Socket: Fix crash non-TLS connections when using a SOCKS proxy

src/drivers/Socket.py

@@ -42,11 +42,7 @@ import threading
 import select
 import socket
 
-try:
-    import ipaddress  # Python >= 3.3 or backported ipaddress
-except ImportError:
-    # Python < 3.3
-    ipaddress = None
+import ipaddress
 
 from .. import (conf, drivers, log, utils, world)
 from ..utils import minisix
@@ -314,8 +310,15 @@ class SocketDriver(drivers.IrcDriver, drivers.ServersMixin):
                 address = address.decode('utf-8')
             elif (not network_config.requireStarttls()) and \
                     (not network_config.ssl()) and \
-                    (not self.currentServer.force_tls_verification) and \
-                    (ipaddress is None or not ipaddress.ip_address(address).is_loopback):
+                    (not self.currentServer.force_tls_verification):
+
+                try:
+                    is_loopback = ipaddress.ip_address(address).is_loopback
+                except ValueError:
+                    # address is a hostname, eg. because we're using a SOCKS
+                    # proxy
+                    is_loopback = False
+                if not is_loopback:
                     drivers.log.warning(('Connection to network %s '
                         'does not use SSL/TLS, which makes it vulnerable to '
                         'man-in-the-middle attacks and passive eavesdropping. '