src/shared/bpf-link.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include "bpf-dlopen.h"
   4 #include "bpf-link.h"
   5 #include "serialize.h"
   6
   7 bool bpf_can_link_program(struct bpf_program *prog) {
   8         _cleanup_(bpf_link_freep) struct bpf_link *link = NULL;
   9
  10         assert(prog);
  11
  12         if (dlopen_bpf() < 0)
  13                 return false;
  14
  15         /* Pass invalid cgroup fd intentionally. */
  16         link = sym_bpf_program__attach_cgroup(prog, /*cgroup_fd=*/-1);
  17
  18         /* EBADF indicates that bpf_link is supported by kernel. */
  19         return sym_libbpf_get_error(link) == -EBADF;
  20 }
  21
  22 int bpf_serialize_link(FILE *f, FDSet *fds, const char *key, struct bpf_link *link) {
  23         assert(key);
  24
  25         if (!link)
  26                 return -ENOENT;
  27
  28         if (sym_libbpf_get_error(link) != 0)
  29                 return -EINVAL;
  30
  31         return serialize_fd(f, fds, key, sym_bpf_link__fd(link));
  32 }
  33
  34 struct bpf_link *bpf_link_free(struct bpf_link *link) {
  35         /* If libbpf wasn't dlopen()ed, sym_bpf_link__destroy might be unresolved (NULL), so let's not try to
  36          * call it if link is NULL. link might also be a non-null "error pointer", but such a value can only
  37          * originate from a call to libbpf, but that means that libbpf is available, and we can let
  38          * bpf_link__destroy() handle it. */
  39         if (link)
  40                 (void) sym_bpf_link__destroy(link);
  41
  42         return NULL;
  43 }