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. 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. 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. The MPLS ethertype is in in the packet itself, however checking that seems expensive. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
