bpftool-map man page

bpftool-map — tool for inspection and simple manipulation of eBPF maps

Synopsis

bpftool [Options] map COMMAND

Options := { { -j | --json } [{ -p | --pretty }] | { -f | --bpffs } }

COMMANDS := { show | list | create | dump | update | lookup | getnext | delete | pin | help }

Map Commands

bpftool map { show | list }   [MAP]
bpftool map create     FILE type TYPE key KEY_SIZE value VALUE_SIZE 
entries MAX_ENTRIES name NAME [flags FLAGS] [dev NAME]
bpftool map dump       MAP
bpftool map update     MAP [key DATA] [value VALUE] [UPDATE_FLAGS]
bpftool map lookup     MAP [key DATA]
bpftool map getnext    MAP [key DATA]
bpftool map delete     MAP  key DATA
bpftool map pin        MAP  FILE
bpftool map event_pipe MAP [cpu N index M]
bpftool map peek       MAP
bpftool map push       MAP value VALUE
bpftool map pop        MAP
bpftool map enqueue    MAP value VALUE
bpftool map dequeue    MAP
bpftool map help

MAP := { id MAP_ID | pinned FILE }
DATA := { [hex] BYTES }
PROG := { id PROG_ID | pinned FILE | tag PROG_TAG }
VALUE := { DATA | MAP | PROG }
UPDATE_FLAGS := { any | exist | noexist }
TYPE := { hash | array | prog_array | perf_event_array | percpu_hash
| percpu_array | stack_trace | cgroup_array | lru_hash
| lru_percpu_hash | lpm_trie | array_of_maps | hash_of_maps
| devmap | sockmap | cpumap | xskmap | sockhash
| cgroup_storage | reuseport_sockarray | percpu_cgroup_storage
| queue | stack }

Description

bpftool map { show | list } [MAP]

Show information about loaded maps.  If MAP is specified show information only about given map, otherwise list all maps currently loaded on the system.

Output will start with map ID followed by map type and zero or more named attributes (depending on kernel version).

bpftool map create FILE type TYPE key KEY_SIZE value VALUE_SIZE entries MAX_ENTRIES name NAME [flags FLAGS] [dev NAME]

Create a new map with given parameters and pin it to bpffs as FILE.

bpftool map dump MAP

Dump all entries in a given MAP.

bpftool map update MAP [key DATA] [value VALUE] [UPDATE_FLAGS]

Update map entry for a given KEY.

UPDATE_FLAGS can be one of: any update existing entry or add if doesn't exit; exist update only if entry already exists; noexist update only if entry doesn't exist.

If the hex keyword is provided in front of the bytes sequence, the bytes are parsed as hexadeximal values, even if no "0x" prefix is added. If the keyword is not provided, then the bytes are parsed as decimal values, unless a "0x" prefix (for hexadecimal) or a "0" prefix (for octal) is provided.

bpftool map lookup MAP [key DATA]

Lookup key in the map.

bpftool map getnext MAP [key DATA]

Get next key.  If key is not specified, get first key.

bpftool map delete MAP key DATA

Remove entry from the map.

bpftool map pin MAP FILE

Pin map MAP as FILE.

Note: FILE must be located in bpffs mount. It must not contain a dot character ('.'), which is reserved for future extensions of bpffs.

bpftool map event_pipe MAP [cpu N index M]

Read events from a BPF_MAP_TYPE_PERF_EVENT_ARRAY map.

Install perf rings into a perf event array map and dump output of any bpf_perf_event_output() call in the kernel. By default read the number of CPUs on the system and install perf ring for each CPU in the corresponding index in the array.

If cpu and index are specified, install perf ring for given cpu at index in the array (single ring).

Note that installing a perf ring into an array will silently replace any existing ring.  Any other application will stop receiving events if it installed its rings earlier.

bpftool map peek MAP

Peek next value in the queue or stack.

bpftool map push MAP value VALUE

Push value onto the stack.

bpftool map pop MAP

Pop and print value from the stack.

bpftool map enqueue MAP value VALUE

Enqueue value into the queue.

bpftool map dequeue MAP

Dequeue and print value from the queue.

bpftool map help

Print short help message.

