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## Installation Instructions for Layer Four Traceroute
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Instructions are provided for different platforms below.

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On WINDOWS:
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   Building this program on Windows is possible without UNIX-like 
compatibility environments.  To compile the program, use the 
Microsoft Visual Studio Express edition which is free and may be 
downloaded from http://www.microsoft.com  You must also download 
and install the Windows Platform SDK which is available from the 
same web site.  The platform SDK provides the necessary Winsock 
header files.  Please read the documentation related to fully
installing the Windows Platform SDK for use with Visual Studio
Express or your alternative compiler to ensure all necessary
files are placed in the appropriate locations, specifically the
header files.

   Using VS Express, you may build LFT by following these 
instructions:  

   Open a Command Prompt window (cmd.exe), change directories to the 
"lft" folder you downloaded, and type the following commands (from 
inside the LFT folder):

    "%VS80COMNTOOLS%vsvars32.bat"
    nmake -f makefile.vc

   This will create lft.exe and whob.exe in the current folder. 
Of course, you may move the files wherever you choose.  Depending
on the Windows platform, you may or may not have TCP raw sockets
functionality, causing TCP traces to fail.  However, in this case 
ICMP and UDP traces should still work.  

   You may also have to explicitly allow lft.exe to use the network 
by creating a rule in Windows (or your 3rd-party) Firewall.

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On UNIX-like operating systems:
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Optional Dependencies
=====================

   LFT requires libpcap (mandatory) and optionally uses c-ares for
asynchronous DNS resolution.  c-ares eliminates the post-trace serial
hostname lookup delay (typically 180-260ms per trace) and is strongly
recommended.  It is auto-detected by ./configure; install it before
running ./configure to enable it:

  Debian/Ubuntu:   apt-get install libc-ares-dev
  RHEL/Fedora:     dnf install c-ares-devel
  macOS Homebrew:  brew install c-ares
  FreeBSD ports:   dns/c-ares
  MacPorts:        port install c-ares

   ./configure searches the standard system paths plus common third-party
prefix directories (/opt/homebrew, /usr/local, /opt/local, /opt/pkg)
automatically, so no manual LDFLAGS or CPPFLAGS are needed on most systems.

   Some special options to consider when running './configure' are:

1. Using '--enable-gtod' is useful on platforms where BPF timestamps are not
precise.  This forces LFT to call gettimeofday() on each packet instead of
relying on the timestamp in the packet's pcap header.

2. Using '--enable-universal' will automatically compile universal binaries
on macOS for arm64 (Apple Silicon) and x86_64 (Intel) architectures.

3. Using '--disable-async-dns' disables c-ares support at compile time even
if the library is installed.

4. Using '--with-cares=PATH' specifies the installation prefix for c-ares
when it is installed in a non-standard location (e.g. --with-cares=/opt/cares).

5. Using '--with-pcap=PATH' specifies the installation prefix for libpcap
when it is installed in a non-standard location.

   Below are generic installation instructions.

   The `configure' shell script attempts to guess correct values for
various system-dependent variables used during compilation.  It uses
those values to create a `Makefile' in each directory of the package.
It may also create one or more `.h' files containing system-dependent
definitions.  Finally, it creates a shell script `config.status' that
you can run in the future to recreate the current configuration, a file
`config.cache' that saves the results of its tests to speed up
reconfiguring, and a file `config.log' containing compiler output
(useful mainly for debugging `configure').

   If you need to do unusual things to compile the package, please try
to figure out how `configure' could check whether to do them, and mail
diffs or instructions to the address given in the `README' so they can
be considered for the next release.  If at some point `config.cache'
contains results you don't want to keep, you may remove or edit it.

   The file `config/configure.ac' is used to create `configure' by a program
called `autoconf'.  You only need `config/configure.ac' if you want to change
it or regenerate `configure' using a newer version of `autoconf'.  To
regenerate `configure' from the project root, run:

     autoconf config/configure.ac > configure

The simplest way to compile this package is:

  1. `cd' to the directory containing the package's source code and type
     `./configure' to configure the package for your system.  If you're
     using `csh' on an old version of System V, you might need to type
     `sh ./configure' instead to prevent `csh' from trying to execute
     `configure' itself.

     Running `configure' takes awhile.  While running, it prints some
     messages telling which features it is checking for.

  2. Type `make' to compile the package.

  3. Optionally, type `make check' to run any self-tests that come with
     the package.

  4. Type `make install' (as root or with sudo) to install the programs
     and any data files and documentation.  On Linux, the installer will
     use setcap(8) to grant lft the raw socket and packet capture
     capabilities it needs without installing it setuid root.  On FreeBSD
     and other platforms, lft is installed setuid root.  In both cases
     root access is required to run `make install'.

     On macOS, lft requires setuid root.  This is because lft uses two
     separate privilege paths: libpcap (via /dev/bpf*) for capturing
     response packets, and a raw socket (SOCK_RAW) for sending probe
     packets.  BPF device permissions (e.g., ChmodBPF / access_bpf
     group) only cover the capture side -- they do not grant the ability
     to create raw sockets, which on macOS requires root.  Unlike Linux,
     macOS has no setcap equivalent to selectively grant raw socket
     capability to a binary.

