net: Guaranetee the proper ordering of the loopback device. v2

I was recently hunting a bug that occurred in network namespace
cleanup.  In looking at the code it became apparrent that we have
and will continue to have cases where if we have anything going
on in a network namespace there will be assumptions that the
loopback device is present.   Things like sending igmp unsubscribe
messages when we bring down network devices invokes the routing
code which assumes that at least the loopback driver is present.

Therefore to avoid magic initcall ordering hackery that is hard
to follow and hard to get right insert a call to register the
loopback device directly from net_dev_init().    This guarantes
that the loopback device is the first device registered and
the last network device to go away.

But do it carefully so we register the loopback device after
we clear dev_boot_phase.

Signed-off-by: Eric W. Biederman <ebiederm@maxwell.aristanetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index f1b0dbe58464..12d7f4469dc9 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1766,6 +1766,7 @@ static inline int skb_bond_should_drop(struct sk_buff *skb)
         return 0;
 }
 
+extern struct pernet_operations __net_initdata loopback_net_ops;
 #endif /* __KERNEL__ */
 
 #endif  /* _LINUX_DEV_H */