1 files changed, 40 insertions, 0 deletions
diff --git a/third_party/dnspython/examples/reverse.py b/third_party/dnspython/examples/reverse.py
new file mode 100755
index 0000000000..8657baed44
--- /dev/null
+++ b/third_party/dnspython/examples/reverse.py
@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+
+# Usage: reverse.py <zone_filename>...
+#
+# This demo script will load in all of the zones specified by the
+# filenames on the command line, find all the A RRs in them, and
+# construct a reverse mapping table that maps each IP address used to
+# the list of names mapping to that address.  The table is then sorted
+# nicely and printed.
+#
+# Note!  The zone name is taken from the basename of the filename, so
+# you must use filenames like "/wherever/you/like/dnspython.org" and
+# not something like "/wherever/you/like/foo.db" (unless you're
+# working with the ".db" GTLD, of course :)).
+#
+# If this weren't a demo script, there'd be a way of specifying the
+# origin for each zone instead of constructing it from the filename.
+
+import dns.zone
+import dns.ipv4
+import os.path
+import sys
+
+reverse_map = {}
+
+for filename in sys.argv[1:]:
+    zone = dns.zone.from_file(filename, os.path.basename(filename),
+                              relativize=False)
+    for (name, ttl, rdata) in zone.iterate_rdatas('A'):
+        try:
+	    reverse_map[rdata.address].append(name.to_text())
+	except KeyError:
+	    reverse_map[rdata.address] = [name.to_text()]
+
+keys = reverse_map.keys()
+keys.sort(lambda a1, a2: cmp(dns.ipv4.inet_aton(a1), dns.ipv4.inet_aton(a2)))
+for k in keys:
+    v = reverse_map[k]
+    v.sort()
+    print k, v