netdev - Re: [PATCH bpf-next v5 3/3] devmap: Allow map lookups from eBPF

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Date:   Mon, 24 Jun 2019 09:41:43 -0700
From:   "Jonathan Lemon" <jonathan.lemon@...il.com>
To:     "Toke Høiland-Jørgensen" <toke@...hat.com>
Cc:     netdev@...r.kernel.org,
        "Jesper Dangaard Brouer" <brouer@...hat.com>,
        "Daniel Borkmann" <daniel@...earbox.net>,
        "Alexei Starovoitov" <ast@...nel.org>,
        "David Miller" <davem@...emloft.net>
Subject: Re: [PATCH bpf-next v5 3/3] devmap: Allow map lookups from eBPF



On 22 Jun 2019, at 19:17, Toke Høiland-Jørgensen wrote:

> From: Toke Høiland-Jørgensen <toke@...hat.com>
>
> We don't currently allow lookups into a devmap from eBPF, because the map
> lookup returns a pointer directly to the dev->ifindex, which shouldn't be
> modifiable from eBPF.
>
> However, being able to do lookups in devmaps is useful to know (e.g.)
> whether forwarding to a specific interface is enabled. Currently, programs
> work around this by keeping a shadow map of another type which indicates
> whether a map index is valid.
>
> Since we now have a flag to make maps read-only from the eBPF side, we can
> simply lift the lookup restriction if we make sure this flag is always set.
>
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
Acked-by: Jonathan Lemon <jonathan.lemon@...il.com>