Options

-h, --help

Print short generic help message (similar to bpftool help).

-V, --version

Print version number (similar to bpftool version).

-j, --json

Generate JSON output. For commands that cannot produce JSON, this option has no effect.

-p, --pretty

Generate human-readable JSON output. Implies -j.

-f, --bpffs

Show file names of pinned maps.

-n, --nomount

Do not automatically attempt to mount any virtual file system (such as tracefs or BPF virtual file system) when necessary.

-d, --debug

Print all logs available from libbpf, including debug-level information.

Examples

# bpftool map show

10: hash  name some_map  flags 0x0
      key 4B  value 8B  max_entries 2048  memlock 167936B

The following three commands are equivalent:

# bpftool map update id 10 key hex   20   c4   b7   00 value hex   0f   ff   ff   ab   01   02   03   4c
# bpftool map update id 10 key     0x20 0xc4 0xb7 0x00 value     0x0f 0xff 0xff 0xab 0x01 0x02 0x03 0x4c
# bpftool map update id 10 key       32  196  183    0 value       15  255  255  171    1    2    3   76

# bpftool map lookup id 10 key 0 1 2 3

key: 00 01 02 03 value: 00 01 02 03 04 05 06 07

# bpftool map dump id 10

key: 00 01 02 03  value: 00 01 02 03 04 05 06 07
key: 0d 00 07 00  value: 02 00 00 00 01 02 03 04
Found 2 elements

# bpftool map getnext id 10 key 0 1 2 3

key:
00 01 02 03
next key:
0d 00 07 00
# mount -t bpf none /sys/fs/bpf/
# bpftool map pin id 10 /sys/fs/bpf/map
# bpftool map del pinned /sys/fs/bpf/map key 13 00 07 00

Note that map update can also be used in order to change the program references hold by a program array map. This can be used, for example, to change the programs used for tail-call jumps at runtime, without having to reload the entry-point program. Below is an example for this use case: we load a program defining a prog array map, and with a main function that contains a tail call to other programs that can be used either to "process" packets or to "debug" processing. Note that the prog array map MUST be pinned into the BPF virtual file system for the map update to work successfully, as kernel flushes prog array maps when they have no more references from user space (and the update would be lost as soon as bpftool exits).

# bpftool prog loadall tail_calls.o /sys/fs/bpf/foo type xdp
# bpftool prog --bpffs
545: xdp  name main_func  tag 674b4b5597193dc3  gpl
        loaded_at 2018-12-12T15:02:58+0000  uid 0
        xlated 240B  jited 257B  memlock 4096B  map_ids 294
        pinned /sys/fs/bpf/foo/xdp
546: xdp  name bpf_func_process  tag e369a529024751fc  gpl
        loaded_at 2018-12-12T15:02:58+0000  uid 0
        xlated 200B  jited 164B  memlock 4096B
        pinned /sys/fs/bpf/foo/process
547: xdp  name bpf_func_debug  tag 0b597868bc7f0976  gpl
        loaded_at 2018-12-12T15:02:58+0000  uid 0
        xlated 200B  jited 164B  memlock 4096B
        pinned /sys/fs/bpf/foo/debug

# bpftool map

294: prog_array  name jmp_table  flags 0x0
        key 4B  value 4B  max_entries 1  memlock 4096B
        owner_prog_type xdp  owner jited
# bpftool map pin id 294 /sys/fs/bpf/bar
# bpftool map dump pinned /sys/fs/bpf/bar
Found 0 elements
# bpftool map update pinned /sys/fs/bpf/bar key 0 0 0 0 value pinned /sys/fs/bpf/foo/debug
# bpftool map dump pinned /sys/fs/bpf/bar
key: 00 00 00 00  value: 22 02 00 00
Found 1 element

See Also

Referenced By

bpftool(8), bpftool-btf(8), bpftool-cgroup(8), bpftool-feature(8), bpftool-net(8), bpftool-perf(8), bpftool-prog(8).