protocol/4118: Client bug: IE 4.0 breaks with "Vary" header

[Nick Kralevich <ni...@cal.alumni.berkeley.edu>]

>Number:         4118
>Category:       protocol
>Synopsis:       Client bug: IE 4.0 breaks with "Vary" header
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    apache
>State:          open
>Class:          doc-bug
>Submitter-Id:   apache
>Arrival-Date:   Wed Mar 24 18:20:00 PST 1999
>Last-Modified:
>Originator:     nickkral@cal.alumni.berkeley.edu
>Organization:
apache
>Release:        1.3.4
>Environment:
Windows 95, Windows NT, Internet Explorer 4.0 -- version 4.72.2106.8
>Description:
Client Bug!  Not an apache bug!  I couldn't find the appropriate 
category for client bugs.

This is also related to problem report 4117 that I filed a few minutes
ago.  That problem is an apache bug, not a client bug.

When Internet Explorer receives a "Vary: Host" header, or a "Vary: *"
header, the system will improperly report "file not found".  The exact
error message is:

"Internet Explorer cannot download from the Internet site viewer.zip from 
palm.dahm.com.  The downloaded file is not available.  This could be due 
to your Security or Language settings or because the server was unable to 
retrieve the requested file."

Specifically, when IE received the following headers, it failed:

  HTTP/1.1 200 OK
  Date: Wed, 24 Mar 1999 21:36:09 GMT
  Server: Apache/1.3.4 (Unix)
  Vary: Host, Host
  Last-Modified: Tue, 16 Mar 1999 21:34:37 GMT
  ETag: "1a4923-684bd-36eece6d"
  Accept-Ranges: bytes
  Content-Length: 427197
  Keep-Alive: timeout=15, max=100
  Connection: Keep-Alive
  Content-Type: application/zip

  [contents of zip file]

However, when the following headers were received, IE had no
problem downloading the file:

  HTTP/1.1 200 OK
  Date: Wed, 24 Mar 1999 21:36:09 GMT
  Server: Apache/1.3.4 (Unix)
  Last-Modified: Tue, 16 Mar 1999 21:34:37 GMT
  ETag: "1a4923-684bd-36eece6d"
  Accept-Ranges: bytes
  Content-Length: 427197
  Keep-Alive: timeout=15, max=100
  Connection: Keep-Alive
  Content-Type: application/zip

  [contents of zip file]

the only difference being the "Vary:" line is missing.

Mod_rewrite (and others) add the "vary" header, so this could be an 
important client issue.
>How-To-Repeat:
This should work, although I haven't tried it.

Add the following line to your apache config file:

  Header append Vary: Host

Then try to download a "zip" file from IE and Netscape.  On IE
it will not work, Netscape it will work.
>Fix:
Server workaround:  Add the following option to the apache config file:

  Header unset Vary:

This may have adverse consequences for other proxy servers.
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