From: Long Li <lon...@microsoft.com>

When a VF is being exposed form the kernel, it should be marked as "slave"
before exposing to the user-mode. The VF is not usable without netvsc running
as master. The user-mode should never see a VF without the "slave" flag.

An example of a user-mode program depending on this flag is cloud-init
(https://github.com/canonical/cloud-init/blob/19.3/cloudinit/net/__init__.py)
When scanning interfaces, it checks on if this interface has a master to
decide if it should be configured. There are other user-mode programs perform
similar checks.

This commit moves the code of setting the slave flag to the time before VF is
exposed to user-mode.

Signed-off-by: Long Li <lon...@microsoft.com>
---

Change since v1:
Use a new function to handle NETDEV_POST_INIT.

Change since v2:
Add "net" in subject. Add more details on the user-mode program behavior.

Change since v3:
Change target to net-next.

 drivers/net/hyperv/netvsc_drv.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index ec77fb9dcf89..fdad58dcc6a8 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -2206,9 +2206,6 @@ static int netvsc_vf_join(struct net_device *vf_netdev,
                goto upper_link_failed;
        }
 
-       /* set slave flag before open to prevent IPv6 addrconf */
-       vf_netdev->flags |= IFF_SLAVE;
-
        schedule_delayed_work(&ndev_ctx->vf_takeover, VF_TAKEOVER_INT);
 
        call_netdevice_notifiers(NETDEV_JOIN, vf_netdev);
@@ -2320,11 +2317,9 @@ static struct net_device *get_netvsc_byslot(const struct 
net_device *vf_netdev)
         */
        list_for_each_entry(ndev_ctx, &netvsc_dev_list, list) {
                ndev = hv_get_drvdata(ndev_ctx->device_ctx);
-               if (ether_addr_equal(vf_netdev->perm_addr, ndev->perm_addr)) {
-                       netdev_notice(vf_netdev,
-                                     "falling back to mac addr based 
matching\n");
+               if (ether_addr_equal(vf_netdev->perm_addr, ndev->perm_addr) ||
+                   ether_addr_equal(vf_netdev->dev_addr, ndev->perm_addr))
                        return ndev;
-               }
        }
 
        netdev_notice(vf_netdev,
@@ -2332,6 +2327,19 @@ static struct net_device *get_netvsc_byslot(const struct 
net_device *vf_netdev)
        return NULL;
 }
 
+static int netvsc_prepare_slave(struct net_device *vf_netdev)
+{
+       struct net_device *ndev;
+
+       ndev = get_netvsc_byslot(vf_netdev);
+       if (!ndev)
+               return NOTIFY_DONE;
+
+       /* set slave flag before open to prevent IPv6 addrconf */
+       vf_netdev->flags |= IFF_SLAVE;
+       return NOTIFY_DONE;
+}
+
 static int netvsc_register_vf(struct net_device *vf_netdev)
 {
        struct net_device_context *net_device_ctx;
@@ -2753,6 +2761,8 @@ static int netvsc_netdev_event(struct notifier_block 
*this,
                return NOTIFY_DONE;
 
        switch (event) {
+       case NETDEV_POST_INIT:
+               return netvsc_prepare_slave(event_dev);
        case NETDEV_REGISTER:
                return netvsc_register_vf(event_dev);
        case NETDEV_UNREGISTER:
-- 
2.34.1


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