netdev - Re: [RFC net-next v2 4/5] net:sched:act_sample: add action cookie to sample

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Message-ID: <56e764b2-1f0b-4785-aba7-d1dbb34e65e8@ovn.org>
Date: Mon, 8 Apr 2024 15:20:40 +0200
From: Ilya Maximets <i.maximets@....org>
To: Adrian Moreno <amorenoz@...hat.com>, netdev@...r.kernel.org
Cc: i.maximets@....org, jiri@...nulli.us, xiyou.wangcong@...il.com,
 cmi@...dia.com, yotam.gi@...il.com, aconole@...hat.com, echaudro@...hat.com,
 horms@...nel.org
Subject: Re: [RFC net-next v2 4/5] net:sched:act_sample: add action cookie to
 sample

[copying my previous reply since this version actually has netdev@ in Cc]

On 4/8/24 14:57, 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@...hat.com>
> ---
>  net/sched/act_sample.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)

Nit: some spaces in the subject would be nice.

> 
> 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] = {};
>  	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();

Not sure what is better - extending rcu critical section
beyond psample_sample_packet() or copying the cookie...
What do you think?

> +
>  		md.trunc_size = s->truncate ? s->trunc_size : skb->len;
>  		psample_sample_packet(psample_group, skb, s->rate, &md);
>