Do not remove ::1 from the loopback interface.

An environment with AF_INET6 sockets but no loopback interface creates
nothing but pain.

If an IPv4 server binds to 0.0.0.0:8080, clients may connect to
0.0.0.0:8080, which automatically picks 127.0.0.1 as a source address.
However, when a server binds to [::]:8080, the absence of ::1 causes
clients to fail with ENETUNREACH.

For a demonstration, run the following in a python shell:

import socket
s = socket.socket(socket.AF_INET6, socket.SOCK_STREAM, 0)
s.bind(("", 0))
print s.getsockname()  # Example: ('::', 39079, 0, 0)
s.listen(10)
c = socket.socket(socket.AF_INET6, socket.SOCK_STREAM, 0)
c.connect(s.getsockname())
print c.getsockname(), c.getpeername()

This yields the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/socket.py", line 224, in meth
    return getattr(self._sock,name)(*args)
socket.error: [Errno 101] Network is unreachable

Author: Paul Marks

bootstrapvz/providers/gce/tasks/host.py

@@ -15,6 +15,7 @@ def run(cls, info):
 		network_configuration_path = os.path.join(info.root, 'etc/sysctl.d/70-disable-ipv6.conf')
 		with open(network_configuration_path, 'w') as config_file:
 			print >>config_file, "net.ipv6.conf.all.disable_ipv6 = 1"
+			print >>config_file, "net.ipv6.conf.lo.disable_ipv6 = 0"
 
 
 class InstallHostnameHook(Task):