be a little more clever about interface default
the interface default of eth0 has become more wrong since we've
got a generation of Linux distros that don't use eth* as their
interface naming. Instead of that do a slightly more clever, but
probably still wrong thing, of picking an interface that exists
and is a physical interface.
This is still overridable, however won't cause really cryptic
failures in nova-compute because it's trying to use an interface
that doesn't exist *really* late in the network creation.
Change-Id: I93016ff5a25678de76254418155c839a269486a0
diff --git a/lib/nova b/lib/nova
index c51d584..722eabb 100644
--- a/lib/nova
+++ b/lib/nova
@@ -75,8 +75,13 @@
# Set default defaults here as some hypervisor drivers override these
PUBLIC_INTERFACE_DEFAULT=br100
-GUEST_INTERFACE_DEFAULT=eth0
FLAT_NETWORK_BRIDGE_DEFAULT=br100
+# set the GUEST_INTERFACE_DEFAULT to some interface on the box so that
+# the default isn't completely crazy. This will match eth*, em*, or
+# the new p* interfaces, then basically picks the first
+# alphabetically. It's probably wrong, however it's less wrong than
+# always using 'eth0' which doesn't exist on new Linux distros at all.
+GUEST_INTERFACE_DEFAULT=$(route -n | awk '{print $8}' | grep ^[ep] | sort | head -1)
# Get hypervisor configuration
# ----------------------------