从远程URL提交帖子表单

I have two sites, both sites have the same form:

<form method="post" action="#">
    <p><label for="u_name">Username: </label><input type="text" name="u_name" value=""></p>

    <p><label for="u_pass">Password: </label><input type="password" name="u_pass" value=""></p>

    <p><button type="submit" name="go">login</button></p>
</form>

The form on site 2 goes to a secret page, but i need the form on site 1 to go to that same secret page on site 2s server.

How can i pass on the post form data from site 1 to site 2 and thus skip the site 2 log in page?

<form method="post" action="http://site2.com/login">

This is bad practice though, see CSRF.