The "generic" notes for putting this thing together are below.  Here's the
short version.

1.) If you are upgrading from a prior version of Snort, it is generally a good
    idea to start with `sudo make uninstall` in your old source tree to remove
    any dynamic modules that could cause you grief later.

2.) *** Make sure you have libdnet, libpcap, libpcre installed!!! ***
    Also make sure that dnet-config, pcre-config, and daq-modules-config are in
    your PATH (eg you should be able to `which` these).

3.) ./configure

4.) make

5.) sudo make install

6.) Check your rules file.  By default, step 3 configures Snort for the features 
    required by the included etc/snort.conf.  You can validate it with:

    src/snort -c etc/snort.conf -T

7.) snort -?

8.) If you've used previous versions of Snort, you may need to rewrite your
    rules to make them compliant to the rules format.  See snort_manual.pdf
    or http://www.snort.org for more information. 

9.) If you used previous versions of Snort and the new Snort dies upon startup,
    try this and then restart:

    sudo make uninstall
    sudo make install

10.) Have fun!

Any questions?  Sign up to the snort-users mailing list at http://www.snort.org!

Snort Configure-time switches
=============================

`--enable-debug'
     Enable debugging options (bugreports and developers only).
     
`--enable-pthread'
     Enable pthread support (causes snort to be linked with libpthread).

`--enable-rulestate'
     Enable rule state configuration feature that separates the rule
     state (enabled/disabled) from the action (alert, drop, log, etc)
     and definition.

`--enable-dynamicplugin'
     Enable dynamically loadable preprocessors, detection engine
     and rules libraries.

`--enable-so-with-static-lib`
     Enable linking of dynamically loaded preprocessors with a static
     preprocessor library.

`--enable-perfprofiling'
     Enable performance profiling of individual rules and preprocessors.

`--enable-linux-smp-stats'
     Enable CPU performance statistics through proc.

`--enable-react'
     Enable interception and termination of offending HTTP accesses.

`--enable-flexresp3'
     Enable the 'Flexible Response, version 3' code, that allows you to
     reset hostile sessions.  See README.active for details.

`--enable-gre'
     Enable GRE decoder. Allows Snort to decode GRE encapsulated traffic.
     Only supports GRE over IP.  Only one layer of encapsulation will be
     decoded - packets with multiple GRE headers will be alerted and
     discarded/blocked.
     
`--enable-sourcefire'
     Enable Sourcefire specific build options, encompasing
     --enable-perfprofiling and --enable-ppm.
     
`--with-snmp'
     Enable SNMP alerting code.

`--with-dnet-includes=DIR'
     Specify libdnet include directory.

`--with-dnet-libraries=DIR'
     Specify libdnet library directory.

`--with-libpcap-includes=DIR'
     If the configuration script can't find the libpcap include files on its 
     own, the path can be set manually with this switch.

`--with-libpcap-libraries=DIR'
     If the configuration script can't find the libpcap library files on its 
     own, the path can be set manually with this switch.

Basic Installation
==================

These 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 `configure.in' is used to create `configure' by a program called
`autoconf'.  You only need `configure.in' if you want to change it or
regenerate `configure' using a newer version of `autoconf'.

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' to install the programs and any data files and
     documentation.

  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.

The following configuration switches are available for Snort:

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.


Platform Specific Notes
=======================

* 64bit platforms:
------------------
On some 64bit Linux systems (e.g. with Fedora distributions), when configuring
snort with MySQL output support, the necessary library may not be found
automatically by the configure script, giving the following error when
'configure' is run:

**********************************************
  ERROR: unable to find mysqlclient library (libmysqlclient.*)
  checked in the following places
        /usr
        /usr/lib
        /usr/mysql
        /usr/mysql/lib
        /usr/local
        /usr/local/lib
        /usr/local/mysql
        /usr/local/mysql/lib
**********************************************

In this case, libmysqlclient.* may actually be found in /usr/lib64/mysql, and
the path will need to be explicitly specified in this manner: configure
--with-mysql-libraries=/usr/lib64/mysql

Note, you may also specify alternate locations for the mysql header files using
--with-mysql-includes.  Specifying a directory as part of the --with-mysql
option to configure will be deprecated in the future.

Problems may also be encountered if both the 32bit and 64bit libraries are
installed on the system, and configuring snort with MySQL support may result in
a different error:

checking for mysql... yes
checking for compress in -lz... yes
checking for dlsym in -ldl... no
checking for dlsym in -lc... no

   ERROR!  programmatic interface to dynamic link loader
   not found.  Cannot use dynamic plugin libraries.

Reading through config.log, you may see something like this (the numbers are
the line number and may differ):

configure:24280: checking for dlsym in -ldl
configure:24310: gcc -o conftest -g -O2 -Wall  -DDYNAMIC_PLUGIN   -I/usr/include/mysql -DENABLE_MYSQL  -lpcre -L/usr/lib/mysql conftest.c -ldl  -lmysqlclient -lz -lpcre -lpcap -lm -lnsl  >&5
/usr/bin/ld: skipping incompatible /usr/lib/mysql/libmysqlclient.so when searching for -lmysqlclient
/usr/bin/ld: skipping incompatible /usr/lib/mysql/libmysqlclient.a when searching for -lmysqlclient
/usr/bin/ld: cannot find -lmysqlclient
collect2: ld returned 1 exit status
configure:24316: $? = 1 

This likely indicates a compatibility issue between a 32bit library from mysql
(found in its normal location), and a 64bit library for libdl (dynamic loader).
Use the --with-mysql-libraries option to specify the location of the 64bit
mysql library (e.g. /usr/lib64/mysql).


