[Rdiff-backup-bugs] [bug #26847] Eliminating "AF_UNIX path too long" when backing up sockets

[Joe Steele]

URL:
  <http://savannah.nongnu.org/bugs/?26847>

                 Summary: Eliminating "AF_UNIX path too long" when backing up
sockets
                 Project: rdiff-backup
            Submitted by: j_steele
            Submitted on: Fri 19 Jun 2009 08:02:12 PM GMT
                Category: None
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

Currently, rdiff-backup (v. 1.2.8) will attempt to back up socket files by
using socket() and bind() to recreate the socket file on the destination
system.  I suggest using os.mknod() instead.  The main advantage for mknod()
is that it can create socket type files using paths of arbitrary length,
whereas bind() is limited to a maximum of 107 characters.  A disadvantage is
that os.mknod() is only available for python >= 2.3.

Using mknod() instead of bind() should help to eliminate the error:

        SpecialFileError somewhere/foo/bar/socket Socket error: AF_UNIX path too
long

I've attached a file to this bug report that contains a patch to rpath.py
which seems to work for me.  It's written so that if mknod() fails, the
program reverts to its current behavior for creating sockets using bind().

By the way, I don't see where anyone has ever mentioned it, but one of the
reasons the "AF_UNIX path too long" error occurs is because, sooner or later,
the socket changes (e.g., when a daemon is restarted) and another backup is
run, creating an increment/snapshot file that looks something like this:


/somewhere-else/my-backup/rdiff-backup-data/increments/somewhere/foo/bar/socket.2009-06-12T19:35:55-04:00.snapshot


At 114 characters, this path will generate the "AF_UNIX path too long" error
when passed to bind(), even though the lengths of the paths for the original
socket (/somewhere/foo/bar/socket) and the backup destination
(/somewhere-else/my-backup) are not particularly long.

Another approach for eliminating these errors would be to do what the tar
command does -- ALWAYS ignore sockets when backing up (don't even permit them
to be optionally backed up).  After all, there really isn't much point in
backing up sockets.



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File Attachments:


-------------------------------------------------------
Date: Fri 19 Jun 2009 08:02:12 PM GMT  Name: rpath.py.patch.txt  Size: 788B  
By: j_steele

<http://savannah.nongnu.org/bugs/download.php?file_id=18293>

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