[Dnsmasq-discuss] dnsmasq lease file not updating properly

Discussion:

Gopi Krishna M

2016-05-25 13:47:31 UTC

Hi All,

I have been using dnsmasq 2.70 vesrion as dhcp server for ipv4 and ipv6. My
lease file is not getting updated properly when
running dnsmasq. It is updating properly for ipv4 but not correct for ipv6.

#cat /etc/dnsmasq_new.leases
2082886681 00:80:48:4b:83:12 192.168.10.161 host-mysy *
duid 00:01:00:01:43:b8:34:78:00:80:a3:a0:bb:38
2082843195 1212908306 *18:2001:2002:2003:: ** 00:01:00:01:00:80:10:7e:ea:09

It is marked as above and its actual lease ip is *2001:2002:2003::10a* but
its not showing. Meanwhile even if we
connect multiple clients then the same *18:2001:2002:2003:: *is getting
repeated. Meanwhile it is not showing the
proper mac also.

for your kind ref:

config file
# cat /etc/dnsmasq_gateway.conf
interface=lan0
except-interface=lo
bind-interfaces
dhcp-range=192.168.10.20, 192.168.10.254, 14h
dhcp-range=2001:2002:2003::105, 2001:2002:2003::110, 64, 14h
enable-ra

Interface IP: 192.168.10.1
IPv6: 2001:2002:2003::100

running as

*dnsmasq -C /etc/dnsmasq_gateway.conf -l /etc/dnsmasq_new.leases*
Please tell your suggestions.

Note: Clients are getting IPv4 and IPv6 properly. Everything is fine apart
from updating the lease file. Compiled for ARM(linux 3.10)

Thanks in advance.

Regards,
Gopi krishna M
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Albert ARIBAUD

2016-05-25 14:50:22 UTC

Permalink

Hi,

Le Wed, 25 May 2016 19:17:31 +0530

Post by Gopi Krishna M
Hi All,
I have been using dnsmasq 2.70 vesrion as dhcp server for ipv4 and
ipv6. My lease file is not getting updated properly when
running dnsmasq. It is updating properly for ipv4 but not correct for ipv6.
#cat /etc/dnsmasq_new.leases
2082886681 00:80:48:4b:83:12 192.168.10.161 host-mysy *
duid 00:01:00:01:43:b8:34:78:00:80:a3:a0:bb:38
2082843195 1212908306 *18:2001:2002:2003:: **
00:01:00:01:00:80:10:7e:ea:09
It is marked as above and its actual lease ip is
*2001:2002:2003::10a* but its not showing. Meanwhile even if we
connect multiple clients then the same *18:2001:2002:2003:: *is
getting repeated. Meanwhile it is not showing the
proper mac also.
config file
# cat /etc/dnsmasq_gateway.conf
interface=lan0
except-interface=lo
bind-interfaces
dhcp-range=192.168.10.20, 192.168.10.254, 14h
dhcp-range=2001:2002:2003::105, 2001:2002:2003::110, 64, 14h
enable-ra
Interface IP: 192.168.10.1
IPv6: 2001:2002:2003::100
running as
*dnsmasq -C /etc/dnsmasq_gateway.conf -l /etc/dnsmasq_new.leases*
Please tell your suggestions.
Note: Clients are getting IPv4 and IPv6 properly. Everything is fine
apart from updating the lease file. Compiled for ARM(linux 3.10)
Thanks in advance.
Regards,
Gopi krishna M

(anyone feel free to correct me if I got the following wrong)

You are using SLAAC for IPv6 configuration. In this mode, it is the
client, not the DHCP server, which selects its own IPv6.

Therefore there are no actual IPv6 leases: dnsmasq just informs the
client about the /64 subnet under which the client, not dnsmasq, shall
select its address; the client does not inform dnsmasq back.

This is /probably/ why the actual address does not show up in the lease
file.

If you want dnsmasq to control which address the client receives (and
possibly log this in the lease file) then you should use DHCPv6 rather
than SLAAC.

Amicalement,

--
Albert.

Gopi Krishna M

2016-05-26 13:57:33 UTC

Permalink

Hi Albert,

Thanks for your suggestion.

I believe it is not in the slaac mode and in dhcpv6 only.

I confirmed with below things.

1) Router advertise, solicit, request things are happening while every
client getting connected.
2) The bit Managed address configuration is set. Checked through wireshark.
It will be set
in DHCPv6 only and not for slaac.

If you believe still it is in slaac mode, Please tell the config changes to
make
dnsmasq run as a dhcpv6 server.

Thanks,
Gopi krishna M

Post by Albert ARIBAUD
Hi,
Le Wed, 25 May 2016 19:17:31 +0530

(anyone feel free to correct me if I got the following wrong)
You are using SLAAC for IPv6 configuration. In this mode, it is the
client, not the DHCP server, which selects its own IPv6.
Therefore there are no actual IPv6 leases: dnsmasq just informs the
client about the /64 subnet under which the client, not dnsmasq, shall
select its address; the client does not inform dnsmasq back.
This is /probably/ why the actual address does not show up in the lease
file.
If you want dnsmasq to control which address the client receives (and
possibly log this in the lease file) then you should use DHCPv6 rather
than SLAAC.
Amicalement,
--
Albert.

