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BPF_MAP_GET_NEXT_KEY.md

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Syscall command 'BPF_MAP_GET_NEXT_KEY'
This page documents the 'BPF_MAP_GET_NEXT_KEY' eBPF syscall command, including its defintion, usage, program types that can use it, and examples.

BPF Syscall BPF_MAP_GET_NEXT_KEY command

:octicons-tag-24: v3.18

The BPF_MAP_GET_NEXT_KEY command is used to iterate over the keys of a map.

Behavior and return value

If the given key isn't found within the map, 0 is returned and the value pointed to by next_key will be set to the first key in the map.

If the given key is found withing the map, 0 is returned and the value pointed to by next_key will be set to the key after the current key.

If the given key is found within the map and it is the last key, an error number of -ENOENT will be returned.

Attributes

map_fd

This attribute specifies the file descriptor of the map in which you wish to lookup a value.

key

This attribute holds a pointer to the current key, a null pointer can be passed in to indicate you have no current value. The size of the key is derived from the key_size attribute of the map you specified with map_fd.

The memory indicated by this field will not be modified.

next_key

This attribute holds a pointer to a memory location where the kernel will write the next key to. The size of the key is derived from the key_size attribute of the map you specified with map_fd.