twisted.web.server.Request does not honor Host HTTP headers

[orestis]

When a twisted web server is placed behind a proxy, requests should honor the proxy-set Host: header in order to set the hostname and port at _prePathURL.

Current behavior picks up the correct hostname, but use the internal listening port, instead of the proxy-used listening port. In my particular instance, this breaks an athena-powered service when placed behind a proxy.

A patch is floating on the twisted-web mailing list: ​http://twistedmatrix.com/pipermail/twisted-web/2005-December/002241.html

Pasted here for reference, original author Richard Wall:

home/richard/lib/Twisted/trunk/twisted/web/server.py

@@ -342 +342 @@
         return self.session
 
     def _prePathURL(self, prepath):
-        port = self.getHost().port
         if self.isSecure():
             default = 443
         else:
             default = 80
+        
+        # There won't always be a hostheader, but if it's present, try and find 
+        # the port number from it.
+        hostheader = self.getHeader('host')
+        if hostheader:
+            hostheader = hostheader.split(":", 1)
+            if len(hostheader) == 2:
+                port = int(hostheader[1])
+            else:
+                port = default
+        else:
+            port = self.getHost().port
+            
         if port == default:
             hostport = ''
         else:

The current twisted literature suggests using a VHostMonsterResource, but this feels clunky. If it covers any additional use-cases that using Host: doesn't, it should explain so in the documentation.