On Mon, Apr 29, 2013 at 8:21 PM, Simon Horman <[email protected]> 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 <[email protected]> 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. _______________________________________________ dev mailing list [email protected] http://openvswitch.org/mailman/listinfo/dev
