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Message-ID: <CAJ+HfNiOh+2_tLmjhbbGC2H3gMhfr57uhCYho5OcfVwty0TWvg@mail.gmail.com>
Date: Wed, 5 Jun 2019 11:03:44 +0200
From: Björn Töpel <bjorn.topel@...il.com>
To: Maciej Fijalkowski <maciejromanfijalkowski@...il.com>
Cc: Björn Töpel <bjorn.topel@...el.com>,
"Karlsson, Magnus" <magnus.karlsson@...el.com>,
Netdev <netdev@...r.kernel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Jakub Kicinski <jakub.kicinski@...ronome.com>,
Jonathan Lemon <jonathan.lemon@...il.com>,
Song Liu <songliubraving@...com>, bpf <bpf@...r.kernel.org>
Subject: Re: [RFC PATCH bpf-next 3/4] libbpf: move xdp program removal to libbpf
On Tue, 4 Jun 2019 at 17:07, Maciej Fijalkowski
<maciejromanfijalkowski@...il.com> wrote:
>
> On Tue, 4 Jun 2019 10:07:25 +0200
> Björn Töpel <bjorn.topel@...el.com> wrote:
>
> >
> > On 2019-06-03 15:19, Maciej Fijalkowski wrote:
> > > Since xsk support in libbpf loads the xdp program interface, make it
> > > also responsible for its removal. Store the prog id in xsk_socket_config
> > > so when removing the program we are still able to compare the current
> > > program id with the id from the attachment time and make a decision
> > > onward.
> > >
> > > While at it, remove the socket/umem in xdpsock's error path.
> > >
> >
> > We're loading a new, or reusing an existing XDP program at socket
> > creation, but tearing it down at *socket delete* is explicitly left to
> > the application.
>
> Are you describing here the old behavior?
>
> >
> > For a per-queue XDP program (tied to the socket), this kind cleanup would
> > make sense.
> >
> > The intention with the libbpf AF_XDP support was to leave the XDP
> > handling to whatever XDP orchestration process availble. It's not part
> > of libbpf. For convenience, *loading/lookup of the XDP program* was
> > added even though this was an asymmetry.
>
> Hmmm ok and I tried to make it symmetric :p
>
Thought a bit more about this, and I think you're right here. It
should be symmetric! Please continue this work! (But keep in mind that
it might go away if/once per-queue programs appear. :-P)
> >
> > For the sample application, this makes sense, but for larger/real
> > applications?
> >
>
> Tough questions on those real apps!
>
:-D
>
> > OTOH I like the idea of a scoped cleanup "when all sockets are gone",
> > the XDP program + maps are removed.
>
> That's happening with patch 4 included from this set (in case it gets fixed :))
>
Ok!
Björn
> >
> > > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> > > ---
> > > samples/bpf/xdpsock_user.c | 33 ++++++++++-----------------------
> > > tools/lib/bpf/xsk.c | 32 ++++++++++++++++++++++++++++++++
> > > tools/lib/bpf/xsk.h | 1 +
> > > 3 files changed, 43 insertions(+), 23 deletions(-)
> > >
> > > diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
> > > index e9dceb09b6d1..123862b16dd4 100644
> > > --- a/samples/bpf/xdpsock_user.c
> > > +++ b/samples/bpf/xdpsock_user.c
> > > @@ -68,7 +68,6 @@ static int opt_queue;
> > > static int opt_poll;
> > > static int opt_interval = 1;
> > > static u32 opt_xdp_bind_flags;
> > > -static __u32 prog_id;
> > >
> > > struct xsk_umem_info {
> > > struct xsk_ring_prod fq;
> > > @@ -170,22 +169,6 @@ static void *poller(void *arg)
> > > return NULL;
> > > }
> > >
> > > -static void remove_xdp_program(void)
> > > -{
> > > - __u32 curr_prog_id = 0;
> > > -
> > > - if (bpf_get_link_xdp_id(opt_ifindex, &curr_prog_id, opt_xdp_flags)) {
> > > - printf("bpf_get_link_xdp_id failed\n");
> > > - exit(EXIT_FAILURE);
> > > - }
> > > - if (prog_id == curr_prog_id)
> > > - bpf_set_link_xdp_fd(opt_ifindex, -1, opt_xdp_flags);
> > > - else if (!curr_prog_id)
> > > - printf("couldn't find a prog id on a given interface\n");
> > > - else
> > > - printf("program on interface changed, not removing\n");
> > > -}
> > > -
