On Tue, Apr 30, 2013 at 09:19:51AM -0700, Jesse Gross wrote: > On Mon, Apr 29, 2013 at 8:21 PM, Simon Horman <ho...@verge.net.au> wrote: > > On Fri, Apr 26, 2013 at 04:03:21PM -0700, Jesse Gross wrote: > >> On Thu, Apr 25, 2013 at 12:36 AM, Simon Horman <ho...@verge.net.au> wrote: > >> > On Tue, Apr 23, 2013 at 02:00:19PM -0700, Joseph Gasparakis wrote: > >> >> Any particular reason to introduce skb->encapsulation_features instead > >> >> of > >> >> using the existing skb->encapsulation? Also I don't see it used in your > >> >> second patch either. > >> > > >> > My reasoning is that skb->encapsulation seems to alter the behaviour of > >> > many different locations and I'm not sure that any of them, other than > >> > the > >> > one in dev_hard_start_xmit() make sense for MPLS. > >> > >> The problem is the meaning of skb->encapsulation isn't really defined > >> clearly and I'm certain that the current implementation is not going > >> to work in the future. Depending on your perspective, vlans, MPLS, > >> tunnels, etc. can all be considered forms of encapsulation but clearly > >> there are many NICs that have different capabilities across those. I > >> believe the intention here was really to describe L3 tunnels as > >> encapsulation, in which case MPLS really shouldn't be using this > >> mechanism at all. > >> > >> Now there is some overlap, especially today since most currently > >> shipping silicon wasn't designed to support tunnels and so is using > >> some form of offset based offloads. In that case, all forms of > >> encapsulation are pretty similar. However, in the future that won't be > >> the case as support for specific protocols is implemented for higher > >> performance and richer support. When that happens, not only will MPLS > >> and tunnels have different capabilities but various forms tunnels > >> might as well. > > > > Wouldn't be possible to describe those differences using, > > dev->hw_enc_features? I assumed that was its purpose. > > If there truly are differences between the offload capabilities of > MPLS and L3 tunnels then no, it's not possible, because it's a single > field. It's certainly not a valid assumption that a NIC that can do > TSO over GRE can also do it over MPLS. > > However, it's unlikely that there are truly significant differences > between various encapsulation formats on a per-feature basis. I think > what we need to do is separate out the ability to understand the > headers from the capabilities so you have two fields: header (none, > VLAN, QinQ, MPLS, VXLAN, GRE, etc.) and feature (checksum, SG, TSO, > etc.) rather than the product of each. Otherwise, we end up with a ton > of different combinations.
I'm not quite sure that I follow. Is your idea to replace skb->encapsulation (a single bit) with a field that corresponds to the outer-most (encapsulation) header in use and has bits for none, VLAN, QinQ, MPLS, VXLAN, GRE, etc...? If so, I believe that would solve the problem I was trying to address with this patch. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
