Connection tracking labels


Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>Network packet filtering framework (Netfilter)
└─>Core Netfilter Configuration
└─>Connection tracking labels
In linux kernel since version 3.1 (release Date: 2011-10-24)  
This option enables support for assigning user-defined flag bits
to connection tracking entries. It can be used with xtables connlabel
match and the nftables ct expression.