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Subject: Re: [virtio-dev] Re: net_failover slave udev renaming (was Re: [RFC PATCH net-next v6 4/4] netvsc: refactor notifier/event handling code to use the bypass framework)
On Mon, Feb 25, 2019 at 04:58:07PM -0800, si-wei liu wrote: > > > On 2/22/2019 7:14 AM, Michael S. Tsirkin wrote: > > On Thu, Feb 21, 2019 at 11:55:11PM -0800, si-wei liu wrote: > > > > > > On 2/21/2019 11:00 PM, Samudrala, Sridhar wrote: > > > > > > > > On 2/21/2019 7:33 PM, si-wei liu wrote: > > > > > > > > > > On 2/21/2019 5:39 PM, Michael S. Tsirkin wrote: > > > > > > On Thu, Feb 21, 2019 at 05:14:44PM -0800, Siwei Liu wrote: > > > > > > > Sorry for replying to this ancient thread. There was some remaining > > > > > > > issue that I don't think the initial net_failover patch got addressed > > > > > > > cleanly, see: > > > > > > > > > > > > > > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1815268 > > > > > > > > > > > > > > The renaming of 'eth0' to 'ens4' fails because the udev userspace was > > > > > > > not specifically writtten for such kernel automatic enslavement. > > > > > > > Specifically, if it is a bond or team, the slave would typically get > > > > > > > renamed *before* virtual device gets created, that's what udev can > > > > > > > control (without getting netdev opened early by the other part of > > > > > > > kernel) and other userspace components for e.g. initramfs, > > > > > > > init-scripts can coordinate well in between. The in-kernel > > > > > > > auto-enslavement of net_failover breaks this userspace convention, > > > > > > > which don't provides a solution if user care about consistent naming > > > > > > > on the slave netdevs specifically. > > > > > > > > > > > > > > Previously this issue had been specifically called out when IFF_HIDDEN > > > > > > > and the 1-netdev was proposed, but no one gives out a solution to this > > > > > > > problem ever since. Please share your mind how to proceed and solve > > > > > > > this userspace issue if netdev does not welcome a 1-netdev model. > > > > > > Above says: > > > > > > > > > > > > there's no motivation in the systemd/udevd community at > > > > > > this point to refactor the rename logic and make it work well with > > > > > > 3-netdev. > > > > > > > > > > > > What would the fix be? Skip slave devices? > > > > > > > > > > > There's nothing user can get if just skipping slave devices - the > > > > > name is still unchanged and unpredictable e.g. eth0, or eth1 the > > > > > next reboot, while the rest may conform to the naming scheme (ens3 > > > > > and such). There's no way one can fix this in userspace alone - when > > > > > the failover is created the enslaved netdev was opened by the kernel > > > > > earlier than the userspace is made aware of, and there's no > > > > > negotiation protocol for kernel to know when userspace has done > > > > > initial renaming of the interface. I would expect netdev list should > > > > > at least provide the direction in general for how this can be > > > > > solved... > > > > I was just wondering what did you mean when you said > > "refactor the rename logic and make it work well with 3-netdev" - > > was there a proposal udev rejected? > No. I never believed this particular issue can be fixed in userspace alone. > Previously someone had said it could be, but I never see any work or > relevant discussion ever happened in various userspace communities (for e.g. > dracut, initramfs-tools, systemd, udev, and NetworkManager). IMHO the root > of the issue derives from the kernel, it makes more sense to start from > netdev, work out and decide on a solution: see what can be done in the > kernel in order to fix it, then after that engage userspace community for > the feasibility... > > > Anyway, can we write a time diagram for what happens in which order that > > leads to failure? That would help look for triggers that we can tie > > into, or add new ones. > > > > See attached diagram. > > > > > > > > > > > > > Is there an issue if slave device names are not predictable? The user/admin scripts are expected > > > > to only work with the master failover device. > > > Where does this expectation come from? > > > > > > Admin users may have ethtool or tc