From b2c26ef18f34978ef4495fbac3a66c85fec6e494 Mon Sep 17 00:00:00 2001
From: davidsarah <>
Date: Tue, 16 Mar 2010 21:27:57 +0000
Subject: [PATCH] more about webdav

[Imported from Trac: page GSoCIdeas2010, version 93]
---
 GSoCIdeas2010.md | 52 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 50 insertions(+), 2 deletions(-)

diff --git a/GSoCIdeas2010.md b/GSoCIdeas2010.md
index 28efac0..c31a609 100644
--- a/GSoCIdeas2010.md
+++ b/GSoCIdeas2010.md
@@ -78,9 +78,57 @@ Difficulty: easy to hard, depending on project choice and how far you want to pu
 
 Invent your own Summer-of-Code project by building a new web app on top of Tahoe-LAFS. The [#SecureDecentralizedWiki Secure Decentralized Wiki] is one example of a Cloud App. See [GSoCIdeas](GSoCIdeas)/CloudApps for other ideas.
 
-# WebDAV
+# WebDAV support
+
+Difficulty: medium to hard, depending on how much of an existing WebDAV implementation you are able to reuse
+
+Implement a WebDAV front-end for Tahoe-LAFS so that files and directories stored in a distributed grid can be
+accessed by operating systems and applications that speak the WebDAV protocol. WebDAV is specified in
+[RFC 2518](http://tools.ietf.org/html/rfc2518.html) and [a few other documents](http://www.ics.uci.edu/~ejw/authoring/);
+it essentially extends HTTP to act as a filesystem access protocol. For details see #451 which describes what the Tahoe-LAFS web server does now, how this differs from what a WebDAV web server does, and how to get started experimenting with the relevant source code.
+
+The main attraction of implementing a WebDAV interface is that
+several operating systems have bundled and somewhat integrated support
+for it, including Windows, Mac OS X, and most distributions of Linux.
+In fact WebDAV may turn out to be an easier alternative to
+[SMB/CIFS](http://en.wikipedia.org/wiki/Server_Message_Block)
+for allowing filesystem access from Windows.
+
+However, there is currently no working WebDAV implementation in Twisted
+Python. There used to be one (the `web2.dav` package),
+[but it bitrotted](http://twistedmatrix.com/trac/ticket/3081).
+You'll have to decide whether to help fix that implementation, use a
+non-Twisted implementation such as [WsgiDAV](http://code.google.com/p/wsgidav/)
+that might be more difficult to integrate wth the existing Tahoe code,
+or write your own. In any case, WebDAV is a complicated protocol and
+you will need to decide what subset of it gives most "bang for the buck"
+and is practical to support in the time available. For example, locking
+is optional in the WebDAV spec; is it needed to interoperate with commonly
+used WebDAV clients?
+
+Unlike most filesystems which are constrained to be trees, the structure
+of a Tahoe is in general a cyclic graph.
+[draft-ietf-webdav-bind](http://tools.ietf.org/html/draft-ietf-webdav-bind) is
+an Internet Draft that clarifies how WebDAV servers should handle cycles.
+
+[davfs2](http://savannah.nongnu.org/projects/davfs2) is a FUSE-based
+WebDAV filesystem client for Linux. To ensure that this runs correctly
+over your implementation of WebDAV, you'll probably need to adapt the
+tests for the existing Tahoe
+["blackmatch"]source:contrib/fuse/impl_c/blackmatch.py FUSE interface
+(this would not be redundant since the blackmatch implementation has
+limitations, especially for write access, that davfs2 would not have).
+
+The [WebDAV mini-redirector](http://en.wikipedia.org/wiki/WebDAV#Microsoft_Windows)
+is the component of Windows providing its WebDAV filesystem support. It is
+actually the less buggy of
+[two implementations](http://www.zorched.net/2006/03/01/more-webdav-tips-tricks-and-bugs/), but it still has had
+[bugs](http://greenbytes.de/tech/webdav/webdav-redirector-list.html) and
+[security vulnerabilities](http://www.microsoft.com/technet/security/bulletin/MS08-007.mspx)
+that you may need to take into account.
+
+[Tickets labelled 'webdav'](http://allmydata.org/trac/tahoe-lafs/query?status=!closed&order=priority&keywords=~webdav)
 
-Implement a WebDAV front-end for Tahoe-LAFS so that files and directories stored in a distributed grid can be accessed by operating systems (including Windows, Mac, and Linux) and applications that speak the WebDAV protocol. For details see #451 which describes what the Tahoe-LAFS web server does now, how this differs from what a WebDAV web server does, and how to get started experimenting with the relevant source code.
 
 # Distributed Introduction