Setting packet metainformation

You can set some metainformation in a packet. Current supported options are:

• mark -- packet mark
• priority -- packet priority
• nftrace -- nftrace debugging bit
• pkttype -- packet type
• secmark -- packet secmark

Please note that you require a Linux kernel >= 3.14 to use these features.

mark

The following example shows how to set the packet mark:

% nft add rule route output mark set 123

mark and conntrack mark

You can save/restore conntrack mark like in iptables.

In this example, the nf_tables engine set the packet mark to 1. In the last rule, that mark is store in the conntrack entry associated with the flow:

% nft add rule filter forward meta mark set 1
% nft add rule filter forward ct mark set mark

In this example, the conntrack mark is stored in the packet.

% nft add rule filter forward meta mark set ct mark

secmark

New in nftables 0.9.3, you can set the packet secmark from its associated conntrack secmark:

meta secmark set ct secmark

priority

You can set the priority of a packet.

This example shows a similar operation to what "-j CLASSIFY" does in iptables:

% nft add table mangle
% nft add chain postrouting {type route hook output priority -150\; }
% nft add rule mangle postrouting tcp sport 80 meta priority set 1

Warning: There is a bug in the priority syntax that will be fixed in following versions of nftables.

nftrace

Setting nftrace in a packet will report the journey through the nf_tables stack.

% nft add rule filter forward udp dport 53 meta nftrace set 1

combination of options

Given the flexible design of nftables, remember you can perform several actions to a packet in one rule:

% nft add rule filter forward ip saddr 192.168.1.1 meta nftrace set 1 meta priority set 2 meta mark set 123