mirror of
https://github.com/apache/httpd.git
synced 2025-10-31 19:10:37 +03:00
382c21439a
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@88609 13f79535-47bb-0310-9956-ffa450edef68
306 lines
13 KiB
HTML
306 lines
13 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
|
|
<HTML>
|
|
<HEAD>
|
|
<TITLE>Apache HTTP Server Project</TITLE>
|
|
</HEAD>
|
|
|
|
<!-- Background white, links blue (unvisited), navy (visited), red (active) -->
|
|
<BODY
|
|
BGCOLOR="#FFFFFF"
|
|
TEXT="#000000"
|
|
LINK="#0000FF"
|
|
VLINK="#000080"
|
|
ALINK="#FF0000"
|
|
>
|
|
<!--#include virtual="header.html" -->
|
|
<H1 ALIGN="CENTER">Known Problems in Clients</H1>
|
|
|
|
<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>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>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>Various of these workarounds are triggered by environment variables.
|
|
The admin typically controls which are set, and for which clients, by using
|
|
<A HREF="../mod/mod_browser.html">mod_browser</A>. Unless otherwise
|
|
noted all of these workarounds exist in versions 1.2 and later.
|
|
|
|
<H3><A NAME="trailing-crlf">Trailing CRLF on POSTs</A></H3>
|
|
|
|
<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.
|
|
|
|
<H3><A NAME="broken-keepalive">Broken keepalive</A></H3>
|
|
|
|
<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:
|
|
<BLOCKQUOTE><CODE>
|
|
BrowserMatch Mozilla/2 nokeepalive
|
|
</CODE></BLOCKQUOTE>
|
|
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>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:
|
|
<BLOCKQUOTE><CODE>
|
|
BrowserMatch "MSIE 4\.0b2;" nokeepalive
|
|
</CODE></BLOCKQUOTE>
|
|
|
|
<H3><A NAME="force-response-1.0">Incorrect interpretation of
|
|
<CODE>HTTP/1.1</CODE> in response</A></H3>
|
|
|
|
<P>To quote from section 3.1 of RFC1945:
|
|
<BLOCKQUOTE>
|
|
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.
|
|
</BLOCKQUOTE>
|
|
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>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>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:
|
|
<BLOCKQUOTE><CODE>
|
|
BrowserMatch Java/1.0 force-response-1.0 <BR>
|
|
BrowserMatch JDK/1.0 force-response-1.0
|
|
</CODE></BLOCKQUOTE>
|
|
|
|
<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:
|
|
<BLOCKQUOTE><CODE>
|
|
BrowserMatch "RealPlayer 4.0" force-response-1.0
|
|
</CODE></BLOCKQUOTE>
|
|
|
|
<H3><A NAME="msie4.0b2">Requests use HTTP/1.1 but responses must be
|
|
in HTTP/1.0</A></H3>
|
|
|
|
<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.
|
|
<BLOCKQUOTE><CODE>
|
|
BrowserMatch "MSIE 4\.0b2;" downgrade-1.0 force-response-1.0
|
|
</CODE></BLOCKQUOTE>
|
|
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.
|
|
|
|
<H3><A NAME="257th-byte">Boundary problems with header parsing</A></H3>
|
|
|
|
<P>All versions of Navigator from 2.0 through 4.0b2 (and possibly later)
|
|
have a problem if the trailing CRLF of the response header starts at
|
|
offset 256, 257 or 258 of the response. A BrowserMatch for this would
|
|
match on nearly every hit, so the workaround is enabled automatically
|
|
on all responses. The workaround implemented detects when this condition would
|
|
occur in a response and adds extra padding to the header to push the
|
|
trailing CRLF past offset 258 of the response.
|
|
|
|
<H3><A NAME="boundary-string">Multipart responses and Quoted Boundary
|
|
Strings</A></H3>
|
|
|
|
<P>On multipart responses some clients will not accept quotes (")
|
|
around the boundary string. The MIME standard recommends that
|
|
such quotes be used. But the clients were probably written based
|
|
on one of the examples in RFC2068, which does not include quotes.
|
|
Apache does not include quotes on its boundary strings to workaround
|
|
this problem.
|
|
|
|
<H3><A NAME="byterange-requests">Byterange requests</A></H3>
|
|
|
|
<P>A byterange request is used when the client wishes to retrieve a
|
|
portion of an object, not necessarily the entire object. There
|
|
was a very old draft which included these byteranges in the URL.
