netdev - Question on IPv6 addresses and netlink message ordering

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Message-ID: <CAL7k4TzeJAb8ONJyK1ED3sLbpGeoL6_gBobkphbQvD6YYkhL0Q@mail.gmail.com>
Date:	Wed, 25 Apr 2012 08:41:16 +0530
From:	Pradeep Kanyar <pradeep.kanyar@...il.com>
To:	netdev@...r.kernel.org
Subject: Question on IPv6 addresses and netlink message ordering

Hi,
If we configure a global IPv6 address on an interface in linux, and if
we monitor the netlink messages
[using nl-monitor from libnl for e.g,] I see that we get RTM_NEWROUTE
for the global address subnet
first, and then RTM_NEWADDR. Isn't this strange? Shouldn't we be
seeing RTM_NEWADDR first
andRTM_NEWROUTE subsequently ....? I put some prints in the path and I
see that the following
seems to be order of events [initially at least] when I configure a
global v6 address on an interface:

1. RTM_NEWROUTE notify in fib6_add_rt2node
2. RTM_NEWADDR notify in addrconf_dad_completed

I saw this on a system running 2.6.32 but a cursory look at more
recent kernels seemed to indicate
that the code path hasn't changed much in this area [ but I might be wrong ].

Why is this out-of-order? On the contrary, in case of IPv4 addresses,
we always see RTM_NEWADDR
first followed by RTM_NEWROUTE [for the directly connected network]

Thanks,
Pradeep
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