     `make install' performs this step automatically when run as root.
     If you are installing manually:

          sudo chown root lft && sudo chmod u+s lft

     This is standard practice for network diagnostic tools on macOS --
     ping and traceroute ship setuid root for the same reason.

  5. You can remove the program binaries and object files from the
     source code directory by typing `make clean'.  To also remove the
     files that `configure' created (so you can compile the package for
     a different kind of computer), type `make distclean'.  There is
     also a `make maintainer-clean' target, but that is intended mainly
     for the package's developers.  If you use it, you may have to get
     all sorts of other programs in order to regenerate files that came
     with the distribution.

Compilers and Options
=====================

   Some systems require unusual options for compilation or linking that
the `configure' script does not know about.  You can give `configure'
initial values for variables by setting them in the environment.  Using
a Bourne-compatible shell, you can do that on the command line like
this:
     CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure

Or on systems that have the `env' program, you can do it like this:
     env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure

Compiling For Multiple Architectures
====================================

   You can compile the package for more than one kind of computer at the
same time, by placing the object files for each architecture in their
own directory.  To do this, you must use a version of `make' that
supports the `VPATH' variable, such as GNU `make'.  `cd' to the
directory where you want the object files and executables to go and run
the `configure' script.  `configure' automatically checks for the
source code in the directory that `configure' is in and in `..'.

   If you have to use a `make' that does not supports the `VPATH'
variable, you have to compile the package for one architecture at a time
in the source code directory.  After you have installed the package for
one architecture, use `make distclean' before reconfiguring for another
architecture.

Installation Names
==================

   By default, `make install' will install the package's files in
`/usr/local/bin', `/usr/local/man', etc.  You can specify an
installation prefix other than `/usr/local' by giving `configure' the
option `--prefix=PATH'.

   You can specify separate installation prefixes for
architecture-specific files and architecture-independent files.  If you
give `configure' the option `--exec-prefix=PATH', the package will use
PATH as the prefix for installing programs and libraries.
Documentation and other data files will still use the regular prefix.

   In addition, if you use an unusual directory layout you can give
options like `--bindir=PATH' to specify different values for particular
kinds of files.  Run `configure --help' for a list of the directories
you can set and what kinds of files go in them.

   If the package supports it, you can cause programs to be installed
with an extra prefix or suffix on their names by giving `configure' the
option `--program-prefix=PREFIX' or `--program-suffix=SUFFIX'.

Optional Features
=================

   Some packages pay attention to `--enable-FEATURE' options to
`configure', where FEATURE indicates an optional part of the package.
They may also pay attention to `--with-PACKAGE' options, where PACKAGE
is something like `gnu-as' or `x' (for the X Window System).  The
`README' should mention any `--enable-' and `--with-' options that the
package recognizes.

   For packages that use the X Window System, `configure' can usually
find the X include and library files automatically, but if it doesn't,
you can use the `configure' options `--x-includes=DIR' and
`--x-libraries=DIR' to specify their locations.

Specifying the System Type
==========================

   There may be some features `configure' can not figure out
automatically, but needs to determine by the type of host the package
will run on.  Usually `configure' can figure that out, but if it prints
a message saying it can not guess the host type, give it the
`--host=TYPE' option.  TYPE can either be a short name for the system
type, such as `sun4', or a canonical name with three fields:
     CPU-COMPANY-SYSTEM

See the file `config.sub' for the possible values of each field.  If
`config.sub' isn't included in this package, then this package doesn't
need to know the host type.

   If you are building compiler tools for cross-compiling, you can also
use the `--target=TYPE' option to select the type of system they will
produce code for and the `--build=TYPE' option to select the type of
system on which you are compiling the package.

Sharing Defaults
================

   If you want to set default values for `configure' scripts to share,
you can create a site shell script called `config.site' that gives
default values for variables like `CC', `cache_file', and `prefix'.
`configure' looks for `PREFIX/share/config.site' if it exists, then
`PREFIX/etc/config.site' if it exists.  Or, you can set the
`CONFIG_SITE' environment variable to the location of the site script.
A warning: not all `configure' scripts look for a site script.

Operation Controls
==================

   `configure' recognizes the following options to control how it
operates.

`--cache-file=FILE'
     Use and save the results of the tests in FILE instead of
     `./config.cache'.  Set FILE to `/dev/null' to disable caching, for
     debugging `configure'.

`--help'
     Print a summary of the options to `configure', and exit.

`--quiet'
`--silent'
`-q'
     Do not print messages saying which checks are being made.  To
     suppress all normal output, redirect it to `/dev/null' (any error
     messages will still be shown).

`--srcdir=DIR'
     Look for the package's source code in directory DIR.  Usually
     `configure' can determine that directory automatically.

`--version'
     Print the version of Autoconf used to generate the `configure'
     script, and exit.

`configure' also accepts some other, not widely useful, options.
