Re: [rfc] Merging the Open vSwitch datapath

[Simon Horman <horms@verge.net.au>]

On Mon, Aug 30, 2010 at 06:11:30PM -0700, Jesse Gross wrote:
> On Mon, Aug 30, 2010 at 6:01 PM, Simon Horman <horms@verge.net.au> wrote:
> > On Mon, Aug 30, 2010 at 05:54:10PM -0700, Chris Wright wrote:
> >> * Simon Horman (horms@verge.net.au) wrote:
> >> > On Mon, Aug 30, 2010 at 01:59:07PM -0700, Chris Wright wrote:
> >> > > * Rose, Gregory V (gregory.v.rose@intel.com) wrote:
> >> > > > >From: Ben Pfaff [mailto:blp@nicira.com]
> >> > > > >On Mon, Aug 30, 2010 at 11:26:17AM -0700, Rose, Gregory V wrote:
> >> > > > >> I just want to put in a plug for the netlink interface.  For NICs with
> >> > > > >> EVB we'll need it.
> >> > > > >
> >> > > > >Off-hand, the main reasons to use Netlink, instead of the existing
> >> > > > >character device interface, are that Netlink is easier to extend and
> >> > > > >that it should reduce or eliminate the 32-to-64 bit compat layer
> >> > > > >currently in the Open vSwitch tree.
> >> > >
> >> > > That, plus it's a typical way to do network configuration.  Esp. with
> >> > > bi-directional communication.  So the userspace bit both listens to
> >> > > netlink messages, like any of the routing daemons or lldpad or similar
> >> > > do, and sends netlink messasges to update driver's flow table.
> >> > >
> >> > > BTW, this kind of discussion was why Herbert felt strongly against
> >> > > drivers/staging/.  He wanted to be sure the interfaces were well-defined
> >> > > first.
> >> >
> >> > Is the implication that there is a preference for finalising
> >> > the interface (as much as that is possible) before merging?
> >>
> >> I'll let Herbert chime in, just reminder that was his thought earlier
> >> this month at LinuxCon.
> >
> > Thanks, I must confess that had slipped my mind.
> 
> I think it might be worth delaying the merge until we at least have a
> starting point.  As the userspace interface is such an important
> aspect of the code, I don't want to ask people to review code that is
> expected to undergo a large change soon (obviously comments are always
> welcome at any time).  It's probably also more productive to have a
> discussion about minor improvements to a proposed interface than a
> free-for-all.
> 
> As Ben mentioned, he's working on designing a Netlink-based interface
> now.  It shouldn't take too long to get a first cut out the door so
> we'll have something concrete to discuss.  I'll certainly be the first
> one to promote the different uses that are possible with Open vSwitch
> but I don't want too get bogged down in the details of future features
> now.  As long as the interface doesn't have serious problems
> precluding future work, we can merge the existing code and then move
> onto new things.

That sounds entirely reasonable.