Subject: Re: [xdp-hints] Re: [RFC bpf-next v2 06/14] xdp: Carry over xdp metadata into skb context

From: Martin KaFai Lau <[email-masked]>
Date: Thu, 10 Nov 2022 15:58:22 -0800

On 11/10/22 10:52 AM, Stanislav Fomichev wrote:
>>> Oh, that seems even better than returning it from
>>> bpf_xdp_metadata_export_to_skb.
>>> bpf_xdp_metadata_export_to_skb can return true/false and the rest goes
>>> via default verifier ctx resolution mechanism..
>>> (returning ptr from a kfunc seems to be a bit complicated right now)

What is the complication in returning ptr from a kfunc?  I want to see if it can 
be solved because it will be an easier API to use instead of calling another 
kfunc to get the ptr.

>> See my response to John in the other thread about mixing stable UAPI (in
>> xdp_md) and unstable BTF structures in the xdp_md struct: I think this
>> is confusing and would prefer a kfunc.

hmm... right, it will be one of the first considering the current __bpf_md_ptr() 
usages are only exposing another struct in uapi, eg. __bpf_md_ptr(struct 
bpf_sock *, sk).

A kfunc will also be fine.