mininet.node.SWITCH_PORT_BASE specifies first switch port number.

This should be mostly cosmetic, but it causes switches to number
their ports consistently with OpenFlow 1.0, which starts at 1.
For older versions of OpenFlow, SWITCH_PORT_BASE may be set to zero.

mininet/topo.py

@@ -12,7 +12,7 @@ setup for testing, and can even be emulated with the Mininet package.
 '''
 
 from networkx.classes.graph import Graph
-
+from mininet.node import SWITCH_PORT_BASE
 
 class NodeID(object):
     '''Topo node identifier.'''
@@ -127,15 +127,18 @@ class Topo(object):
         @param src source switch DPID
         @param dst destination switch DPID
         '''
+        src_base = SWITCH_PORT_BASE if self.is_switch(src) else 0
+        dst_base = SWITCH_PORT_BASE if self.is_switch(dst) else 0
         if src not in self.ports:
             self.ports[src] = {}
         if dst not in self.ports[src]:
-            self.ports[src][dst] = len(self.ports[src])  # num outlinks
-
+            # num outlinks    
+            self.ports[src][dst] = len(self.ports[src]) + src_base
         if dst not in self.ports:
             self.ports[dst] = {}
         if src not in self.ports[dst]:
-            self.ports[dst][src] = len(self.ports[dst])  # num outlinks
+            # num outlinks 
+            self.ports[dst][src] = len(self.ports[dst]) + dst_base
 
     def node_enabled(self, dpid):
         '''Is node connected, admin on, powered on, and fault-free?
@@ -178,6 +181,11 @@ class Topo(object):
         '''
         return [str(self.id_gen(dpid = dpid)) for dpid in dpids]
 
+    def is_switch(self, n):
+        '''Returns true if node is a switch.'''
+        return self.node_info[n].is_switch
+
+
     def switches(self, enabled = True):
         '''Return switches.
 
@@ -185,12 +193,7 @@ class Topo(object):
 
         @return dpids list of dpids
         '''
-
-        def is_switch(n):
-            '''Returns true if node is a switch.'''
-            return self.node_info[n].is_switch
-
-        nodes = [n for n in self.g.nodes() if is_switch(n)]
+        nodes = [n for n in self.g.nodes() if self.is_switch(n)]
         return self.nodes_enabled(nodes, enabled)
 
     def hosts(self, enabled = True):