Full image link back to post

Hello,
I edit a few the attachment.php k2 template for open full size image with header, link:

https://zaasrvr.com/2007/03/test/p1300472jpg/

Now, i don’t know how set a link to the image for back to the post like the title post.

The code:

<?php get_header(); ?>
<br /><br /><br />
<h2 align="center" class="entry-title"><a href="<?php echo get_permalink($post->post_parent); ?>"><?php echo get_the_title($post->post_parent); ?></a><br />
</h2>
<div align="center"><br />
  <br />

  <div align="center">
  <?php $attachment_link = get_the_attachment_link($post->ID, true); ?>

  <? echo $attachment_link;?>
  <br />
  <br />
</div

Any idea how add the image link to click in the image to back the post?
Thanks
excuses me English.