Fork of alistair23 Linux kernel for reMarkable from https://github.com/alistair23/linux
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A later patch will introduce a BPF_MAP_TYPE_REUSEPORT_ARRAY which allows a SO_REUSEPORT sk to be added to a bpf map. When a sk is removed from reuse->socks[], it also needs to be removed from the bpf map. Also, when adding a sk to a bpf map, the bpf map needs to ensure it is indeed in a reuse->socks[]. Hence, reuseport_lock is needed by the bpf map to ensure its map_update_elem() and map_delete_elem() operations are in-sync with the reuse->socks[]. The BPF_MAP_TYPE_REUSEPORT_ARRAY map will only acquire the reuseport_lock after ensuring the adding sk is already in a reuseport group (i.e. reuse->socks[]). The map_lookup_elem() will be lockless. This patch also adds an ID to sock_reuseport. A later patch will introduce BPF_PROG_TYPE_SK_REUSEPORT which allows a bpf prog to select a sk from a bpf map. It is inflexible to statically enforce a bpf map can only contain the sk belonging to a particular reuse->socks[] (i.e. same IP:PORT) during the bpf verification time. For example, think about the the map-in-map situation where the inner map can be dynamically changed in runtime and the outer map may have inner maps belonging to different reuseport groups. Hence, when the bpf prog (in the new BPF_PROG_TYPE_SK_REUSEPORT type) selects a sk, this selected sk has to be checked to ensure it belongs to the requesting reuseport group (i.e. the group serving that IP:PORT). The "sk->sk_reuseport_cb" pointer cannot be used for this checking purpose because the pointer value will change after reuseport_grow(). Instead of saving all checking conditions like the ones preced calling "reuseport_add_sock()" and compare them everytime a bpf_prog is run, a 32bits ID is introduced to survive the reuseport_grow(). The ID is only acquired if any of the reuse->socks[] is added to the newly introduced "BPF_MAP_TYPE_REUSEPORT_ARRAY" map. If "BPF_MAP_TYPE_REUSEPORT_ARRAY" is not used, the changes in this patch is a no-op. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> |
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| README | ||
README
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.