libnet1 binary package in Ubuntu Precise i386

 libnet provides a portable framework for low-level network packet
 writing and handling.
 .
 libnet features portable packet creation interfaces at the IP layer
 and link layer, as well as a host of supplementary functionality.
 .
 Using libnet, quick and simple packet assembly applications can be
 whipped up with little effort. With a bit more time, more complex
 programs can be written (Traceroute and ping were easily rewritten
 using libnet and libpcap).
 .
 This package contains the shared library.

Source package