+ If the "insmod" operation fails, look at the last few kernel log
+ messages (e.g. with "dmesg | tail"):
+
+ - The message "openvswitch_mod: exports duplicate symbol
+ br_should_route_hook (owned by bridge)" means that the bridge
+ module is loaded. Run "/sbin/rmmod bridge" to remove it.
+
+ If "/sbin/rmmod bridge" fails with "ERROR: Module bridge does
+ not exist in /proc/modules", then the bridge is compiled into
+ the kernel, rather than as a module. Open vSwitch does not
+ support this configuration (see "Build Requirements", above).
+
+ - The message "openvswitch_mod: exports duplicate symbol
+ dp_ioctl_hook (owned by ofdatapath)" means that the ofdatapath
+ module from the OpenFlow reference implementation is loaded.
+ Run "/sbin/rmmod ofdatapath" to remove it. (You might have to
+ delete any existing datapaths beforehand, using the "dpctl"
+ program included with the OpenFlow reference implementation.
+ "ovs-dpctl" will not work.)
+
+ - Otherwise, the most likely problem is that Open vSwitch was
+ built for a kernel different from the one into which you are
+ trying to load it. Run "modinfo" on openvswitch_mod.ko and on
+ a module built for the running kernel, e.g.:
+
+ % /sbin/modinfo openvswitch_mod.ko
+ % /sbin/modinfo /lib/modules/`uname -r`/kernel/net/bridge/bridge.ko
+
+ Compare the "vermagic" lines output by the two commands. If
+ they differ, then Open vSwitch was built for the wrong kernel.
+
+ - If you decide to report a bug or ask a question related to
+ module loading, please include the output from the "dmesg" and
+ "modinfo" commands mentioned above.
+
+ There is an optional module parameter to openvswitch_mod.ko called
+ vlan_tso that enables TCP segmentation offload over VLANs on NICs
+ that support it. Many drivers do not expose support for TSO on VLANs
+ in a way that Open vSwitch can use but there is no way to detect
+ whether this is the case. If you know that your particular driver can
+ handle it (for example by testing sending large TCP packets over VLANs)
+ then passing in a value of 1 may improve performance. Modules built for
+ Linux kernels 2.6.37 and later, as well as specially patched versions
+ of earlier kernels, do not need this and do not have this parameter. If
+ you do not understand what this means or do not know if your driver
+ will work, do not set this.
+