ifupdownmain: squash multiple iface stanzas for the same interface

Ticket:
Reviewed By: CCR-4268
Testing Done: Tested squashing of interfaces with multiple iface stanzas

This is controlled by ifaceobj_squash config variable in
/etc/network/ifupdown2/ifupdown2.conf.

With ifaceobj_squash=1, ifquery and all commands will
output squashed interfaces.

$cat /etc/network/interfaces
auto swp3
iface swp3
    mtu 9000

auto swp3
iface swp3 inet static
    address 10.0.17.3/24

auto swp3
iface swp3 inet static
    address 10.0.18.3/24
    address 2000:1000:1000:1000:3::5/128

$ifquery -a
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

auto swp3
iface swp3
        mtu 9000
        address 10.0.17.3/24
        address 10.0.18.3/24
        address 2000:1000:1000:1000:3::5/128

When and why do we need this ?
- If we preserve multiple ifaceobjects for the same iface,
it gets tricky in some cases to set default policy
values because the addon module run methods are called
on each ifaceobject.
- Each ifaceobject belonging to the same interface
is treated as a separate interface. It is difficult
to remember things accross addon module run methods
- we have a few hacks in place which we would like to
get rid of

Why not turn it on by default ?
- still debating about it. Dont want to break existing
scripts with change of output. Will get some feedback before
I switch the default to squash.

config/ifupdown2.conf

@@ -53,3 +53,8 @@ ifreload_down_changed=0
 
 # squash all addr config when you process the first interface
 addr_config_squash=0
+
+# squash iface config into one when you have multiple
+# ifaces stanzas for an interface
+ifaceobj_squash=0
+

ifupdown/iface.py

@@ -527,6 +527,16 @@ class iface():
                     if v != dstiface.config.get(k)): return False
         return True
 
+    def squash(self, newifaceobj):
+        """ This squashes the iface object """
+        for attrname, attrlist in newifaceobj.config.iteritems():
+            # if allready present add it to the list
+            # else add it to the end of the dictionary
+            # We need to maintain order.
+            if self.config.get(attrname):
+                self.config[attrname].extend(attrlist)
+            else:
+                self.config.update([(attrname, attrlist)])
 
     def __getstate__(self):
         odict = self.__dict__.copy()

ifupdown/ifupdownmain.py

@@ -262,6 +262,9 @@ class ifupdownMain(ifupdownBase):
                              'state changes will be delayed till the ' +
                              'masters admin state change.')
 
+        self._ifaceobj_squash = True if self.config.get(
+                            'ifaceobj_squash', '0') == '1' else False
+
         # initialize global config object with config passed by the user
         # This makes config available to addon modules
         ifupdownConfig.config = self.config
@@ -661,9 +664,14 @@ class ifupdownMain(ifupdownBase):
            ifaceobj.link_type = ifaceLinkType.LINK_NA
         currentifaceobjlist = self.ifaceobjdict.get(ifaceobj.name)
         if not currentifaceobjlist:
-           self.ifaceobjdict[ifaceobj.name]= [ifaceobj]
-           ifaceobj.flags |= ifaceobj.YOUNGEST_SIBLING
-           return
+            self.ifaceobjdict[ifaceobj.name]= [ifaceobj]
+            if not self._ifaceobj_squash:
+                ifaceobj.flags |= ifaceobj.YOUNGEST_SIBLING
+            return
+        if self._ifaceobj_squash:
+            # squash with old iface object
+            currentifaceobjlist[0].squash(ifaceobj)
+            return
         if ifaceobj.compare(currentifaceobjlist[0]):
             self.logger.warn('duplicate interface %s found' %ifaceobj.name)
             return