On 23 Sep 2022, at 18:29, Peng He wrote:

> When PMDs perform upcalls, the newly generated ukey will replace
> the old, however, the newly generated mageflow will be discard
> to reuse the old one without checking if the actions of new and
> old are equal.
>
> This code prevents in case someone runs dpctl/add-flow to add
> a dp flow with inconsistent actions with the actions of ukey,
> and causes more confusion.
>
> Signed-off-by: Peng He <[email protected]>
> ---
>  lib/dpif-netdev.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index a45b46014..b316e59ef 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -8304,7 +8304,22 @@ handle_packet_upcall(struct dp_netdev_pmd_thread *pmd,
>           * to be locking revalidators out of making flow modifications. */
>          ovs_mutex_lock(&pmd->flow_mutex);
>          netdev_flow = dp_netdev_pmd_lookup_flow(pmd, key, NULL);
> -        if (OVS_LIKELY(!netdev_flow)) {
> +        if (OVS_UNLIKELY(netdev_flow)) {
> +            struct dp_netdev_actions *old_act =
> +                dp_netdev_flow_get_actions(netdev_flow);
> +
> +            if ((add_actions->size != old_act->size) ||
> +                    memcmp(old_act->actions, add_actions->data,
> +                                             add_actions->size)) {
> +
> +               struct dp_netdev_actions *new_act =
> +                   dp_netdev_actions_create(add_actions->data,
> +                                            add_actions->size);
> +
> +               ovsrcu_set(&netdev_flow->actions, new_act);
> +               ovsrcu_postpone(dp_netdev_actions_free, old_act);

Do we really need this patch? Asking as this is in the fastpath code?
And it only happens if someone is messing with dpctl commands, which they 
should not.

I we want it, we should add a good comment on why it’s there.

> +            }
> +        } else {
>              netdev_flow = dp_netdev_flow_add(pmd, &match, &ufid,
>                                               add_actions->data,
>                                               add_actions->size, 
> orig_in_port);
> -- 
> 2.25.1
>
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