BPF Syscall BPF_MAP_GET_NEXT_KEY command
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.