[ovs-dev] [PATCH V3 18/19] netdev-offload-dpdk: Support offload of clone tnl_push/output actions

[Sathya Perla]

On Tue, Dec 10, 2019 at 1:21 PM Eli Britstein <elibr at mellanox.com> wrote:
>
>
> On 12/10/2019 8:52 AM, Sathya Perla wrote:
> > On Sun, Dec 8, 2019 at 6:53 PM Eli Britstein <elibr at mellanox.com> wrote:
> > ...
> >> +static int
> >> +parse_clone_actions(struct netdev *netdev,
> >> +                    struct flow_actions *actions,
> >> +                    const struct nlattr *clone_actions,
> >> +                    const size_t clone_actions_len,
> >> +                    struct offload_info *info)
> >> +{
> >> +    const struct nlattr *ca;
> >> +    unsigned int cleft;
> >> +
> >> +    NL_ATTR_FOR_EACH_UNSAFE (ca, cleft, clone_actions, clone_actions_len) {
> >> +        int clone_type = nl_attr_type(ca);
> >> +
> >> +        if (clone_type == OVS_ACTION_ATTR_TUNNEL_PUSH) {
> >> +            const struct ovs_action_push_tnl *tnl_push = nl_attr_get(ca);
> >> +            struct rte_flow_action_raw_encap *raw_encap =
> >> +                xzalloc(sizeof *raw_encap);
> >> +
> >> +            raw_encap->data = (uint8_t *)tnl_push->header;
> >> +            raw_encap->preserve = NULL;
> >> +            raw_encap->size = tnl_push->header_len;
> >> +
> >> +            add_flow_action(actions, RTE_FLOW_ACTION_TYPE_RAW_ENCAP,
> >> +                            raw_encap);
> > Hi, converting OVS_TUNNLE_PUSH into RTE_RAW_ENCAP loses the 'tnl_type'
> > information provided by OVS. RAW_ENCAP provides the tunnel header just
> > as a blob of bits which may not be ideal for NIC HW to offload.
> >
> > How about using tnl_push->tnl_type field to parse the header and
> > compose specific tunnel encap actions like RTE_VXLAN_ENCAP,
> > RTE_NVGRE_ENCAP etc.
> > This would be also be more inline with how it's done with TC-offload.
>
> I see your point. However, struct ovs_action_push_tnl has the "header"
> field just as a raw binary buffer, and not detailed like in TC.
> "tnl_type" has a comment /* For logging. */. It is indeed used for
> logging, as in lib/odp-util.c, in function format_odp_tnl_push_header.

This is not entirely true. Checkout propagate_tunnel_data_to_flow()
where tnl_type is being used
to figure out nw_proto.

>
> using VXLAN_ENCAP instead of RAW_ENCAP will make the push less generic,
> as I will have to parse the header to build the vxlan_encap fields, just
> so they can re-build as a raw header in the PMD level, so I don't see
> the offload benefit of it.

Why are you assuming that all PMDs will rebuild the tunnel header
fields as a 'raw header'?
What if the NIC HW needs tunnel specific headers to be programmed
separately for each tunnel type?

>
> Another point is that this way it will support any header, not just
> VXLAN (as an example).

Given that VXLAN and NVGRE ENCAP and DECAP actions are already defined
in rte_flow, how about
we use them for vxlan and nvgre and use RAW for the rest of the tunnel types?
We can support all tunnel headers even this way.....

thanks!