Вот, может поможет:
<?php
function getIp($checkProxy = true) {
if ($checkProxy && !empty($_SERVER['HTTP_CLIENT_IP'])) {
$ip = $_SERVER['HTTP_CLIENT_IP'];
} else if ($checkProxy && !empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
$ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
} else {
$ip = $_SERVER['REMOTE_ADDR'];
}
return $ip;
}
echo getIp();
?>

<?php

/**
* Implements hook_user_login().
*/
function YOURMODULE_user_login($edit, $user) {
drupal_set_message(t('You have successfuly logged in. Your IP: @ip.',
array('@ip' =>ip_address())
)
);
}

?>

hook_user_login() — http://api.drupal.org/api/drupal/modules%21user%21user.api.php/function/...
drupal_set_message() — http://api.drupal.org/api/drupal/includes%21bootstrap.inc/function/drupa...
ip_address() — http://api.drupal.org/api/drupal/includes%21bootstrap.inc/function/ip_ad...
t() — http://api.drupal.org/api/drupal/includes%21bootstrap.inc/function/t/7