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bpftool-iter - tool to create BPF iterators


bpftool [OPTIONS] iter COMMAND

COMMANDS := { pin | help }


bpftool iter pin OBJ PATH [map MAP]
bpftool iter help
OBJ := /a/file/of/bpf_iter_target.o
MAP := { id MAP_ID | pinned FILE }


A bpf iterator combines a kernel iterating of particular kernel data (e.g., tasks, bpf_maps, etc.) and a bpf program called for each kernel data object (e.g., one task, one bpf_map, etc.). User space can read kernel iterator output through read() syscall.

The pin command creates a bpf iterator from OBJ, and pin it to PATH. The PATH should be located in bpffs mount. It must not contain a dot character ('.'), which is reserved for future extensions of bpffs.

Map element bpf iterator requires an additional parameter MAP so bpf program can iterate over map elements for that map. User can have a bpf program in kernel to run with each map element, do checking, filtering, aggregation, etc. without copying data to user space.

User can then cat PATH to see the bpf iterator output.

Print short help message.


Print short help message (similar to bpftool help).
Print version number (similar to bpftool version), and optional features that were included when bpftool was compiled. Optional features include linking against libbfd to provide the disassembler for JIT-ted programs (bpftool prog dump jited) and usage of BPF skeletons (some features like bpftool prog profile or showing pids associated to BPF objects may rely on it).
Generate JSON output. For commands that cannot produce JSON, this option has no effect.
Generate human-readable JSON output. Implies -j.
Print all logs available, even debug-level information. This includes logs from libbpf as well as from the verifier, when attempting to load programs.


# bpftool iter pin bpf_iter_netlink.o /sys/fs/bpf/my_netlink

Create a file-based bpf iterator from bpf_iter_netlink.o and pin it
to /sys/fs/bpf/my_netlink

# bpftool iter pin bpf_iter_hashmap.o /sys/fs/bpf/my_hashmap map id 20

Create a file-based bpf iterator from bpf_iter_hashmap.o and map with
id 20, and pin it to /sys/fs/bpf/my_hashmap