Network: handle object cleanup

src/network.py

@@ -0,0 +1,78 @@
+""" Network objects """
+
+import settings
+import util
+from xml_template import XMLTemplate
+
+import uuid
+import libvirt
+
+
+class Network(util.NumberedClass):
+    class AlreadyExists(Exception):
+        def __str__(self):
+            return "This network is already instanciated"
+
+    class TooMany(Exception):
+        def __init__(self, count):
+            self.count = count
+
+        def __str__(self):
+            return (
+                "Limit number reached. The current instance #{} does not fit in IPv4"
+            ).format(self.count)
+
+    def __init__(self, conn, name=None):
+        super().__init__()
+
+        if self.id > 250:
+            raise self.TooMany(self.id)
+
+        if not name:
+            name = str(self.id)
+
+        self.conn = conn
+        self.uuid = uuid.uuid4()
+        self.name = settings.PREFIX + "_" + name
+        self.bridge_id = settings.NETWORK_ID * 0xFF + self.id
+        self.bridge_mac = util.MACAddress(self.id, None)
+        self.ipv4 = util.Addrv4(self.id, None)
+        self.ipv6 = util.Addrv6(self.id, None)
+        self.lxc_network = None
+
+        try:
+            if self.conn.networkLookupByName(self.name):
+                raise self.AlreadyExists()
+        except libvirt.libvirtError:
+            pass
+
+    def create(self):
+        if self.lxc_network:
+            raise self.AlreadyExists()
+
+        xml = XMLTemplate("templates/network.xml").inst(
+            name=self.name,
+            uuid=self.uuid,
+            bridge_id=self.bridge_id,
+            mac=self.bridge_mac,
+            addrv4=self.ipv4,
+            netmaskv4=self.ipv4.netmask,
+            addrv6=self.ipv6,
+            prefixv6=self.ipv6.prefix,
+        )
+
+        self.lxc_network = self.conn.networkCreateXML(xml)
+
+    def cleanup(self):
+        if self.lxc_network:
+            self.lxc_network.destroy()
+
+    def __enter__(self):
+        self.create()
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.cleanup()
+
+    def __del__(self):
+        self.cleanup()

src/settings.py

@@ -0,0 +1,19 @@
+""" General settings """
+
+# Prefix to all the networks and containers created
+PREFIX = "testnw"
+
+# Container base installation path -- will be overlaid
+CONTAINER_BASE_ROOT = "/var/lib/machines/lxc-base-" + PREFIX
+
+# Overlayfs mount dir
+OVERLAYFS_MOUNT_DIR = "/tmp/{}-overlays/".format(PREFIX)
+
+# The ID of the whole generated network -- below 0xff
+NETWORK_ID = 132
+
+# IPv4 /16 range
+IPV4_RANGE = "10.{}".format(NETWORK_ID)
+
+# IPv6 /32 range
+IPV6_RANGE = "fd80:ba{:02x}".format(NETWORK_ID)

src/templates/network.xml

@@ -0,0 +1,11 @@
+<network>
+  <name>{name}</name>
+  <uuid>{uuid}</uuid>
+  <bridge name='virbr{bridge_id}' stp='on' delay='0'/>
+  <mac address='{mac}'/>
+  <domain name='{name}'/>
+  <ip address='{addrv4}' netmask='{netmaskv4}'>
+  </ip>
+  <ip family='ipv6' address='{addrv6}' prefix='{prefixv6}'>
+  </ip>
+</network>

src/util.py

@@ -0,0 +1,84 @@
+""" Various utils """
+
+import settings
+
+
+class NumberedClass:
+    """ A class that counts its current instance number """
+
+    next_id = 0
+
+    @classmethod
+    def get_id(cls):
+        out = cls.next_id
+        cls.next_id += 1
+        return out
+
+    def __init__(self):
+        self.id = self.get_id()
+
+
+class MACAddress:
+    """ A MAC address for a NIC or bridge """
+
+    def __init__(self, link_id, dev_id):
+        """ link_id: id of the current link
+            dev_id: id of the current NIC. If the device is a bridge, use None
+        """
+        if not dev_id:
+            dev_id = 0xFF
+
+        self.link_id = link_id
+        self.dev_id = dev_id
+
+    def __str__(self):
+        return "52:54:00:{nwid:02x}:{link_id:02x}:{dev_id:02x}".format(
+            nwid=settings.NETWORK_ID, link_id=self.link_id, dev_id=self.dev_id
+        )
+
+    def __repr__(self):
+        return str(self)
+
+
+class Addrv4:
+    """ An address in IPv4 """
+
+    def __init__(self, link_id, dev_id):
+        """ link_id: id of the current link
+            dev_id: id of the current NIC. Use None to get the base address
+        """
+        if not dev_id:
+            dev_id = 0
+
+        self.link_id = link_id
+        self.dev_id = dev_id
+        self.netmask = "255.255.255.0"
+        self.prefix = 24
+
+    def __str__(self):
+        return "{base_range}.{link_id}.{dev_id}".format(
+            base_range=settings.IPV4_RANGE, link_id=self.link_id, dev_id=self.dev_id
+        )
+
+    def __repr__(self):
+        return str(self)
+
+
+class Addrv6:
+    """ An address in IPv6 """
+
+    def __init__(self, link_id, dev_id):
+        """ link_id: id of the current link
+            dev_id: id of the current NIC. Use None to get the base address
+        """
+        if not dev_id:
+            dev_id = 0
+
+        self.link_id = link_id
+        self.dev_id = dev_id
+        self.prefix = 64
+
+    def __str__(self):
+        return "{base_range}:{link_id:04x}::{dev_id:04x}".format(
+            base_range=settings.IPV6_RANGE, link_id=self.link_id, dev_id=self.dev_id
+        )

src/xml_template.py

@@ -0,0 +1,16 @@
+""" Reads an XML template from a file """
+
+import os
+
+
+class XMLTemplate:
+    """ Reads and instanciates a template from a file """
+
+    def __init__(self, path):
+        self.path = os.path.join(os.path.dirname(os.path.abspath(__file__)), path)
+        with open(self.path, "r") as handle:
+            self.template_str = handle.read()
+
+    def inst(self, *args, **kwargs):
+        """ instanciates the template """
+        return self.template_str.format(*args, **kwargs)