* Linux:
-------- With kernels 2.2.x and higher you may get `snort [pid] uses obsolete
(PF_INET, SOCK_PACKET)' warnings. This is because you use some older
implementation of libpcap library and you need an upgrade. The recent version
of libpcap could be found at www.tcpdump.org page.  On linux with kernels 2.2.x
and higher you may also get feature to monitor several interfaces down to
network level (session + TCP + IP) if you link your snort with the latest
version of libpcap which incorporates Sebastian Krahmer's patch for interface
'any'.  (Consult http://www.tcpdump.org for details).


* IRIX
------
[ noticed by Scott A. McIntyre <scott@whoi.edu> ]
There's problem with GCC on IRIX platform which causes certain misbehaviour
of snort.

From the SGI web site:

Gcc does not correctly pass/return structures which are smaller than 16 bytes
and which are not 8 bytes. The problem is very involved and difficult to fix.
It affects a number of other targets also, but irix6 is affected the most,
because it is a 64 bit target, and 4 byte structures are common.  The exact
problem is that structures are being padded at the wrong end, e.g.  a 4 byte
structure is loaded into the lower 4 bytes of the register when it should be
loaded into the upper 4 bytes of the register. 

Gcc is consistent with itself, but not consistent with the SGI C compiler [and
the SGI supplied runtime libraries], so the only failures that can happen are
when there are library functions that take/return such structures.  There are
very few such library functions. I can only recall seeing a few of them:
inet_ntoa, inet_aton, inet_lnaof, inet_netof, and semctl. 

A possible workaround: if you have a program that calls inet_ntoa and friends
or semctl, and your kernel supports 64-bit binaries (i.e. uname -a prints
IRIX64 rather than just IRIX), then you may compile with gcc -mabi=64 to
workaround this problem. 

More information is available at:
http://freeware.sgi.com/2000Feb/Installable/gcc-2.8.1-sgipl2.html


* MAC OSX
---------
On Darwin (maybe others), the configure script shipped as part of the source
distribution may need to be recreated.  To do this, run the following commands:

glibtoolize --force
aclocal -I m4
autoheader
automake --add-missing --copy
autoconf

Snort needs to be linked using the two level namespace.  To do this, set the
LD_TWOLEVEL_NAMESPACE environment variable to something prior to running
configure. An example:

$ export LD_TWOLEVEL_NAMESPACE=1
$ ./configure
$ make


* MAC OSX TIGER & LEOPARD
-------------------------
For users of MAC OSX 10.5 (Leopard), the following environment variables must
be set before running configure & make. 

For users of MAC OSX 10.4 (Tiger), this also applies if the compiler has been
updated, otherwise, the instructions above may be used.

Reference information for MAC OSX can be found at these two links.

http://developer.apple.com/releasenotes/Darwin/SymbolVariantsRelNotes
http://lists.apple.com/archives/xcode-users/2007/Jun/msg00163.html

$ export LD_TWOLEVEL_NAMESPACE=1
$ export MACOSX_DEPLOYMENT_TARGET=10.5 
$ ./configure
$ make


* Open BSD / Free BSD / MAC OSX
-------------------------------
For Open BSD and some versions of Free BSD, use the --disable-static-daq
option to Snort's configure script.  This is a work-around to an issue with
building shared libraries that link against a static library.  Without this
option to configure, libsf_engine.so and the dynamic preprocessors may not
be built correctly.

On certain BSD-based platforms, the make install may not symlink the version
specific shared libraries to the non-versioned shared library.  This could
cause a failure to load when using dynamic libraries.

Work arounds:

1) Create the symlinks by hand after make install.  The shared libraries can
be located under /usr/local/lib/snort_dynamicengine and
/usr/local/lib/snort_dynamicpreprocessor.  If necessary, symlink the .so.0 or
.0.so files to a corresponding .so.

2) Use the --dynamic-preprocessor-lib (rather than
--dynamic-preprocessor-lib-dir) to load the version specific shared library.

3) Use the config directive dynamicpreprocessor file (rather than
dynamicpreprocessor directory) to load the version specific shared library.

Note that on FreeBSD and OpenBSD, divert sockets don't work with bridges. Please 
refer to the DAQ distro README for work arounds and more details.

* FreeBSD 6.x
-------------
If you run the auto tools (instead of using the delivered configure script),
you may need to include -I /usr/local/share/aclocal (in addition to -I m4) as
arguments to aclocal.  This is required to set up the correct info for using
LIBTOOL with aclocal version 1.9 that ships with FreeBSD.

In this case, the following recommended commands should be used to configure
snort prior to using make:

libtoolize --automake --copy
aclocal -I m4 -I /usr/local/share/aclocal
autoheader
automake --add-missing --copy
autoconf

Then run configure with any desired options (--enable-dynamicplugin,
etc).

