Commit 074a0d00 authored by Julien Muchembled's avatar Julien Muchembled

Remove automatic fallback when kernel has no support for source address based routing

It's normally safe to use --table=0 because most nodes use SLAAC and by default,
any existing default route is deleted.
It's better to abort if someone who explicitely wants to use a separate table
whereas the kernel is limited.
parent d2d799f1
......@@ -27,6 +27,15 @@ USAGE
Use ``re6stnet --help`` to get the complete list of options.
If you already have IPv6 connectivity by autoconfiguration and still want to
use it for communications that are unrelated to this network, then:
- your kernel must support source address based routing (because you can't
use ``--table 0`` option).
- you must set ``net.ipv6.conf.<iface>.accept_ra`` sysctl to value 2 and
trigger SLAAC with ``rdisc6 <iface>`` to restore the default route if the
kernel removed while enabling forwarding.
......@@ -68,9 +68,6 @@ def router(subnet, hello_interval, table, log_path, state_path, pidfile,
'-C', 'redistribute deny']
if table:
cmd += '-t%u' % table, '-T%u' % table
elif table is None:
# Tell peers not to route external IP via me.
cmd += '-C', 'out eq 0 deny'
cmd[-2:-2] = '-C', 'redistribute ip ::/0 eq 0'
for iface in tunnel_interfaces:
......@@ -51,9 +51,12 @@ def getConfig():
" hello interval for Babel to re-establish connection with a"
" node for which the direct connection has been cut.")
_('--table', type=int, default=42,
help="Use given table id. If 0, the main table will be used and any"
" existing default route will be exported.")
help="Use given table id. Set 0 to use the main table, if:\n"
"- you are a gateway of this network (the default route will be"
" exported)\n"
"- or you want to use the default route of this network for all"
" communications (in this case, make sure you don't already have"
" a default route).\n")
_ = parser.add_argument_group('tunnelling').add_argument
_('-O', dest='openvpn_args', metavar='ARG', action='append', default=[],
help="Extra arguments to forward to both server and client OpenVPN"
......@@ -234,22 +237,15 @@ def main():
ip('rule', 'from', *x)
except EnvironmentError:
logging.warning("I refuse to forward packets whose"
" destination IP is not part of %s, because your kernel"
" was compiled without support for source-based routing"
" policy. Pass --table 0 if you are sure you don't"
" have any default route.", my_network)
# XXX: The issue with such fallback is that a node will be
# unreachable from outside if it is only connected to
# limited peers. This could be fixed the same way as
# for checking connectedness.
config.table = None
del x[1:]
ip('rule', 'to', *x)
if_rt += x[1:]
call(if_rt[:3] + ['add', 'proto', 'static'] + if_rt[4:])
logging.error("It seems that your kernel was compiled"
" without support for source address based routing"
" (CONFIG_IPV6_SUBTREES). Consider using --table=0"
" option if you can't change your kernel.")
ip('rule', 'to', *x)
if_rt += x[1:]
call(if_rt[:3] + ['add', 'proto', 'static'] + if_rt[4:])
ip('route', 'unreachable', *x)
config.babel_args += config.iface_list
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