netdev - Re: [PATCH bpf-next 2/2] xdp: Use bulking for non-map XDP

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Message-ID: <87a76vxq29.fsf@toke.dk>
Date:   Fri, 10 Jan 2020 16:57:02 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     Netdev <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        David Miller <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [PATCH bpf-next 2/2] xdp: Use bulking for non-map XDP_REDIRECT

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

> On Fri, 10 Jan 2020 at 16:30, Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>>
>> Björn Töpel <bjorn.topel@...il.com> writes:
>>
> [...]
>> >
>> > After these changes, does the noinline (commit 47b123ed9e99 ("xdp:
>> > split code for map vs non-map redirect")) still make sense?
>>
>> Hmm, good question. The two code paths are certainly close to one
>> another; and I guess they could be consolidated further.
>>
>> The best case would be if we had a way to lookup the ifindex directly in
>> the helper. Do you know if there's a way to get the current net
>> namespace from the helper? Can we use current->nsproxy->net_ns in that
>> context?
>>
>
> Nope, interrupt context. :-( Another (ugly) way is adding a netns
> member to the bpf_redirect_info, that is populated by the driver
> (driver changes everywhere -- ick). So no.

Yup, that's what I thought. OK, too bad; I'll see what other
consolidation I can do with the current code, then.

> (And *if* one would go the route of changing all drivers, I think the
> percpu bpf_redirect_info should be replaced a by a context that is
> passed from the driver to the XDP program execution and
> xdp_do_redirect/flush. But that's a much bigger patch. :-))

Yeah, let's leave that until the next time we figure out we have to
change all the drivers, then ;)

-Toke