[Samba] dmapi doesn't work on aix; possible fix included

[James Peach]

On 29/10/06, J Raynor <raynorj at mn.rr.com> wrote:
> I'm running samba 3.0.23c on aix 5.3 TL4.  I'm using Tivoli HSM 5.3.4.0
> on a JFS2 filesystem.  Samba compiled fine, and I set "dmapi support =
> yes" in smb.conf, but samba wouldn't recognize offline files ("migrated
> files" in tsm terminology).  After setting a higher log level I think
> I've tracked down the problem.  The patch is at the bottom of this email.
>
> The first problem is this snippet in dmapi_file_flags() in smbd/dmapi.c:
>
>          err = dm_path_to_handle(CONST_DISCARD(char *, path),
>                  &dm_handle, &dm_handle_len);
>          if (err < 0) {
>                  DEBUG(DMAPI_TRACE, ("dm_path_to_handle(%s): %s\n",
>                              path, strerror(errno)));
>
>                  if (errno != EPERM) {
>                          return 0;
>                  }
>
>
>
> On AIX, dm_path_to_handle() is returning EACCES instead of EPERM, so it
> hits the return 0.  Is EPERM supposed to be the only allowed error, or
> is this something that's likely implementation dependent?

This code was originally written for Linux and IRIX. IIRC in Linux there was
a problem where the process capabilities were reset across fork() because
Samba changes its effective user ID. So when we get a permission error
we go back and try to re-acquire our capabilities.

> Changing the if-condition to (errno != EPERM && errno != EACCES) lets
> things continue on.  The rest of the problem in dmapi_file_flags() is
> that things are running with the effective uid of the user, so dmapi
> calls are failing.  The posix capability DMAPI_ACCESS_CAPABILITY is

Note that DMAPI_ACCESS_CAPABILITY is not a real capability, it's just
a name for whatever capability set is needed to do DMAPI operations on
the current platform.

> supposed to allow the functions to work, but to my knowledge AIX doesn't
>   have posix capabilties.

This is well beyond my knowledge of AIX. I used capabilities for this,
rather than
(un)become_root for performance reasons. If there's no other way to achieve the
functionality, then I guess this is fine.

I'd prefer a feature-based test for whether this is necessary, rather
than a platform-
based test. Something like

#if !defined(HAVE_POSIX_CAPABILITIES)
become_root();
#endif

> I used become_root/unbecome_root around the dmapi calls, and this
> appeared to get things to work.  Samba's log messages are indicating
> that files are offline, and Windows Explorer is picking up on this and
> changing the file icons to indicate that the files are offline. However,
> I don't know if my solution is entirely correct.  Here's the patch:
>
>
>
>
> *** dmapi.c.orig        Sat Oct 28 02:33:13 2006
> --- dmapi.c     Sat Oct 28 11:12:54 2006
> ***************
> *** 246,252 ****
>                  DEBUG(DMAPI_TRACE, ("dm_path_to_handle(%s): %s\n",
>                              path, strerror(errno)));
>
> !               if (errno != EPERM) {
>                          return 0;
>                  }
>
> --- 246,252 ----
>                  DEBUG(DMAPI_TRACE, ("dm_path_to_handle(%s): %s\n",
>                              path, strerror(errno)));
>
> !               if (errno != EPERM && errno != EACCES) {
>                          return 0;
>                  }
>
> ***************
> *** 259,266 ****
> --- 259,274 ----
>
>                  set_effective_capability(DMAPI_ACCESS_CAPABILITY);
>
> + #ifdef AIX
> +               become_root();
> + #endif
> +
>                  err = dm_path_to_handle(CONST_DISCARD(char *, path),
>                          &dm_handle, &dm_handle_len);
> +
> + #ifdef AIX
> +               unbecome_root();
> + #endif
>                  if (err < 0) {
>                          DEBUG(DMAPI_TRACE,
>                              ("retrying dm_path_to_handle(%s): %s\n",
> ***************
> *** 269,276 ****
> --- 277,293 ----
>                  }
>          }
>
> + #ifdef AIX
> +       become_root();
> + #endif
> +
>          err = dm_get_eventlist(dmapi_session, dm_handle, dm_handle_len,
>                  DM_NO_TOKEN, DM_EVENT_MAX, &events, &nevents);
> +
> + #ifdef AIX
> +       unbecome_root();
> + #endif
> +
>          if (err < 0) {
>                  DEBUG(DMAPI_TRACE, ("dm_get_eventlist(%s): %s\n",
>                              path, strerror(errno)));
>
>
>
>
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-- 
James Peach | jorgar at gmail.com