def allocate_subnets(network, address_block=IPNetwork("10.0.0.0/8")):
"""Allocates subnets and IP addresses to links in the network.
Args:
address_block (IPNetwork): The address block to use.
Returns:
ip_as_allocs
Example usage:
>>> network = ank.example_multi_as()
>>> allocate_subnets(network)
>>> print ank.debug_nodes(network.graph, "lo_ip")
{'1a.AS1': IPNetwork('10.0.0.32/32'),
'1b.AS1': IPNetwork('10.0.0.33/32'),
'1c.AS1': IPNetwork('10.0.0.34/32'),
'2a.AS2': IPNetwork('10.1.0.64/32'),
'2b.AS2': IPNetwork('10.1.0.65/32'),
'2c.AS2': IPNetwork('10.1.0.66/32'),
'2d.AS2': IPNetwork('10.1.0.67/32'),
'3a.AS3': IPNetwork('10.2.0.0/32')}
>>> print ank.debug_edges(network.graph, "ip")
{('1a.AS1', '1b.AS1'): IPAddress('10.0.0.10'),
('1a.AS1', '1c.AS1'): IPAddress('10.0.0.22'),
('1b.AS1', '1a.AS1'): IPAddress('10.0.0.9'),
('1b.AS1', '1c.AS1'): IPAddress('10.0.0.26'),
('1b.AS1', '3a.AS3'): IPAddress('10.0.0.17'),
('1c.AS1', '1a.AS1'): IPAddress('10.0.0.21'),
('1c.AS1', '1b.AS1'): IPAddress('10.0.0.25'),
('1c.AS1', '2a.AS2'): IPAddress('10.0.0.29'),
('2a.AS2', '1c.AS1'): IPAddress('10.0.0.30'),
('2a.AS2', '2b.AS2'): IPAddress('10.1.0.10'),
('2a.AS2', '2d.AS2'): IPAddress('10.1.0.26'),
('2b.AS2', '2a.AS2'): IPAddress('10.1.0.9'),
('2b.AS2', '2c.AS2'): IPAddress('10.1.0.18'),
('2c.AS2', '2b.AS2'): IPAddress('10.1.0.17'),
('2c.AS2', '2d.AS2'): IPAddress('10.1.0.30'),
('2d.AS2', '2a.AS2'): IPAddress('10.1.0.25'),
('2d.AS2', '2c.AS2'): IPAddress('10.1.0.29'),
('2d.AS2', '3a.AS3'): IPAddress('10.1.0.33'),
('3a.AS3', '1b.AS1'): IPAddress('10.0.0.18'),
('3a.AS3', '2d.AS2'): IPAddress('10.1.0.34')}
>>> print ank.debug_edges(network.graph, "sn")
{('1a.AS1', '1b.AS1'): IPNetwork('10.0.0.8/30'),
('1a.AS1', '1c.AS1'): IPNetwork('10.0.0.20/30'),
('1b.AS1', '1a.AS1'): IPNetwork('10.0.0.8/30'),
('1b.AS1', '1c.AS1'): IPNetwork('10.0.0.24/30'),
('1b.AS1', '3a.AS3'): IPNetwork('10.0.0.16/30'),
('1c.AS1', '1a.AS1'): IPNetwork('10.0.0.20/30'),
('1c.AS1', '1b.AS1'): IPNetwork('10.0.0.24/30'),
('1c.AS1', '2a.AS2'): IPNetwork('10.0.0.28/30'),
('2a.AS2', '1c.AS1'): IPNetwork('10.0.0.28/30'),
('2a.AS2', '2b.AS2'): IPNetwork('10.1.0.8/30'),
('2a.AS2', '2d.AS2'): IPNetwork('10.1.0.24/30'),
('2b.AS2', '2a.AS2'): IPNetwork('10.1.0.8/30'),
('2b.AS2', '2c.AS2'): IPNetwork('10.1.0.16/30'),
('2c.AS2', '2b.AS2'): IPNetwork('10.1.0.16/30'),
('2c.AS2', '2d.AS2'): IPNetwork('10.1.0.28/30'),
('2d.AS2', '2a.AS2'): IPNetwork('10.1.0.24/30'),
('2d.AS2', '2c.AS2'): IPNetwork('10.1.0.28/30'),
('2d.AS2', '3a.AS3'): IPNetwork('10.1.0.32/30'),
('3a.AS3', '1b.AS1'): IPNetwork('10.0.0.16/30'),
('3a.AS3', '2d.AS2'): IPNetwork('10.1.0.32/30')}
"""
LOG.debug("Allocating subnets")
# Initialise IP list to be graph edge format
ip_as_allocs = {}