|
|
Old clients such as Navigator 2.0b1 and MSIE 3.0 for the MAC
|
|
exhibit this behaviour, and
|
|
it will appear in the servers' access logs as (failed) attempts to
|
|
retrieve a URL with a trailing ";xxx-yyy". Apache does not attempt
|
|
to implement this at all.
|
|
|
|
<P>A subsequent draft of this standard defines a header
|
|
<CODE>Request-Range</CODE>, and a response type
|
|
<CODE>multipart/x-byteranges</CODE>. The HTTP/1.1 standard includes
|
|
this draft with a few fixes, and it defines the header
|
|
<CODE>Range</CODE> and type <CODE>multipart/byteranges</CODE>.
|
|
|
|
<P>Navigator (versions 2 and 3) sends both <CODE>Range</CODE> and
|
|
<CODE>Request-Range</CODE> headers (with the same value), but does not
|
|
accept a <CODE>multipart/byteranges</CODE> response. The response must
|
|
be <CODE>multipart/x-byteranges</CODE>. As a workaround, if Apache
|
|
receives a <CODE>Request-Range</CODE> header it considers it "higher
|
|
priority" than a <CODE>Range</CODE> header and in response uses
|
|
<CODE>multipart/x-byteranges</CODE>.
|
|
|
|
<P>The Adobe Acrobat Reader plugin makes extensive use of byteranges and
|
|
prior to version 3.01 supports only the <CODE>multipart/x-byterange</CODE>
|
|
response. Unfortunately there is no clue that it is the plugin
|
|
making the request. If the plugin is used with Navigator, the above
|
|
workaround works fine. But if the plugin is used with MSIE 3 (on
|
|
Windows) the workaround won't work because MSIE 3 doesn't give the
|
|
<CODE>Range-Request</CODE> clue that Navigator does. To workaround this,
|
|
Apache special cases "MSIE 3" in the <CODE>User-Agent</CODE> and serves
|
|
<CODE>multipart/x-byteranges</CODE>. Note that the necessity for this
|
|
with MSIE 3 is actually due to the Acrobat plugin, not due to the browser.
|
|
|
|
<P>Netscape Communicator appears to not issue the non-standard
|
|
<CODE>Request-Range</CODE> header. When an Acrobat plugin prior to
|
|
version 3.01 is used with it, it will not properly understand byteranges.
|
|
The user must upgrade their Acrobat reader to 3.01.
|
|
|
|
<H3><A NAME="cookie-merge"><CODE>Set-Cookie</CODE> header is
|
|
unmergeable</A></H3>
|
|
|
|
<P>The HTTP specifications say that it is legal to merge headers with
|
|
duplicate names into one (separated by commas). Some browsers
|
|
that support Cookies don't like merged headers and prefer that each
|
|
<CODE>Set-Cookie</CODE> header is sent separately. When parsing the
|
|
headers returned by a CGI, Apache will explicitly avoid merging any
|
|
<CODE>Set-Cookie</CODE> headers.
|
|
|
|
<H3><A NAME="gif89-expires"><CODE>Expires</CODE> headers and GIF89A
|
|
animations</A></H3>
|
|
|
|
<P>Navigator versions 2 through 4 will erroneously re-request
|
|
GIF89A animations on each loop of the animation if the first
|
|
response included an <CODE>Expires</CODE> header. This happens
|
|
regardless of how far in the future the expiry time is set. There
|
|
is no workaround supplied with Apache, however there are hacks for <A
|
|
HREF="http://www.arctic.org/~dgaudet/patches/apache-1.2-gif89-expires-hack.patch">1.2</A>
|
|
and for <A
|
|
HREF="http://www.arctic.org/~dgaudet/patches/apache-1.3-gif89-expires-hack.patch">1.3</A>.
|
|
|
|
<H3><A NAME="no-content-length"><CODE>POST</CODE> without
|
|
<CODE>Content-Length</CODE></A></H3>
|
|
|
|
<P>In certain situations Navigator 3.01 through 3.03 appear to incorrectly
|
|
issue a POST without the request body. There is no
|
|
known workaround. It has been fixed in Navigator 3.04, Netscapes
|
|
provides some
|
|
<A HREF="http://help.netscape.com/kb/client/971014-42.html">information</A>.
