libbpf: Add link-based API for tcx

Implement tcx BPF link support for libbpf.

The bpf_program__attach_fd() API has been refactored slightly in order to pass
bpf_link_create_opts pointer as input.

A new bpf_program__attach_tcx() 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@iogearbox.net>

tools/lib/bpf/bpf.c

@@ -717,9 +717,9 @@ int bpf_link_create(int prog_fd, int target_fd,
  const struct bpf_link_create_opts *opts)
 {
  const size_t attr_sz = offsetofend(union bpf_attr, link_create);
- __u32 target_btf_id, iter_info_len;
+ __u32 target_btf_id, iter_info_len, relative_id;
+ int fd, err, relative;
  union bpf_attr attr;
- int fd, err;
 
  if (!OPTS_VALID(opts, bpf_link_create_opts))
  return libbpf_err(-EINVAL);
@@ -781,6 +781,21 @@ int bpf_link_create(int prog_fd, int target_fd,
  if (!OPTS_ZEROED(opts, netfilter))
  return libbpf_err(-EINVAL);
  break;
+ case BPF_TCX_INGRESS:
+ case BPF_TCX_EGRESS:
+ relative = OPTS_GET(opts, tcx.relative_fd, 0);
+ relative_id = OPTS_GET(opts, tcx.relative_id, 0);
+ if (relative > 0 && relative_id)
+ return libbpf_err(-EINVAL);
+ if (relative_id) {
+ relative = relative_id;
+ attr.link_create.flags |= BPF_F_ID;
+ }
+ attr.link_create.tcx.relative_fd = relative;
+ attr.link_create.tcx.expected_revision = OPTS_GET(opts, tcx.expected_revision, 0);
+ if (!OPTS_ZEROED(opts, tcx))
+ return libbpf_err(-EINVAL);
+ break;
  default:
  if (!OPTS_ZEROED(opts, flags))
  return libbpf_err(-EINVAL);

tools/lib/bpf/bpf.h

@@ -401,6 +401,11 @@ struct bpf_link_create_opts {
  __s32 priority;
  __u32 flags;
  } netfilter;
+ struct {
+ __u32 relative_fd;
+ __u32 relative_id;
+ __u64 expected_revision;
+ } tcx;
  };
  size_t :0;
 };

tools/lib/bpf/libbpf.c

@@ -134,6 +134,7 @@ 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[] = {
@@ -11845,11 +11846,10 @@ 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(const struct bpf_program *prog,
+ int target_fd, const char *target_name,
+ const struct bpf_link_create_opts *opts)
 {
- 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;
@@ -11867,7 +11867,7 @@ 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);
@@ -11883,19 +11883,58 @@ bpf_program__attach_fd(const struct bpf_program *prog, int target_fd, int btf_id
 struct bpf_link *
 bpf_program__attach_cgroup(const struct bpf_program *prog, int cgroup_fd)
 {
- return bpf_program__attach_fd(prog, cgroup_fd, 0, "cgroup");
+ return bpf_program_attach_fd(prog, cgroup_fd, "cgroup", NULL);
 }
 
 struct bpf_link *
 bpf_program__attach_netns(const struct bpf_program *prog, int netns_fd)
 {
- return bpf_program__attach_fd(prog, netns_fd, 0, "netns");
+ return bpf_program_attach_fd(prog, netns_fd, "netns", NULL);
 }
 
 struct bpf_link *bpf_program__attach_xdp(const struct bpf_program *prog, int ifindex)
 {
  /* target_fd/target_ifindex use the same field in LINK_CREATE */
- return bpf_program__attach_fd(prog, ifindex, 0, "xdp");
+ return bpf_program_attach_fd(prog, ifindex, "xdp", NULL);
+}
+
+struct bpf_link *
+bpf_program__attach_tcx(const struct bpf_program *prog,
+ const struct bpf_tcx_opts *opts)
+{
+ LIBBPF_OPTS(bpf_link_create_opts, link_create_opts);
+ __u32 relative_id, flags;
+ int ifindex, relative_fd;
+
+ if (!OPTS_VALID(opts, bpf_tcx_opts))
+ return libbpf_err_ptr(-EINVAL);
+
+ relative_id = OPTS_GET(opts, relative_id, 0);
+ relative_fd = OPTS_GET(opts, relative_fd, 0);
+ flags = OPTS_GET(opts, flags, 0);
+ ifindex = OPTS_GET(opts, ifindex, 0);
+
+ /* validate we don't have unexpected combinations of non-zero fields */
+ if (!ifindex) {
+ pr_warn("prog '%s': target netdevice ifindex cannot be zero\n",
+ prog->name);
+ return libbpf_err_ptr(-EINVAL);
+ }
+ if (relative_fd > 0 && relative_id) {
+ pr_warn("prog '%s': relative_fd and relative_id cannot be set at the same time\n",
+ prog->name);
+ return libbpf_err_ptr(-EINVAL);
+ }
+ if (relative_id)
+ flags |= BPF_F_ID;
+
+ link_create_opts.tcx.expected_revision = OPTS_GET(opts, expected_revision, 0);
+ link_create_opts.tcx.relative_fd = relative_fd;
+ link_create_opts.tcx.relative_id = relative_id;
+ link_create_opts.flags = flags;
+
+ /* target_fd/target_ifindex use the same field in LINK_CREATE */
+ return bpf_program_attach_fd(prog, ifindex, "tc", &link_create_opts);
 }
 
 struct bpf_link *bpf_program__attach_freplace(const struct bpf_program *prog,
@@ -11917,11 +11956,16 @@ struct bpf_link *bpf_program__attach_freplace(const struct bpf_program *prog,
  }
 
  if (target_fd) {
+ LIBBPF_OPTS(bpf_link_create_opts, target_opts);
+
  btf_id = libbpf_find_prog_btf_id(attach_func_name, target_fd);
  if (btf_id < 0)
  return libbpf_err_ptr(btf_id);
 
- return bpf_program__attach_fd(prog, target_fd, btf_id, "freplace");
+ target_opts.target_btf_id = btf_id;
+
+ return bpf_program_attach_fd(prog, target_fd, "freplace",
+ &target_opts);
  } else {
  /* no target, so use raw_tracepoint_open for compatibility
  * with old kernels

tools/lib/bpf/libbpf.h

@@ -733,6 +733,22 @@ LIBBPF_API struct bpf_link *
 bpf_program__attach_netfilter(const struct bpf_program *prog,
  const struct bpf_netfilter_opts *opts);
 
+struct bpf_tcx_opts {
+ /* size of this struct, for forward/backward compatibility */
+ size_t sz;
+ int ifindex;
+ __u32 flags;
+ __u32 relative_fd;
+ __u32 relative_id;
+ __u64 expected_revision;
+ size_t :0;
+};
+#define bpf_tcx_opts__last_field expected_revision
+
+LIBBPF_API struct bpf_link *
+bpf_program__attach_tcx(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);

tools/lib/bpf/libbpf.map

@@ -397,4 +397,5 @@ LIBBPF_1.3.0 {
  bpf_obj_pin_opts;
  bpf_program__attach_netfilter;
  bpf_prog_detach_opts;
+ bpf_program__attach_tcx;
 } LIBBPF_1.2.0;