• Daniel Borkmann's avatar
    filter: bpf_asm: add minimal bpf asm tool · 3f356385
    Daniel Borkmann authored
    There are a couple of valid use cases for a minimal low-level bpf asm
    like tool, for example, using/linking to libpcap is not an option, the
    required BPF filters use Linux extensions that are not supported by
    libpcap's compiler, a filter might be more complex and not cleanly
    implementable with libpcap's compiler, particular filter codes should
    be optimized differently than libpcap's internal BPF compiler does,
    or for security audits of emitted BPF JIT code for prepared set of BPF
    instructions resp. BPF JIT compiler development in general.
    Then, in such cases writing such a filter in low-level syntax can be
    an good alternative, for example, xt_bpf and cls_bpf users might have
    requirements that could result in more complex filter code, or one that
    cannot be expressed with libpcap (e.g. different return codes in
    cls_bpf for flowids on various BPF code paths).
    Moreover, BPF JIT implementors may wish to manually write test cases
    in order to verify the resulting JIT image, and thus need low-level
    access to BPF code generation as well. Therefore, complete the available
    toolchain for BPF with this small bpf_asm helper tool for the tools/net/
    directory. These 3 complementary minimal helper tools round up and
    facilitate BPF development.
    Signed-off-by: default avatarDaniel Borkmann <dborkman@redhat.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>