An application based on libnetfilter_conntrack and libnfnetlink failed to get counters in CentOS 6.x, but it works works fine with the same code in CentOS 5.x. How to enable the counter functionality? Sample code: handle_conntrack_ = nfct_open(CONNTRACK, NF_NETLINK_CONNTRACK_DESTROY); nfct_callback_register(handle_conntrack_, NFCT_T_ALL, conntrack_callback, NULL); static int conntrack_callback(enum nf_conntrack_msg_type type, struct nf_conntrack* ct, void* data) { struct __nfct_counters orig_counter = ct->counters[__DIR_ORIG]; struct __nfct_counters repl_counter = ct->counters[__DIR_REPL]; //in CentOS 6.x, orig_counter.packets,orig_counter.bytes,repl_counter.packets and repl_counter.bytes are not set(zero) } OS and library version: CentOS 6.4 x86_64 libnfnetlink-1.0.0 libnetfilter_conntrack-0.0.100��.n��������+%������w��{.n����z�����n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