GENETLINK(4) FreeBSD Kernel Interfaces Manual GENETLINK(4)
NAME
genetlink - Generic Netlink
SYNOPSIS
#include <netlink/netlink.h>
#include <netlink/netlink_generic.h>
int
socket(AF_NETLINK, SOCK_DGRAM, NETLINK_GENERIC);
DESCRIPTION
The NETLINK_GENERIC is a "container" family, used for dynamic
registration of other families belonging to the various subsystems.
These subsystems provide a string family name during registration and
receive a dynamically-allocated family id. Allocated family identifiers
are then used by applications to get access to functions provided by that
subsystem via netlink. There are standard methods for resolving string
family names to family identifiers. A similar mechanism works for the
notification groups provided by those families.
All generic netlink families share a common header:
struct genlmsghdr {
uint8_t cmd; /* command within the family */
uint8_t version; /* ABI version for the cmd */
uint16_t reserved; /* reserved: set to 0 */
};
The family id is encoded in the nlmsg_type of the base netlink header.
The cmd field is the command identifier within the family. The version
field is the command version.
METHODS
The generic Netlink framework provides the base family, GENL_ID_CTRL
("nlctrl") with a fixed family id. This family is used to list the
details of all registered families.
The following messages are supported by the framework:
CTRL_CMD_GETFAMILY
Fetches a single family or all registered families, depending on the
NLM_F_DUMP flag. Each family is reported as CTRL_CMD_NEWFAMILY message.
The following filters are recognised by the kernel:
CTRL_ATTR_FAMILY_ID (uint16_t) current family id assigned by kernel
CTRL_ATTR_FAMILY_NAME (string) family name
TLVs
CTRL_ATTR_FAMILY_ID
(uint16_t) Dynamically-assigned family identifier.
CTRL_ATTR_FAMILY_NAME
(string) Family name.
CTRL_ATTR_HDRSIZE
(uint32_t) Family mandatory header size (typically 0).
CTRL_ATTR_MAXATTR
(uint32_t) Maximum attribute number valid for the family.
CTRL_ATTR_OPS
(nested) List of the operations supported by the family. The
attribute consists of a list of nested TLVs, with attribute
values monotonically incremented, starting from 0. The following
attributes are present in each TLV:
CTRL_ATTR_OP_ID
Operation (message) number.
CTRL_ATTR_OP_FLAGS
Operation flags. The following flags are supported:
GENL_ADMIN_PERM requires elevated permissions
GENL_CMD_CAP_DO operation is a modification request
GENL_CMD_CAP_DUMP operation is a get/dump request
CTRL_ATTR_MCAST_GROUPS
(nested) List of the notification groups supported by the family.
The attribute consists of a list of nested TLVs, with attribute
values monotonically incremented, starting from 0. The following
attributes are present in each TLV:
CTRL_ATTR_MCAST_GRP_ID
Group id that can be used in NETLINK_ADD_MEMBERSHIP
setsockopt(2).
CTRL_ATTR_MCAST_GRP_NAME
(string) Human-readable name of the group.
Groups
The following groups are defined:
"notify" Notifies on family registrations/removal.
SEE ALSO
netlink(4)
HISTORY
The NETLINK_GENERIC protocol family appeared in FreeBSD 13.2.
AUTHORS
The netlink was implementated by Alexander Chernikov
<
[email protected]>. It was derived from the Google Summer of Code
2021 project by Ng Peng Nam Sean.
FreeBSD 14.1-RELEASE-p8 November 1, 2022 FreeBSD 14.1-RELEASE-p8