BPF Syscall BPF_MAP_GET_FD_BY_ID command
This syscall command is used to get a file descriptor to an already existing map via its unique identifier.
Return type
This command will return the file descriptor of the map (positive integer) or an error number (negative integer) if something went wrong.
Usage
This command is used to get a file descriptor to map so that you might use it in other syscall commands or map values. This mechanism is usually used by inspection tools in combination with the BPF_OBJ_GET_INFO_BY_FD.
Attributes
map_id
This field holds the unique identifier of the map for which a file descriptor should be opened.