# allocates subnets to the edges and loopback in network graph
# Put into dictionary, indexed by ASN (the name attribute of each as graph)
# for easy appending of eBGP links
asgraphs = dict((my_as.asn, my_as) for my_as in ank.get_as_graphs(network))
# Simple method: break address_block into a /16 for each network
#TODO: check this is feasible - ie against required host count
subnet_list = address_block.subnet(16)
ebgp_edges = ank.ebgp_edges(network)
visited_ebgp_edges = set()
for src, dst in sorted(ebgp_edges):
# Add the dst (external peer) to AS of src node so they are allocated
# a subnet. (The AS choice is arbitrary)
if (dst, src) in visited_ebgp_edges:
continue
src_as = asgraphs[src.asn]
src_as.add_edge(src, dst)
# record for DNS purposes
ank.dns_advertise_link(src, dst)
visited_ebgp_edges.add( (src, dst))
for my_as in sorted(asgraphs.values(), key = lambda x: x.asn):
asn = my_as.asn
as_subnet = subnet_list.next()
as_internal_nodes = [n for n in sorted(my_as.nodes()) if network.asn(n) == asn]
host_count = my_as.number_of_nodes()
# record this subnet
ip_as_allocs[my_as.asn] = as_subnet
# split into subnets for loopback and ptp
ptp_count = my_as.number_of_edges()
# Now subnet network into subnets of the larger of these two
# TODO tidy up this comment
# Note ptp subnets required a /30 ie 4 ips
req_sn_count = max(host_count, 4*ptp_count)
if req_sn_count == 0:
# Nothing to allocate for this AS
continue
req_pref_len = int(32 - math.ceil(math.log(req_sn_count, 2)) )
# Subnet as subnet into subnets of this size
sn_iter = as_subnet.subnet(req_pref_len)
# And allocate a subnet for each ptp and loopback
if ptp_count > 0:
# Don't allocate a ptp subnet if there are no ptp links
ptp_subnet = sn_iter.next()
loopback_subnet = sn_iter.next()
if ptp_count > 0:
link_subnet = ptp_subnet.subnet(30)
# Now iterate over edges in this as and apply
for src, dst in sorted(my_as.edges()):
# Note we apply this back to the main graph
# not to the as graph!
subnet = link_subnet.next()
#TODO: fix the technique for accessing edges
# as it breaks with multigraphs, as it creates a new edge
if network.asn(dst) != asn:
# eBGP link where dst has IP allocated from subnet of this AS
network.graph[dst][src]['remote_as_sn_block'] = True
network.graph[src][dst]['sn'] = subnet
network.graph[dst][src]['sn'] = subnet
# allocate an ip to each end
network.graph[src][dst]['ip'] = subnet[1]
network.graph[dst][src]['ip'] = subnet[2]
# Allocate an loopback interface to each router
#TODO: check if next step is necessary
loopback_ips = loopback_subnet.subnet(32)
for rtr in sorted(as_internal_nodes):
lo_ip = loopback_ips.next()
network.graph.node[rtr]['lo_ip'] = lo_ip
network.ip_as_allocs = ip_as_allocs
