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Re: Collections and Request-URIs

From: Greg Stein <gstein@lyra.org>
Date: Tue, 18 Jun 2002 15:37:04 -0700
To: Jim Luther <luther.j@apple.com>
Cc: w3c-dist-auth@w3c.org, fielding@apache.org
Message-ID: <20020618153704.F1848@lyra.org>

On Mon, Jun 17, 2002 at 04:45:44PM -0700, Jim Luther wrote:
>...
> So by my reading, abs_path should not have a trailing slash. Did I miss 
> something? If not, I think the WebDAV spec should say that servers MUST 
> handle Request-URIs to collections without the trail slash.

As mentioned previously, the trailing-slash form matches the BNF.

> Anyway, trailing slashes issue causes an interoperability problem for 
> our WebDAV file system and Apache 2.0 servers.  Since Mac OS X's WebDAV 
> file system doesn't know if the end path component passed to it is a 
> collection or non-collection resource, it doesn't put a trailing slash 
> on the Request-URI. This works on all servers except for Apache 2 which 
> sends us a "301 Moved Permanently" response. We don't redirect because 
> the HTTP spec (RFC 2616, section 10.3.2) says:
> 
> "If the 301 status code is received in response to a request other than 
> GET or HEAD, the user agent MUST NOT automatically redirect the request 
> unless it can be confirmed by the user, since this might change the 
> conditions under which the request was issued."

Roy Fielding has previous stated that RFC 2616's language is incorrect. The
spec is supposed to allow things like PROPFIND. I forget the exact
terminology that Roy used (i.e. was it "*all* idempotent methods"? or
something else), but PROPFIND was among them.

This topic was extensively discussed on the Apache development list when we
added that redirection code (actually, we fixed a bug that prevented the
"proper" behavior of redirecting for all methods). That was when Roy chimed
in about RFC 2616 being slightly incorrect, that a redirection is legal,
that Apache 2.0 "should" go ahead and redirect, and that the clients who are
*not* following the redirect are simply broken.

And given that the non-following clients are "broken", we went ahead and
made the default behavior to do the redirection, and called out the broken
clients in the standard distribution of httpd.conf.

>...
> 	#
> 	# The following directive disables redirects on non-GET requests for
> 	# a directory that does not include the trailing slash.  This fixes a
> 	# problem with Microsoft WebFolders which does not appropriately handle
> 	# redirects for folders with DAV methods.
> 	#
> 	BrowserMatch "Microsoft Data Access Internet Publishing Provider" 
> redirect-carefully
> 	BrowserMatch "^WebDrive" redirect-carefully
> 
> So if we add a similar line:
> 
> 	BrowserMatch "^WebDAVFS" redirect-carefully
> 
> to Apache's httpd.conf file to do a redirect-carefully for our 
> User-Agent, our client works great with Apache 2 DAV servers.

My response would be "fix your client. do the redirect."  :-)

If that is going to be impossible to do, then I can add that line to
httpd.conf. But I'm reluctant to just start adding stuff. Your client really
is "broken" (for some definition thereof :-) if it isn't following the 301.

Cheers,
-g

-- 
Greg Stein, http://www.lyra.org/
Received on Tuesday, 18 June 2002 18:35:03 GMT

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