I'm getting this netfilter error when compiling 3.3.11 on Centos 6.5: checking if __va_copy is implemented... no configure: IPF-based transparent proxying enabled: no configure: error: Linux Netfilter support requested but needed headers not found I've already got the following installed: libnetfilter_conntrack.x86_64 libnetfilter_conntrack-devel.x86_64 libnfnetlink.x86_64 1.0.0-1.el6 @base libnfnetlink-devel.x86_64 What else am I missing? There are some earlier Google hits about this message, but they don't seem relevant (to me).