Subject: Re: [PATCH ipsec-next,v2 2/3] xfrm: interface: Add unstable helpers for setting/getting XFRM metadata from TC-BPF

From: Martin KaFai Lau <[email-masked]>
Date: Thu, 1 Dec 2022 12:21:33 -0800

On 11/30/22 9:55 PM, Eyal Birger wrote:
>>> +
>>> +     info->if_id = from->if_id;
>>> +     info->link = from->link;
>>> +     skb_dst_force(skb);
>>> +     info->dst_orig = skb_dst(skb);
>>> +
>>> +     dst_hold((struct dst_entry *)md_dst);
>>> +     skb_dst_set(skb, (struct dst_entry *)md_dst);
>>> +     return 0;
>>> +}
>>> +
>>> +__diag_pop()
>>> +
>>> +BTF_SET8_START(xfrm_ifc_kfunc_set)
>>> +BTF_ID_FLAGS(func, bpf_skb_get_xfrm_info)
>>> +BTF_ID_FLAGS(func, bpf_skb_set_xfrm_info)
>>> +BTF_SET8_END(xfrm_ifc_kfunc_set)
>>> +
>>> +static const struct btf_kfunc_id_set xfrm_interface_kfunc_set = {
>>> +     .owner = THIS_MODULE,
>>> +     .set   = &xfrm_ifc_kfunc_set,
>>> +};
>>> +
>>> +int __init register_xfrm_interface_bpf(void)
>>> +{
>>> +     int err;
>>> +
>>> +     xfrm_md_dst = metadata_dst_alloc_percpu(0, METADATA_XFRM,
>>> +                                             GFP_KERNEL);
>>
>> May be DEFINE_PER_CPU() instead?
> 
> Are you suggesting duplicating the dst init/cleanup logic here?
> Personally given that this happens once at module load, I think it's best to
> use the existing infrastructure, but am willing to add this here if you think
> it's better.

Agree, staying with the current patch is better.  I somehow thought 
metadata_dst_alloc_percpu() was newly added in this patch also.