linux-kernel - Re: [RFC v2 6/6] flow_dissector: Parse batman-adv unicast headers

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Date:   Tue, 5 Dec 2017 09:19:45 -0800
From:   Tom Herbert <tom@...bertland.com>
To:     Sven Eckelmann <sven.eckelmann@...nmesh.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>,
        Eric Dumazet <edumazet@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        b.a.t.m.a.n@...ts.open-mesh.org
Subject: Re: [RFC v2 6/6] flow_dissector: Parse batman-adv unicast headers

On Tue, Dec 5, 2017 at 6:35 AM, Sven Eckelmann
<sven.eckelmann@...nmesh.com> wrote:
> The batman-adv unicast packets contain a full layer 2 frame in encapsulated
> form. The flow dissector must therefore be able to parse the batman-adv
> unicast header to reach the layer 2+3 information.
>
>   +--------------------+
>   | ip(v6)hdr          |
>   +--------------------+
>   | inner ethhdr       |
>   +--------------------+
>   | batadv unicast hdr |
>   +--------------------+
>   | outer ethhdr       |
>   +--------------------+
>
> The obtained information from the upper layer can then be used by RPS to
> schedule the processing on separate cores. This allows better distribution
> of multiple flows from the same neighbor to different cores.
>
> Signed-off-by: Sven Eckelmann <sven.eckelmann@...nmesh.com>
> ---
>  net/core/flow_dissector.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
>
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index 15ce30063765..784cc07fc58e 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -24,6 +24,7 @@
>  #include <linux/tcp.h>
>  #include <net/flow_dissector.h>
>  #include <scsi/fc/fc_fcoe.h>
> +#include <uapi/linux/batadv.h>
>
>  static void dissector_set_key(struct flow_dissector *flow_dissector,
>                               enum flow_dissector_key_id key_id)
> @@ -696,6 +697,35 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
>
>                 break;
>         }
> +       case htons(ETH_P_BATMAN): {
> +               struct {
> +                       struct batadv_unicast_packet batadv_unicast;
> +                       struct ethhdr eth;
> +               } *hdr, _hdr;
> +
> +               hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr), data, hlen,
> +                                          &_hdr);
> +               if (!hdr) {
> +                       fdret = FLOW_DISSECT_RET_OUT_BAD;
> +                       break;
> +               }
> +
> +               if (hdr->batadv_unicast.version != BATADV_COMPAT_VERSION) {
> +                       fdret = FLOW_DISSECT_RET_OUT_BAD;
> +                       break;
> +               }
> +
> +               if (hdr->batadv_unicast.packet_type != BATADV_UNICAST) {
> +                       fdret = FLOW_DISSECT_RET_OUT_BAD;
> +                       break;
> +               }
> +
> +               proto = hdr->eth.h_proto;
> +               nhoff += sizeof(*hdr);
> +
> +               fdret = FLOW_DISSECT_RET_PROTO_AGAIN;
> +               break;
> +       }
>         case htons(ETH_P_8021AD):
>         case htons(ETH_P_8021Q): {
>                 const struct vlan_hdr *vlan;
> --
> 2.11.0
>
Switch statements with cases having many LOC is hard to read and
__skb_flow_dissect is aleady quite convoluted to begin with.

I suggest putting this in a static function similar to how MPLS and
GRE are handled.

Tom