Fix check for IPv6 enabled on host

gns3server/compute/qemu/qemu_vm.py

@@ -47,7 +47,7 @@ from ..base_node import BaseNode
 from ...schemas.qemu import QEMU_OBJECT_SCHEMA, QEMU_PLATFORMS
 from ...utils.asyncio import monitor_process
 from ...utils.images import md5sum
-from ...utils import macaddress_to_int, int_to_macaddress
+from ...utils import macaddress_to_int, int_to_macaddress, is_ipv6_enabled
 
 
 import logging
@@ -1672,13 +1672,14 @@ class QemuVM(BaseNode):
         if self._console:
             console_host = self._manager.port_manager.console_host
             if console_host == "0.0.0.0":
-                if socket.has_ipv6:
+                try:
+                    if is_ipv6_enabled():
                         # to fix an issue with Qemu when IPv4 is not enabled
                         # see https://github.com/GNS3/gns3-gui/issues/2352
                         # FIXME: consider making this more global (not just for Qemu + SPICE)
                         console_host = "::"
-                else:
+                except OSError as e:
-                    raise QemuError("IPv6 must be enabled in order to use the SPICE console")
+                    raise QemuError("Could not check if IPv6 is enabled: {}".format(e))
             return ["-spice",
                     "addr={},port={},disable-ticketing".format(console_host, self._console),
                     "-vga", "qxl"]

gns3server/utils/__init__.py

@@ -21,6 +21,8 @@ import re
 import shlex
 import textwrap
 import posixpath
+import socket
+import errno
 
 
 def force_unix_path(path):
@@ -100,3 +102,21 @@ def shlex_quote(s):
         return s if re.match(r'^[-_\w./]+$', s) else '"%s"' % s.replace('"', '\\"')
     else:
         return shlex.quote(s)
+
+
+def is_ipv6_enabled() -> bool:
+
+    if not socket.has_ipv6:
+        return False  # the socket library has no support for IPv6
+    try:
+        with socket.socket(socket.AF_INET6, socket.SOCK_STREAM) as sock:
+            sock.bind(("::1", 0))
+        return True
+    except OSError as e:
+        if e.errno in (errno.EADDRNOTAVAIL, errno.EAFNOSUPPORT):
+            # EADDRNOTAVAIL is the errno if IPv6 modules/drivers are loaded but disabled.
+            # EAFNOSUPPORT is the errno if IPv6 modules/drivers are not loaded at all.
+            return False
+        if e.errno == errno.EADDRINUSE:
+            return True
+        raise