[Dnsmasq-discuss] Network booting with stateful IPv6 addressing

Tue Feb 28 16:43:03 GMT 2017

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Could you post (or send to me) you complete dnsmasq configuration. I'd
expect, if the IP address associated with the MAC address is in use,
for dnsmasq to log that and use a dynamically allocated address instead.

Why not nail the IP address using the client-id of the final OS
booted, rather thna using MAC addresses?

Cheers,

Simon.

On 28/02/17 10:07, Derek Higgins wrote:
> On 27 February 2017 at 21:51, Simon Kelley
> <simon at thekelleys.org.uk> wrote: I'm slightly confused as to the
> problem here. The identity of a lease if defined by the Client-ID
> and IAID, if those change then dnsmasq will allocate a new address.
> That means that your boot process will go through three different
> addresses, but should end up with a usable and stable address. It's
> not as if there is a shortage of IPv6 addresses, you can afford a
> couple of disposable addresses that only get used during the boot.
> 
> What have I missed?
> 
>> IPs are being allocated to the MAC addresses in question via a 
>> hostfile (see below), so I guess dnsmasq is attempting to
>> allocate the same IP address mutiple times, as its the same MAC
>> but can't because of the changing IDs.
> 
>> This is dnsmasq as configured be openstack newtron
> 
>> bash-4.2$ cat
>> /var/lib/neutron/dhcp/5cf3b57b-72a3-4044-9528-1f5019e21826/host 
>> fa:16:3e:59:ef:60,host-fc00-101--2,[fc00:101::2] 
>> fa:16:3e:d8:9e:dd,host-fc00-101--3,[fc00:101::3] 
>> fa:16:3e:d2:03:61,host-fc00-101--8,[fc00:101::8],set:ccbc492d-7b5d-4f
9a-891c-92d66828f6dd
>>
>> 
fa:16:3e:69:89:d5,host-fc00-101--b,[fc00:101::b],set:ea1e2384-7ed7-4956-
bae0-d653c86c840c
> 
> 
> 
> Cheers,
> 
> Simon.
> 
> 
> 
> On 27/02/17 16:04, Derek Higgins wrote:
>>>> I've recently been trying to use dnsmasq IPv6 to network
>>>> boot, after a number of hurdles the last problem I've been
>>>> having is that during the boot process (after dnsmasq
>>>> initially hands out an IP address as part of PXE boot), it
>>>> starts responding with "no addresses available".
>>>> 
>>>> The problem I'm hitting is that the IAID and the ClientID in
>>>> the dhcp request changes during the process, - the IAID being
>>>> used in PXE generated by the OVMF UEFI firmware is a function
>>>> including a time based seed[1] - this chain loads(in my case)
>>>> to an iPXE image that is using a crc of the mac address to
>>>> generate the IAID[2], - dhclient on the OS then uses the last
>>>> 4 octets of the MAC address for the IAID[3]
>>>> 
>>>> I have similar problems with ClientID but I havn't looked
>>>> into them in as much detail
>>>> 
>>>> check_address in dnsmasq/src/rfc3315.c is asserting that the
>>>> ID's can't change, and the only way I've gotten the boot
>>>> process to work locally is to comment out the checks in
>>>> check_address
>>>> 
>>>> As best I can see RFC 3315 does say that the IAID MUST
>>>> remain consistent across restarts of the DHCP client, but
>>>> then recognizes that "There may be no way for a client to
>>>> maintain consistency of the IAIDs if it does not have
>>>> non-volatile storage and the client's hardware configuration
>>>> changes"
>>>> 
>>>> Is there a way to allow these IDs to change? and if not
>>>> should this check be in dnsmasq? or would a patch to
>>>> optionally disable the check be acceptable?
>>>> 
>>>> thanks, Derek.
>>>> 
>>>> 
>>>> [1] - 
>>>> https://github.com/tianocore/edk2/blob/418373a1cd97abc0c0e3557f7a00
105
>
>>>> 
291829e6f/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c#L866
>>>> 
>>>> 
> [2] -
> https://github.com/qemu/ipxe/blob/c34d151/src/net/udp/dhcpv6.c#L97 
> 2
>>>> [3] - 
>>>> https://source.isc.org/cgi-bin/gitweb.cgi?p=dhcp.git;a=blob;f=clien
t/d
>
>>>> 
hc6.c;h=be604ac988a983b2829f76fe2bff6a5f036d8019;hb=HEAD#l1716
>>>> 
>>>> _______________________________________________
>>>> Dnsmasq-discuss mailing list
>>>> Dnsmasq-discuss at lists.thekelleys.org.uk 
>>>> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
>>>>
>>
>>
>>>> 
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> 
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