[OpenWrt-Devel] DHCPv6 flash renumbering patches with HE tunnel breaks

Arjen de Korte arjen+openwrt at de-korte.org
Fri Mar 27 08:16:52 EDT 2015

Citeren Steven Barth <cyrus at openwrt.org>:

>> The problem is that you try to be "smart" by abusing the ability to set
>> the address preferred lifetime lower than T1.  I don't dispute that it
>> is allowed by the RFC, but it is definitely not recommended.
> There is no formal requirement (not even a SHOULD) that says  
> otherwise. The recommendation made is usually based on the basis  
> that DHCPv6 is your only source of addresses which it isn't for us.

That may be, but I think it is sufficiently hacky that it really not  
should be the default (or even only) mode of operation. I will provide  
a patch shortly to make this configurable.

>> Based on this, it should not come as an surprise that a number of
>> clients start behaving erratically if you set T1 much higher than the
>> preferred lifetime.  Don't do that. It causes problems.
>> You can of course continue to argue that not honouring T1 is a bug, but
>> that will not fix any of the failing clients.
> Now we know that they actually don't. The clients behave well, that  
> seemed to be a misunderstanding.

No, they don't. With regard to the renewal storms, that was a  
misunderstanding. But even with the latest odhcpd from trunk,  
especially webmail clients *will* see loss of connection, as the  
source IP on outgoing connections will be different 1 second of every  
T1 interval. Depending on the leasetime that is configured on the  
server, this may be infrequent enough to be hardly noticeable, or will  
lead to support calls. In my case, it was the latter.

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