netdev - Re: [PATCH bpf-next v2 06/14] bpf: net_sched: Add basic bpf qdisc kfuncs

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Message-ID: <5e1c5729-9bc0-4cb7-969a-a334fb544595@linux.dev>
Date: Thu, 9 Jan 2025 16:24:08 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Amery Hung <ameryhung@...il.com>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, daniel@...earbox.net,
 andrii@...nel.org, alexei.starovoitov@...il.com, martin.lau@...nel.org,
 sinquersw@...il.com, toke@...hat.com, jhs@...atatu.com, jiri@...nulli.us,
 stfomichev@...il.com, ekarani.silvestre@....ufcg.edu.br,
 yangpeihao@...u.edu.cn, xiyou.wangcong@...il.com, yepeilin.cs@...il.com
Subject: Re: [PATCH bpf-next v2 06/14] bpf: net_sched: Add basic bpf qdisc
 kfuncs

On 12/20/24 11:55 AM, Amery Hung wrote:
> +BTF_KFUNCS_START(qdisc_kfunc_ids)
> +BTF_ID_FLAGS(func, bpf_skb_get_hash, KF_TRUSTED_ARGS)
> +BTF_ID_FLAGS(func, bpf_kfree_skb, KF_RELEASE)
> +BTF_ID_FLAGS(func, bpf_qdisc_skb_drop, KF_RELEASE)
> +BTF_ID_FLAGS(func, bpf_dynptr_from_skb, KF_TRUSTED_ARGS)
> +BTF_KFUNCS_END(qdisc_kfunc_ids)
> +
> +BTF_SET_START(qdisc_common_kfunc_set)
> +BTF_ID(func, bpf_skb_get_hash)
> +BTF_ID(func, bpf_kfree_skb)

I think bpf_dynptr_from_skb should also be here.

> +BTF_SET_END(qdisc_common_kfunc_set)
> +
> +BTF_SET_START(qdisc_enqueue_kfunc_set)
> +BTF_ID(func, bpf_qdisc_skb_drop)
> +BTF_SET_END(qdisc_enqueue_kfunc_set)
> +
> +static int bpf_qdisc_kfunc_filter(const struct bpf_prog *prog, u32 kfunc_id)
> +{
> +	if (bpf_Qdisc_ops.type != btf_type_by_id(prog->aux->attach_btf,
> +						 prog->aux->attach_btf_id))
> +		return 0;
> +
> +	/* Skip the check when prog->attach_func_name is not yet available
> +	 * during check_cfg().

Instead of using attach_func_name, it is better to directly use the 
prog->expected_attach_type provided by the user space. It is essentially the 
member index of the "struct Qdisc_ops". Take a look at the prog_ops_moff() in 
bpf_tcp_ca.c.

> +	 */
> +	if (!btf_id_set8_contains(&qdisc_kfunc_ids, kfunc_id) ||
> +	    !prog->aux->attach_func_name)
> +		return 0;
> +
> +	if (!strcmp(prog->aux->attach_func_name, "enqueue")) {
> +		if (btf_id_set_contains(&qdisc_enqueue_kfunc_set, kfunc_id))
> +		       return 0;
> +	}
> +
> +	return btf_id_set_contains(&qdisc_common_kfunc_set, kfunc_id) ? 0 : -EACCES;
> +}