Empty or stale alias on interface when using ifdown

Ticket: CM-6795
Reviewed By: CCR-4270
Testing Done:

root@debian:~# cat /etc/network/interfaces
auto lo
iface lo inet loopback
  alias foo_bar
root@debian:~# ip link show lo
  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
          alias foo_bar
root@debian:~# ifdown -v lo
	  info: loading builtin modules from /usr/share/ifupdown2/addons
	  info: module ethtool not loaded (module init failed: no /sbin/ethtool found)

info: module ethtool not loaded (module init failed: no /sbin/ethtool found)

info: looking for user scripts under /etc/network
info: loading scripts under /etc/network/if-pre-up.d ...
info: loading scripts under /etc/network/if-up.d ...
info: loading scripts under /etc/network/if-post-up.d ...
info: loading scripts under /etc/network/if-pre-down.d ...
info: loading scripts under /etc/network/if-down.d ...
info: loading scripts under /etc/network/if-post-down.d ...
info: lo: running ops ...
info: rtnetlink: setting link lo down
info: executing ip -o addr show dev lo
info: Executing echo "" > /sys/class/net/lo/ifalias
info: Executing /etc/network/if-down.d/avahi-autoipd
info: Executing /etc/network/if-down.d/upstart
info: Executing /etc/network/if-down.d/wpasupplicant
info: Executing /etc/network/if-post-down.d/wireless-tools
info: Executing /etc/network/if-post-down.d/avahi-daemon
info: Executing /etc/network/if-post-down.d/wpasupplicant
root@debian:~# ip link show lo
1: lo: <LOOPBACK> mtu 65536 qdisc noqueue state DOWN mode DEFAULT group default
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
root@debian:~# ifup -v lo
    info: loading builtin modules from /usr/share/ifupdown2/addons
    info: module ethtool not loaded (module init failed: no /sbin/ethtool found)

info: module ethtool not loaded (module init failed: no /sbin/ethtool found)

info: looking for user scripts under /etc/network
info: loading scripts under /etc/network/if-pre-up.d ...
info: loading scripts under /etc/network/if-up.d ...
info: loading scripts under /etc/network/if-post-up.d ...
info: loading scripts under /etc/network/if-pre-down.d ...
info: loading scripts under /etc/network/if-down.d ...
info: loading scripts under /etc/network/if-post-down.d ...
info: processing interfaces file /etc/network/interfaces
info: lo: running ops ...
info: Executing /etc/network/if-pre-up.d/wireless-tools
info: Executing /etc/network/if-pre-up.d/wpasupplicant
info: rtnetlink: setting link lo up
info: executing ip -o addr show dev lo
info: executing ip link set dev lo alias foo_bar
info: Executing /etc/network/if-up.d/mountnfs
info: Executing /etc/network/if-up.d/avahi-autoipd
info: Executing /etc/network/if-up.d/openssh-server
info: Executing /etc/network/if-up.d/upstart
info: Executing /etc/network/if-up.d/avahi-daemon
info: Executing /etc/network/if-up.d/wpasupplicant
root@debian:~# ip link show lo
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
        alias foo_bar

addons/address.py

@@ -4,6 +4,8 @@
 # Author: Roopa Prabhu, roopa@cumulusnetworks.com
 #
 
+import os
+
 try:
     from ipaddr import IPNetwork
     from sets import Set
@@ -306,7 +308,9 @@ class address(moduleBase):
                     self.ipcmd.del_addr_all(ifaceobj.name)
             alias = ifaceobj.get_attr_value_first('alias')
             if alias:
-                self.ipcmd.link_set(ifaceobj.name, 'alias', "\'\'")
+                filename = '/sys/class/net/%s/ifalias' %ifaceobj.name
+                self.logger.info('Executing echo "" > %s' %filename)
+                os.system('echo "" > %s' %filename)
             # XXX hwaddress reset cannot happen because we dont know last
             # address.