Use IPv4-Mapping to have IPv4 compatibility

Signed-off-by: Yohann D'ANELLO <ynerant@crans.org>

squinnondation/squinnondation.py

@@ -340,8 +340,16 @@ class Hazelnut:
     """
     def __init__(self, nickname: str = "anonymous", address: str = "localhost", port: int = 2500):
         self.nickname = nickname
+
+        try:
             # Resolve DNS as an IPv6
             address = socket.getaddrinfo(address, None, socket.AF_INET6)[0][4][0]
+        except socket.gaierror:
+            # This is not a valid IPv6. Assume it can be resolved as an IPv4, and we use IPv4-mapping
+            # to compute a valid IPv6.
+            # See https://fr.wikipedia.org/wiki/Adresse_IPv6_mappant_IPv4
+            address = "::ffff:" + socket.getaddrinfo(address, None, socket.AF_INET)[0][4][0]
+
         self.address = IPv6Address(address)
         self.port = port
 
@@ -352,8 +360,11 @@ class Squirrel(Hazelnut):
     """
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
+        # Create UDP socket
         self.socket = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
+        # Bind the socket
         self.socket.bind((str(self.address), self.port))
+
         self.hazelnuts = dict()
         print(f"Listening on {self.address}:{self.port}")