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Andrii Nakryiko says: ==================== Following cgroup and netns examples, implement bpf_link support for XDP. The semantics is described in patch #2. Program and link attachments are mutually exclusive, in the sense that neither link can replace attached program nor program can replace attached link. Link can't replace attached link as well, as is the case for any other bpf_link implementation. Patch #1 refactors existing BPF program-based attachment API and centralizes high-level query/attach decisions in generic kernel code, while drivers are kept simple and are instructed with low-level decisions about attaching and detaching specific bpf_prog. This also makes QUERY command unnecessary, and patch #8 removes support for it from all kernel drivers. If that's a bad idea, we can drop that patch altogether. With refactoring in patch #1, adding bpf_xdp_link is completely transparent to drivers, they are still functioning at the level of "effective" bpf_prog, that should be called in XDP data path. Corresponding libbpf support for BPF XDP link is added in patch #5. v3->v4: - fix a compilation warning in one of drivers (Jakub); v2->v3: - fix build when CONFIG_BPF_SYSCALL=n (kernel test robot); v1->v2: - fix prog refcounting bug (David); - split dev_change_xdp_fd() changes into 2 patches (David); - add extack messages to all user-induced errors (David). ==================== Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.