? filter_absolute_urls.patch
? sites/default/settings.php
Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.687
diff -u -F^f -r1.687 common.inc
--- includes/common.inc	15 Sep 2007 07:33:46 -0000	1.687
+++ includes/common.inc	19 Sep 2007 19:18:36 -0000
@@ -850,6 +850,30 @@ function check_url($uri) {
 }
 
 /**
+ * Convert relative URLs in a block of HTML to absolute URLs.
+ *
+ * @param $url
+ *   A possibly relative URL.
+ * @param $absolute_url
+ *   Any absolute URL to this Drupal website.
+ */
+function filter_absolute_urls($url, $absolute_url) {
+  $absolute_url_root = (preg_match('%(.*://.*?)/%', $absolute_url, $matches) > 0) ? $matches[1] : $absolute_url;
+
+  // Relative URLs.
+  $src = '%( href| src)="(?!\w+://)([^/][^"]*)"%';
+  $dst = '$1="'. $absolute_url .'/$2"';
+  $url = preg_replace($src, $dst, $url);
+
+  // URLs that are relative to the root.
+  $src = '%( href| src)="(?!\w+://)/?([^"]*)"%';
+  $dst = '$1="'. trim($absolute_url_root, '/') .'/$2"';
+  $url = preg_replace($src, $dst, $url);
+
+  return $url;
+}
+
+/**
  * @defgroup format Formatting
  * @{
  * Functions to format numbers, strings, dates, etc.
@@ -889,7 +913,7 @@ function format_rss_item($title, $link, 
   $output = "<item>\n";
   $output .= ' <title>'. check_plain($title) ."</title>\n";
   $output .= ' <link>'. check_url($link) ."</link>\n";
-  $output .= ' <description>'. check_plain($description) ."</description>\n";
+  $output .= ' <description>'. check_plain(filter_absolute_urls($description, $link)) ."</description>\n";
   $output .= format_xml_elements($args);
   $output .= "</item>\n";