• Quentin Monnet's avatar
    tools: bpftool: add probes for a network device · f9499fed
    Quentin Monnet authored
    bpftool gained support for probing the current system in order to see
    what program and map types, and what helpers are available on that
    system. This patch adds the possibility to pass an interface index to
    libbpf (and hence to the kernel) when trying to load the programs or to
    create the maps, in order to see what items a given network device can
    support.
    
    A new keyword "dev <ifname>" can be used as an alternative to "kernel"
    to indicate that the given device should be tested. If no target ("dev"
    or "kernel") is specified bpftool defaults to probing the kernel.
    
    Sample output:
    
        # bpftool -p feature probe dev lo
        {
            "syscall_config": {
                "have_bpf_syscall": true
            },
            "program_types": {
                "have_sched_cls_prog_type": false,
                "have_xdp_prog_type": false
            },
            ...
        }
    
    As the target is a network device, /proc/ parameters and kernel
    configuration are NOT dumped. Availability of the bpf() syscall is
    still probed, so we can return early if that syscall is not usable
    (since there is no point in attempting the remaining probes in this
    case).
    
    Among the program types, only the ones that can be offloaded are probed.
    All map types are probed, as there is no specific rule telling which one
    could or could not be supported by a device in the future. All helpers
    are probed (but only for offload-able program types).
    
    Caveat: as bpftool does not attempt to attach programs to the device at
    the moment, probes do not entirely reflect what the device accepts:
    typically, for Netronome's nfp, results will announce that TC cls
    offload is available even if support has been deactivated (with e.g.
    ethtool -K eth1 hw-tc-offload off).
    
    v2:
    - All helpers are probed, whereas previous version would only probe the
      ones compatible with an offload-able program type. This is because we
      do not keep a default compatible program type for each helper anymore.
    Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
    Reviewed-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
    Reviewed-by: default avatarStanislav Fomichev <sdf@google.com>
    Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
    f9499fed
bpftool-feature.rst 2.56 KB