linux-kernel - Re: [PATCH v2 0/8] io_uring: Initial support for {s,g}etsockopt commands

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Date:   Wed, 9 Aug 2023 09:26:52 -0700
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Breno Leitao <leitao@...ian.org>
Cc:     axboe@...nel.dk, asml.silence@...il.com,
        willemdebruijn.kernel@...il.com, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        io-uring@...r.kernel.org, kuba@...nel.org, pabeni@...hat.com
Subject: Re: [PATCH v2 0/8] io_uring: Initial support for {s,g}etsockopt commands

On Wed, Aug 9, 2023 at 2:41 AM Breno Leitao <leitao@...ian.org> wrote:
>
> On Tue, Aug 08, 2023 at 10:35:08AM -0700, Stanislav Fomichev wrote:
> > On 08/08, Breno Leitao wrote:
> > > This patchset adds support for getsockopt (SOCKET_URING_OP_GETSOCKOPT)
> > > and setsockopt (SOCKET_URING_OP_SETSOCKOPT) in io_uring commands.
> > > SOCKET_URING_OP_SETSOCKOPT implements generic case, covering all levels
> > > nad optnames. On the other hand, SOCKET_URING_OP_GETSOCKOPT just
> > > implements level SOL_SOCKET case, which seems to be the
> > > most common level parameter for get/setsockopt(2).
> > >
> > > struct proto_ops->setsockopt() uses sockptr instead of userspace
> > > pointers, which makes it easy to bind to io_uring. Unfortunately
> > > proto_ops->getsockopt() callback uses userspace pointers, except for
> > > SOL_SOCKET, which is handled by sk_getsockopt(). Thus, this patchset
> > > leverages sk_getsockopt() to imlpement the SOCKET_URING_OP_GETSOCKOPT
> > > case.
> > >
> > > In order to support BPF hooks, I modified the hooks to use  sockptr, so,
> > > it is flexible enough to accept user or kernel pointers for
> > > optval/optlen.
> > >
> > > PS1: For getsockopt command, the optlen field is not a userspace
> > > pointers, but an absolute value, so this is slightly different from
> > > getsockopt(2) behaviour. The new optlen value is returned in cqe->res.
> > >
> > > PS2: The userspace pointers need to be alive until the operation is
> > > completed.
> > >
> > > These changes were tested with a new test[1] in liburing. On the BPF
> > > side, I tested that no regression was introduced by running "test_progs"
> > > self test using "sockopt" test case.
> > >
> > > [1] Link: https://github.com/leitao/liburing/blob/getsock/test/socket-getsetsock-cmd.c
> > >
> > > RFC -> V1:
> > >     * Copy user memory at io_uring subsystem, and call proto_ops
> > >       callbacks using kernel memory
> > >     * Implement all the cases for SOCKET_URING_OP_SETSOCKOPT
> >
> > I did a quick pass, will take a close look later today. So far everything makes
> > sense to me.
> >
> > Should we properly test it as well?
> > We have tools/testing/selftests/bpf/prog_tests/sockopt.c which does
> > most of the sanity checks, but it uses regular socket/{g,s}etsockopt
> > syscalls.
>
> Right, that is what I've been using to test the changes.
>
> > Seems like it should be pretty easy to extend this with
> > io_uring path? tools/testing/selftests/net/io_uring_zerocopy_tx.c
> > already implements minimal wrappers which we can most likely borrow.
>
> Sure, I can definitely do it. Do you want to see the new tests in this
> patchset, or, in a following patches?

Let's keep it in the same series if possible?