Linux Virtualization - Feb 2019 - [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 Wed, 27 Feb 2019 20:26:02 -0500, Michael S. Tsirkin
wrote:
> On Wed, Feb 27, 2019 at 04:52:05PM -0800, Jakub Kicinski wrote:
> > On Wed, 27 Feb 2019 19:41:32 -0500, Michael S. Tsirkin wrote:  
> > > > As this scheme adds much complexity to the kernel naming
convention
> > > > (currently it's just ethX names) that no userspace can
understand.
> > > 
> > > Anything that pokes at slaves needs to be specially designed
anyway.
> > > Naming seems like a minor issue.  
> > 
> > Can the users who care about the naming put net_failover into
> > "user space will do the bond enslavement" mode, and do the
bond
> > creation/management themselves from user space (in systemd/ 
> > Network Manager) based on the failover flag?  
> 
> Putting issues of compatibility aside (userspace tends to be confused if
> you give it two devices with same MAC), how would you have it work in
> practice? Timer based hacks like netvsc where if userspace didn't
> respond within X seconds we assume it won't and do everything
ourselves?
Well, what I'm saying is basically if user space knows how to deal with
the auto-bonding, we can put aside net_failover for the most part.  It
can either be blacklisted or it can have some knob which will
effectively disable the auto-enslavement.

Auto-bonding capable user space can do the renames, spawn the bond,
etc. all by itself.  I'm basically going back to my initial proposal
here :)  There is a RedHat bugzilla for the NetworkManager team to do
this, but we merged net_failover before those folks got around to
implementing it.

IOW if NM/systemd is capable of doing the auto-bonding itself it can
disable the kernel mechanism and take care of it all.  If kernel is
booted with an old user space which doesn't have capable NM/systemd -
net_failover will kick in and do its best.

On Wed, Feb 27, 2019 at 05:52:18PM -0800, Jakub Kicinski
wrote:
> On Wed, 27 Feb 2019 20:26:02 -0500, Michael S. Tsirkin wrote:
> > On Wed, Feb 27, 2019 at 04:52:05PM -0800, Jakub Kicinski wrote:
> > > On Wed, 27 Feb 2019 19:41:32 -0500, Michael S. Tsirkin wrote:  
> > > > > As this scheme adds much complexity to the kernel
naming convention
> > > > > (currently it's just ethX names) that no userspace
can understand.
> > > > 
> > > > Anything that pokes at slaves needs to be specially designed
anyway.
> > > > Naming seems like a minor issue.  
> > > 
> > > Can the users who care about the naming put net_failover into
> > > "user space will do the bond enslavement" mode, and do
the bond
> > > creation/management themselves from user space (in systemd/ 
> > > Network Manager) based on the failover flag?  
> > 
> > Putting issues of compatibility aside (userspace tends to be confused
if
> > you give it two devices with same MAC), how would you have it work in
> > practice? Timer based hacks like netvsc where if userspace didn't
> > respond within X seconds we assume it won't and do everything
ourselves?
> 
> Well, what I'm saying is basically if user space knows how to deal with
> the auto-bonding, we can put aside net_failover for the most part.  It
> can either be blacklisted or it can have some knob which will
> effectively disable the auto-enslavement.
OK I guess we could add a module parameter to skip this.
Is this what you mean?
> Auto-bonding capable user space can do the renames, spawn the bond,
> etc. all by itself.  I'm basically going back to my initial proposal
> here :)  There is a RedHat bugzilla for the NetworkManager team to do
> this, but we merged net_failover before those folks got around to
> implementing it.
In particular because there's no policy involved whatsoever
here so it's just mechanism being pushed up to userspace.
> IOW if NM/systemd is capable of doing the auto-bonding itself it can
> disable the kernel mechanism and take care of it all.  If kernel is
> booted with an old user space which doesn't have capable NM/systemd -
> net_failover will kick in and do its best.
Sure - it's just 2 lines of code, see below.

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>

But I don't intend to bother until there's actual interest from
userspace developers to bother. In particular it is not just NM/systemd
even on Fedora - e.g. you will need to teach dracut to somehow detect
and handle this - right now it gets confused if there are two devices
with same MAC addresses.

