From: Si-Wei Liu si-wei.liu@oracle.com
[ Upstream commit 8065a779f17e94536a1c4dcee4f9d88011672f97 ]
When a netdev appears through hot plug then gets enslaved by a failover master that is already up and running, the slave will be opened right away after getting enslaved. Today there's a race that userspace (udev) may fail to rename the slave if the kernel (net_failover) opens the slave earlier than when the userspace rename happens. Unlike bond or team, the primary slave of failover can't be renamed by userspace ahead of time, since the kernel initiated auto-enslavement is unable to, or rather, is never meant to be synchronized with the rename request from userspace.
As the failover slave interfaces are not designed to be operated directly by userspace apps: IP configuration, filter rules with regard to network traffic passing and etc., should all be done on master interface. In general, userspace apps only care about the name of master interface, while slave names are less important as long as admin users can see reliable names that may carry other information describing the netdev. For e.g., they can infer that "ens3nsby" is a standby slave of "ens3", while for a name like "eth0" they can't tell which master it belongs to.
Historically the name of IFF_UP interface can't be changed because there might be admin script or management software that is already relying on such behavior and assumes that the slave name can't be changed once UP. But failover is special: with the in-kernel auto-enslavement mechanism, the userspace expectation for device enumeration and bring-up order is already broken. Previously initramfs and various userspace config tools were modified to bypass failover slaves because of auto-enslavement and duplicate MAC address. Similarly, in case that users care about seeing reliable slave name, the new type of failover slaves needs to be taken care of specifically in userspace anyway.
It's less risky to lift up the rename restriction on failover slave which is already UP. Although it's possible this change may potentially break userspace component (most likely configuration scripts or management software) that assumes slave name can't be changed while UP, it's relatively a limited and controllable set among all userspace components, which can be fixed specifically to listen for the rename events on failover slaves. Userspace component interacting with slaves is expected to be changed to operate on failover master interface instead, as the failover slave is dynamic in nature which may come and go at any point. The goal is to make the role of failover slaves less relevant, and userspace components should only deal with failover master in the long run.
Fixes: 30c8bd5aa8b2 ("net: Introduce generic failover module") Signed-off-by: Si-Wei Liu si-wei.liu@oracle.com Reviewed-by: Liran Alon liran.alon@oracle.com Acked-by: Sridhar Samudrala sridhar.samudrala@intel.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/netdevice.h | 3 +++ net/core/dev.c | 16 +++++++++++++++- net/core/failover.c | 6 +++--- 3 files changed, 21 insertions(+), 4 deletions(-)
--- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1484,6 +1484,7 @@ struct net_device_ops { * @IFF_FAILOVER: device is a failover master device * @IFF_FAILOVER_SLAVE: device is lower dev of a failover master device * @IFF_L3MDEV_RX_HANDLER: only invoke the rx handler of L3 master device + * @IFF_LIVE_RENAME_OK: rename is allowed while device is up and running */ enum netdev_priv_flags { IFF_802_1Q_VLAN = 1<<0, @@ -1516,6 +1517,7 @@ enum netdev_priv_flags { IFF_FAILOVER = 1<<27, IFF_FAILOVER_SLAVE = 1<<28, IFF_L3MDEV_RX_HANDLER = 1<<29, + IFF_LIVE_RENAME_OK = 1<<30, };
#define IFF_802_1Q_VLAN IFF_802_1Q_VLAN @@ -1547,6 +1549,7 @@ enum netdev_priv_flags { #define IFF_FAILOVER IFF_FAILOVER #define IFF_FAILOVER_SLAVE IFF_FAILOVER_SLAVE #define IFF_L3MDEV_RX_HANDLER IFF_L3MDEV_RX_HANDLER +#define IFF_LIVE_RENAME_OK IFF_LIVE_RENAME_OK
/** * struct net_device - The DEVICE structure. --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1184,7 +1184,21 @@ int dev_change_name(struct net_device *d BUG_ON(!dev_net(dev));
net = dev_net(dev); - if (dev->flags & IFF_UP) + + /* Some auto-enslaved devices e.g. failover slaves are + * special, as userspace might rename the device after + * the interface had been brought up and running since + * the point kernel initiated auto-enslavement. Allow + * live name change even when these slave devices are + * up and running. + * + * Typically, users of these auto-enslaving devices + * don't actually care about slave name change, as + * they are supposed to operate on master interface + * directly. + */ + if (dev->flags & IFF_UP && + likely(!(dev->priv_flags & IFF_LIVE_RENAME_OK))) return -EBUSY;
write_seqcount_begin(&devnet_rename_seq); --- a/net/core/failover.c +++ b/net/core/failover.c @@ -80,14 +80,14 @@ static int failover_slave_register(struc goto err_upper_link; }
- slave_dev->priv_flags |= IFF_FAILOVER_SLAVE; + slave_dev->priv_flags |= (IFF_FAILOVER_SLAVE | IFF_LIVE_RENAME_OK);
if (fops && fops->slave_register && !fops->slave_register(slave_dev, failover_dev)) return NOTIFY_OK;
netdev_upper_dev_unlink(slave_dev, failover_dev); - slave_dev->priv_flags &= ~IFF_FAILOVER_SLAVE; + slave_dev->priv_flags &= ~(IFF_FAILOVER_SLAVE | IFF_LIVE_RENAME_OK); err_upper_link: netdev_rx_handler_unregister(slave_dev); done: @@ -121,7 +121,7 @@ int failover_slave_unregister(struct net
netdev_rx_handler_unregister(slave_dev); netdev_upper_dev_unlink(slave_dev, failover_dev); - slave_dev->priv_flags &= ~IFF_FAILOVER_SLAVE; + slave_dev->priv_flags &= ~(IFF_FAILOVER_SLAVE | IFF_LIVE_RENAME_OK);
if (fops && fops->slave_unregister && !fops->slave_unregister(slave_dev, failover_dev))