4. Questions about netfilter development

4.1 I don't understand how to use the QUEUE target from userspace

A library called libipq is provided for userspace packet handling. Unfortunately there is no documentation about libipq. But there are some examples of code using libipq.

• testsuite/tools/intercept.c from netfilter CVS
• ipqmpd (see http://www.gnumonks.org/projects)
• nfqtest, part of netfilter-tools (see http://www.gnumonks.org/projects)