netdev - Re: [PATCH bpf-next v2 4/8] xsk: register XDP sockets at bind(), and add new AF

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Date:   Wed, 20 Jan 2021 14:25:58 +0100
From:   Björn Töpel <bjorn.topel@...el.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>,
        Björn Töpel <bjorn.topel@...il.com>,
        ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Cc:     magnus.karlsson@...el.com, maciej.fijalkowski@...el.com,
        kuba@...nel.org, jonathan.lemon@...il.com, maximmi@...dia.com,
        davem@...emloft.net, hawk@...nel.org, john.fastabend@...il.com,
        ciara.loftus@...el.com, weqaar.a.janjua@...el.com
Subject: Re: [PATCH bpf-next v2 4/8] xsk: register XDP sockets at bind(), and
 add new AF_XDP BPF helper

On 2021-01-20 13:50, Toke Høiland-Jørgensen wrote:
> Björn Töpel <bjorn.topel@...il.com> writes:
> 
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index c001766adcbc..bbc7d9a57262 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -3836,6 +3836,12 @@ union bpf_attr {
>>    *	Return
>>    *		A pointer to a struct socket on success or NULL if the file is
>>    *		not a socket.
>> + *
>> + * long bpf_redirect_xsk(struct xdp_buff *xdp_md, u64 action)
>> + *	Description
>> + *		Redirect to the registered AF_XDP socket.
>> + *	Return
>> + *		**XDP_REDIRECT** on success, otherwise the action parameter is returned.
>>    */
> 
> I think it would be better to make the second argument a 'flags'
> argument and make values > XDP_TX invalid (like we do in
> bpf_xdp_redirect_map() now). By allowing any value as return you lose
> the ability to turn it into a flags argument later...
>

Yes, but that adds a run-time check. I prefer this non-checked version,
even though it is a bit less futureproof.


Björn