Re: [PATCH nf] sched: act_ct: additional checks for outdated flows

[Vlad Buslov <vladbu@nvidia.com>]

On Tue 24 Oct 2023 at 22:02, Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> From: Vlad Buslov <vladbu@nvidia.com>
>
> Current nf_flow_is_outdated() implementation considers any flow table flow
> which state diverged from its underlying CT connection status for teardown
> which can be problematic in the following cases:
>
> - Flow has never been offloaded to hardware in the first place either
> because flow table has hardware offload disabled (flag
> NF_FLOWTABLE_HW_OFFLOAD is not set) or because it is still pending on 'add'
> workqueue to be offloaded for the first time. The former is incorrect, the
> later generates excessive deletions and additions of flows.
>
> - Flow is already pending to be updated on the workqueue. Tearing down such
> flows will also generate excessive removals from the flow table, especially
> on highly loaded system where the latency to re-offload a flow via 'add'
> workqueue can be quite high.
>
> When considering a flow for teardown as outdated verify that it is both
> offloaded to hardware and doesn't have any pending updates.
>
> Fixes: 41f2c7c342d3 ("net/sched: act_ct: Fix promotion of offloaded unreplied tuple")
> Reviewed-by: Paul Blakey <paulb@nvidia.com>
> Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
> ---
> I am taking Vlad's patch and rebasing as per his request:
>
> This patch requires:
> https://patchwork.ozlabs.org/project/netfilter-devel/patch/20231024193815.1987-1-pablo@netfilter.org/
>

Signed-off-by: Vlad Buslov <vladbu@nvidia.com>