On Wed, May 01, 2013 at 09:53:42PM -0700, Jesse Gross wrote: > On Wed, May 1, 2013 at 3:57 PM, Simon Horman <ho...@verge.net.au> wrote: > > On Wed, May 01, 2013 at 11:16:40AM -0700, Jesse Gross wrote: > >> On Wed, May 1, 2013 at 12:50 AM, Simon Horman <ho...@verge.net.au> wrote: > >> > 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...? > >> > >> No, I'm talking about netdev features. You can already tell the > >> encapsulation type of a packet by looking at the EtherType. > > > > Now I am completely confused about what are the two fields that you > > refer to in your previous email. > > I have always been referring to the netdev features for various > protocol types. This is because considering MPLS as a form of > encapsulation for the purpose of offloads buckets too many protocols > into the same set and NICs will have varying features for those. > Trying to avoid this by having a bit for offloadable encapsulations is > just going to be very confusing and not very future proof. > > > In regards to looking ath the ethernet type: > > > > One of the tricky parts of MPLS is that the packet itself does not contain > > the ethernet type or any other way of knowing the type of the inner-packet. > > Information that is needed for GSO. > > I'm aware of that. However, you were referring to the type of > encapsulation. It is easy to determine that a packet is MPLS. > > > My proposal to get around this is to leave skb->protocol as the > > original, in the case we are interested in non-MPLS, ethernet type. > > At the very least, this is not consistent with how it is currently > handled (for example, with VLANs) and seems difficult to do properly. > However, I have not seen any further analysis since the last time that > we discussed this.
Unfortunately my efforts to solicit feedback from others regarding that have not been successful. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
