+SET(iptc_libs ip4tc)
+
+SET(sed_match "^[[:space:]]*__ipt_module(\\(.*\\)).*")
+SET(sed_replace "-Wl,--undefined=libxt_\\1_init -Wl,--undefined=libipt_\\1_init -Wl,--undefined=libip6t_\\1_init")
+
+EXECUTE_PROCESS(COMMAND sed -n -e "s/${sed_match}/${sed_replace}/; T n; H; :n; \${ x; s/^\\n//; s/\\n/ /gp }" ${CMAKE_SOURCE_DIR}/iptables.h
+ OUTPUT_VARIABLE ext_syms OUTPUT_STRIP_TRAILING_WHITESPACE)
+