## ProFTPD module `mod_sql_odbc`

ODBC means Open Database Connectivity, and defines a standard way of connecting to a database server such as MySQL, Postgres, SQL Server, Oracle, etc. Many of the these databases also provide their own native APIs for connectivity, in addition to supporting ODBC. Other databases provide ODBC support, but no support for native connectivity.

The ProFTPD distribution includes the `mod_sql_mysql` module for talking to a MySQL database using the native MySQL API, and a `mod_sql_postgres` for connecting to Postgres databases using the native Postgres API. However, there was no support for databases other than these -- until now. The purpose of the `mod_sql_odbc` module is to allow ProFTPD's `mod_sql` module to connect to any database that supports ODBC. This module also allows proftpd to work with databases that may already provide APIs for native connectivity, but for which a specific `mod_sql` has not yet been developed.

This module is contained in the `mod_sql_odbc.c` file for ProFTPD 1.3.x, and is not compiled by default. Installation instructions are discussed here.

The most current version of `mod_sql_odbc` is distributed with ProFTPD.

## Author

Please contact TJ Saunders <tj at castaglia.org> with any questions, concerns, or suggestions regarding this module.

## Installation

The `mod_sql_odbc` relies on one of the two following libraries for ODBC support:

      http://www.iodbc.org
      http://www.unixodbc.org

One of these ODBC libraries must be installed prior to using `mod_sql_odbc`.

Follow the usual steps for using contrib modules in proftpd, making sure to list `mod_sql`. Note that you will need to use the `LIBS` environment variable for indicating which ODBC library to link against.

For example, if you wish to use the unixODBC library, you would use:

      ./configure LIBS=-lodbc --with-modules=mod_sql:mod_sql_odbc ...
      make
      make install

On the other hand, for using the iODBC library, the invocation is slightly different, specifying a different library name:

      ./configure LIBS=-liodbc --with-modules=mod_sql:mod_sql_odbc ...
      make
      make install

You may need to specify the location of the ODBC header and library files in your `configure` command, e.g.:

      ./configure \
        LD_LIBRARY_PATH=/usr/local/odbc/lib \
        LDFLAGS=-L/usr/local/odbc/lib \
        LIBS=-lodbc \
        --with-modules=mod_sql:mod_sql_odbc \
        --with-includes=/usr/local/odbc/include \
        --with-libraries=/usr/local/odbc/lib

## Usage

Note: some of the following information is taken from:

      http://www.mysql.com/products/myodbc/manual.html#Introduction_to_ODBC

What is ODBC?
ODBC (Open Data Base Connectivity) provides a way for client programs to access a wide range of databases or data sources.

ODBC is a standardized API, developed according to the specifications of the SQL Access Group, that allows one to connect to SQL databases. It defines a set of function calls, error codes and data types that can be used to develop database-independent applications. ODBC is usually used when database independence, or simultaneous access to different data sources, is required.

For more information about ODBC, refer to:

      http://www.microsoft.com/data/odbc/

When should `mod_sql_odbc` be used?
There are two cases where a site might need to use the `mod_sql_odbc` module: when the site's database does not provide a native connectivity API (e.g. FrontBase), and when the site's database does not have a corresponding `mod_sql_db` module for it. For example, ProFTPD does not have a `mod_sql_oracle` module. Using `mod_sql_odbc` and an Oracle-provided ODBC driver would allow a site to have `proftpd` communicate with their Oracle database.

How does ODBC work?
An ODBC driver is a dynamically loadable library that knows how to talk to a specific database. Many databases come bundled with an ODBC driver. The following lists where to find ODBC drivers for the popular MySQL and Postgres databases:

MySQL ODBC Driver (MyODBC)
  http://www.mysql.com/products/myodbc/

Postgres ODBC Driver (psqlODBC)
  http://gborg.postgresql.org/project/psqlodbc/

The ODBC driver manager is a library that manages communication between the ODBC-aware application and ODBC drivers. Its main functionality includes:

- resolving Data Source Names (DSN)
- loading and unloading of the drivers
- processing ODBC function calls or passing them to the driver

The following lists some commonly used driver managers:

iODBC ODBC Driver Manager for Unix
  http://www.iodbc.org

unixODBC Driver Manager for Unix
  http://www.unixodbc.org

Microsoft Windows ODBC Driver Manager
  http://www.microsoft.com/data/

Environment Variables
There are two environment variables that both the iODBC and unixODBC libraries use: `LD_LIBRARY_PATH` and `ODBCINI`. The `ODBCINI` environment variable specifies the configuration file used by the library; this file specifies the driver to use, and any database connection information that driver may need.The `LD_LIBRARY_PATH` environment variable is used to tell the Driver Manager where it may find the driver libraries. Note that on a Linux system, if the `/etc/ld.so.conf` contains the directory where the ODBC driver libraries live (and `/sbin/ldconfig` has been run), use of the `LD_LIBRARY_PATH` setting may not be necessary.

Configuring ODBC
The hard part about using the iODBC or unixODBC Unix driver managers is their configuration. Often in ODBC documentation you will mention of DSNs, or Data Source Names. A data source identifies a path to data that can include a network library, server, database, and other attributes. To connect to a data source, the driver manager checks for specific connection information. This specific connection information is recorded in a file usually called "odbc.ini".

Example iODBC `odbc.ini` file:

      [ODBC Data Sources]
      mysql = MySQL ODBC Connector (MyODBC)

      [mysql]
      Driver = /usr/local/iodbc/lib/libmyodbc3.so
      Description = MySQL Driver
      Server = localhost
      Database = proftpd
      Port = 3306
      Socket = /tmp/mysql.sock

Example unixODBC `odbc.ini` file:

      [mysql]
      Description = MySQL
      Driver = mysql
      Server = localhost
      Database = proftpd
      Port = 3306
      Socket = /tmp/mysql.sock

More details on the contents of `odbc.ini` files, and the different meanings of configuration options, can be found in the respective driver manager documentation.

Configuring `mod_sql_odbc`
For the most part, `mod_sql_odbc` requires little configuration. It relies on the ODBC driver managers, which in turn use the above environment variables. This means that `ODBCINI` and `LD_LIBRARY_PATH` can be set in the environment, before starting `proftpd`, and `mod_sql_odbc` would then just work.

Starting with proftpd 1.2.10rc1, it is possible to use the `SetEnv` configuration directives to set the environment variables directly in the `proftpd.conf` file, which makes configuration more centralized. Example configuration using `SetEnv`:

      <IfModule mod_sql_odbc.c>
        SetEnv LD_LIBRARY_PATH /path/to/odbc/lib
        SetEnv ODBCINI /path/to/odbc.ini
      </IfModule>

Please contact the author directly with any questions or comments.

Author: $Author: castaglia $
Last Updated: $Date: 2008/03/13 17:27:28 $

© Copyright 2003-2008 TJ Saunders
All Rights Reserved