netdev - Re: [PATCH bpf-next 1/3] libbpf: xsk: use bpf

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Date:   Mon, 15 Feb 2021 22:38:52 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     John Fastabend <john.fastabend@...il.com>,
        Björn Töpel 
        <bjorn.topel@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        daniel@...earbox.net, ast@...nel.org, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     andrii@...nel.org, magnus.karlsson@...el.com,
        ciara.loftus@...el.com
Subject: Re: [PATCH bpf-next 1/3] libbpf: xsk: use bpf_link

John Fastabend <john.fastabend@...il.com> writes:

>> > However, in libxdp we can solve the original problem in a different way,
>> > and in fact I already suggested to Magnus that we should do this (see
>> > [1]); so one way forward could be to address it during the merge in
>> > libxdp? It should be possible to address the original issue (two
>> > instances of xdpsock breaking each other when they exit), but
>> > applications will still need to do an explicit unload operation before
>> > exiting (i.e., the automatic detach on bpf_link fd closure will take
>> > more work, and likely require extending the bpf_link kernel support)...
>> >
>> 
>> I'd say it's depending on the libbpf 1.0/libxdp merge timeframe. If
>> we're months ahead, then I'd really like to see this in libbpf until the
>> merge. However, I'll leave that for Magnus/you to decide!
>
> Did I miss some thread? What does this mean libbpf 1.0/libxdp merge?

The idea is to keep libbpf focused on bpf, and move the AF_XDP stuff to
libxdp (so the socket stuff in xsk.h). We're adding the existing code
wholesale, and keeping API compatibility during the move, so all that's
needed is adding -lxdp when compiling. And obviously the existing libbpf
code isn't going anywhere until such a time as there's a general
backwards compatibility-breaking deprecation in libbpf (which I believe
Andrii is planning to do in an upcoming and as-of-yet unannounced v1.0
release).

While integrating the XSK code into libxdp we're trying to make it
compatible with the rest of the library (i.e., multi-prog). Hence my
preference to avoid introducing something that makes this harder :)

-Toke