From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: David Ahern <dsahern@gmail.com>, David Ahern <dsahern@kernel.org>,
netdev@vger.kernel.org
Cc: davem@davemloft.net, kuba@kernel.org,
prashantbhole.linux@gmail.com, brouer@redhat.com,
daniel@iogearbox.net, john.fastabend@gmail.com, ast@kernel.org,
kafai@fb.com, songliubraving@fb.com, yhs@fb.com, andriin@fb.com,
David Ahern <dahern@digitalocean.com>
Subject: Re: [PATCH v5 bpf-next 00/11] net: Add support for XDP in egress path
Date: Mon, 18 May 2020 20:00:45 +0200 [thread overview]
Message-ID: <87h7wdnmwi.fsf@toke.dk> (raw)
In-Reply-To: <76e2e842-19c0-fd9a-3afa-07e2793dedcd@gmail.com>
David Ahern <dsahern@gmail.com> writes:
> On 5/18/20 3:08 AM, Toke Høiland-Jørgensen wrote:
>> I can see your point that fixing up the whole skb after the program has
>> run is not a good idea. But to me that just indicates that the hook is
>> in the wrong place: that it really should be in the driver, executed at
>> a point where the skb data structure is no longer necessary (similar to
>> how the ingress hook is before the skb is generated).
>
> Have you created a cls_bpf program to modify skbs? Have you looked at
> the helpers, the restrictions and the tight management of skb changes?
> Have you followed the skb from create to device handoff through the
> drivers? Have you looked at the history of encapsulations, gso handling,
> offloads, ...?
Have you tried re-reading the first sentence of the paragraph you're
replying to? You know, the one that started with "I can see your point
that..."
>> Otherwise, what you're proposing is not an egress hook, but rather a
>> 'post-REDIRECT hook', which is strictly less powerful. This may or may
>> not be useful in its own right, but let's not pretend it's a full egress
>> hook. Personally I feel that the egress hook is what we should be going
>> for, not this partial thing.
>
> You are hand waving. Be specific, with details.
Are you deliberately trying to antagonise me or something? It's a really
odd way to try to make your case...
> Less powerful how? There are only so many operations you can do to a
> packet. What do you want to do and what can't be done with this proposed
> change? Why must it be done as XDP vs proper synergy between the 2 paths.
I meant 'less powerful' in the obvious sense: it only sees a subset of
the packets going out of the interface. And so I worry that it will (a)
make an already hard to use set of APIs even more confusing, and (b)
turn out to not be enough so we'll end up needing a "real" egress hook.
As I said in my previous email, a post-REDIRECT hook may or may not be
useful in its own right. I'm kinda on the fence about that, but am
actually leaning towards it being useful; however, I am concerned that
it'll end up being redundant if we do get a full egress hook.
-Toke
next prev parent reply other threads:[~2020-05-18 18:00 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-13 1:45 [PATCH v5 bpf-next 00/11] net: Add support for XDP in egress path David Ahern
2020-05-13 1:45 ` [PATCH v5 bpf-next 01/11] net: Refactor convert_to_xdp_frame David Ahern
2020-05-13 1:45 ` [PATCH v5 bpf-next 02/11] net: uapi for XDP programs in the egress path David Ahern
2020-05-13 1:45 ` [PATCH v5 bpf-next 03/11] net: Add XDP setup and query commands for Tx programs David Ahern
2020-05-13 1:46 ` [PATCH v5 bpf-next 04/11] net: Add BPF_XDP_EGRESS as a bpf_attach_type David Ahern
2020-05-13 1:46 ` [PATCH v5 bpf-next 05/11] xdp: Add xdp_txq_info to xdp_buff David Ahern
2020-05-13 1:46 ` [PATCH v5 bpf-next 06/11] net: set XDP egress program on netdevice David Ahern
2020-05-13 1:46 ` [PATCH v5 bpf-next 07/11] net: Support xdp in the Tx path for xdp_frames David Ahern
2020-05-13 1:46 ` [PATCH v5 bpf-next 08/11] libbpf: Add egress XDP support David Ahern
2020-05-13 1:46 ` [PATCH v5 bpf-next 09/11] bpftool: Add support for XDP egress David Ahern
2020-05-13 1:46 ` [PATCH v5 bpf-next 10/11] selftest: Add xdp_egress attach tests David Ahern
2020-05-13 1:46 ` [PATCH v5 bpf-next 11/11] samples/bpf: add XDP egress support to xdp1 David Ahern
2020-05-13 10:43 ` [PATCH v5 bpf-next 00/11] net: Add support for XDP in egress path Toke Høiland-Jørgensen
2020-05-13 19:37 ` David Ahern
2020-05-15 22:54 ` John Fastabend
2020-05-15 23:15 ` David Ahern
2020-05-18 18:10 ` John Fastabend
2020-05-18 23:52 ` David Ahern
2020-05-19 6:04 ` John Fastabend
2020-05-18 3:40 ` David Ahern
2020-05-18 9:08 ` Toke Høiland-Jørgensen
2020-05-18 14:44 ` David Ahern
2020-05-18 18:00 ` Toke Høiland-Jørgensen [this message]
2020-05-18 21:06 ` Daniel Borkmann
2020-05-19 0:02 ` David Ahern
2020-05-19 13:31 ` Daniel Borkmann
2020-05-19 14:21 ` Jesper Dangaard Brouer
2020-05-19 16:58 ` Lorenzo Bianconi
2020-05-19 14:52 ` Toke Høiland-Jørgensen
2020-05-19 16:37 ` David Ahern
2020-05-18 23:37 ` David Ahern
2020-05-18 21:23 ` Daniel Borkmann
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