Re: [PATCH net-next v2 2/9] net: sched: act_sample: add action cookie to sample

[Ilya Maximets]

On 6/3/24 20:56, Adrian Moreno wrote:
> If the action has a user_cookie, pass it along to the sample so it can
> be easily identified.
> 
> Signed-off-by: Adrian Moreno <amorenoz@xxxxxxxxxx>
> ---
>  net/sched/act_sample.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/net/sched/act_sample.c b/net/sched/act_sample.c
> index a69b53d54039..5c3f86ec964a 100644
> --- a/net/sched/act_sample.c
> +++ b/net/sched/act_sample.c
> @@ -165,9 +165,11 @@ TC_INDIRECT_SCOPE int tcf_sample_act(struct sk_buff *skb,
>  				     const struct tc_action *a,
>  				     struct tcf_result *res)
>  {
> +	u8 cookie_data[TC_COOKIE_MAX_SIZE] = {};

Is it necessary to initialize these 16 bytes on every call?
Might be expensive.  We're passing the data length around,
so the uninitialized parts should not be accessed.

Best regards, Ilya Maximets.

>  	struct tcf_sample *s = to_sample(a);
>  	struct psample_group *psample_group;
>  	struct psample_metadata md = {};
> +	struct tc_cookie *user_cookie;
>  	int retval;
>  
>  	tcf_lastuse_update(&s->tcf_tm);
> @@ -189,6 +191,16 @@ TC_INDIRECT_SCOPE int tcf_sample_act(struct sk_buff *skb,
>  		if (skb_at_tc_ingress(skb) && tcf_sample_dev_ok_push(skb->dev))
>  			skb_push(skb, skb->mac_len);
>  
> +		rcu_read_lock();
> +		user_cookie = rcu_dereference(a->user_cookie);
> +		if (user_cookie) {
> +			memcpy(cookie_data, user_cookie->data,
> +			       user_cookie->len);
> +			md.user_cookie = cookie_data;
> +			md.user_cookie_len = user_cookie->len;
> +		}
> +		rcu_read_unlock();
> +
>  		md.trunc_size = s->truncate ? s->trunc_size : skb->len;
>  		psample_sample_packet(psample_group, skb, s->rate, &md);
>