[Dnsmasq-discuss] Dnsmasq - dnsmasq.leases IPv6 example

[Albert ARIBAUD]

Hi Siva,

Le Tue, 5 Apr 2016 22:57:10 -0700
Sivabalakrishnan M <sivabalakrishnan.m at gmail.com> a écrit:

> Thanks much Albert for the reply. Sorry, I meant 6 bytes for MAC and
> it was a typo. Please find more details below.
> 
> We use --dhcp-script & --leasefile-ro options for maintaining lease
> database instead of the default dnsmasq leases file. The issue that am
> facing is -  the script is invoked by Dnsmasq daemon with mac address
> of size of more than 6 bytes as you can see below. Our script
> validates the mac address and since it exceeds the 6 byte, we return
> error.
> 
> Dnsmasq logs:
> Apr  1 21:59:34 dnsmasq-dhcp[620]: DHCPSOLICIT(5)
> 00:01:00:01:1e:97:03:eb:00:50:56:96:42:c2
> Apr  1 21:59:34 dnsmasq-dhcp[620]: DHCPADVERTISE(5) 20:1::1:1b7
> 00:01:00:01:1e:97:03:eb:00:50:56:96:42:c2
> Apr  1 21:59:35 dnsmasq-dhcp[620]: DHCPREQUEST(5)
> 00:01:00:01:1e:97:03:eb:00:50:56:96:42:c2
> Apr  1 21:59:35 dnsmasq-dhcp[620]: DHCPREPLY(5) 20:1::1:1b7
> 00:01:00:01:1e:97:03:eb:00:50:56:96:42:c2
> 
> The mac address passed to script by Dnsmasq is also
> 00:01:00:01:1e:97:03:eb:00:50:56:96:42:c2 for IPv6 address
> 20:1::1:1b7. The actual mac address is :50:56:96:42:c2. But I don't
> know how 00:01:00:01:1e:97:03:eb:00: gets prefixed to the real mac
> address. This is the problem am facing now. Please let me know if
> this is expected in any scenario or if not, what could be the issue
> here? Any help on this is really appreciated.

Look up man dnsmasq, and more specifically the --dhcp-script option.
You'll see that for IPv4 the MAC address is passed, but for IPv6, it is
the DUID, which is 12 to 20 bytes depending on the exact situation --
in your case it seems to be 14 bytes.

> Thanks,

NP, HTH.

> Siva
> 
> On Tue, Apr 5, 2016 at 10:40 PM, Albert ARIBAUD
> <albert.aribaud at free.fr> wrote:
> 
> > Hi,
> >
> > Le Tue, 5 Apr 2016 18:48:37 -0700
> > Sivabalakrishnan M <sivabalakrishnan.m at gmail.com> a écrit:
> >
> > > Hi,
> > >
> > > Could anyone please share the sample output of dnsmasq.leases file
> > > for IPv6 entries? Is it possible to have mac address with size
> > > more than 8 bytes for IPv6? Please let me know.
> >
> > MAC addresses are standard, have 6 bytes, not 8, and do not differ
> > in IPv6 from what they are in IPv6.
> >
> > Are you maybe referring to the EUI-64 format address in SLAAC ? But
> > that too is fixed-format, so you cannot have an EIU-64 address
> > longer (or shorter, for that matter) than 8 bytes.
> >
> > Can you expand on what the actual problem is that you are
> > encountering?
> >
> > > Thanks,
> > > Siva
> >
> > Amicalement,
> > --
> > Albert.
> >



Amicalement,
-- 
Albert.