> > > static void int_exit(int sig)
> > > {
> > > struct xsk_umem *umem = xsks[0]->umem->umem;
> > > @@ -195,7 +178,6 @@ static void int_exit(int sig)
> > > dump_stats();
> > > xsk_socket__delete(xsks[0]->xsk);
> > > (void)xsk_umem__delete(umem);
> > > - remove_xdp_program();
> > >
> > > exit(EXIT_SUCCESS);
> > > }
> > > @@ -206,7 +188,16 @@ static void __exit_with_error(int error, const char *file, const char *func,
> > > fprintf(stderr, "%s:%s:%i: errno: %d/\"%s\"\n", file, func,
> > > line, error, strerror(error));
> > > dump_stats();
> > > - remove_xdp_program();
> > > +
> > > + if (xsks[0]->xsk)
> > > + xsk_socket__delete(xsks[0]->xsk);
> > > +
> > > + if (xsks[0]->umem) {
> > > + struct xsk_umem *umem = xsks[0]->umem->umem;
> > > +
> > > + (void)xsk_umem__delete(umem);
> > > + }
> > > +
> > > exit(EXIT_FAILURE);
> > > }
> > >
> > > @@ -312,10 +303,6 @@ static struct xsk_socket_info *xsk_configure_socket(struct xsk_umem_info *umem)
> > > if (ret)
> > > exit_with_error(-ret);
> > >
> > > - ret = bpf_get_link_xdp_id(opt_ifindex, &prog_id, opt_xdp_flags);
> > > - if (ret)
> > > - exit_with_error(-ret);
> > > -
> > > return xsk;
> > > }
> > >
> > > diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> > > index 514ab3fb06f4..e28bedb0b078 100644
> > > --- a/tools/lib/bpf/xsk.c
> > > +++ b/tools/lib/bpf/xsk.c
> > > @@ -259,6 +259,8 @@ int xsk_umem__create(struct xsk_umem **umem_ptr, void *umem_area, __u64 size,
> > > static int xsk_load_xdp_prog(struct xsk_socket *xsk)
> > > {
> > > static const int log_buf_size = 16 * 1024;
> > > + struct bpf_prog_info info = {};
> > > + __u32 info_len = sizeof(info);
> > > char log_buf[log_buf_size];
> > > int err, prog_fd;
> > >
> > > @@ -321,6 +323,14 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
> > > return err;
> > > }
> > >
> > > + err = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
> > > + if (err) {
> > > + pr_warning("can't get prog info - %s\n", strerror(errno));
> > > + close(prog_fd);
> > > + return err;
> > > + }
> > > + xsk->config.prog_id = info.id;
> > > +
> > > xsk->prog_fd = prog_fd;
> > > return 0;
> > > }
> > > @@ -483,6 +493,25 @@ static int xsk_set_bpf_maps(struct xsk_socket *xsk)
> > > return err;
> > > }
> > >
> > > +static void xsk_remove_xdp_prog(struct xsk_socket *xsk)
> > > +{
> > > + __u32 prog_id = xsk->config.prog_id;
> > > + __u32 curr_prog_id = 0;
> > > + int err;
> > > +
> > > + err = bpf_get_link_xdp_id(xsk->ifindex, &curr_prog_id,
> > > + xsk->config.xdp_flags);
> > > + if (err)
> > > + return;
> > > +
> > > + if (prog_id == curr_prog_id)
> > > + bpf_set_link_xdp_fd(xsk->ifindex, -1, xsk->config.xdp_flags);
> > > + else if (!curr_prog_id)
> > > + pr_warning("couldn't find a prog id on a given interface\n");
> > > + else
> > > + pr_warning("program on interface changed, not removing\n");
> > > +}
> > > +
> > > static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
> > > {
> > > __u32 prog_id = 0;
> > > @@ -506,6 +535,7 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
> > > err = xsk_lookup_bpf_maps(xsk);
> > > if (err)
> > > goto out_load;
> > > + xsk->config.prog_id = prog_id;
> > > }
> > >
> > > err = xsk_set_bpf_maps(xsk);
> > > @@ -744,6 +774,8 @@ void xsk_socket__delete(struct xsk_socket *xsk)
> > >
> > > }
> > >
> > > + xsk_remove_xdp_prog(xsk);
> > > +
> > > xsk->umem->refcount--;
> > > /* Do not close an fd that also has an associated umem connected
> > > * to it.
> > > diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
> > > index 82ea71a0f3ec..e1b23e9432c9 100644
> > > --- a/tools/lib/bpf/xsk.h
> > > +++ b/tools/lib/bpf/xsk.h
> > > @@ -186,6 +186,7 @@ struct xsk_socket_config {
> > > __u32 tx_size;
> > > __u32 libbpf_flags;
> > > __u32 xdp_flags;
> > > + __u32 prog_id;
> > > __u16 bind_flags;
> > > };
> > >
> > >
>
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