configurations that need to deal with > > > predictable interface name. Third-party app which was built upon specifying > > > certain interface name can't be modified to chase dynamic names. > > > > > > Specifically, we have pre-canned image that uses ethtool to fine tune VF > > > offload settings post boot for specific workload. Those images won't work > > > well if the name is constantly changing just after couple rounds of live > > > migration. > > It should be possible to specify the ethtool configuration on the > > master and have it automatically propagated to the slave. > > > > BTW this is something we should look at IMHO. > I was elaborating a few examples that the expectation and assumption that > user/admin scripts only deal with master failover device is incorrect. It > had never been taken good care of, although I did try to emphasize it from > the very beginning. > > Basically what you said about propagating the ethtool configuration down to > the slave is the key pursuance of 1-netdev model. However, what I am seeking > now is any alternative that can also fix the specific udev rename problem, > before concluding that 1-netdev is the only solution. Generally a 1-netdev > scheme would take time to implement, while I'm trying to find a way out to > fix this particular naming problem under 3-netdev. > > > > > > > Moreover, you were suggesting hiding the lower slave devices anyway. There was some discussion > > > > about moving them to a hidden network namespace so that they are not visible from the default namespace. > > > > I looked into this sometime back, but did not find the right kernel api to create a network namespace within > > > > kernel. If so, we could use this mechanism to simulate a 1-netdev model. > > > Yes, that's one possible implementation (IMHO the key is to make 1-netdev > > > model as much transparent to a real NIC as possible, while a hidden netns is > > > just the vehicle). However, I recall there was resistance around this > > > discussion that even the concept of hiding itself is a taboo for Linux > > > netdev. I would like to summon potential alternatives before concluding > > > 1-netdev is the only solution too soon. > > > > > > Thanks, > > > -Siwei > > Your scripts would not work at all then, right? > At this point we don't claim images with such usage as SR-IOV live > migrate-able. We would flag it as live migrate-able until this ethtool > config issue is fully addressed and a transparent live migration solution > emerges in upstream eventually. > > > Thanks, > -Siwei > > > > > > > > > -Siwei > > > > > > > > > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org > > > > > net_failover(kernel) | network.service (user) | systemd-udevd (user) > --------------------------------------------------+------------------------------+-------------------------------------------- > (standby virtio-net and net_failover | | > devices created and initialized, | | > i.e. virtnet_probe()-> | | > net_failover_create() | | > was done.) | | > | | > | runs `ifup ens3' -> | > | ip link set dev ens3 up | > net_failover_open() | | > dev_open(virtnet_dev) | | > virtnet_open(virtnet_dev) | | > netif_carrier_on(failover_dev) | | > ... | | > | | > (VF hot plugged in) | | > ixgbevf_probe() | | > register_netdev(ixgbevf_netdev) | | > netdev_register_kobject(ixgbevf_netdev) | | > kobject_add(ixgbevf_dev) | | > device_add(ixgbevf_dev) | | > kobject_uevent(&ixgbevf_dev->kobj, KOBJ_ADD) | | > netlink_broadcast() | | > ... | | > call_netdevice_notifiers(NETDEV_REGISTER) | | > failover_event(..., NETDEV_REGISTER, ...) | | > failover_slave_register(ixgbevf_netdev) | | > net_failover_slave_register(ixgbevf_netdev) | | > dev_open(ixgbevf_netdev) | | > | | > | | > | | received ADD uevent from netlink fd > | | ... > | | udev-builtin-net_id.c:dev_pci_slot() > | | (decided to renamed 'eth0' ) > | | ip link set dev eth0 name ens4 > (dev_change_name() returns -EBUSY as | | > ixgbevf_netdev->flags has IFF_UP) | | > | | > Given renaming slaves does not work anyway: would it work if we just hard-coded slave names instead? E.g. 1. fail slave renames 2. rename of failover to XX automatically renames standby to XXnsby and primary to XXnpry -- MST
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