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Message-ID: <CAEf4Bzaey8c86vLh8sMfvU5KepbYOuej0cKXb88ANp8kZnpCQQ@mail.gmail.com>
Date: Thu, 8 Jun 2023 14:45:48 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Daniel Borkmann <daniel@...earbox.net>
Cc: ast@...nel.org, andrii@...nel.org, martin.lau@...ux.dev,
razor@...ckwall.org, sdf@...gle.com, john.fastabend@...il.com,
kuba@...nel.org, dxu@...uu.xyz, joe@...ium.io, toke@...nel.org,
davem@...emloft.net, bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 4/7] libbpf: Add link-based API for tcx
On Wed, Jun 7, 2023 at 12:26 PM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> Implement tcx BPF link support for libbpf.
>
> The bpf_program__attach_fd_opts() API has been refactored slightly in order to
> pass bpf_link_create_opts pointer as input.
>
> A new bpf_program__attach_tcx_opts() has been added on top of this which allows
> for passing all relevant data via extensible struct bpf_tcx_opts.
>
> The program sections tcx/ingress and tcx/egress correspond to the hook locations
> for tc ingress and egress, respectively.
>
> For concrete usage examples, see the extensive selftests that have been
> developed as part of this series.
>
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
> ---
> tools/lib/bpf/bpf.c | 5 +++++
> tools/lib/bpf/bpf.h | 7 +++++++
> tools/lib/bpf/libbpf.c | 44 +++++++++++++++++++++++++++++++++++-----
> tools/lib/bpf/libbpf.h | 17 ++++++++++++++++
> tools/lib/bpf/libbpf.map | 1 +
> 5 files changed, 69 insertions(+), 5 deletions(-)
>
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index a3d1b7ebe224..c340d3cbc6bd 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -746,6 +746,11 @@ int bpf_link_create(int prog_fd, int target_fd,
> if (!OPTS_ZEROED(opts, tracing))
> return libbpf_err(-EINVAL);
> break;
> + case BPF_TCX_INGRESS:
> + case BPF_TCX_EGRESS:
> + attr.link_create.tcx.relative_fd = OPTS_GET(opts, tcx.relative_fd, 0);
> + attr.link_create.tcx.expected_revision = OPTS_GET(opts, tcx.expected_revision, 0);
can you also add an OPTS_ZEROED check like for other types of links?
> + break;
> default:
> if (!OPTS_ZEROED(opts, flags))
> return libbpf_err(-EINVAL);
> diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
> index 480c584a6f7f..12591516dca0 100644
> --- a/tools/lib/bpf/bpf.h
> +++ b/tools/lib/bpf/bpf.h
> @@ -370,6 +370,13 @@ struct bpf_link_create_opts {
> struct {
> __u64 cookie;
> } tracing;
> + struct {
> + union {
> + __u32 relative_fd;
> + __u32 relative_id;
> + };
same comment about union, let's not add it and have two separate fields
> + __u32 expected_revision;
> + } tcx;
> };
> size_t :0;
> };
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index b89127471c6a..d7b6ff49f02e 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -133,6 +133,7 @@ static const char * const link_type_name[] = {
> [BPF_LINK_TYPE_KPROBE_MULTI] = "kprobe_multi",
> [BPF_LINK_TYPE_STRUCT_OPS] = "struct_ops",
> [BPF_LINK_TYPE_NETFILTER] = "netfilter",
> + [BPF_LINK_TYPE_TCX] = "tcx",
> };
>
> static const char * const map_type_name[] = {
> @@ -11685,11 +11686,10 @@ static int attach_lsm(const struct bpf_program *prog, long cookie, struct bpf_li
> }
>
> static struct bpf_link *
> -bpf_program__attach_fd(const struct bpf_program *prog, int target_fd, int btf_id,
> - const char *target_name)
> +bpf_program__attach_fd_opts(const struct bpf_program *prog,
> + const struct bpf_link_create_opts *opts,
> + int target_fd, const char *target_name)
nit: please keep opts as the last argument
> {
> - DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts,
> - .target_btf_id = btf_id);
> enum bpf_attach_type attach_type;
> char errmsg[STRERR_BUFSIZE];
> struct bpf_link *link;
> @@ -11707,7 +11707,7 @@ bpf_program__attach_fd(const struct bpf_program *prog, int target_fd, int btf_id
> link->detach = &bpf_link__detach_fd;
>
> attach_type = bpf_program__expected_attach_type(prog);
> - link_fd = bpf_link_create(prog_fd, target_fd, attach_type, &opts);
> + link_fd = bpf_link_create(prog_fd, target_fd, attach_type, opts);
> if (link_fd < 0) {
> link_fd = -errno;
> free(link);
> @@ -11720,6 +11720,17 @@ bpf_program__attach_fd(const struct bpf_program *prog, int target_fd, int btf_id
> return link;
> }
>
> +static struct bpf_link *
> +bpf_program__attach_fd(const struct bpf_program *prog, int target_fd, int btf_id,
> + const char *target_name)
> +{
> + LIBBPF_OPTS(bpf_link_create_opts, opts,
> + .target_btf_id = btf_id,
> + );
> +
> + return bpf_program__attach_fd_opts(prog, &opts, target_fd, target_name);
it seems like the only user of btf_id is bpf_program__attach_freplace,
so I'd just inline this there, and for all other 4 cases let's just
pass NULL as options?
