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bc84e959e5
Move the general maps documentation into the maps.rst file from the overall networking filter documentation and add a link instead. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-5-hch@lst.de
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=========
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eBPF maps
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=========
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'maps' is a generic storage of different types for sharing data between kernel
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and userspace.
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The maps are accessed from user space via BPF syscall, which has commands:
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- create a map with given type and attributes
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``map_fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)``
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using attr->map_type, attr->key_size, attr->value_size, attr->max_entries
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returns process-local file descriptor or negative error
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- lookup key in a given map
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``err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)``
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using attr->map_fd, attr->key, attr->value
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returns zero and stores found elem into value or negative error
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- create or update key/value pair in a given map
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``err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)``
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using attr->map_fd, attr->key, attr->value
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returns zero or negative error
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- find and delete element by key in a given map
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``err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)``
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using attr->map_fd, attr->key
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- to delete map: close(fd)
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Exiting process will delete maps automatically
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userspace programs use this syscall to create/access maps that eBPF programs
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are concurrently updating.
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maps can have different types: hash, array, bloom filter, radix-tree, etc.
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The map is defined by:
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- type
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- max number of elements
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- key size in bytes
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- value size in bytes
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Map Types
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=========
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.. toctree::
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:maxdepth: 1
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:glob:
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map_* |