mod_dav_svn and symbolic links

["M.Eng. René Schwarz" <ma...@rene-schwarz.com>]

Hello,


I am using mod_dav_svn with Apache2 in combination with a SVN repository 
containing symbolic links. When a URL pointing to a symbolic link is 
accessed, the web server does not follow this link, but provides a text 
file with the content "link [path to file or directory]".

I was wondering if there is a possibility to make mod_dav_svn actually 
not providing this text file but the contents of the linked file directly?

Background:
An installer is downloading several files for installation from the 
repository over the web server whereas the flexibility to specify a 
certain repository revision via the "!svn/bc/" special syntax is used, 
without the need for the installer to be aware of the SVN repo itself. 
For the installer, this address is just an ordinary URL. This worked 
well for a couple of years, but now symbolic links have been used in the 
repository which is causing the trouble for the installer now as it gets 
not the actual file, but the text representation of a symbolic link.

As I am not a member of this mailing list, I would appreciate to be set 
in CC upon reply.


Thank you very much in advance for your support and kind regards,
René
-- 


Sincerely yours,


M.Eng. *René Schwarz*
mail@rene-schwarz.com
https://www.rene-schwarz.com

Re: mod_dav_svn and symbolic links

[Daniel Shahaf <d....@daniel.shahaf.name>]

Ryan Schmidt wrote on Thu, 17 Dec 2020 09:59 +00:00:
> 
> 
> On Dec 16, 2020, at 13:13, M.Eng. René Schwarz wrote:
> 
> > I am using mod_dav_svn with Apache2 in combination with a SVN repository containing symbolic links. When a URL pointing to a symbolic link is accessed, the web server does not follow this link, but provides a text file with the content "link [path to file or directory]".
> > 
> > I was wondering if there is a possibility to make mod_dav_svn actually not providing this text file but the contents of the linked file directly?
> > 
> > Background:
> > An installer is downloading several files for installation from the repository over the web server whereas the flexibility to specify a certain repository revision via the "!svn/bc/" special syntax is used, without the need for the installer to be aware of the SVN repo itself. For the installer, this address is just an ordinary URL. This worked well for a couple of years, but now symbolic links have been used in the repository which is causing the trouble for the installer now as it gets not the actual file, but the text representation of a symbolic link.
> 
> As far as I know, mod_dav_svn does not have this capability.

+1

> mod_dav_svn is a server process, and symlinks are a client-side-only 
> feature. The server has no knowledge of symlinks and just stores the 
> files and their properties. The Subversion client stores symlinks in 
> the repository exactly as you're experiencing: as a text file with the 
> contents "link [path to file or directory]" and a property 
> "svn:special" set to the value "*".
> 
> In this case, your installer is acting as the Subversion client, so you 
> would have to modify your installer code to get it to notice when a 
> file it's accessing is a symlink and to make it send another request to 
> get the real file from its actual location. If you want to do it right, 
> you should consider that there could of course be multiple levels of 
> symlink indirection, and any of the directories leading up to the file 
> you want could be symlinks.

The need for Ω(1) round trips is a good argument for adding a server-side
symlink resolution thing (similar to the ?p= query argument already
supported), though we'd have to be careful about dot-dot symlinks that
point to above the repository root or into !svn (which is a perfectly
valid dirent name to lower layers), symlink loops, etc..

It's possible some repository viewers (ViewVC-like tools) already
provide this functionality.

Note that !svn and everything under it are implementation details.

Cheers,

Daniel

Re: mod_dav_svn and symbolic links

[Ryan Schmidt <su...@ryandesign.com>]

On Dec 16, 2020, at 13:13, M.Eng. René Schwarz wrote:

> I am using mod_dav_svn with Apache2 in combination with a SVN repository containing symbolic links. When a URL pointing to a symbolic link is accessed, the web server does not follow this link, but provides a text file with the content "link [path to file or directory]".
> 
> I was wondering if there is a possibility to make mod_dav_svn actually not providing this text file but the contents of the linked file directly?
> 
> Background:
> An installer is downloading several files for installation from the repository over the web server whereas the flexibility to specify a certain repository revision via the "!svn/bc/" special syntax is used, without the need for the installer to be aware of the SVN repo itself. For the installer, this address is just an ordinary URL. This worked well for a couple of years, but now symbolic links have been used in the repository which is causing the trouble for the installer now as it gets not the actual file, but the text representation of a symbolic link.

As far as I know, mod_dav_svn does not have this capability.

mod_dav_svn is a server process, and symlinks are a client-side-only feature. The server has no knowledge of symlinks and just stores the files and their properties. The Subversion client stores symlinks in the repository exactly as you're experiencing: as a text file with the contents "link [path to file or directory]" and a property "svn:special" set to the value "*".

In this case, your installer is acting as the Subversion client, so you would have to modify your installer code to get it to notice when a file it's accessing is a symlink and to make it send another request to get the real file from its actual location. If you want to do it right, you should consider that there could of course be multiple levels of symlink indirection, and any of the directories leading up to the file you want could be symlinks.