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<title>Known Problems in Clients - Apache HTTP Server</title>
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<p class="apache">Apache HTTP Server Version 2.0</p>
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.0</a> > <a href="./">Miscellaneous Documentation</a></div><div id="page-content"><div id="preamble"><h1>Known Problems in Clients</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="../en/misc/known_client_problems.html" title="English"> en </a></p>
</div>
<div class="warning"><h3>Warning:</h3>
<p>This document has not been fully updated
to take into account changes made in the 2.0 version of the
Apache HTTP Server. Some of the information may still be
relevant, but please use it with care.</p>
</div>
<p>Over time the Apache Group has discovered or been notified
of problems with various clients which we have had to work
around, or explain. This document describes these problems and
the workarounds available. It's not arranged in any particular
order. Some familiarity with the standards is assumed, but not
necessary.</p>
<p>For brevity, <em>Navigator</em> will refer to Netscape's
Navigator product (which in later versions was renamed
"Communicator" and various other names), and <em>MSIE</em> will
refer to Microsoft's Internet Explorer product. All trademarks
and copyrights belong to their respective companies. We welcome
input from the various client authors to correct
inconsistencies in this paper, or to provide us with exact
version numbers where things are broken/fixed.</p>
<p>For reference, <a href="ftp://ds.internic.net/rfc/rfc1945.txt">RFC1945</a>
defines HTTP/1.0, and <a href="ftp://ds.internic.net/rfc/rfc2068.txt">RFC2068</a>
defines HTTP/1.1. Apache as of version 1.2 is an HTTP/1.1
server (with an optional HTTP/1.0 proxy).</p>
<p>Various of these workarounds are triggered by environment
variables. The admin typically controls which are set, and for
which clients, by using <code>mod_browser</code>. Unless
otherwise noted all of these workarounds exist in versions 1.2
and later.</p>
</div>
<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#trailing-crlf">Trailing CRLF on POSTs</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#broken-keepalive">Broken KeepAlive</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#force-response-1.0">Incorrect interpretation of
<code>HTTP/1.1</code> in response</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#msie4.0b2">Requests use HTTP/1.1 but
responses must be in HTTP/1.0</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#byte-257">Boundary problems with
header parsing</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#boundary-string">Multipart responses and
Quoted Boundary Strings</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#byterange-requests">Byterange Requests</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#cookie-merge"><code>Set-Cookie</code> header is
unmergeable</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#gif89-expires"><code>Expires</code> headers
and GIF89A animations</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#no-content-length"><code>POST</code> without
<code>Content-Length</code></a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#jdk-12-bugs">JDK 1.2 betas lose
parts of responses.</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#content-type-persistent"><code>Content-Type</code>
change is not noticed after reload</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#msie-cookie-y2k">MSIE Cookie
problem with expiry date in the year 2000</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#lynx-negotiate-trans">Lynx incorrectly asking for
transparent content negotiation</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#ie40-vary">MSIE 4.0 mishandles Vary
response header</a></li>
</ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="trailing-crlf" id="trailing-crlf">Trailing CRLF on POSTs</a></h2>
<p>This is a legacy issue. The CERN webserver required
<code>POST</code> data to have an extra <code>CRLF</code>
following it. Thus many clients send an extra <code>CRLF</code>
that is not included in the <code>Content-Length</code> of the
request. Apache works around this problem by eating any empty
lines which appear before a request.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="broken-keepalive" id="broken-keepalive">Broken KeepAlive</a></h2>
<p>Various clients have had broken implementations of
<em>keepalive</em> (persistent connections). In particular the
Windows versions of Navigator 2.0 get very confused when the
server times out an idle connection. The workaround is present
in the default config files:</p>
<div class="example"><p><code>
BrowserMatch Mozilla/2 nokeepalive
</code></p></div>
<p>Note that this matches some earlier versions of MSIE, which
began the practice of calling themselves <em>Mozilla</em> in
their user-agent strings just like Navigator.</p>
<p>MSIE 4.0b2, which claims to support HTTP/1.1, does not
properly support keepalive when it is used on 301 or 302
(redirect) responses. Unfortunately Apache's
<code>nokeepalive</code> code prior to 1.2.2 would not work
with HTTP/1.1 clients. You must apply <a href="http://www.apache.org/dist/httpd/patches/apply_to_1.2.1/msie_4_0b2_fixes.patch">
this patch</a> to version 1.2.1. Then add this to your
config:</p>
<div class="example"><p><code>
BrowserMatch "MSIE 4\.0b2;" nokeepalive
</code></p></div>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="force-response-1.0" id="force-response-1.0">Incorrect interpretation of
<code>HTTP/1.1</code> in response</a></h2>
<p>To quote from section 3.1 of RFC1945:</p>
<div class="note">
HTTP uses a "<MAJOR>.<MINOR>" numbering scheme to
indicate versions of the protocol. The protocol versioning
policy is intended to allow the sender to indicate the format
of a message and its capacity for understanding further HTTP
communication, rather than the features obtained via that
communication.
</div>
<p>Since Apache is an HTTP/1.1 server, it indicates so as part of
its response. Many client authors mistakenly treat this part of
the response as an indication of the protocol that the response
is in, and then refuse to accept the response.</p>
<p>The first major indication of this problem was with AOL's
proxy servers. When Apache 1.2 went into beta it was the first
wide-spread HTTP/1.1 server. After some discussion, AOL fixed
their proxies. In anticipation of similar problems, the
<code>force-response-1.0</code> environment variable was added
to Apache. When present Apache will indicate "HTTP/1.0" in
response to an HTTP/1.0 client, but will not in any other way
change the response.</p>
<p>The pre-1.1 Java Development Kit (JDK) that is used in many
clients (including Navigator 3.x and MSIE 3.x) exhibits this
problem. As do some of the early pre-releases of the 1.1 JDK.
We think it is fixed in the 1.1 JDK release. In any event the
workaround:</p>
<div class="example"><p><code>
BrowserMatch Java/1.0 force-response-1.0<br />
BrowserMatch JDK/1.0 force-response-1.0
</code></p></div>
<p>RealPlayer 4.0 from Progressive Networks also exhibits this
problem. However they have fixed it in version 4.01 of the
player, but version 4.01 uses the same <code>User-Agent</code>
as version 4.0. The workaround is still:</p>
<div class="example"><p><code>
BrowserMatch "RealPlayer 4.0" force-response-1.0
</code></p></div>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="msie4.0b2" id="msie4.0b2">Requests use HTTP/1.1 but
responses must be in HTTP/1.0</a></h2>
<p>MSIE 4.0b2 has this problem. Its Java VM makes requests in
HTTP/1.1 format but the responses must be in HTTP/1.0 format
(in particular, it does not understand <em>chunked</em>
responses). The workaround is to fool Apache into believing the
request came in HTTP/1.0 format.</p>
<div class="example"><p><code>
BrowserMatch "MSIE 4\.0b2;" downgrade-1.0
force-response-1.0
</code></p></div>
<p>This workaround is available in 1.2.2, and in a <a href="http://www.apache.org/dist/httpd/patches/apply_to_1.2.1/msie_4_0b2_fixes.patch">
patch</a> against 1.2.1.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="byte-257" id="byte-257">Boundary problems with
header parsing</a></h2>
<p>All versions of Navigator from 2.0 through 4.0b2 (and
possibly later) have a problem if the trailing CRLF of the
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