demo: fix graph generation for empty prefixes

demo/demo

@@ -94,6 +94,7 @@ class Re6stNode(nemu.Node):
 
     def __init__(self, name, short):
         super().__init__()
+        print("Re6stNode ctor %r %r" % (name, short))
         self.name = name
         self.short = short
         self.Popen(('sysctl', '-q',
@@ -427,11 +428,12 @@ def route_svg(ipv4, z=4, default=type('', (), {'short': None})):
         g = graph[n] = defaultdict(list)
         g: dict[tuple[Re6stNode, bool], list[Re6stNode]]
         for r in n.get_routes():
+            print("route_svg: %r" % r)
             if (r.prefix and r.prefix.startswith('10.42.') if ipv4 else
             r.prefix is None or r.prefix.startswith('2001:db8:')):
                 try:
-                    g[node_by_ll(r.nexthop)].append(
-                        node_by_ll(r.prefix)[0] if r.prefix else default)
+                    if r.prefix:
+                        g[node_by_ll(r.nexthop)].append(node_by_ll(r.prefix)[0])
                 except KeyError:
                     pass
     gv = ["digraph { splines = true; edge[color=grey, labelangle=0];"]
@@ -452,7 +454,9 @@ def route_svg(ipv4, z=4, default=type('', (), {'short': None})):
             p2: Re6stNode
             l2: list[str] = []
             arrowhead = 'none'
-            for r2 in sorted(r2.short for r2 in r):
+            print("r=%r" % r)
+            print("processing: " + ", ".join("%r" % ((r2.name, r2.short),) for r2 in r))
+            for r2 in sorted(r2.short if r2.short else "NONE" for r2 in r):
                 if r2:
                     if r2 == p2.short:
                         r2 = '<font color="grey">%s</font>' % r2