Fixed #11877 -- Documented that HttpRequest.get_host() fails behind multiple reverse proxies, and added an example middleware solution. Thanks to Tom Evans for the report, and arnav for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14493 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/ref/request-response.txt

@@ -221,6 +221,29 @@ Methods
 
     Example: ``"127.0.0.1:8000"``
 
+    .. note:: The :meth:`~HttpRequest.get_host()` method fails when the host is
+        behind multiple proxies. One solution is to use middleware to rewrite
+        the proxy headers, as in the following example::
+
+            class MultipleProxyMiddleware(object):
+                FORWARDED_FOR_FIELDS = [
+                    'HTTP_X_FORWARDED_FOR',
+                    'HTTP_X_FORWARDED_HOST',
+                    'HTTP_X_FORWARDED_SERVER',
+                ]
+
+                def process_request(self, request):
+                    """
+                    Rewrites the proxy headers so that only the most
+                    recent proxy is used.
+                    """
+                    for field in self.FORWARDED_FOR_FIELDS:
+                        if field in request.META:
+                            if ',' in request.META[field]:
+                                parts = request.META[field].split(',')
+                                request.META[field] = parts[-1].strip()
+
+
 .. method:: HttpRequest.get_full_path()
 
    Returns the ``path``, plus an appended query string, if applicable.