I want to develope a firewall for Linux. I prefer C/C++ language.
Is there any simple sample code for writing a firewall?
Which libraries should I use?
Update: There are some firewalls for Linux, but I want develope a simple firewall for learning.
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You can start by using the Netfilters API (http://www.netfilter.org/). I think it is a good starting point for packet filtering. I’ve worked a lot with this API in kernel space. I’m not sure if there is a library for user land, but I must tell you that it’s pretty easy to develop something with netfilters in the kernel.
As an example, iptables use the netfilters API.