On Wed, Mar 20, 2019 at 11:43:41PM +0200, Liran Alon wrote: > > > > On 20 Mar 2019, at 16:09, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > > > On Wed, Mar 20, 2019 at 02:23:36PM +0200, Liran Alon wrote: > >> > >> > >>> On 20 Mar 2019, at 12:25, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > >>> > >>> On Wed, Mar 20, 2019 at 01:25:58AM +0200, Liran Alon wrote: > >>>> > >>>> > >>>>> On 19 Mar 2019, at 23:19, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > >>>>> > >>>>> On Tue, Mar 19, 2019 at 08:46:47AM -0700, Stephen Hemminger wrote: > >>>>>> On Tue, 19 Mar 2019 14:38:06 +0200 > >>>>>> Liran Alon <liran.alon@xxxxxxxxxx> wrote: > >>>>>> > >>>>>>> b.3) cloud-init: If configured to perform network-configuration, it attempts to configure all available netdevs. It should avoid however doing so on net-failover slaves. > >>>>>>> (Microsoft has handled this by adding a mechanism in cloud-init to blacklist a netdev from being configured in case it is owned by a specific PCI driver. Specifically, they blacklist Mellanox VF driver. However, this technique doesn’t work for the net-failover mechanism because both the net-failover netdev and the virtio-net netdev are owned by the virtio-net PCI driver). > >>>>>> > >>>>>> Cloud-init should really just ignore all devices that have a master device. > >>>>>> That would have been more general, and safer for other use cases. > >>>>> > >>>>> Given lots of userspace doesn't do this, I wonder whether it would be > >>>>> safer to just somehow pretend to userspace that the slave links are > >>>>> down? And add a special attribute for the actual link state. > >>>> > >>>> I think this may be problematic as it would also break legit use case > >>>> of userspace attempt to set various config on VF slave. > >>>> In general, lying to userspace usually leads to problems. > >>> > >>> I hear you on this. So how about instead of lying, > >>> we basically just fail some accesses to slaves > >>> unless a flag is set e.g. in ethtool. > >>> > >>> Some userspace will need to change to set it but in a minor way. > >>> Arguably/hopefully failure to set config would generally be a safer > >>> failure. > >> > >> Once userspace will set this new flag by ethtool, all operations done by other userspace components will still work. > > > > Sorry about being unclear, the idea would be to require the flag on each ethtool operation. > > Oh. I have indeed misunderstood your previous email then. :) > Thanks for clarifying. > > > > >> E.g. Running dhclient without parameters, after this flag was set, will still attempt to perform DHCP on it and will now succeed. > > > > I think sending/receiving should probably just fail unconditionally. > > You mean that you wish that somehow kernel will prevent Tx on net-failover slave netdev > unless skb is marked with some flag to indicate it has been sent via the net-failover master? We can maybe avoid binding a protocol socket to the device? > This indeed resolves the group of userspace issues around performing DHCP on net-failover slaves directly (By dracut/initramfs, dhclient and etc.). > > However, I see a couple of down-sides to it: > 1) It doesn’t resolve all userspace issues listed in this email thread. For example, cloud-init will still attempt to perform network config on net-failover slaves. > It also doesn’t help with regard to Ubuntu’s netplan issue that creates udev rules that match only by MAC. How about we fail to retrieve mac from the slave? > 2) It brings non-intuitive customer experience. For example, a customer may attempt to analyse connectivity issue by checking the connectivity > on a net-failover slave (e.g. the VF) but will see no connectivity when in-fact checking the connectivity on the net-failover master netdev shows correct connectivity. > > The set of changes I vision to fix our issues are: > 1) Hide net-failover slaves in a different netns created and managed by the kernel. But that user can enter to it and manage the netdevs there if wishes to do so explicitly. > (E.g. Configure the net-failover VF slave in some special way). > 2) Match the virtio-net and the VF based on a PV attribute instead of MAC. (Similar to as done in NetVSC). E.g. Provide a virtio-net interface to get PCI slot where the matching VF will be hot-plugged by hypervisor. > 3) Have an explicit virtio-net control message to command hypervisor to switch data-path from virtio-net to VF and vice-versa. Instead of relying on intercepting the PCI master enable-bit > as an indicator on when VF is about to be set up. (Similar to as done in NetVSC). > > Is there any clear issue we see regarding the above suggestion? > > -Liran The issue would be this: how do we avoid conflicting with namespaces created by users? > > > >> Therefore, this proposal just effectively delays when the net-failover slave can be operated on by userspace. > >> But what we actually want is to never allow a net-failover slave to be operated by userspace unless it is explicitly stated > >> by userspace that it wishes to perform a set of actions on the net-failover slave. > >> > >> Something that was achieved if, for example, the net-failover slaves were in a different netns than default netns. > >> This also aligns with expected customer experience that most customers just want to see a 1:1 mapping between a vNIC and a visible netdev. > >> But of course maybe there are other ideas that can achieve similar behaviour. > >> > >> -Liran > >> > >>> > >>> Which things to fail? Probably sending/receiving packets? Getting MAC? > >>> More? > >>> > >>>> If we reach > >>>> to a scenario where we try to avoid userspace issues generically and > >>>> not on a userspace component basis, I believe the right path should be > >>>> to hide the net-failover slaves such that explicit action is required > >>>> to actually manipulate them (As described in blog-post). E.g. > >>>> Automatically move net-failover slaves by kernel to a different netns. > >>>> > >>>> -Liran > >>>> > >>>>> > >>>>> -- > >>>>> MST _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
