If you want to build mod_tsunami as a dynamic module:

apxs -o mod_tsunami.so -c mod_tsunami.c
cp mod_tsunami.so /path/to/the/apache/modules/directory/.

Use these directives in your httpd.conf:

TsunamiActive		On/Off
TsunamiTrigger		total simultaneous requests needed to start protection
TsunamiMaxConnections	maximum simultaneous requests allowed per vhost

When the value of TsunamiMaxConnections is set to '0' (default behaviour), mod_tsunami doesn't reject any request.
