Re: [Dnsmasq-discuss] dnsmasq not responding to DHCPv6 DHCPCONFIRM messages attempting to confirm an unknown lease

[Simon Kelley]

One line patch to log DHCPCONFIM failure applied. That seems sensible.
Thanks for the suggestion, and apologies for leading you up a blind alley.


Cheers,

Simon.


On 20/07/18 15:43, Michael Marley wrote:
> On 2018-07-20 09:01, Michael Marley wrote:
> 
>> Hi,
>>
>> I have dnsmasq set to be a DHCPv6 and DHCPv6 server for my local
>> network.  Here is the relevant part of the configuration:
>>
>> interface=vlan1
>> interface=vlan2
>> interface=vlan3
>> interface=vlan4
>> interface=vlan5
>> dhcp-authoritative
>> dhcp-range=interface:vlan1,10.1.0.2,10.1.255.253,1h
>> dhcp-range=interface:vlan2,10.2.0.2,10.2.255.253,1h
>> dhcp-range=interface:vlan3,10.3.0.2,10.3.255.253,1h
>> dhcp-range=interface:vlan4,10.4.0.2,10.4.255.253,1h
>> dhcp-range=interface:vlan5,10.5.0.2,10.5.255.253,1h
>> dhcp-range=interface:vlan1,fdda:5f29:421b:1::2,fdda:5f29:421b:1::,64,1h
>> dhcp-range=interface:vlan2,fdda:5f29:421b:2::2,fdda:5f29:421b:2::,64,1h
>> dhcp-range=interface:vlan3,fdda:5f29:421b:3::2,fdda:5f29:421b:3::,64,1h
>> dhcp-range=interface:vlan4,fdda:5f29:421b:4::2,fdda:5f29:421b:4::,64,1h
>> dhcp-range=interface:vlan5,fdda:5f29:421b:5::2,fdda:5f29:421b:5::,64,1h
>>
>> My problem is that if a DHCPv6 client attempts to confirm an unknown
>> lease (from another network, for example if I unplug a computer from
>> vlan4 and plug it into vlan3), dnsmasq doesn't respond to the
>> DHCPCONFIRM messages that the client sends.  I just get a long string of
>>
>> DHCPCONFIRM(vlan4) 00:01:00:01:20:65:91:d7:3c:97:0e:7f:f5:ba
>>
>> until the client finally gives up and acquires a new lease from
>> scratch.  This also happens if I connect a client to my network that
>> was previously connected to another network with a DHCPv6 lease.  For
>> DHCPv4 in the same situation, it works correctly and sends a DHCPNAK,
>> causing the client to retry from scratch immediately and get a new
>> lease quickly as described in the documentation for the
>> "dhcp-authoritative" option.  It seems to me this ought to take place
>> for DHCPv6 as well, preventing the client from having to time out
>> before obtaining a lease.  Have I configured something wrong or is
>> there a bug?
>>
>> Thanks,
>>
>> Michael Marley
>>
>> ___
>> Dnsmasq-discuss mailing list
>> Dnsmasq-discuss@lists.thekelleys.org.uk
>> 
>> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
> 
> I apologize for my ineptness, but it seems dnsmasq does actually send a
> NOTONLINK reply in this case (rfc3315.c:1105).  It just doesn't log that
> it is doing so, which is what led me to believe that it wasn't.  My
> actual problem appears to be caused by defective/bugged DHCPv6 snooping
> on a switch, which I will report to the manufacturer.  I do think that
> logging the NOTONLINK reply would probably be a good idea though, to
> avoid confusion.
> 
> Michael
> 
> 
> 
> ___
> Dnsmasq-discuss mailing list
> Dnsmasq-discuss@lists.thekelleys.org.uk
> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
> 


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Re: [Dnsmasq-discuss] dnsmasq not responding to DHCPv6 DHCPCONFIRM messages attempting to confirm an unknown lease

[Michael Marley]

On 2018-07-20 09:01, Michael Marley wrote:

> Hi,
> 
> I have dnsmasq set to be a DHCPv6 and DHCPv6 server for my local network.  
> Here is the relevant part of the configuration:
> 
> interface=vlan1
> interface=vlan2
> interface=vlan3
> interface=vlan4
> interface=vlan5
> dhcp-authoritative
> dhcp-range=interface:vlan1,10.1.0.2,10.1.255.253,1h
> dhcp-range=interface:vlan2,10.2.0.2,10.2.255.253,1h
> dhcp-range=interface:vlan3,10.3.0.2,10.3.255.253,1h
> dhcp-range=interface:vlan4,10.4.0.2,10.4.255.253,1h
> dhcp-range=interface:vlan5,10.5.0.2,10.5.255.253,1h
> dhcp-range=interface:vlan1,fdda:5f29:421b:1::2,fdda:5f29:421b:1::,64,1h
> dhcp-range=interface:vlan2,fdda:5f29:421b:2::2,fdda:5f29:421b:2::,64,1h
> dhcp-range=interface:vlan3,fdda:5f29:421b:3::2,fdda:5f29:421b:3::,64,1h
> dhcp-range=interface:vlan4,fdda:5f29:421b:4::2,fdda:5f29:421b:4::,64,1h
> dhcp-range=interface:vlan5,fdda:5f29:421b:5::2,fdda:5f29:421b:5::,64,1h
> 
> My problem is that if a DHCPv6 client attempts to confirm an unknown lease 
> (from another network, for example if I unplug a computer from vlan4 and plug 
> it into vlan3), dnsmasq doesn't respond to the DHCPCONFIRM messages that the 
> client sends.  I just get a long string of
> 
> DHCPCONFIRM(vlan4) 00:01:00:01:20:65:91:d7:3c:97:0e:7f:f5:ba
> 
> until the client finally gives up and acquires a new lease from scratch.  
> This also happens if I connect a client to my network that was previously 
> connected to another network with a DHCPv6 lease.  For DHCPv4 in the same 
> situation, it works correctly and sends a DHCPNAK, causing the client to 
> retry from scratch immediately and get a new lease quickly as described in 
> the documentation for the "dhcp-authoritative" option.  It seems to me this 
> ought to take place for DHCPv6 as well, preventing the client from having to 
> time out before obtaining a lease.  Have I configured something wrong or is 
> there a bug?
> 
> Thanks,
> 
> Michael Marley
> 
> ___
> Dnsmasq-discuss mailing list
> Dnsmasq-discuss@lists.thekelleys.org.uk
> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

I apologize for my ineptness, but it seems dnsmasq does actually send a
NOTONLINK reply in this case (rfc3315.c:1105).  It just doesn't log that
it is doing so, which is what led me to believe that it wasn't.  My
actual problem appears to be caused by defective/bugged DHCPv6 snooping
on a switch, which I will report to the manufacturer.  I do think that
logging the NOTONLINK reply would probably be a good idea though, to
avoid confusion. 

Michael___
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