Problem with cache manager complaining about not supported msg during cache fill

[Roopa Prabhu]

Hi,

We have seen a problem with nl_cache_mngr_add doing a fill cache on the 
manager socket (cm_sock). The problem is that when libnl is waiting to 
process the response to get dump request sent to the kernel during fill, 
it may receive an async event, resulting in libnl complaining about 
unexpected msg (I think it is NLE_MSGTYPE_NOSUPPORT).

The simplest fix that works is using a new non-async socket (possibly 
passed in by the user) for the manager to use for fill instead of using 
the netlink event notification socket. This is usually reproducible when
there is heavy netlink async event traffic during nl_cache_mngr_add.

I wanted to see if we can fix this in the new version of cache manager 
api we recently added.

I will submit a patch if we decide on a possible fix.

Thanks,
Roopa