Do Omnia or OpenWRT distributions contain the “nfct” command ?
It can be used to configure a specific timeout in iptables/conntrack overriding the global timeouts defined in /proc/sys/net/netfilter/*
Example given in manpage : http://manpages.ubuntu.com/manpages/bionic/en/man8/nfct.8.html
Default Omnia installation already contains libnetfilter_cttimeout.so shared library used by conntrack-tools
nfct executable should be in conntrack-tools package developed by Pablo Neira Ayuso and it is available on desktop distributions like Debian/Ubuntu