Jiri Pirko
2019-Mar-06 12:04 UTC
[RFC PATCH net-next] failover: allow name change on IFF_UP slave interfaces
Tue, Mar 05, 2019 at 01:50:59AM CET, si-wei.liu at oracle.com wrote:>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. > >For that to work, now introduce a module-level tunable, >"slave_rename_ok" that allows users to lift up the rename restriction on >failover slave which is already UP. Although it's possible this change >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 work with the new naming >behavior of the failover slave. Userspace component interacting with >slaves should be changed to operate on failover master 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 >all userspace should only deal with master in the long run. The default >for the "slave_rename_ok" is set to true(1). If userspace doesn't have >the right support in place meanwhile users don't care about reliable >userspace naming, the value can be set to false(0). > >Signed-off-by: Si-Wei.Liu at oracle.com >Reviewed-by: Liran Alon <liran.alon at oracle.com> >--- > include/linux/netdevice.h | 3 +++ > net/core/dev.c | 3 ++- > net/core/failover.c | 11 +++++++++-- > 3 files changed, 14 insertions(+), 3 deletions(-) > >diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h >index 857f8ab..6d9e4e0 100644 >--- a/include/linux/netdevice.h >+++ b/include/linux/netdevice.h >@@ -1487,6 +1487,7 @@ struct net_device_ops { > * @IFF_NO_RX_HANDLER: device doesn't support the rx_handler hook > * @IFF_FAILOVER: device is a failover master device > * @IFF_FAILOVER_SLAVE: device is lower dev of a failover master device >+ * @IFF_SLAVE_RENAME_OK: rename is allowed while slave device is running > */ > enum netdev_priv_flags { > IFF_802_1Q_VLAN = 1<<0, >@@ -1518,6 +1519,7 @@ enum netdev_priv_flags { > IFF_NO_RX_HANDLER = 1<<26, > IFF_FAILOVER = 1<<27, > IFF_FAILOVER_SLAVE = 1<<28, >+ IFF_SLAVE_RENAME_OK = 1<<29, > }; > > #define IFF_802_1Q_VLAN IFF_802_1Q_VLAN >@@ -1548,6 +1550,7 @@ enum netdev_priv_flags { > #define IFF_NO_RX_HANDLER IFF_NO_RX_HANDLER > #define IFF_FAILOVER IFF_FAILOVER > #define IFF_FAILOVER_SLAVE IFF_FAILOVER_SLAVE >+#define IFF_SLAVE_RENAME_OK IFF_SLAVE_RENAME_OK > > /** > * struct net_device - The DEVICE structure. >diff --git a/net/core/dev.c b/net/core/dev.c >index 722d50d..ae070de 100644 >--- a/net/core/dev.c >+++ b/net/core/dev.c >@@ -1180,7 +1180,8 @@ int dev_change_name(struct net_device *dev, const char *newname) > BUG_ON(!dev_net(dev)); > > net = dev_net(dev); >- if (dev->flags & IFF_UP) >+ if (dev->flags & IFF_UP && >+ !(dev->priv_flags & IFF_SLAVE_RENAME_OK)) > return -EBUSY; > > write_seqcount_begin(&devnet_rename_seq); >diff --git a/net/core/failover.c b/net/core/failover.c >index 4a92a98..1fd8bbb 100644 >--- a/net/core/failover.c >+++ b/net/core/failover.c >@@ -16,6 +16,11 @@ > > static LIST_HEAD(failover_list); > static DEFINE_SPINLOCK(failover_lock); >+static bool slave_rename_ok = true; >+ >+module_param(slave_rename_ok, bool, (S_IRUGO | S_IWUSR)); >+MODULE_PARM_DESC(slave_rename_ok, >+ "If set allow renaming the slave when failover master is up");No module parameters please. If you need to set something do it using rtnl_link_ops. Thanks.> > static struct net_device *failover_get_bymac(u8 *mac, struct failover_ops **ops) > { >@@ -81,13 +86,15 @@ static int failover_slave_register(struct net_device *slave_dev) > } > > slave_dev->priv_flags |= IFF_FAILOVER_SLAVE; >+ if (slave_rename_ok) >+ slave_dev->priv_flags |= IFF_SLAVE_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_SLAVE_RENAME_OK); > err_upper_link: > netdev_rx_handler_unregister(slave_dev); > done: >@@ -121,7 +128,7 @@ int failover_slave_unregister(struct net_device *slave_dev) > > 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_SLAVE_RENAME_OK); > > if (fops && fops->slave_unregister && > !fops->slave_unregister(slave_dev, failover_dev)) >-- >1.8.3.1 >