Subject: Re: [PATCH RFC net-next 0/4] improve hw flow offload byte accounting

From: Pablo Neira Ayuso <[email-masked]>
Date: Thu, 9 Apr 2026 15:52:41 +0200

On Thu, Apr 09, 2026 at 02:07:22PM +0100, Daniel Golle wrote:
> Hardware flow counters report raw byte counts whose semantics
> vary by vendor -- some count ingress L2 frames, others egress
> L2, others L3. The nf_flow_table framework currently passes
> these bytes straight to conntrack without conversion, and
> sub-interfaces (VLAN, PPPoE) that are bypassed by hw offload
> never see any counter updates at all.

I see, but that is part of the feature itself? Why pretend that these
interface are really seeing traffic while they don't. This aspiration
of trying to do all hardware offload fully transparent (when it is not
the case, not mentioning semantic changes in how packet handling is
done compared to the software plane) does not sound convincing to me.

On top of this, this issue also exists in the software plane: Devices
that are bypasses do not get their counters bumped.

Maybe if this is really a requirement, then this should address the
issue for software too, but is it worth the effort to add
infrastructure for this purpose?

> This series lets drivers declare what their counters represent,
> so the framework can normalize to L3 for conntrack and
> propagate per-layer stats to encap sub-interfaces.
> 
> Questions:
>  - Sub-interface stats accesses vlan_dev_priv() directly --
>    should there be a generic netdev callback instead?
>  - Are there hw offload drivers whose counters do not fit the
>    ingress-L2 / egress-L2 / L3 model?
> 
> Daniel Golle (4):
>   net: flow_offload: let drivers report byte counter semantics
>   nf_flow_table: track sub-interface and bridge ifindex in flow tuple
>   nf_flow_table: convert hw byte counts and update sub-interface stats
>   net: ethernet: mtk_eth_soc: report INGRESS_L2 byte_type in flow stats
> 
>  .../net/ethernet/mediatek/mtk_ppe_offload.c   |   1 +
>  include/net/flow_offload.h                    |   7 +
>  include/net/netfilter/nf_flow_table.h         |   5 +
>  net/netfilter/nf_flow_table_core.c            |   2 +
>  net/netfilter/nf_flow_table_offload.c         | 174 +++++++++++++++++-
>  net/netfilter/nf_flow_table_path.c            |   8 +
>  6 files changed, 195 insertions(+), 2 deletions(-)
> 
> -- 
> 2.53.0