52 lines
1.4 KiB
ReStructuredText
52 lines
1.4 KiB
ReStructuredText
|
|
||
|
|
=========
|
||
|
|
eBPF maps
|
||
|
|
=========
|
||
|
|
|
||
|
|
'maps' is a generic storage of different types for sharing data between kernel
|
||
|
|
and userspace.
|
||
|
|
|
||
|
|
The maps are accessed from user space via BPF syscall, which has commands:
|
||
|
|
|
||
|
|
- create a map with given type and attributes
|
||
|
|
``map_fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)``
|
||
|
|
using attr->map_type, attr->key_size, attr->value_size, attr->max_entries
|
||
|
|
returns process-local file descriptor or negative error
|
||
|
|
|
||
|
|
- lookup key in a given map
|
||
|
|
``err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)``
|
||
|
|
using attr->map_fd, attr->key, attr->value
|
||
|
|
returns zero and stores found elem into value or negative error
|
||
|
|
|
||
|
|
- create or update key/value pair in a given map
|
||
|
|
``err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)``
|
||
|
|
using attr->map_fd, attr->key, attr->value
|
||
|
|
returns zero or negative error
|
||
|
|
|
||
|
|
- find and delete element by key in a given map
|
||
|
|
``err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)``
|
||
|
|
using attr->map_fd, attr->key
|
||
|
|
|
||
|
|
- to delete map: close(fd)
|
||
|
|
Exiting process will delete maps automatically
|
||
|
|
|
||
|
|
userspace programs use this syscall to create/access maps that eBPF programs
|
||
|
|
are concurrently updating.
|
||
|
|
|
||
|
|
maps can have different types: hash, array, bloom filter, radix-tree, etc.
|
||
|
|
|
||
|
|
The map is defined by:
|
||
|
|
|
||
|
|
- type
|
||
|
|
- max number of elements
|
||
|
|
- key size in bytes
|
||
|
|
- value size in bytes
|
||
|
|
|
||
|
|
Map Types
|
||
|
|
=========
|
||
|
|
|
||
|
|
.. toctree::
|
||
|
|
:maxdepth: 1
|
||
|
|
:glob:
|
||
|
|
|
||
|
|
map_*
|