message to the console.
- Prints version information to the console.