Use Oxid eShop with nginx

config.inc.php

if (@$_SERVER['SERVER_NAME'] == 'katzentest-ssl.local'){
        $this->_blIsSsl = true;                                                                                                                             
}                                                                                                                                                       
                                                                                                                                                        
if(isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {
        $list = explode(',',$_SERVER['HTTP_X_FORWARDED_FOR']);
        $_SERVER['REMOTE_ADDR'] = $list[0];
        $_SERVER['HTTP_HOST'] = 'katzentest.com';
        $_SERVER['SERVER_NAME'] = 'katzentest.com';                                                                                                            
}

And in the nginx location you will have to specify the HTTP_X_FORWARDED_FOR header:
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;