[PATCH 0/3] Sysctl shadow management

[Pavel Emelyanov]

Hi guys!

You all know, that with multiple namespaces we have to take
special care about sysctls. E.g. IPC sysctl handlers are 
equipped with kludges to alter the sysctl parameters of
appropriate namespace. The same thing should be done for UTS
namespace (but it is not - we have a BUG in mainstream) and 
(!) for network namespaces.

Unlike all the other namespaces, network will have to not 
just address different variables via same sysctl names, but
to have different tables with different sysctl names. E.g.
/proc/sys/net/conf have entries for devices, which differ
across namespaces.

Eric currently have some work done in that directions, I
like the approach in general very much, but it looks rather 
raw (Eric, take this in good part). You know, ifdefs in the 
middle of the code, explicit references to net namespace 
and so on and so forth.

So here's the RFC for a bit better sysctls shadow management.

I will provide 3 patches:
  1. the sysctl shadows themselves;
  2. using shadows in UTS namespace;
  3. using shadows in IPC namespace;

If someone want I can send

  4. example on how to create a /proc/sys/net/conf/-like
     structure with different names.

Using them in net namespace is already checked (I created
sysctl entries with different names), but I don't have any
patches against any David's tree yet. If we're OK with this
set I will start talking to Andrew and David about who to
send these patches to and making shadows for net-related
sysctl variables.

Signed-off-by: Pavel Emelyanov <xemul at openvz.org>