Packet Construction and Injection

Libnet is an API to help with the construction and injection of network packets. It provides a portable framework for low-level network packet writing and handling (use libnet in conjunction with libpcap and you can write some really cool stuff). Libnet includes packet creation at the IP layer and at the link layer as well as a host of supplementary and complementary functionality.

Libnet is very handy with which to write network tools and network test code. Some projects, available in Debian/Ubuntu and OpenBSD, using libnet are:

• arping
• ettercap
• ipguard
• isic
• nemesis
• packit
• tcptraceroute
• yersinia

NOTE: Legacy code written for libnet-1.0.x is unfortunately incompatible with libnet-1.1.x and later.
See the Migration Guide for porting help.

Using -lnet

Libnet is installed as a library and a set of include files. The main include file to use in your program is:

#include <libnet.h>

To get the correct search paths to both the header and library files, use the standard pkg-config tool (old libnet-config is deprecated):

$ pkg-config --libs --static --cflags libnet
-I/usr/local/include -L/usr/local/lib -lnet

The prefix path /usr/local/ shown here is only the default. Use the configure script to select a different prefix when installing libnet.

For GNU autotools based projects, use the following in configure.ac:

# Check for required libraries
PKG_CHECK_MODULES([libnet], [libnet >= 1.2])

and in your Makefile.am:

proggy_CFLAGS = $(libnet_CFLAGS)
proggy_LDADD  = $(libnet_LIBS)

Online docs available at https://codedocs.xyz/libnet/libnet/. See the man page and sample test code for more information.

Building

First download the latest release from GitHub. Libnet employs the GNU configure and build system. The release tarballs and zip files ship with a pre-built configure script:

$ tar xf libnet-x.y.z.tar.gz
$ cd libnet-x.y.z/
$ ./configure && make
$ sudo make install

To list available options, type ./configure --help

Building from GIT/GitHub

When building from GIT, use ./autogen.sh to generate the configure script. For this you need the full suite of the GNU autotools: autoconf (>=2.69), automake (>=1.14), libtool (>=2.4.2).

How to install the dependencies varies by system, but on many Debian derived systems, apt can be used:

$ sudo apt install autoconf automake libtool
$ ./autogen.sh
$ ./configure && make
$ sudo make install

Using Conan

Libnet is available on Conan Center. To use, add libnet/1.2 to your conanfile.txt

Building with Docker

First build the dev. contrainer:

$ cd .devcontainer
$ docker build -t libnet-builder .

Then compile libnet with docker:

$ cd ..
$ docker run -it --rm -v $(pwd):$(pwd) --workdir=$(pwd) libnet-builder
$ ./autogen.sh                 # If you've cloned from GitHub
$ ./configure
$ make

Running Unit Tests with CMocka

Running tests in the dev. container (above):

$ ./autogen.sh                 # If you've cloned from GitHub
$ ./configure --enable-tests
$ make check
make  check-TESTS
PASS: udld 1 - libnet_udld__checksum_calculation
PASS: udld 2 - libnet_build_udld__pdu_header_only
PASS: udld 3 - libnet_build_udld__tlv_device_id
PASS: udld 4 - libnet_build_udld__tlv_port_id
PASS: udld 5 - libnet_build_udld__tlv_echo
PASS: udld 6 - libnet_build_udld__tlv_message_interval
PASS: udld 7 - libnet_build_udld__tlv_timeout_interval
PASS: udld 8 - libnet_build_udld__tlv_device_name
PASS: udld 9 - libnet_build_udld__tlv_sequence_number
PASS: udld 10 - libnet_build_udld__build_whole_packet_with_checksum
PASS: ethernet 1 - test_libnet_build_ethernet
============================================================================
Testsuite summary for libnet 1.3
============================================================================
# TOTAL: 11
# PASS:  11
# SKIP:  0
# XFAIL: 0
# FAIL:  0
# XPASS: 0
# ERROR: 0
============================================================================

Note: on Linux the tests run in a separate network namespace (using unshare), so no root (sudo) access is needed, but on other systems you may need to to be root, or have to correct capabilities or permissions.

Building the Documentation

To build the documentation (optional) you need doxygen and pod2man:

$ sudo apt install doxygen
$ sudo apt install pod2man || sudo apt install perl

For neat graphics in the HTML documentation, also install graphviz. There is also a PDF version of the docs, to build that you need quite a few more packages:

$ sudo apt install texlive-extra-utils texlive-latex-extra \
                   texlive-fonts-recommended latex-xcolor  \
                   texlive-font-utils

For Microsoft CHM docs you need the HTML Help Workshop, which is part of Visual Studio: http://go.microsoft.com/fwlink/p/?linkid=154968, on UNIX and GNU/Linux systems, see chmcmd, which is available in the FreePascal suite:

$ sudo apt install fp-utils-3.0.4

Origin & References

Libnet is widely used, but had been unmaintained for a long time and its author unreachable. This version was forked from the 1.1.3 release candidate from packetfactory.net, bug fixed, developed, and re-released.

Use GitHub issues and pull request feature for questions and patches:

http://github.com/libnet/libnet

Some old docs are available at:

http://packetfactory.openwall.net/projects/libnet/index.html

---

• v1.1 (c) 1998 - 2004 Mike D. Schiffman mike@infonexus.com
  http://www.packetfactory.net/libnet
• v1.1.3 and later (c) 2009 - 2013 Sam Roberts vieuxtech@gmail.com
  http://github.com/libnet/libnet

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