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 955b3e76eb8d..dd2b2c370003 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -43,6 +43,7 @@ static bool csum = true, gso = true, napi_tx;
 module_param(csum, bool, 0444);
 module_param(gso, bool, 0444);
 module_param(napi_tx, bool, 0644);
+module_param(disable_failover, bool, 0644);
 
 /* FIXME: MTU in config. */
 #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
@@ -3163,6 +3164,7 @@ static int virtnet_probe(struct virtio_device *vdev)
 	virtnet_init_settings(dev);
 
-	if (virtio_has_feature(vdev, VIRTIO_NET_F_STANDBY)) {
+	if (virtio_has_feature(vdev, VIRTIO_NET_F_STANDBY) &&
+		!disable_failover) {
 		vi->failover = net_failover_create(vi->dev);
 		if (IS_ERR(vi->failover)) {
 			err = PTR_ERR(vi->failover);

On Wed, 27 Feb 2019 23:47:33 -0500, Michael S. Tsirkin
wrote:
> On Wed, Feb 27, 2019 at 05:52:18PM -0800, Jakub Kicinski wrote:
> > > > Can the users who care about the naming put net_failover
into
> > > > "user space will do the bond enslavement" mode,
and do the bond
> > > > creation/management themselves from user space (in systemd/ 
> > > > Network Manager) based on the failover flag?    
> > > 
> > > Putting issues of compatibility aside (userspace tends to be
confused if
> > > you give it two devices with same MAC), how would you have it
work in
> > > practice? Timer based hacks like netvsc where if userspace
didn't
> > > respond within X seconds we assume it won't and do everything
ourselves?
> > 
> > Well, what I'm saying is basically if user space knows how to deal
with
> > the auto-bonding, we can put aside net_failover for the most part.  It
> > can either be blacklisted or it can have some knob which will
> > effectively disable the auto-enslavement.  
> 
> OK I guess we could add a module parameter to skip this.
> Is this what you mean?
Yup.
> > Auto-bonding capable user space can do the renames, spawn the bond,
> > etc. all by itself.  I'm basically going back to my initial
proposal
> > here :)  There is a RedHat bugzilla for the NetworkManager team to do
> > this, but we merged net_failover before those folks got around to
> > implementing it.  
> 
> In particular because there's no policy involved whatsoever
> here so it's just mechanism being pushed up to userspace.
> 
> > IOW if NM/systemd is capable of doing the auto-bonding itself it can
> > disable the kernel mechanism and take care of it all.  If kernel is
> > booted with an old user space which doesn't have capable
NM/systemd -
> > net_failover will kick in and do its best.  
> 
> Sure - it's just 2 lines of code, see below.
> 
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> 
> But I don't intend to bother until there's actual interest from
> userspace developers to bother. In particular it is not just NM/systemd
> even on Fedora - e.g. you will need to teach dracut to somehow detect
> and handle this - right now it gets confused if there are two devices
> with same MAC addresses.
It is a bit of a the chicken or the egg situation ;)  But users can
just blacklist, too.  Anyway, I think this is far better than module
parameters for twiddling kernel-based interface naming policy.. :S
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 955b3e76eb8d..dd2b2c370003 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -43,6 +43,7 @@ static bool csum = true, gso = true, napi_tx;
>  module_param(csum, bool, 0444);
>  module_param(gso, bool, 0444);
>  module_param(napi_tx, bool, 0644);
> +module_param(disable_failover, bool, 0644);
>  
>  /* FIXME: MTU in config. */
>  #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
> @@ -3163,6 +3164,7 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	virtnet_init_settings(dev);
>  
> -	if (virtio_has_feature(vdev, VIRTIO_NET_F_STANDBY)) {
> +	if (virtio_has_feature(vdev, VIRTIO_NET_F_STANDBY) &&
> +		!disable_failover) {
>  		vi->failover = net_failover_create(vi->dev);
>  		if (IS_ERR(vi->failover)) {
>  			err = PTR_ERR(vi->failover);
>