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Map type BPF_MAP_TYPE_QUEUE

v4.20

The queue map type is a generic map type, resembling a FIFO (First-In First-Out) queue.

Usage

This map type has no keys, only values. The size and type of the values can be specified by the user to fit a large variety of use cases. The typical use-case for this map type is to keep track of a pool of elements such as available network ports when implementing NAT (network address translation).

As apposed to most map types, this map type uses a custom set of helpers to pop, peek and push elements, noted in the helper functions section below.

Attributes

While the value_size is essentially unrestricted, the key_size must always be 0 since this map type has no keys.

Syscall commands

The following syscall commands work with this map type:

Note

The BPF_MAP_LOOKUP_ELEM syscall command acts as peek, BPF_MAP_LOOKUP_AND_DELETE_ELEM as pop, and BPF_MAP_UPDATE_ELEM as push.

Helper functions

Flags

BPF_F_NUMA_NODE

v4.14

When set, the numa_node attribute is respected during map creation.

BPF_F_RDONLY

v4.15

Setting this flag will make it so the map can only be read via the syscall interface, but not written to.

For details please check the generic description.

BPF_F_WRONLY

v4.15

Setting this flag will make it so the map can only be written to via the syscall interface, but not read from.

BPF_F_RDONLY_PROG

v5.2

Setting this flag will make it so the map can only be read via helper functions, but not written to.

For details please check the generic description.

BPF_F_WRONLY_PROG

v5.2

Setting this flag will make it so the map can only be written to via helper functions, but not read from.

For details please check the generic description.