Moving from ipset to nftables

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If you use ipset with iptables, you need to consider the following when moving to nftables:

  • There are no tools or compatibility layers that automatically transform ipsets into nftables sets. The translation is typically straightforward, but you must do it manually.
  • You will need to translate ipset set types into nftables set data types, which will often be concatenated types. For example, an ipset of type hash:net,port,net becomes an nftables set of type ipv4_addr . inet_service . ipv4_addr.
  • nftables sets do not support negated elements, as with ipset nomatch. To translate an ipset that has nomatch elements you can use a pair of nftables sets, one for the usual positive elements and one for negated elements, along with compound rule expressions like ip saddr @pos_set  ip saddr != @neg_set.
  • You can often use nftables maps and verdict maps to make your ruleset more efficient.

Following is an example of translating a basic iptables/ipset configuration into nftables.

Here is the iptables/ipset setup:

user@debian:~ $ sudo ipset save
create myset hash:ip,port,ip family inet hashsize 1024 maxelem 65536
add myset 172.16.0.1,tcp:80,10.0.0.1

user@debian:~ $ sudo iptables-save
# Generated by iptables-save v1.8.3 on Wed Oct 30 11:26:41 2019
*filter
:INPUT ACCEPT [3:212]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [4:250]
-A INPUT -m set --match-set myset src,dst,dst -j ACCEPT
COMMIT

The above translates into nftables as:

user@debian:~ $ sudo nft list ruleset
table inet filter {
	map myset {
		type ipv4_addr . inet_service . ipv4_addr : verdict
		elements = { 172.16.0.1 . 80 . 10.0.0.1 : accept }
	}

	chain input {
		type filter hook input priority filter; policy accept;
		meta nfproto ipv4 ip saddr . tcp dport . ip daddr vmap @myset
	}
}

Note that we have used an nftables verdict map, which takes action directly from each map element. Using such powerful new structures can greatly reduce the number of rules required by your filtering policy, compared with iptables/ipset.

We recommend reading about concatenations.

Here are some additional examples of nftables equivalents for some ipset data types:

hash:net,net

% nft add rule tablename chainname ip saddr . ip daddr vmap { 10.10.10.0/24 . 10.10.20.0/24 : accept }

hash:net,port,net

% nft add rule tablename chainname ip saddr . tcp dport . ip daddr vmap { 10.10.10.0/24 . 80 . 10.10.20.0/24 : accept }

hash:net,iface

% nft add rule tablename chainname ip saddr . iif vmap { 10.10.10.0/24 . eth0 : accept }

NOTE that before Linux kernel 5.6 and nftables 0.9.4 the CIDR notation used above was not yet available. If you are unable to upgrade, you can work around this limitation as noted in the concatenation examples.

See also