[PATCH bpf-next v3 7/8] bpf: add sockopt documentation
From: Stanislav Fomichev <hidden>
Date: 2019-06-07 16:29:41
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), documentation, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Jonathan Corbet, Linus Torvalds
Provide user documentation about sockopt prog type and cgroup hooks. v2: * use return code 2 for kernel bypass Signed-off-by: Stanislav Fomichev <redacted> --- Documentation/bpf/index.rst | 1 + Documentation/bpf/prog_cgroup_sockopt.rst | 39 +++++++++++++++++++++++ 2 files changed, 40 insertions(+) create mode 100644 Documentation/bpf/prog_cgroup_sockopt.rst
diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst
index d3fe4cac0c90..801a6ed3f2e5 100644
--- a/Documentation/bpf/index.rst
+++ b/Documentation/bpf/index.rst@@ -42,6 +42,7 @@ Program types .. toctree:: :maxdepth: 1 + prog_cgroup_sockopt prog_cgroup_sysctl prog_flow_dissector
diff --git a/Documentation/bpf/prog_cgroup_sockopt.rst b/Documentation/bpf/prog_cgroup_sockopt.rst
new file mode 100644
index 000000000000..b117451ab571
--- /dev/null
+++ b/Documentation/bpf/prog_cgroup_sockopt.rst@@ -0,0 +1,39 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================== +BPF_PROG_TYPE_SOCKOPT +===================== + +``BPF_PROG_TYPE_SOCKOPT`` program type can be attached to two cgroup hooks: + +* ``BPF_CGROUP_GETSOCKOPT`` - called every time process executes ``getsockopt`` + system call. +* ``BPF_CGROUP_SETSOCKOPT`` - called every time process executes ``setsockopt`` + system call. + +The context (``struct bpf_sockopt``) has associated socket (``sk``) and +all input arguments: ``level``, ``optname``, ``optval`` and ``optlen``. + +BPF_CGROUP_SETSOCKOPT +===================== + +``BPF_CGROUP_SETSOCKOPT`` has a read-only context and this hook has +access to cgroup and socket local storage. + +BPF_CGROUP_GETSOCKOPT +===================== + +``BPF_CGROUP_GETSOCKOPT`` has to fill in ``optval`` and adjust +``optlen`` accordingly. Input ``optlen`` contains the maximum length +of data that can be returned to the userspace. In other words, BPF +program can't increase ``optlen``, it can only decrease it. + +Return Type +=========== + +* ``0`` - reject the syscall, ``EPERM`` will be returned to the userspace. +* ``1`` - success: after returning from the BPF hook, kernel will also + handle this socket option. +* ``2`` - success: after returning from the BPF hook, kernel will _not_ + handle this socket option; control will be returned to the userspace + instead.
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2.22.0.rc1.311.g5d7573a151-goog