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Date: Tue, 4 Jun 2019 10:07:25 +0200
From: Björn Töpel <bjorn.topel@...el.com>
To: Maciej Fijalkowski <maciejromanfijalkowski@...il.com>,
magnus.karlsson@...el.com, netdev@...r.kernel.org
Cc: ast@...nel.org, daniel@...earbox.net, jakub.kicinski@...ronome.com,
jonathan.lemon@...il.com, songliubraving@...com,
bpf <bpf@...r.kernel.org>
Subject: Re: [RFC PATCH bpf-next 3/4] libbpf: move xdp program removal to
libbpf
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.
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.
For the sample application, this makes sense, but for larger/real
applications?
OTOH I like the idea of a scoped cleanup "when all sockets are gone",
the XDP program + maps are removed.
> 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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