netdev - Re: [PATCH bpf-next 3/9] xdp: Support setting and getting device chain map

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Message-ID: <CACAyw9-vS7zC0dg-rqkt=hwWkKD-a=WvX92-apiD=wp9vSsGcA@mail.gmail.com>
Date:   Wed, 2 Oct 2019 16:50:18 +0100
From:   Lorenz Bauer <lmb@...udflare.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Marek Majkowski <marek@...udflare.com>,
        David Miller <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        kernel-team <kernel-team@...udflare.com>
Subject: Re: [PATCH bpf-next 3/9] xdp: Support setting and getting device
 chain map

On Wed, 2 Oct 2019 at 14:30, Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> From: Toke Høiland-Jørgensen <toke@...hat.com>
>
> This adds support to rtnetlink for setting and getting the per-device XDP
> chain map. The map is set by means of a new netlink attribute that contains
> a pointer to a BPF map of the XDP chain type. If such an attribute is
> included, it will be inserted into the struct net_device so that the XDP
> chain call code will pick it up on program execution.
>
> To prevent old userspace programs that do not understand the chain map
> attribute from messing up the chain call order, a netlink message with no
> chain map attribute set will be rejected if a chain map has already been
> installed.
>
> When installing a new chain call map, an XDP program fd must also be
> provided, otherwise the operation will be rejected.

Why is the program required? I kind of expected the chain call map
to override any program.

--
Lorenz Bauer  |  Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK

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