confd: allow interface description as ifAlias

This patch adds support for setting the free form description string as
the interface alias.  This can be read from /sys/class/net/*/ifalias, or
using the 'ip link show' command.  The ifalias is reported by SNMP and
LLDP by default, and now also in the operational datastore.

Linux supports 250 characters in ifalias, but the IF-MIB is restricted
to 64 characters, so we add a local deviation to limit the type.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/statd/python/yanger/yanger.py

@@ -645,6 +645,9 @@ def add_ip_link(ifname, iface_in, iface_out):
     if 'ifindex' in iface_in:
         iface_out['if-index'] = iface_in['ifindex']
 
+    if 'ifalias' in iface_in:
+        iface_out['description'] = iface_in['ifalias']
+
     if 'address' in iface_in:
         iface_out['phys-address'] = iface_in['address']