Re: [DOC]: generic netlink

[Jamal Hadi Salim <hadi@cyberus.ca>]

On Thu, 2006-13-07 at 10:50 -0700, Randy.Dunlap wrote:
> On Mon, 19 Jun 2006 09:41:22 -0400 jamal wrote:
> 
> > 
> > Folks,
> > 
> > Attached is a document that should help people wishing to use generic
> > netlink interface. It is a WIP so a lot more to go if i see interest.
> 
> Hi,
> I have a few random questions about gen-netlink.
> 
> 1.  Provider IDs (numbers) and names must be unique.  Does
> this affect virtualization in any way or is it just transparent?
> 

You are referring to the openvz type of virtualization i suspect, no?
i.e not XEN or UML etc.
Good question. I think whatever those folks do for standard sockets will
work in this case as well; it is related to the way they handle process
management in the different virtual compartments. So if standard netlink
is transparent, I believe gen-netlink will be as well. A quick test is
to run "ip mon" on one VE and see if adding a route on another generates
an event on the former VE.

> 2.  Is (generic) netlink meant (expected, OK) to be used for
> non-networking ioctl/sysfs replacements?

It is OK to be used but i am not sure if we are saying it is _the_
replacement for ioctls for example. It certainly has many advantages
over ioctl/sysfs - eg (an incomplete list):
- ability to generate asynchronous events from the kernel. 
- ability to do bulk transfers from/to the kernel to/from user-space
(look at the way what Shailabh is working on may end up transmitting
upto a few MB of data from the kernel at a time)
- ability to do simple attribute set/get/event or a complex
(multi-nested) vector of such attributes
- ability to act as an IPC between user-user or user-kernel
- ability to do  one to many communication; so a single user space
message could be sent to many kernel _and user_ destinations and the
reverse a single kernel message could be sent to many kernel or user
listeners.
- the fact that it is a "a network wire" format allows for it to be used
for inter-machine communication (in a distributed system type setup for
example). 

etc

Try doing the above with ioctl or sysfs ;->

cheers,
jamal