On Wed, Oct 15, 2014 at 06:14:16AM -0400, Thomas F Herbert wrote: > I am late in commenting on Ben's comments on Dave's patch but I > thought I would add my two cents.
I need to review your patches, too, obviously. I'll try to do that soon. My guess is that your patches are more mature, because you have a longer history of contributing to OVS and the Linux kernel, but I have not read them yet. > On 10/10/14, 6:43 PM, Ben Pfaff wrote: > >On Fri, Oct 10, 2014 at 10:06:29AM -0400, Dave Benson wrote: > > > > > >One direction that we will probably have to take at some point is to > >allow matching and setting the DEI bit. > I think this will be near impossible at least for now at least in > the Linux datapath. The upstream kernel also uses the DEI (CFI) bit > to indicate VLAN present and uses it to trigger HW acceleration and > vlan offloading. > > OVS may be wrong in OVS to use this bit but we are consistent with > upstream Linux 802.1q/ad implementation. Any way, my understanding > is that this bit is rarely used in real-world networks. Yes, I'm aware of all of that. DEI support is a low priority, but I do want to keep it in mind as we continue to evolve all the pieces. If some other piece of software can't support DEI, that's fine, but I'd rather not having OVS block it. (This was brought to my attention some time ago by ONF issue EXT-366 "Need to create OXM field for DEI bit to set/push DEI bit for Ethernet frames". Somehow until then I hadn't realized that the CFI bit had ever been repurposed.) > >For compatibility with old datapaths, userspace needs to be able to > >detect whether the datapath supports non-0x8100 VLANs and fall back to > >userspace processing for them if it doesn't. > What datapaths support non 0x8100 vlans? I am not sure what Dave > did, but I only tested my patch with 0x8100 and 0x88a8. I am not > sure how to test for this. Since userspace and kernel can be arbitrarily paired, userspace must be able to tell whether the kernel supports the new feature. This is probably as easy as trying to "execute" a set of actions that push an non-8100 VLAN or to "flow_add" a flow that matches on a non-8100 VLAN. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