|
|
There's also
|
|
<A HREF="http://www.arctic.org/~dgaudet/apache/no-content-length/">
|
|
some information</A> about the actual problem.
|
|
|
|
<H3><A NAME="jdk-12-bugs">JDK 1.2 betas lose parts of responses.</A></H3>
|
|
|
|
<P>The http client in the JDK1.2beta2 and beta3 will throw away the first part of
|
|
the response body when both the headers and the first part of the body are sent
|
|
in the same network packet AND keep-alive's are being used. If either condition
|
|
is not met then it works fine.
|
|
|
|
<P>See also Bug-ID's 4124329 and 4125538 at the java developer connection.
|
|
|
|
<P>If you are seeing this bug yourself, you can add the following BrowserMatch
|
|
directive to work around it:
|
|
|
|
<BLOCKQUOTE><CODE>
|
|
BrowserMatch "Java1\.2beta[23]" nokeepalive
|
|
</CODE></BLOCKQUOTE>
|
|
|
|
<P>We don't advocate this though since bending over backwards for beta software
|
|
is usually not a good idea; ideally it gets fixed, new betas or a final release
|
|
comes out, and no one uses the broken old software anymore. In theory.
|
|
|
|
<H3><A NAME="content-type-persistence"><CODE>Content-Type</CODE> change
|
|
is not noticed after reload</A></H3>
|
|
|
|
<P>Navigator (all versions?) will cache the <CODE>content-type</CODE>
|
|
for an object "forever". Using reload or shift-reload will not cause
|
|
Navigator to notice a <CODE>content-type</CODE> change. The only
|
|
work-around is for the user to flush their caches (memory and disk). By
|
|
way of an example, some folks may be using an old <CODE>mime.types</CODE>
|
|
file which does not map <CODE>.htm</CODE> to <CODE>text/html</CODE>,
|
|
in this case Apache will default to sending <CODE>text/plain</CODE>.
|
|
If the user requests the page and it is served as <CODE>text/plain</CODE>.
|
|
After the admin fixes the server, the user will have to flush their caches
|
|
before the object will be shown with the correct <CODE>text/html</CODE>
|
|
type.
|
|
|
|
<h3><a name="msie-cookie-y2k">MSIE Cookie problem with expiry date in
|
|
the year 2000</a></h3>
|
|
|
|
<p>MSIE versions 3.00 and 3.02 (without the Y2K patch) do not handle
|
|
cookie expiry dates in the year 2000 properly. Years after 2000 and
|
|
before 2000 work fine. This is fixed in IE4.01 service pack 1, and in
|
|
the Y2K patch for IE3.02. Users should avoid using expiry dates in the
|
|
year 2000.
|
|
|
|
<h3><a name="lynx-negotiate-trans">Lynx incorrectly asking for transparent
|
|
content negotiation</a></h3>
|
|
|
|
<p>The Lynx browser versions 2.7 and 2.8 send a "negotiate: trans" header
|
|
in their requests, which is an indication the browser supports transparent
|
|
content negotiation (TCN). However the browser does not support TCN.
|
|
As of version 1.3.4, Apache supports TCN, and this causes problems with
|
|
these versions of Lynx. As a workaround future versions of Apache will
|
|
ignore this header when sent by the Lynx client.
|
|
|
|
<h3><a name="ie40-vary">MSIE 4.0 mishandles Vary response header</a></h3>
|
|
|
|
<p>MSIE 4.0 does not handle a Vary header properly. The Vary header is
|
|
generated by mod_rewrite in apache 1.3. The result is an error from MSIE
|
|
saying it cannot download the requested file. There are more details
|
|
in <a href="http://bugs.apache.org/index/full/4118">PR#4118</a>.
|
|
</P>
|
|
<P>
|
|
A workaround is to add the following to your server's configuration
|
|
files:
|
|
</P>
|
|
<PRE>
|
|
BrowserMatch "MSIE 4\.0" force-no-vary
|
|
</PRE>
|
|
<P>
|
|
(This workaround is only available with releases <STRONG>after</STRONG>
|
|
1.3.6 of the Apache Web server.)
|
|
</P>
|
|
|
|
|
|
<!--#include virtual="footer.html" -->
|
|
</BODY>
|
|
</HTML>
|
|
|