Add ![CDATA] to permalink rss

Hello,

i have this feed http://www.jobseeker.gr/?feed=job_feed
i am trying to add ![CDATA] to the link tag using the_permalink_rss filter. This is the code i have so far:

//Add cdata to job permalink rss
add_filter( 'the_permalink_rss', 'add_cdata_to_permalink' );

function add_cdata_to_permalink ( $permalink) {
       $permalink = get_post_type_archive_link( get_query_var('job_listing') );
       return '<![CDATA[' . $permalink . ']]>';

And this is the output <link>http://![CDATA[]]</link> when it should be

<link><![CDATA[permalink]]></link>

What am i missing here?
Any help is welcome