udev: net_id - support predictable ifnames on virtio buses

Virtio buses are undeterministically enumerated, so we cannot use them as a basis
for deterministic naming (see bf81e792f3c0). However, we are guaranteed that there
is only ever one virtio bus for every parent device, so we can simply skip over
the virtio buses when naming the devices.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/udev/udev-builtin-net_id.c b/src/udev/udev-builtin-net_id.c
index 6e7e1271fb..589f1f7822 100644
--- a/src/udev/udev-builtin-net_id.c
+++ b/src/udev/udev-builtin-net_id.c
@@ -280,8 +280,16 @@ static int names_pci(struct udev_device *dev, struct netnames *names) {
         assert(names);
 
         parent = udev_device_get_parent(dev);
+
+        /* there can only ever be one virtio bus per parent device, so we can
+           safely ignore any virtio buses. see
+           <http://lists.linuxfoundation.org/pipermail/virtualization/2015-August/030331.html> */
+        while (parent && streq_ptr("virtio", udev_device_get_subsystem(parent)))
+                parent = udev_device_get_parent(parent);
+
         if (!parent)
                 return -ENOENT;
+
         /* check if our direct parent is a PCI device with no other bus in-between */
         if (streq_ptr("pci", udev_device_get_subsystem(parent))) {
                 names->type = NET_PCI;