[tproxy] Question about warning message

While running stress tests on our application, which uses the tproxy patch, we see the following warning messages in dmesg: IP_TPROXY: error applying NAT mapping, hooknum=4 .... This warning message comes from the function ip_tproxy_setup_nat_bidir in iptable_tproxy.c. It's printed if the result of calling ip_nat_setup_info is different than NF_ACCEPT. I'm not sure what this warning means. The ip_tproxy_setup_nat_bidir function continues normally after the warning is printed out. Any help in shedding light on this will be greatly appreciated. Thanks in advance, -- Yuval Pemper