Data types

Data types used in Netfilter

The following data types are used in nft selectors:

Netfilter Data Types
Data Type	Description	nft Selector	Notes
iface_index	Interface index (32 bit integer).	meta	Can be specified numerically or as name of an existing interface. Use ifname instead for interfaces whose name and/or index can change (i.e. those that appear / disappear dynamically).
ifname	Interface name (16 byte string).	meta	Does not have to exist. Slower than iface_index but good for interfaces that can dynamically appear / disappear.
iface_type	Interface type (16 bit integer).	meta
uid	User ID (32 bit integer).	meta	Can be specified numerically or as user name.
gid	Group ID (32 bit integer).	meta	Can be specified numerically or as group name.
realm	Routing Realm (32 bit integer).	meta	Can be specified numerically or as symbolic name defined in /etc/iproute2/rt_realms.
devgroup_type	Device group (32 bit number).	meta	Can be specified numerically or as symbolic name defined in /etc/iproute2/group.
pkt_type	Packet type: host - addressed to local host broadcast - to all multicast - to group other - addressed to another host	meta
ifkind	Interface kind (16 byte string).	meta	List of ifkinds is in man 8 ip-link TYPES section.
time	Either an integer or a date in ISO format. For example: "2019-06-06 17:00". Hour and seconds are optional and can be omitted if desired. If omitted, midnight will be assumed. The following three would be equivalent: "2019-06-06", "2019-06-06 00:00" and "2019-06-06 00:00:00". When an integer is given, it is assumed to be a UNIX timestamp.	meta
day	Either a day of week ("Monday", "Tuesday", etc.), or an integer between 0 and 6. Strings are matched case-insensitively, and a full match is not expected (e.g. "Mon" would match "Monday"). When an integer is given, 0 is Sunday and 6 is Saturday.	meta
hour	A string representing an hour in 24-hour format. Seconds can optionally be specified. For example, 17:00 and 17:00:00 would be equivalent.	meta