The Research And Implementation Of Firewall In Linux

Netfilter fire wall in Linux have good code structure so it is easy to maintain and extend it .For going down to principle of linux firewall' s realization, and bring net application to success,the paper have carried an internal research of firewall' s code. The analyse has five period, First, obtain the way of kernel get net data, which make analyse of code easier;secondly, analyse principle of firewall hook in ip protocol stack; later, analyse the core module of firewall to get essential structure of firewall;later, analyse the process of rule added into firewall in kernel to obtaininteractive of kernel and user program;final, analyse iptables to obtain rule of organize in kernel and process added into kernel.On the basement of obtain firewall work principle , the paper used a few technology to extended firewall:first, make custom program to bring about custom rules; secondly, added program in user side to handle the data from kernel side; final, make an ip control program in kernel.To make the extend , the paper made full use of the framework in the open source.