1 files changed, 79 insertions, 0 deletions
diff --git a/potpourri/expand-roa-prefixes.py b/potpourri/expand-roa-prefixes.py
new file mode 100644
index 00000000..ae34ea0a
--- /dev/null
+++ b/potpourri/expand-roa-prefixes.py
@@ -0,0 +1,79 @@
+# $Id$
+# 
+# Copyright (C) 2011  Internet Systems Consortium ("ISC")
+# 
+# Permission to use, copy, modify, and distribute this software for any
+# purpose with or without fee is hereby granted, provided that the above
+# copyright notice and this permission notice appear in all copies.
+# 
+# THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+# REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+# AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+# LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+# OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+# PERFORMANCE OF THIS SOFTWARE.
+
+"""
+I got tired of trying to explain in English how the maxLength macro
+hack works in ROAs, so this is an attempt to explain it as code.
+
+Given one or more ROA prefix sets on the command line, this script
+prints out the expansion as a list of prefixes.
+"""
+
+import sys
+import rpki.resource_set
+import rpki.ipaddrs
+
+class NotAPrefix(Exception):
+  """
+  Address is not a proper prefix.
+  """
+
+class address_range(object):
+  """
+  Iterator for rpki.ipaddrs address objects.
+  """
+
+  def __init__(self, start, stop, step):
+    self.addr = start
+    self.stop = stop
+    self.step = step
+    self.type = type(start)
+
+  def __iter__(self):
+    while self.addr < self.stop:
+      yield self.addr
+      self.addr = self.type(self.addr + self.step)
+
+def main(argv):
+
+  prefix_sets = []
+  for arg in argv:
+    if ":" in arg:
+      prefix_sets.extend(rpki.resource_set.roa_prefix_set_ipv6(arg))
+    else:
+      prefix_sets.extend(rpki.resource_set.roa_prefix_set_ipv4(arg))
+
+  for prefix_set in prefix_sets:
+    sys.stdout.write("%s expands to:\n" % prefix_set)
+
+    prefix_type = prefix_set.range_type.datum_type
+    prefix_min = prefix_set.prefix
+    prefix_max = prefix_set.prefix + (1L << (prefix_type.bits - prefix_set.prefixlen))
+
+    for prefixlen in xrange(prefix_set.prefixlen, prefix_set.max_prefixlen + 1):
+
+      step = (1L << (prefix_type.bits - prefixlen))
+      mask = step - 1
+
+      for addr in address_range(prefix_min, prefix_max, step):
+        if (addr & mask) != 0:
+          raise NotAPrefix, "%s is not a /%d prefix" % (addr, prefixlen)
+        sys.stdout.write("  %s/%d\n" % (addr, prefixlen))
+
+    sys.stdout.write("\n")
+
+if __name__ == "__main__":
+  main(sys.argv[1:] if len(sys.argv) > 1 else ["18.0.0.0/8-24"])