Re: [PATCH 00/13] SCTP: Enable netns

On 08/06/2012 03:50 PM, Eric W. Biederman wrote:

Vlad Yasevich [off-list ref] writes:

quoted

Hi Eric

Associations are looked up by ports, but then verifyed by addresses.
Also, associations belong to sockets and simply validating the socket
namespace should be sufficient.

True.  Your set of patches isn't quite as likely to malfunction as it
looked at first glance.  It requires address reuse which happens accross
namespaces but not too frequently.

Last time I looked at Jan's patches, I though she took care of the 
address re-use issue.  It isn't technically necessary to include 
namespace into the hash mix, but I think it will make chains shorter 
when namespaces are involved.  Might be interesting to look.

As for validating the socket namespace I agree that is the fix and my
patchset winds up doing it.

Yes, I saw that.

quoted

quoted

The downside with my version is that it does not make all of the sctp
tunables per network namespace the way yours does, but making all of
the tunables per network namespace should be straight forward from
my base.

My patchset also misses some nice to haves like making the association
id allocation per network namespace.  It is not important for
correctness of the code but it might allow an information leak between
namespaces.

Hmm.. this one might be nice to have not from the perspective of leak,
but from resource limitation.  Without this, once the id space is
global is can be exhausted faster.

It takes a lot of associtations to exhaust the id space, but I have no
fundamental problems problems with the id allocation being per
namespace.  I had actually overlooked the local association id when I
did my patches.   After looking it became clear that making the
association id global was not necessary so I left it.

The sctp association id is a strange beast.  My personal inclination is
that the sctp association id really ought to be per sctp socket, but I
have not looked enough at the sctp userspace API to see if that works in
practice.  Shrug.

Mostly I am in favor of simple and correct.

Technically association id must be unique within a namespace.  Having 
global id space may be simpler and correct enough as there would be no 
duplication of ids between namespaces.  The only thing of value the 
per/namespace id space provides is that it restored the theoretical 
maximum on sctp associations one can have.

However, this means teaching IDR about namespaces... :)

We can skip it for now.

-vlad

Eric