On 24/07/13 19:16, Uwe Schindler wrote:
Hi,
RA's are not the same as DHCP, there's no such thing as a "lease
time". What there is, is preferred and valid lifetimes. What should
happen is that when old address is about to go away, the address
for that prefix on the network adaptor should have its preferred
lifetime set to zero, and dnsmasq will then notice that and send
RA's with the preferred lifetime also set to zero.
I meant the life time, it was just a typo somehow :-) The idea here
was to send preferred_lifetime=0 in RAs for prefixes that disappeared
from the interface to "inform" the clients that they are no longer
useable (my provider does not route old prefixes after a reconnect
with PPP). Currently you have to set the lifetime very low (which
produces more traffic on the wire) or manually delete or switch
on/off the network adaptors once the router reconnects or the prefix
changes for some reason.
My proposal is to keep a list of "previous prefixes" from the
constructor:ethX code and also send those prefixes, but with
lifetime=0 to inform all client to no longer use that address. Those
0-lifetime RAs should be sent at least for the length of the original
lifetime. Radvd has code to handle this (although it’s a bit buggy).
My understanding of this is that it's something that should happen in
the DHCP client and/or ISP DHCP server.
Ie, when the prefix has to change, the ISP's DHCP server renews the
existing prefix delegation, but with the preferred lifetime==0. It also
offers a new prefix delegation. The old and new prefixes get installed
in the network adaptor with the preferred lifetime values. Dnsmasq
starts to advertise the new prefix and continues to advertise the old
prefix, but with the pref-lifetime at zero taken from the value in the
adaptor.
Again, this is new territory, I'm not saying has to be done like that,
but that's the process I was thinking of when I wrote the existing code.
Cheers,
Simon.
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