​The patch was applied successfully and I was able to build on Fedora 21
with these commands (if you have opinions about these, I'm happy to learn
more about your build system - I'm still a Linux noob):

$ ./autogen.sh \
  --prefix=/usr        \
  --sysconfdir=/etc    \
  --localstatedir=/var \
  --with-nmtui
$ make
$ make install

​The DHCP packets look good now and I got the occasional DDNS update to
happen successfully. I write "occassional", because there's a new
outstanding issue.

Windows DHCP has the option to protect DNS entries with a DHCID RR
<https://tools.ietf.org/html/draft-ietf-dnsext-dhcid-rr-13> next to the
A/AAAA RR to prevents name squatting (examples
<https://technet.microsoft.com/en-us/library/dd759188.aspx?f=255&MSPPError=-2147217396>).
It's not really Windows-specific, but from my 30 minute research there
seems to be a problem with two dhclient instances (-4 and -6) requesting
IPv4 and IPv6 addresses in short succession.

For illustration, let's say IPv4 is the first DHCP server transaction to
finish. The DHCP server will request a DDNS update with a DHCID computed
based on the DHCPv4 request. The DHCID RR is placed next to the A RR in
DNS. The last string is the DHCID:

30,02/26/15,00:15:39,DNS Update
Request,172.16.0.27,fedora.wghoch4.local,,,0,6,,AAIB9bp2uTdfLzJh0EvCVjZaAX8wFfhJnVtyWlwdswZmz6A=,
32,02/26/15,00:15:40,DNS Update
Successful,172.16.0.27,fedora.wghoch4.local,,,0,6,,AAIB9bp2uTdfLzJh0EvCVjZaAX8wFfhJnVtyWlwdswZmz6A=,

When the DHCPv6 transaction finishes a couple of milliseconds later, the
DHCPv6 server will request a DDNS update with a DHCID computed based on the
DHCPv6 request, which is different:

11022,02/26/15,00:15:41,DNS IPV6 Update
Request,2001:470:1f0b:c9a:d0fe:3fdd:9808:be77,fedora.wghoch4.local,,,,AAIBcviuOsLCzN+gMgFRRnSu7vCDQgeQWo3TyWyt6hbOyCc=,
11024,02/26/15,00:15:41,DNS IPV6 Update
Successful,2001:470:1f0b:c9a:d0fe:3fdd:9808:be77,fedora.wghoch4.local,,,,AAIBcviuOsLCzN+gMgFRRnSu7vCDQgeQWo3TyWyt6hbOyCc=,

​The DNS server will check the second DHCID against the one it already
knows and reject the DDNS update (the log above says it was successful, but
Windows logs generally suck ;-)

It's easy to confirm that the DHCID RR is actually the culprit. Just delete
it from the DNS, re-request DHCPv6 and the AAAA RR shows up.

My dhclient man page has the following snippet:

-df duid-lease-file
              Path  to a secondary lease file.  If the primary lease file
doesn't contain a DUID this file will be searched.  The
              DUID read from the secondary will be written to the primary.
This option can be used to allow an IPv4 instance  of
              the  client  to  share a DUID with an IPv6 instance.  After
starting one of the instances the second can be started
              with this option pointing to the lease file of the first
instance.  There is no default.  If no file  is  specified
              no search is made for a DUID should one not be found in the
main lease file.

The DUID <https://tools.ietf.org/html/rfc3315#section-9> is a main
contributor to the DHCID. As both IPv4 and IPv6 addresses are requested
by/for the same interface it seems NM should make sure to use the same DUID
for its requests.

I'll try forging my DUIDs to be the same and also try "send dhcp6.client-id
<something>" and report my findings.

Beste Grüße,

Alex
-- 
Alexander Groß
http://therightstuff.de/

On Wed, Feb 25, 2015 at 5:43 PM, Dan Williams <[email protected]> wrote:

> On Wed, 2015-02-25 at 17:40 +0100, Alexander Groß wrote:
> > On Wed, Feb 25, 2015 at 5:33 PM, Dan Williams <[email protected]> wrote:
> >
> > > Hmm, it seems to apply with 'git am < /path/to/mail.mbox' for me.  What
> > > version of NetworkManager are you using?  I'll generate a non-git patch
> > > for that version.
> > >
> >
> > I made a fresh clone and tried to apply if on the master branch.​ The
> > version of NM is use on CentOS or Fedora shouldn't be relevant to that,
> but
> > I have
> >
> > * NetworkManager-0.9.10.1-3.20150219git.fc21.x86_64 and
> > * NetworkManager-0.9.9.1-29.git20140326.4dba720.el7_0.x86_64.
> >
> > I have to admit I don't have any mailbox setup on my boxes. I copied the
> > patch from the nm-list web interface and made sure line endings are
> correct.
>
> Try the attached patch which I've done against 0.9.10; I believe it'll
> apply with just:
>
> cd NetworkManager/
> patch -p1 < /path/to/patch
>
> Thanks!
> Dan
>
>
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