Fall back to guessing the external IP address if local IP address is unusable.

diff --git a/src/ddns/system.py b/src/ddns/system.py
index 89f415510b737cbfd081f4d8a9be52900b643adf..9214cce6ab287068fdd72df1263e13e81880c081 100644 (file)
--- a/src/ddns/system.py
+++ b/src/ddns/system.py
@@ -247,15 +247,52 @@ class DDNSSystem(object):
                # Check if the external IP address should be guessed from
                # a remote server.
                guess_ip = self.core.settings.get("guess_external_ip", "true")
+               guess_ip = guess_ip in ("true", "yes", "1")
 
-               # If the external IP address should be used, we just do
-               # that.
-               if guess_ip in ("true", "yes", "1"):
+               # If the external IP address should be used, we just do that.
+               if guess_ip:
                        return self.guess_external_ip_address(proto)
 
-               # Get the local IP addresses.
-               else:
-                       return self.get_local_ip_address(proto)
+               # Get the local IP address.
+               local_ip_address = self.get_local_ip_address(proto)
+
+               # If the local IP address is not usable, we must guess
+               # the correct IP address...
+               if not self._is_usable_ip_address(proto, local_ip_address):
+                       local_ip_address = self.guess_external_ip_address(proto)
+
+               return local_ip_address
+
+       def _is_usable_ip_address(self, proto, address):
+               """
+                       Returns True is the local IP address is usable
+                       for dynamic DNS (i.e. is not a RFC1918 address or similar).
+               """
+               if proto == "ipv4":
+                       # This is not the most perfect solution to match
+                       # these addresses, but instead of pulling in an entire
+                       # library to handle the IP addresses better, we match
+                       # with regular expressions instead.
+                       matches = (
+                               # RFC1918 address space
+                               r"^10\.\d+\.\d+\.\d+$",
+                               r"^192\.168\.\d+\.\d+$",
+                               r"^172\.(1[6-9]|2[0-9]|31)\.\d+\.\d+$",
+
+                               # Dual Stack Lite address space
+                               r"^100\.(6[4-9]|[7-9][0-9]|1[01][0-9]|12[0-7])\.\d+\.\d+",
+                       )
+
+                       for match in matches:
+                               m = re.match(match, address)
+                               if m is None:
+                                       continue
+
+                               # Found a match. IP address is not usable.
+                               return False
+
+               # In all other cases, return OK.
+               return True
 
        def resolve(self, hostname, proto=None):
                addresses = []