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diff --git a/mininet/topo.py b/mininet/topo.py
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+#!/usr/bin/env python
+'''@package topo
+
+Network topology creation.
+
+@author Brandon Heller (brandonh@stanford.edu)
+
+This package includes code to represent network topologies.
+
+A Topo object can be a topology database for NOX, can represent a physical
+setup for testing, and can even be emulated with the Mininet package.
+'''
+
+# BL: we may have to fix compatibility here.
+# networkx is also a fairly heavyweight dependency
+# from networkx.classes.graph import Graph
+
+from networkx import Graph
+from mininet.util import irange, natural, naturalSeq
+
+class Topo(object):
+ "Data center network representation for structured multi-trees."
+
+ def __init__(self, hopts=None, sopts=None, lopts=None):
+ """Topo object:
+ hinfo: default host options
+ sopts: default switch options
+ lopts: default link options"""
+ self.g = Graph()
+ self.node_info = {}
+ self.link_info = {} # (src, dst) tuples hash to EdgeInfo objects
+ self.hopts = {} if hopts is None else hopts
+ self.sopts = {} if sopts is None else sopts
+ self.lopts = {} if lopts is None else lopts
+ self.ports = {} # ports[src][dst] is port on src that connects to dst
+
+ def addNode(self, name, **opts):
+ """Add Node to graph.
+ name: name
+ opts: node options
+ returns: node name"""
+ self.g.add_node(name)
+ self.node_info[name] = opts
+ return name
+
+ def addHost(self, name, **opts):
+ """Convenience method: Add host to graph.
+ name: host name
+ opts: host options
+ returns: host name"""
+ if not opts and self.hopts:
+ opts = self.hopts
+ return self.addNode(name, **opts)
+
+ def addSwitch(self, name, **opts):
+ """Convenience method: Add switch to graph.
+ name: switch name
+ opts: switch options
+ returns: switch name"""
+ if not opts and self.sopts:
+ opts = self.sopts
+ result = self.addNode(name, isSwitch=True, **opts)
+ return result
+
+ def addLink(self, node1, node2, port1=None, port2=None,
+ **opts):
+ """node1, node2: nodes to link together
+ port1, port2: ports (optional)
+ opts: link options (optional)
+ returns: link info key"""
+ if not opts and self.lopts:
+ opts = self.lopts
+ self.addPort(node1, node2, port1, port2)
+ key = tuple(self.sorted([node1, node2]))
+ self.link_info[key] = opts
+ self.g.add_edge(*key)
+ return key
+
+ def addPort(self, src, dst, sport=None, dport=None):
+ '''Generate port mapping for new edge.
+ @param src source switch name
+ @param dst destination switch name
+ '''
+ self.ports.setdefault(src, {})
+ self.ports.setdefault(dst, {})
+ # New port: number of outlinks + base
+ src_base = 1 if self.isSwitch(src) else 0
+ dst_base = 1 if self.isSwitch(dst) else 0
+ if sport is None:
+ sport = len(self.ports[src]) + src_base
+ if dport is None:
+ dport = len(self.ports[dst]) + dst_base
+ self.ports[src][dst] = sport
+ self.ports[dst][src] = dport
+
+ def nodes(self, sort=True):
+ "Return nodes in graph"
+ if sort:
+ return self.sorted( self.g.nodes() )
+ else:
+ return self.g.nodes()
+
+ def isSwitch(self, n):
+ '''Returns true if node is a switch.'''
+ info = self.node_info[n]
+ return info and info.get('isSwitch', False)
+
+ def switches(self, sort=True):
+ '''Return switches.
+ sort: sort switches alphabetically
+ @return dpids list of dpids
+ '''
+ return [n for n in self.nodes(sort) if self.isSwitch(n)]
+
+ def hosts(self, sort=True):
+ '''Return hosts.
+ sort: sort hosts alphabetically
+ @return dpids list of dpids
+ '''
+ return [n for n in self.nodes(sort) if not self.isSwitch(n)]
+
+ def links(self, sort=True):
+ '''Return links.
+ sort: sort links alphabetically
+ @return links list of name pairs
+ '''
+ if not sort:
+ return self.g.edges()
+ else:
+ links = [tuple(self.sorted(e)) for e in self.g.edges()]
+ return sorted( links, key=naturalSeq )
+
+ def port(self, src, dst):
+ '''Get port number.
+
+ @param src source switch name
+ @param dst destination switch name
+ @return tuple (src_port, dst_port):
+ src_port: port on source switch leading to the destination switch
+ dst_port: port on destination switch leading to the source switch
+ '''
+ if src in self.ports and dst in self.ports[src]:
+ assert dst in self.ports and src in self.ports[dst]
+ return (self.ports[src][dst], self.ports[dst][src])
+
+ def linkInfo( self, src, dst ):
+ "Return link metadata"
+ src, dst = self.sorted([src, dst])
+ return self.link_info[(src, dst)]
+
+ def setlinkInfo( self, src, dst, info ):
+ "Set link metadata"
+ src, dst = self.sorted([src, dst])
+ self.link_info[(src, dst)] = info
+
+ def nodeInfo( self, name ):
+ "Return metadata (dict) for node"
+ info = self.node_info[ name ]
+ return info if info is not None else {}
+
+ def setNodeInfo( self, name, info ):
+ "Set metadata (dict) for node"
+ self.node_info[ name ] = info
+
+ @staticmethod
+ def sorted( items ):
+ "Items sorted in natural (i.e. alphabetical) order"
+ return sorted(items, key=natural)
+
+class SingleSwitchTopo(Topo):
+ '''Single switch connected to k hosts.'''
+
+ def __init__(self, k=2, **opts):
+ '''Init.
+
+ @param k number of hosts
+ @param enable_all enables all nodes and switches?
+ '''
+ super(SingleSwitchTopo, self).__init__(**opts)
+
+ self.k = k
+
+ switch = self.addSwitch('s1')
+ for h in irange(1, k):
+ host = self.addHost('h%s' % h)
+ self.addLink(host, switch)
+
+
+class SingleSwitchReversedTopo(Topo):
+ '''Single switch connected to k hosts, with reversed ports.
+
+ The lowest-numbered host is connected to the highest-numbered port.
+
+ Useful to verify that Mininet properly handles custom port numberings.
+ '''
+ def __init__(self, k=2, **opts):
+ '''Init.
+
+ @param k number of hosts
+ @param enable_all enables all nodes and switches?
+ '''
+ super(SingleSwitchReversedTopo, self).__init__(**opts)
+ self.k = k
+ switch = self.addSwitch('s1')
+ for h in irange(1, k):
+ host = self.addHost('h%s' % h)
+ self.addLink(host, switch,
+ port1=0, port2=(k - h + 1))
+
+class LinearTopo(Topo):
+ "Linear topology of k switches, with one host per switch."
+
+ def __init__(self, k=2, **opts):
+ """Init.
+ k: number of switches (and hosts)
+ hconf: host configuration options
+ lconf: link configuration options"""
+
+ super(LinearTopo, self).__init__(**opts)
+
+ self.k = k
+
+ lastSwitch = None
+ for i in irange(1, k):
+ host = self.addHost('h%s' % i)
+ switch = self.addSwitch('s%s' % i)
+ self.addLink( host, switch)
+ if lastSwitch:
+ self.addLink( switch, lastSwitch)
+ lastSwitch = switch