Create link with node id parameter
You do not need a link field for that. You can generate link at theme level for example. Or even better in hook_node_view:


  The module may add elements to $node-&gt;content prior to rendering. This hook will be called after hook_view(). The structure of $node-&gt;content is a renderable array as expected by drupal_render().


Last but not least, if you really want it to be a field, use Computed Field and have it calculated at save.


  Computed Field is a very powerful field module that lets you add a custom "computed fields" to your content types. These computed fields are populated with values that you define via PHP code. You may draw on anything available to Drupal, including other fields, the current user, database tables, you name it.