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 15:54:41 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Björn Töpel <bjorn.topel@...el.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

Björn Töpel <bjorn.topel@...el.com> writes:

> 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.

That...seems a bit short-sighted? :)
Can you actually see a difference in your performance numbers?

-Toke