On Fri, 8 Jun 2018 15:54:38 -0700 Siwei Liu <losewe...@gmail.com> wrote:
> On Wed, Jun 6, 2018 at 2:54 PM, Samudrala, Sridhar > <sridhar.samudr...@intel.com> wrote: > > > > > > On 6/6/2018 2:24 PM, Stephen Hemminger wrote: > >> > >> On Wed, 6 Jun 2018 15:30:27 +0300 > >> "Michael S. Tsirkin" <m...@redhat.com> wrote: > >> > >>> On Wed, Jun 06, 2018 at 09:25:12AM +0200, Jiri Pirko wrote: > >>>> > >>>> Tue, Jun 05, 2018 at 05:42:31AM CEST, step...@networkplumber.org wrote: > >>>>> > >>>>> The net failover should be a simple library, not a virtual > >>>>> object with function callbacks (see callback hell). > >>>> > >>>> Why just a library? It should do a common things. I think it should be a > >>>> virtual object. Looks like your patch again splits the common > >>>> functionality into multiple drivers. That is kind of backwards attitude. > >>>> I don't get it. We should rather focus on fixing the mess the > >>>> introduction of netvsc-bonding caused and switch netvsc to 3-netdev > >>>> model. > >>> > >>> So it seems that at least one benefit for netvsc would be better > >>> handling of renames. > >>> > >>> Question is how can this change to 3-netdev happen? Stephen is > >>> concerned about risk of breaking some userspace. > >>> > >>> Stephen, this seems to be the usecase that IFF_HIDDEN was trying to > >>> address, and you said then "why not use existing network namespaces > >>> rather than inventing a new abstraction". So how about it then? Do you > >>> want to find a way to use namespaces to hide the PV device for netvsc > >>> compatibility? > >>> > >> Netvsc can't work with 3 dev model. MS has worked with enough distro's and > >> startups that all demand eth0 always be present. And VF may come and go. > >> After this history, there is a strong motivation not to change how kernel > >> behaves. Switching to 3 device model would be perceived as breaking > >> existing userspace. > > > > > > I think it should be possible for netvsc to work with 3 dev model if the > > only > > requirement is that eth0 will always be present. With net_failover, you will > > see eth0 and eth0nsby OR with older distros eth0 and eth1. It may be an > > issue > > if somehow there is userspace requirement that there can be only 2 netdevs, > > not 3 > > when VF is plugged. > > > > eth0 will be the net_failover device and eth0nsby/eth1 will be the netvsc > > device > > and the IP address gets configured on eth0. Will this be an issue? > > > Did you realize that the eth0 name in the current 3-netdev code can't > be consistently persisted across reboot, if you have more than one VFs > to pair with? On one boot it got eth0/eth0nsby, on the next it may get > eth1/eth1nsby on the same interface. > > It won't be useable by default until you add some custom udev rules. > I think there is no reason to break things by moving netvsc to 3 device model. The first device probed is always the same on Hyper-V/Azure, and always comes up as eth0. The order comes from the fact that they are reported to guest in that order and currently vmbus probe is single threaded.
