focal (8) bpftool-link.8.gz

NAME

       bpftool-link - tool for inspection and simple manipulation of eBPF links

SYNOPSIS

          bpftool [OPTIONS] link COMMAND

          OPTIONS  :=  {  {  -j  |  --json  } [{ -p | --pretty }] | { -d | --debug } | { -f | --bpffs } | { -n |
          --nomount } }

          COMMANDS := { show | list | pin | help }

LINK COMMANDS

       bpftool link { show | list } [LINK]
       bpftool link pin LINK FILE
       bpftool link detach LINK
       bpftool link help

       LINK := { id LINK_ID | pinned FILE }

DESCRIPTION

          bpftool link { show | list } [LINK]
                 Show information about active links. If LINK is specified show  information  only  about  given
                 link, otherwise list all links currently active on the system.

                 Output will start with link ID followed by link type and zero or more named attributes, some of
                 which depend on type of link.

                 Since Linux 5.8 bpftool is able to discover information about processes  that  hold  open  file
                 descriptors  (FDs)  against  BPF  links.  On  such kernels bpftool will automatically emit this
                 information as well.

          bpftool link pin LINK FILE
                 Pin link LINK as FILE.

                 Note: FILE must be located in bpffs mount. It must not contain a dot character ('.'), which  is
                 reserved for future extensions of bpffs.

          bpftool link detach LINK
                 Force-detach  link LINK. BPF link and its underlying BPF program will stay valid, but they will
                 be detached from the respective BPF hook and BPF link will  transition  into  a  defunct  state
                 until last open file descriptor for that link is closed.

          bpftool link help
                 Print short help message.

OPTIONS

          -h, --help
                 Print short help message (similar to bpftool help).

          -V, --version
                 Print  version  number  (similar  to bpftool version), and optional features that were included
                 when bpftool was compiled. Optional features include linking  against  libbfd  to  provide  the
                 disassembler  for  JIT-ted  programs (bpftool prog dump jited) and usage of BPF skeletons (some
                 features like bpftool prog profile or showing pids associated to BPF objects may rely on it).

          -j, --json
                 Generate JSON output. For commands that cannot produce JSON, this option has no effect.

          -p, --pretty
                 Generate human-readable JSON output. Implies -j.

          -d, --debug
                 Print all logs available, even debug-level information. This includes logs from libbpf as  well
                 as from the verifier, when attempting to load programs.

          -f, --bpffs
                 When showing BPF links, show file names of pinned links.

          -n, --nomount
                 Do  not  automatically attempt to mount any virtual file system (such as tracefs or BPF virtual
                 file system) when necessary.

EXAMPLES

       # bpftool link show

          10: cgroup  prog 25
                  cgroup_id 614  attach_type egress
                  pids test_progs(223)

       # bpftool --json --pretty link show

          [{
                  "type": "cgroup",
                  "prog_id": 25,
                  "cgroup_id": 614,
                  "attach_type": "egress",
                  "pids": [{
                          "pid": 223,
                          "comm": "test_progs"
                      }
                  ]
              }
          ]

       # bpftool link pin id 10 /sys/fs/bpf/link
       # ls -l /sys/fs/bpf/

          -rw------- 1 root root 0 Apr 23 21:39 link

SEE ALSO

          bpf(2),   bpf-helpers(7),   bpftool(8),   bpftool-btf(8),    bpftool-cgroup(8),    bpftool-feature(8),
          bpftool-gen(8),  bpftool-iter(8),  bpftool-map(8),  bpftool-net(8),  bpftool-perf(8), bpftool-prog(8),
          bpftool-struct_ops(8)

                                                                                                 BPFTOOL-LINK(8)