"length" match support

modulename: xt_length.ko

configname: CONFIG_NETFILTER_XT_MATCH_LENGTH

Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>Network packet filtering framework (Netfilter)
└─>Core Netfilter Configuration
└─>"length" match support
In linux kernel since version 2.6.16 (release Date: 2006-03-19)  
This option allows you to match the length of a packet against a
specific value or range of values.

To compile it as a module, choose M here. If unsure, say N.

source code: