Currently only operating systems running on Linux kernels with the option
CONFIG_PACKET_MMAP enabled. This feature can be found even back to the days of
2.4 kernels. Most operating systems ship pre-compiled kernels that have this
config option enabled and even the latest kernel versions got rid of this
option and have this functionality already built-in. However, we recommend a
kernel >= 2.6.31, because the TX_RING is officially integrated since then. In
any case, if you have the possibility, consider getting the latest kernel from
Linus' Git repository, tweak and compile it, and run this one!

A note for distribution package maintainers can be found at the end of the file.

What additional tools next to your build-chain are required?

 - pkg-config:             all
 - flex, bison:            bpfc, trafgen

 - ccache (optional)
 - gpg (optional)
 - sparse (optional)

What libraries are required?

 - libncurses:             ifpps, flowtop
 - libnacl or libsodium:   curvetun
 - libnetfilter-conntrack: flowtop
 - libnl3:                 netsniff-ng, trafgen
 - libpcap:                mausezahn, netsniff-ng (tcpdump-like filters)
 - liburcu:                flowtop
 - libcli:                 mausezahn
 - libnet:                 mausezahn

The following libraries can optionally be used to provide additional
functionality for certain tools:

 - libGeoIP >=1.4.8:       astraceroute, flowtop, netsniff-ng
 - libz:                   astraceroute, flowtop, netsniff-ng

What additional tools are recommended, but not mandatory after the build?

 - cpp:                    trafgen
 - ntpd:                   curvetun
 - gnuplot:                ifpps
 - setcap:                 all

It is common that these libraries are shipped as distribution packages
for an easy installation. We try to keep this as minimal as possible.

One-liner installation for *all* dependencies on Debian:

  $ sudo apt-get install ccache flex bison libnl-3-dev \
  libnl-genl-3-dev libnl-route-3-dev libgeoip-dev \
  libnetfilter-conntrack-dev libncurses5-dev liburcu-dev \
  libnacl-dev libpcap-dev zlib1g-dev libcli-dev libnet1-dev

One-liner installation for *all* dependencies on Fedora:

  $ sudo yum install ccache flex bison ccache libnl3-devel \
  GeoIP-devel libnetfilter_conntrack-devel ncurses-devel \
  userspace-rcu-devel nacl-devel libpcap-devel zlib-devel \
  libcli-devel libnet-devel

After downloading the netsniff-ng toolkit, you should change to the
repository root directory:

  $ cd netsniff-ng/

The installation (deinstallation) process is fairly simple:

  $ ./configure
  $ make
  # make install

  (# make uninstall)

The configure script can be influenced by setting certain command line
options and environment variables (e.g. CC or CROSS_COMPILE). To get a list
of all supported options and variables use:

  $ ./configure --help

The use of the optional libGeoIP and libz libraries can be explicitely
disabled by using the corresponding command line option for the configure
script:

  $ ./configure --disable-geoip
  $ ./configure --disable-zlib

In order to remove all build files from the source tree:

  $ make clean

In any case "make help" will give you some pointers of what can be done.

To bring the source tree into a pristine state, there are two options.
The first one will remove all build and build config file, the latter will
also remove any manually added files:

  $ make distclean
  ($ make mrproper)

You can also build/install/uninstall only a particular tool, e.g.:

  $ make trafgen
  # make trafgen_install

  (# make trafgen_uninstall)

If you want to build all tools, but {curvetun,mausezahn} (i.e. because you
don't need the tunneling software and the NaCl build process lasts quite long):

  $ make allbutcurvetun               (allbutmausezahn)
  # make install_allbutcurvetun       (install_allbutmausezahn)

  (# make uninstall)

In order to build curvetun, libnacl must be built first. A helper script
called nacl_build.sh is there to facilitate this process. If you want to
build NaCl in the directory ~/nacl, the script should be called this way:

  $ cd curvetun
  $ ./nacl_build.sh ~/nacl

There's also an abbreviation for this by simply typing:

  $ make nacl

This gives an initial output such as "Building NaCl for arch amd64 on host
fuuubar (grab a coffee, this takes a while) ...". If the automatically
detected architecture (such as amd64) is not the one you intend to compile
for, then edit the (cc="gcc") variable within the nacl_build.sh script to
your cross compiler. Yes, we know, the build system of NaCl is a bit of a
pain, so you might check for a pre-built package from your distribution in
case you are not cross compiling.

If NaCl already has been built on the target, it is quicker to use
nacl_path.sh this way:

  $ cd curvetun
  $ ./nacl_path.sh ~/nacl/build/include/x86 ~/nacl/build/lib/x86

Instead of libnacl you can also use libsodium which itself is a portable,
cross-compilable, API compatible drop-in replacement for libnacl.

In order to use libsodium you need to provide some little help when running
the configure script, so it will be able to detect the needed header files.
Additionally you need to configure the build to not link against libnacl
but against libsodium.

In the case libsodium was installed into /usr/local you run the netsniff-ng
configure script this way:

  $ NACL_INC_DIR=/usr/local/include/sodium NACL_LIB=sodium ./configure

Alternatively you can use pkg-config for determining the include dir by
setting the NACL_INC_DIR variable for the configure script like this:

  $ NACL_INC_DIR=$(pkg-config --variable=includedir libsodium )/sodium

When done, netsniff-ng's build infrastructure will read those evironment
variables in order to get the needed paths to NaCl.

If you're unsure with any make targets, check out: make help

In order to run the toolkit as a normal user, set the following privilege
separation after the build/installation:

  $ sudo setcap cap_net_raw,cap_ipc_lock,cap_sys_admin,cap_net_admin=eip {toolname}

For cross-compiling netsniff-ng, the process is fairly simple. Assuming you
want to build netsniff-ng for the Microblaze architecture, update the PATH
variable first, e.g.:

  $ export PATH=<cc-tools-path>/microblazeel-unknown-linux-gnu/bin:$PATH

And then, build the toolkit like this:

  $ CROSS_COMPILE=microblazeel-unknown-linux-gnu- \
    SYSROOT=<sysroot-path> ./configure
  $ make

SYSROOT should be set to the path where your cross-compiled libraries are
stored, i.e. the path you specify as prefix when configuring the library using
`./configure --prefix=<prefix>'.

Note that some adaptations might be necessary regarding the CFLAGS, since not
all might be supported by a different architecture. Probably the most simple
way would be to run make CFLAGS="-O2 -Wall".

For power users we have a set of zsh auto completion files, have a look at all
file with ending *.zsh. There's also a BPF vim syntax highlighting file in the
tree called bpf.vim.

For doing a debug build of the toolkit with less optimizations and non-stripped
symbols, do:

  $ make DEBUG=1

For debugging the build system, actual commands are verbosly shown if every
make target is executed with:

  $ make Q=

A hardening option is also available via HARDENING=1 if needed. You can then
build and install the toolkit into prefixed path like:

  $ make PREFIX=<path-prefix-for-package>
  $ make PREFIX=<path-prefix-for-package> install

Additionally to setting the PREFIX you can set DESTDIR if you want to install
the toolkit outside of your current root filesystem but into an alternative
path. This is particularly useful when cross-compiling because most likely
you want to install into a dedicated sandbox or into a mounted root filesystem
for the target architecture and not into the build hosts root filesystem.

  $ make PREFIX=<path-prefix-for-package> DESTDIR=<alternative-rootfs> install

Thanks for maintaining netsniff-ng in your distribution. Further questions will
be answered on the public mailing list.

Last but not least, there is one small utility for advanced users that we have
not integrated into the main build process. This is a minimal BPF JIT image
disassembler for the Linux kernel. You can also find this tool in the Linux
kernel Git tree under 'tools/net/bpf_jit_disasm.c' or within the netsniff-ng
Git tree simply under 'bpf_jit_disasm.c'. To build it, execute:

    $ gcc -Wall -O2 bpf_jit_disasm.c -o bpf_jit_disasm -lopcodes -lbfd -ldl

The rest is described in the file header comment itself, i.e. how to get to the
BPF JIT code.
