From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
Jesper Dangaard Brouer <brouer@redhat.com>,
David Miller <davem@davemloft.net>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next v3 5/6] libbpf: Add bpf_get_link_xdp_info() function to get more XDP information
Date: Fri, 8 Nov 2019 16:51:03 -0800 [thread overview]
Message-ID: <CAEf4BzYvv6pCHygeNyOBE4MRtcLxE1XP4Ww+sxoaPgQw5i1Rjw@mail.gmail.com> (raw)
In-Reply-To: <157325766011.27401.5278664694085166014.stgit@toke.dk>
On Fri, Nov 8, 2019 at 4:01 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> From: Toke Høiland-Jørgensen <toke@redhat.com>
>
> Currently, libbpf only provides a function to get a single ID for the XDP
> program attached to the interface. However, it can be useful to get the
> full set of program IDs attached, along with the attachment mode, in one
> go. Add a new getter function to support this, using an extendible
> structure to carry the information. Express the old bpf_get_link_id()
> function in terms of the new function.
>
> Acked-by: David S. Miller <davem@davemloft.net>
> Acked-by: Song Liu <songliubraving@fb.com>
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> ---
> tools/lib/bpf/libbpf.h | 10 ++++++
> tools/lib/bpf/libbpf.map | 1 +
> tools/lib/bpf/netlink.c | 82 ++++++++++++++++++++++++++++++----------------
> 3 files changed, 65 insertions(+), 28 deletions(-)
>
[...]
>
> -int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags)
> +int bpf_get_link_xdp_info(int ifindex, struct xdp_link_info *info,
> + size_t info_size, __u32 flags)
> {
> struct xdp_id_md xdp_id = {};
> int sock, ret;
> __u32 nl_pid;
> __u32 mask;
>
> - if (flags & ~XDP_FLAGS_MASK)
> + if (flags & ~XDP_FLAGS_MASK || info_size < sizeof(*info))
> return -EINVAL;
Well, now it's backwards-incompatible: older program passes smaller
(but previously perfectly valid) sizeof(struct xdp_link_info) to newer
version of libbpf. This has to go both ways: smaller struct should be
supported as long as program doesn't request (using flags) something,
that can't be put into allowed space.
I know it's PITA to support this, but that's what we have to do for
forward/backward compatibility.
>
> /* Check whether the single {HW,DRV,SKB} mode is set */
> @@ -274,14 +272,42 @@ int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags)
> xdp_id.ifindex = ifindex;
> xdp_id.flags = flags;
>
> - ret = libbpf_nl_get_link(sock, nl_pid, get_xdp_id, &xdp_id);
> - if (!ret)
> - *prog_id = xdp_id.id;
> + ret = libbpf_nl_get_link(sock, nl_pid, get_xdp_info, &xdp_id);
> + if (!ret) {
> + memset(info, 0, info_size);
> + memcpy(info, &xdp_id.info, min(info_size, sizeof(xdp_id.info)));
nit: memset above should start at info + min(info_size, sizeof(xdp_id.info))
> + }
>
> close(sock);
> return ret;
> }
>
[...]
next prev parent reply other threads:[~2019-11-09 0:51 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-09 0:00 [PATCH bpf-next v3 0/6] libbpf: Fix pinning and error message bugs and add new getters Toke Høiland-Jørgensen
2019-11-09 0:00 ` [PATCH bpf-next v3 1/6] libbpf: Unpin auto-pinned maps if loading fails Toke Høiland-Jørgensen
2019-11-09 0:42 ` Andrii Nakryiko
2019-11-09 0:00 ` [PATCH bpf-next v3 2/6] selftests/bpf: Add tests for automatic map unpinning on load failure Toke Høiland-Jørgensen
2019-11-09 0:00 ` [PATCH bpf-next v3 3/6] libbpf: Propagate EPERM to caller on program load Toke Høiland-Jørgensen
2019-11-09 0:44 ` Andrii Nakryiko
2019-11-09 0:00 ` [PATCH bpf-next v3 4/6] libbpf: Use pr_warn() when printing netlink errors Toke Høiland-Jørgensen
2019-11-09 0:01 ` [PATCH bpf-next v3 5/6] libbpf: Add bpf_get_link_xdp_info() function to get more XDP information Toke Høiland-Jørgensen
2019-11-09 0:51 ` Andrii Nakryiko [this message]
2019-11-09 11:20 ` Toke Høiland-Jørgensen
2019-11-09 19:10 ` Andrii Nakryiko
2019-11-09 20:18 ` Toke Høiland-Jørgensen
2019-11-09 0:01 ` [PATCH bpf-next v3 6/6] libbpf: Add getter for program size Toke Høiland-Jørgensen
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