Network management design doc

Signed-off-by: Apollon Oikonomopoulos <apollon@noc.grnet.gr>

doc/design-network.rst

+Network management
+==================
+::
+
+ gnt-network add --network=192.0.2.0/24 --gateway=192.0.2.1 \
+ 		--v6-network=2001:648:2ffc::/64 --v6-gateway=2001:648:2ffc::1 \
+ 		public
+
+ gnt-network reserve-ips public 192.0.2.2 192.0.2.10-192.0.2.20
+
+ gnt-network connect public nodegroup1 link100
+ gnt-network connect public nodegroup2 link200
+ gnt-network disconnect public nodegroup1 (only permitted if no instances are
+                                           currently using this network in the group)
+ 
+ gnt-network list
+  Name		IPv4 Network	IPv4 Gateway	      IPv6 Network		   IPv6Gateway
+  public		 192.0.2.0/24	192.0.2.1	2001:db8:dead:beef::/64		2001:db8:dead:beef::1
+  private	 10.0.1.0/24	   -			 -				-
+ 
+ gnt-network list-connected
+  Network	Node Group	Link
+  public		nodegroup1	link100
+  public		nodegroup2 	link200
+  private	nodegroup1	link50
+ 
+ gnt-network list-connected private
+  Network	Node Group	Link
+  private	nodegroup1	link50
+ 
+ gnt-network info public
+  Name: public
+  IPv4 Network: 192.0.2.0/24
+  IPv4 Gateway: 192.0.2.1
+  IPv6 Network: 2001:db8:dead:beef::/64
+  IPv6 Gateway: 2001:db8:dead:beef::1
+  Connected to: nodegroup1 (link100), nodegroup2 (link200)
+  Total IPv4 count: 256
+  Free address count: 201 (80% free)
+  IPv4 pool status: XXX.........XXXXXXXXXXXXXX...XX.............
+                    XXX..........XXX...........................X
+                    ....XXX..........XXX.....................XXX
+                                            X: occupied  .: free
+  Used by 22 instances:
+   inst1
+   inst2
+   inst32
+   ..
+ 
+NIC "network" parameter
+-----------------------
+
+1. "network" takes precedence over "link"
+
+2. manually setting "link" on a nic with existing "network" is not permitted
+
+3. as a safety guard, setting a "network" parameter on a nic with a "link" is only
+   permitted if the network's link on the instance's node group is the same as
+   the current nic's link
+
+4. "link" is updated on startup according to the network -> nodegroup mapping
+
+Default nic "network" parameter
+add default "network" argument? How do we deal with transitions?
+-> network and link may not be set at the same time
+-> setting network will unset link and vice-versa
+-> setting network is only permitted iff:
+
+   all NICs with a "default" link would result in having the same link right after setting "network".
+     i.e.: for instance in all_instances:
+		for nic in instance.nics:
+			if nic.link == instance.primary_node.group.networks[network]:
+				...
+			else:
+				raise errors.OpPrereqError
+
+IAllocator changes
+------------------
+
+ - Make it network-aware, same as storage-aware
+ - Both, network and storage will act as *constraints*, i.e. "place me a node
+   that has access to network x and storage pool y on the cluster". The
+   iallocator will thus rule out node groups based on these constraints.
+
+
+Helper methods in lib/config.py
+-------------------------------
+
+ - ConfigWriter.GetInstancesByNodeGroup(group_uuid)
+ - ConfigWriter.GetInstancesInfoByNodeGroup(group_uuid)

doc/index.rst

@@ -22,6 +22,7 @@ Contents:
    design-2.4.rst
    cluster-merge.rst
    design-shared-storage.rst
+   design-network.rst
    locking.rst
    hooks.rst
    iallocator.rst