[ovs-discuss] [Solved][Bug] flow deletion before transmission end - transmission stalled

Ben Pfaff blp at nicira.com
Tue Nov 30 20:13:05 UTC 2010


On Tue, Nov 30, 2010 at 12:12:16PM -0800, Justin Pettit wrote:
> On Nov 30, 2010, at 11:50 AM, Christian Fischer wrote:
> 
> > On Tuesday 30 November 2010 20:38:54 Christian Fischer wrote:
> >> On Tuesday 30 November 2010 19:28:07 Ben Pfaff wrote:
> >>> On Tue, Nov 30, 2010 at 09:18:43AM +0100, Christian Fischer wrote:
> >>>> On Saturday 27 November 2010 23:52:20 Ben Pfaff wrote:
> >>>>> Was the problem and solution anything worth documenting so that we
> >>>>> could help others to avoid this problem in the future?
> >>>> 
> >>>> the problem was self made.
> >>>> Having the same mtu for physical interfaces like the virtual interface
> >>>> mtu (ovs, both 1500) isn't a good idea if one likes to use VLANs. 1518
> >>>> is a reasonable value.
> >>>> 
> >>>> Well, both, mtu_setting() from InterfaceReconfigure.py and ovs-vsctl
> >>>> add port, have configured 1500 bytes, but I haven't verified the
> >>>> settings, and therefore it was my fault.
> >>> 
> >>> I'm surprised that this was necessary.  Most NIC drivers allow an extra
> >>> 4 bytes when a VLAN tag is present.  What driver does your NIC use?
> >> 
> >> e1000e: Intel(R) PRO/1000 Network Driver - 1.1.2-NAPI
> > 
> > and igb Intel(R) Gigabit Ethernet Network Driver - version 2.1.9
> 
> This is an issue in the Intel driver that we've seen internally.  The
> driver calculates the size of the receive FIFO based on whether a VLAN
> group is defined.  OVS doesn't use VLAN groups, so the driver sets the
> maximum size to 1514 bytes, but frames with VLANs are 1518.  Jesse
> reworked the way VLANs are handled in Linux to make this class of
> problems go away, which should make it into 2.6.37.  We may look at
> patching the driver to work with existing kernels.  If we do that,
> we'll forward the patch to you.

Should we document the issue somewhere in the tree, e.g. INSTALL.Linux?




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