netdev - Re: [PATCH RFC bpf-next 0/4] bpf: Add support for XDP programs in DEVMAPs

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Date:   Fri, 22 May 2020 17:59:19 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, brouer@...hat.com,
        daniel@...earbox.net, john.fastabend@...il.com, ast@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com, andriin@...com,
        dsahern@...il.com, David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH RFC bpf-next 0/4] bpf: Add support for XDP programs in DEVMAPs

David Ahern <dsahern@...nel.org> writes:

> Implementation of Daniel's proposal for allowing DEVMAP entries to be
> a device index, program id pair. Daniel suggested an fd to specify the
> program, but that seems odd to me that you insert the value as an fd, but
> read it back as an id since the fd can be closed.

While I can be sympathetic to the argument that it seems odd, every
other API uses FD for insert and returns ID, so why make it different
here? Also, the choice has privilege implications, since the CAP_BPF
series explicitly makes going from ID->FD a more privileged operation
than just querying the ID.

-Toke