1
2 ========
3 BPF maps
4 ========
5
6 BPF 'maps' provide generic storage of differen
7 kernel and user space. There are several stora
8 hash, array, bloom filter and radix-tree. Seve
9 support specific BPF helpers that perform acti
10 maps are accessed from BPF programs via BPF he
11 `man-pages`_ for `bpf-helpers(7)`_.
12
13 BPF maps are accessed from user space via the
14 commands to create maps, lookup elements, upda
15 More details of the BPF syscall are available
16 `man-pages`_ for `bpf(2)`_.
17
18 Map Types
19 =========
20
21 .. toctree::
22 :maxdepth: 1
23 :glob:
24
25 map_*
26
27 Usage Notes
28 ===========
29
30 .. c:function::
31 int bpf(int command, union bpf_attr *attr,
32
33 Use the ``bpf()`` system call to perform the o
34 ``command``. The operation takes parameters pr
35 argument is the size of the ``union bpf_attr``
36
37 **BPF_MAP_CREATE**
38
39 Create a map with the desired type and attribu
40
41 .. code-block:: c
42
43 int fd;
44 union bpf_attr attr = {
45 .map_type = BPF_MAP_TYPE_ARRAY; /
46 .key_size = sizeof(__u32); /
47 .value_size = sizeof(__u32); /
48 .max_entries = 256; /
49 .map_flags = BPF_F_MMAPABLE;
50 .map_name = "example_array";
51 };
52
53 fd = bpf(BPF_MAP_CREATE, &attr, sizeof(att
54
55 Returns a process-local file descriptor on suc
56 failure. The map can be deleted by calling ``c
57 file descriptors will be deleted automatically
58
59 .. note:: Valid characters for ``map_name`` ar
60 ``'_'`` and ``'.'``.
61
62 **BPF_MAP_LOOKUP_ELEM**
63
64 Lookup key in a given map using ``attr->map_fd
65 ``attr->value``. Returns zero and stores found
66 success, or negative error on failure.
67
68 **BPF_MAP_UPDATE_ELEM**
69
70 Create or update key/value pair in a given map
71 ``attr->value``. Returns zero on success or ne
72
73 **BPF_MAP_DELETE_ELEM**
74
75 Find and delete element by key in a given map
76 ``attr->key``. Returns zero on success or nega
77
78 .. Links:
79 .. _man-pages: https://www.kernel.org/doc/man-
80 .. _bpf(2): https://man7.org/linux/man-pages/m
81 .. _bpf-helpers(7): https://man7.org/linux/man
82 .. _ebpf-syscall: https://docs.kernel.org/user
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