extensions/libipt_condition.man - platform/external/iptables - Git at Google

 This matches if a specific /proc filename is '0' or '1'.
 .TP
 .BI "--condition " "[!] filename"
 Match on boolean value stored in /proc/net/ipt_condition/filename file
	This matches if a specific /proc filename is '0' or '1'.
	.TP
	.BI "--condition " "[!] filename"
	Match on boolean value stored in /proc/net/ipt_condition/filename file