--
DISCLAIMER

The information in this e-mail is confidential and may be subject to legal
privilege. It is intended solely for the addressee. Access to this e-mail
by anyone else is unauthorized. If you have received this communication in
error, please address with the subject heading "Received in error," send to
***@msystechnologies.com, then delete the e-mail and destroy any copies of
it. If you are not the intended recipient, any disclosure, copying,
distribution or any action taken or omitted to be taken in reliance on it,
is prohibited and may be unlawful. The views, opinions, conclusions and
other information expressed in this electronic mail and any attachments are
not given or endorsed by the company unless otherwise indicated by an
authorized representative independent of this message.
MSys cannot guarantee that e-mail communications are secure or error-free,
as information could be intercepted, corrupted, amended, lost, destroyed,
arrive late or incomplete, or contain viruses, though all reasonable
precautions have been taken to ensure no viruses are present in this e-mail.
As our company cannot accept responsibility for any loss or damage arising
from the use of this e-mail or attachments we recommend that you subject
these to your virus checking procedures prior to use

Albert ARIBAUD

2016-05-26 16:49:03 UTC

Permalink

Hello,

Le Thu, 26 May 2016 19:27:33 +0530

Post by Gopi Krishna M
Hi Albert,
Thanks for your suggestion.
I believe it is not in the slaac mode and in dhcpv6 only.
I confirmed with below things.
1) Router advertise, solicit, request things are happening while every
client getting connected.
2) The bit Managed address configuration is set. Checked through
wireshark. It will be set
in DHCPv6 only and not for slaac.
If you believe still it is in slaac mode, Please tell the config
changes to make
dnsmasq run as a dhcpv6 server.

OK, so this confirms you're indeed not using SLAAC and are indeed using
DHCPv6. Sorr then, I have no other idea why the leases file does not
mention the DHCPv6 lease -- and no idea if it should, actually.

Post by Gopi Krishna M
Thanks,
Gopi krishna M

Amicalement,

--
Albert.

Gopi Krishna M

2016-05-26 16:59:14 UTC

Permalink

Hi,

Thanks for your time albert. I will try to look into that.

Thanks,
Gopi krishna M

Post by Albert ARIBAUD
Hello,
Le Thu, 26 May 2016 19:27:33 +0530

Post by Gopi Krishna M
Thanks,
Gopi krishna M

Amicalement,
--
Albert.

Sachin Garg

2016-06-17 03:37:11 UTC

Permalink

Hi,

My dnsmasq.conf contains the following. Even though SLAAC is enabled,
the hosts that are supposed to get static DHCPv6 leases get them as
configured. I also do not have the IPv6 line that you have. I am using
the "constructor:<interface>" for it to pick up the prefix.

# IPv6
dhcp-range=lan,::F000:0000,::FFFF:FFFF, constructor:br-lan, slaac, 64, 12h
enable-ra
# Static DHCPv6 IP addresses
dhcp-host=<MAC address>,<IPv4 address>,<hostname>,[::dead:beef]

From the manual

slaac tells dnsmasq to offer Router Advertisement on this subnet and
to set the A bit in the router advertisement, so that the client
will use SLAAC addresses. When used with a DHCP range or static DHCP
address this results in the client having both a DHCP-assigned and a
SLAAC address.
ra-names enables a mode which gives DNS names to dual-stack hosts
which do SLAAC for IPv6. Dnsmasq uses the host's IPv4 lease to derive
the name, network segment and MAC address and assumes that the host
will also have an IPv6 address calculated using the SLAAC algorithm,
on the same network segment. The address is pinged, and if a reply is
received, an AAAA record is added to the DNS for this IPv6 address.
Note that this is only happens for directly-connected networks, (not
one doing DHCP via a relay) and it will not work if a host is using
privacy extensions. ra-names can be combined with ra-stateless and
slaac.

(I will be testing this now and will report back)

However, it works only when MAC id is provided, not with DUID. (I think
this is because I was unable to get a cross-platform way to get the DUIDs).

Another thing to note is that *not* all devices are capable of
requesting and accepting an IPv6 address via DHCPv6. Most notably
Android. See the following:

https://code.google.com/p/android/issues/detail?id=32621

A workaround that is this:
https://play.google.com/store/apps/details?id=org.daduke.realmar.dhcpv6client

However, sadly that seems to work (for me) only when manually initialised.

So, is it a possibility that you are only testing your config with
Android machines?

Hope this helps. Off-topic: I am assuming that you are in India.
Wondering how you are getting IPv6 connectivity?

Best,
Sachin