That means we don't really need bpf_program__attach_fd_opts() and can
just add opts to bpf_program__attach_fd(). We'll have shorter name.
BTW, given it's not exposed API, let's drop double underscore and call
it just bpf_program_attach_fd()?
> +}
> +
> struct bpf_link *
> bpf_program__attach_cgroup(const struct bpf_program *prog, int cgroup_fd)
> {
> @@ -11738,6 +11749,29 @@ struct bpf_link *bpf_program__attach_xdp(const struct bpf_program *prog, int ifi
> return bpf_program__attach_fd(prog, ifindex, 0, "xdp");
> }
>
> +struct bpf_link *
> +bpf_program__attach_tcx_opts(const struct bpf_program *prog,
> + const struct bpf_tcx_opts *opts)
we don't have non-opts variant, so let's keep the name short (like we
did with bpf_program__attach_netlink): bpf_program__attach_tcx().
> +{
> + LIBBPF_OPTS(bpf_link_create_opts, link_create_opts);
> + int ifindex = OPTS_GET(opts, ifindex, 0);
let's not do OPTS_GET before we checked OPTS_VALID
> +
> + if (!OPTS_VALID(opts, bpf_tcx_opts))
> + return libbpf_err_ptr(-EINVAL);
> + if (!ifindex) {
> + pr_warn("prog '%s': target netdevice ifindex cannot be zero\n",
> + prog->name);
> + return libbpf_err_ptr(-EINVAL);
> + }
> +
> + link_create_opts.tcx.expected_revision = OPTS_GET(opts, expected_revision, 0);
> + link_create_opts.tcx.relative_fd = OPTS_GET(opts, relative_fd, 0);
> + link_create_opts.flags = OPTS_GET(opts, flags, 0);
> +
> + /* target_fd/target_ifindex use the same field in LINK_CREATE */
> + return bpf_program__attach_fd_opts(prog, &link_create_opts, ifindex, "tc");
> +}
> +
> struct bpf_link *bpf_program__attach_freplace(const struct bpf_program *prog,
> int target_fd,
> const char *attach_func_name)
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 754da73c643b..8ffba0f67c60 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -718,6 +718,23 @@ LIBBPF_API struct bpf_link *
> bpf_program__attach_freplace(const struct bpf_program *prog,
> int target_fd, const char *attach_func_name);
>
> +struct bpf_tcx_opts {
> + /* size of this struct, for forward/backward compatibility */
> + size_t sz;
> + int ifindex;
> + __u32 flags;
> + union {
> + __u32 relative_fd;
> + __u32 relative_id;
> + };
same thing about not using unions here :)
> + __u32 expected_revision;
and let's add `size_t :0;` to prevent compiler from leaving garbage
values in a padding at the end of the struct (once you drop union
there will be padding)
> +};
> +#define bpf_tcx_opts__last_field expected_revision
> +
> +LIBBPF_API struct bpf_link *
> +bpf_program__attach_tcx_opts(const struct bpf_program *prog,
> + const struct bpf_tcx_opts *opts);
> +
> struct bpf_map;
>
> LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map);
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index a29b90e9713c..f66b714512c2 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -396,4 +396,5 @@ LIBBPF_1.3.0 {
> global:
> bpf_obj_pin_opts;
> bpf_prog_detach_opts;
> + bpf_program__attach_tcx_opts;
> } LIBBPF_1.2.0;
> --
> 2.34.1
>
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