netdev - Re: [patch iproute2 v2 0/2] add support for IFA_F

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Date:	Sat, 4 Jan 2014 12:35:43 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Thomas Haller <thaller@...hat.com>
Cc:	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org,
	stephen@...workplumber.org
Subject: Re: [patch iproute2 v2 0/2] add support for IFA_F_MANAGETEMPADDR

On Sat, Jan 04, 2014 at 12:21:51PM +0100, Thomas Haller wrote:
> > > >Also, I saw that NetworkManager switched to install autoconf addresses
> > > >as /128, doesn't this break with IFA_F_MANAGETEMPADDR, as you expect a /64
> > > >prefixlen?
> > > 
> > > /64 is required
> > 
> > Ok, currently NM seems to "violate" that as it installs autoconf addresses
> > with 128 prefixlen, so IFA_F_MANAGETEMPADDR should not work on them.
> > (currently observed on Fedora 20).
> 
> True, I noticed that too. I think that is a bug in NM to add the
> addresses as /128. Probably, we will fix that soon.

The change could be valid. Otherwise currently NM could not correctly handle
prefix information in RAs in some cases:

It is possible to let the client generate an autonomously address in a
prefix which is actually not on-link (L=0). Kernel would automatically
create prefix route by mistake, if NM tries to install such an address
with /64 prefix. This does not happen if the prefix address uses 128
prefixlen.

Would be great to have feedback on this, as this could be easily solved by an
additional ifa_flag.

Greetings,

  Hannes

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