Re: [PATCH net v2] failover: allow name change on IFF_UP slave interfaces
On 3/6/2019 7:08 PM, Si-Wei Liu 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.
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 work with the new naming
behavior of failover slaves. 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.
Fixes: 30c8bd5aa8b2 ("net: Introduce generic failover module")
Signed-off-by: Si-Wei Liu
Reviewed-by: Liran Alon
Acked-by: Michael S. Tsirkin
---
v1 -> v2:
- Drop configurable module parameter (Sridhar)
include/linux/netdevice.h | 3 +++
net/core/dev.c| 3 ++-
net/core/failover.c | 6 +++---
3 files changed, 8 insertions(+), 4 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_SLAVEIFF_FAILOVER_SLAVE
+#define IFF_SLAVE_RENAME_OKIFF_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;
Without the configurable module parameter, i think we don't even need
the new SLAVE_RENAME_OK private flag.
Can't we simply check for IFF_FAILOVER_SLAVE ?
write_seqcount_begin(&devnet_rename_seq);
diff --git a/net/core/failover.c b/net/core/failover.c
index 4a92a98..34c5c87 100644
--- a/net/core/failover.c
+++ b/net/core/failover.c
@@ -80,14 +80,14 @@ static int failover_slave
Re: [PATCH net v2] failover: allow name change on IFF_UP slave interfaces
On 3/19/2019 10:20 PM, si-wei liu wrote:
Hi Sridhar,
Are you fine with leaving the IFF_SLAVE_RENAME_OK flag as is, and thus
can provide your Ack-by or Reviewed-by? I can change the code if you
feel strong.
My preference would be not to introduce a new flag unless there is any
usecase where we want a IFF_FAILOVER_SLAVE type of device to support 2
different behaviors. (rename_ok and rename_not_ok)
Thanks
Sridhar
Thanks,
-Siwei
On 3/6/2019 8:54 PM, si-wei liu wrote:
On 3/6/2019 8:13 PM, Samudrala, Sridhar wrote:
On 3/6/2019 7:08 PM, Si-Wei Liu 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.
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 work with the new naming
behavior of failover slaves. 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.
Fixes: 30c8bd5aa8b2 ("net: Introduce generic failover module")
Signed-off-by: Si-Wei Liu
Reviewed-by: Liran Alon
Acked-by: Michael S. Tsirkin
---
v1 -> v2:
- Drop configurable module parameter (Sridhar)
include/linux/netdevice.h | 3 +++
net/core/dev.c | 3 ++-
net/core/failover.c | 6 +++---
3 files changed, 8 insertions(+), 4 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_
Re: [PATCH net v2] failover: allow name change on IFF_UP slave interfaces
On Wed, Mar 06, 2019 at 10:08:32PM -0500, Si-Wei Liu 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.
>
> 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 work with the new naming
> behavior of failover slaves. 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.
>
> Fixes: 30c8bd5aa8b2 ("net: Introduce generic failover module")
> Signed-off-by: Si-Wei Liu
> Reviewed-by: Liran Alon
> Acked-by: Michael S. Tsirkin
I worry that userspace might have made a bunch of assumptions
that names never change as long as interface is up.
So listening for up events ensures that interface
is not renamed.
How about sending down and up events around such renames?
> ---
> v1 -> v2:
> - Drop configurable module parameter (Sridhar)
>
>
> include/linux/netdevice.h | 3 +++
> net/core/dev.c| 3 ++-
> net/core/failover.c | 6 +++---
> 3 files changed, 8 insertions(+), 4 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_HANDLERIFF_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_R
Re: [PATCH net v2] failover: allow name change on IFF_UP slave interfaces
On Thu, Mar 21, 2019 at 04:20:40PM +0200, Liran Alon wrote:
>
>
> > On 21 Mar 2019, at 16:04, Michael S. Tsirkin wrote:
> >
> > On Wed, Mar 06, 2019 at 10:08:32PM -0500, Si-Wei Liu 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.
> >>
> >> 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 work with the new naming
> >> behavior of failover slaves. 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.
> >>
> >> Fixes: 30c8bd5aa8b2 ("net: Introduce generic failover module")
> >> Signed-off-by: Si-Wei Liu
> >> Reviewed-by: Liran Alon
> >> Acked-by: Michael S. Tsirkin
> >
> > I worry that userspace might have made a bunch of assumptions
> > that names never change as long as interface is up.
> > So listening for up events ensures that interface
> > is not renamed.
>
> That’s true. This is exactly what is described in 3rd paragraph of commit
> message.
> However, as commit message claims, net-failover slaves can be treated
> specially
> because userspace is already broken on their handling and they need to be
> modified
> to behave specially in regards to those slaves. Therefore, it’s less risky to
> lift up the
> rename restriction on failover slave which is already UP.
>
> >
> > How about sending down and up events around such renames?
>
> You mean that dev_change_name() will behave as proposed in this patch but
> also in addition
> send fake DOWN and UP uevents to userspace?
>
> -Liran
That was what I was trying to say.
> >
> >
> >
> >> ---
> >> v1 -> v2:
> >> - Drop configurable module parameter (Sridhar)
> >>
> >>
> >> include/linux/netdevice.h | 3 +++
> >> net/core/dev.c| 3 ++-
> >> net/core/failover.c | 6 +++---
> >> 3 files changed, 8 insertions(+), 4 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_
Re: [PATCH net v2] failover: allow name change on IFF_UP slave interfaces
> On 21 Mar 2019, at 16:04, Michael S. Tsirkin wrote:
>
> On Wed, Mar 06, 2019 at 10:08:32PM -0500, Si-Wei Liu 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.
>>
>> 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 work with the new naming
>> behavior of failover slaves. 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.
>>
>> Fixes: 30c8bd5aa8b2 ("net: Introduce generic failover module")
>> Signed-off-by: Si-Wei Liu
>> Reviewed-by: Liran Alon
>> Acked-by: Michael S. Tsirkin
>
> I worry that userspace might have made a bunch of assumptions
> that names never change as long as interface is up.
> So listening for up events ensures that interface
> is not renamed.
That’s true. This is exactly what is described in 3rd paragraph of commit
message.
However, as commit message claims, net-failover slaves can be treated specially
because userspace is already broken on their handling and they need to be
modified
to behave specially in regards to those slaves. Therefore, it’s less risky to
lift up the
rename restriction on failover slave which is already UP.
>
> How about sending down and up events around such renames?
You mean that dev_change_name() will behave as proposed in this patch but also
in addition
send fake DOWN and UP uevents to userspace?
-Liran
>
>
>
>> ---
>> v1 -> v2:
>> - Drop configurable module parameter (Sridhar)
>>
>>
>> include/linux/netdevice.h | 3 +++
>> net/core/dev.c| 3 ++-
>> net/core/failover.c | 6 +++---
>> 3 files changed, 8 insertions(+), 4 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_f
