RE: Linux still keep the expired prefix 15 seconds after its expiration

From: Jeff Haran
Date: Thu Nov 13 2008 - 18:09:00 EST

> -----Original Message-----
> From: linux-net-owner@xxxxxxxxxxxxxxx
> [mailto:linux-net-owner@xxxxxxxxxxxxxxx] On Behalf Of Wendy Lai
> Sent: Thursday, November 13, 2008 2:42 PM
> To: linux-net@xxxxxxxxxxxxxxx
> Subject: Linux still keep the expired prefix 15 seconds after
> its expiration
> We have observed a behavior on our linux 2.6.20 box where the
> ipv6 address cannot be released 15 seconds after the prefix
> had expired. I have verified that addrconf_verify properly
> called ipv6_del_addr at the time of expiration. However, i am
> suspecting that the reference count of the address was not 0.
> Does anyone know of this problem? What could be possibly
> holding on to the address?
> This linux box is connected to a router on an isolated network.
> Thanks,
> Weiwen

I assume you are aware of the security driven rules in RFC 2462 about rejecting prefixes with lifetimes that are much shorter than the remaining lifetime on the prefix. Just in case:

>From RFC 2462, section 5.5.3.e:

2) If the StoredLifetime is less than or equal to 2 hours and the
received Lifetime is less than or equal to StoredLifetime,
ignore the prefix, ...

If you are already aware of this, my apologies, but if not, this rule might be what's getting in the way of your testing, though I can't explain how that jibes with ipv6_del_addr() being called.

Jeff Haran
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