Dhcpd randomly returns the IP address or the backup IP

Wed Mar 31 11:42:35 UTC 2021

Hi

I've posted a pcap file of the process. There is nothing hitting at exactly
the same moment but I'm digging into how to trigger this differently.

https://drive.google.com/file/d/1mYIIlhq7JPdszT1zeasREIYcP4Fnj1lj/view?usp=sharing

<https://connect-mobile.co.za/mobile_marketing_solutions/>

On Mon, 29 Mar 2021 at 18:27, Sten Carlsen <stenc at s-carlsen.dk> wrote:

> Hi
>
> These two addresses are both in the same pool, so nothing illegal is
> happening. It is still odd that it sometimes gets one address and then the
> other, this should not happen.
>
> Consider the leases file as a historical document, each time something
> happens, the leases file gets added to. Once in a while it gets regenerated
> with just the current status of all leases.
>
> So for this sequence of events you should be able to reconstruct what
> happened by looking into this file.
>
> One thing that comes to mind is timing. The release and the discover
> happens in the same second, so what if the server could not write to the
> leases file before being asked about a new lease - this is not extending an
> existing lease as the discover indicates that the device does not have an
> address at this moment.
>
> Would it be possible to add a pause of a few seconds between the release
> and the discover? at least for an experiment. If that works, some timing is
> at the bottom of this.
>
> Possibly a wireshark trace could reveal the exact timing of these two
> messages.
>
> The leases file snippet did also not have both addresses as active, which
> could uncover other interesting things.
>
> --
> Best regards
> Sten Carlsen
>
> A pessimist is a person that can find a problem for every solution.
>
>
> On 29 Mar 2021, at 12.05, Wayne Gemmell | Connect <
> wayne at connect-mobile.co.za> wrote:
>
> Hi Sten
>
> One of the host I've been testing with in the kannel pool alternates
> between the following
>
>     inet 10.3.2.36/16
>     inet 10.3.2.60/16
>
> Leases look as follows. I don't really understand why each would be both
> free and active.
>
> Here's the log file of the responsible peer: https://pastebin.com/UP6M1Lic
>
> DHCP Lease list on responsible peer. The other one has similar data but no
> host names. https://pastebin.com/WX3NwkM2
>
> Here's snippet of the lease file https://pastebin.com/fKFiZpQ0
>
> <https://connect-mobile.co.za/mobile_marketing_solutions/>
>
>
> On Fri, 26 Mar 2021 at 19:32, Sten Carlsen <stenc at s-carlsen.dk> wrote:
>
>>
>> Thanks
>>
>> Sten
>>
>> On 26 Mar 2021, at 08.43, Wayne Gemmell | Connect <
>> wayne at connect-mobile.co.za> wrote:
>>
>> Thanks Sten
>>
>> I've moved my class out of the subnet  and the issue still persists.
>>
>>
>> Well, that is one can of worms out of the picture.
>>
>> What are the two addresses?
>>
>>
>>
>>
>> <https://connect-mobile.co.za/mobile_marketing_solutions/>
>>
>>
>> On Thu, 25 Mar 2021 at 17:51, Sten Carlsen <stenc at s-carlsen.dk> wrote:
>>
>>> You define the class kannel inside the subnet, so if there are any other
>>> subnets, it will be defined there as well. Class definitions are global
>>> always, defining them inside a subnet may have some "interesting" side
>>> effects as some options are taken from that subnet even if the host gets an
>>> address in a different subnet - routers is one of them.
>>>
>>> So one thought is, if the backup address is not in this subnet, the host
>>> will be given incorrect information.
>>>
>>> --
>>> Best regards
>>> Sten Carlsen
>>>
>>> --------------------------------------------------
>>> Aoccdrnig to rseerach at Cmabrigde Uinervtisy,
>>> it deosn't mttaer in waht oredr the ltteers in a
>>> wrod are, the olny iprmoatnt tihng is taht the
>>> frist and lsat lteter be at the rghit pclae.
>>> The rset can be a ttoal mses and you can slitl
>>> raed it wotihut porbelm. Tihs is bcuseae the
>>> hmuan mnid deos not raed ervey lteter by istlef,
>>> but the wrod as a wlohe. Amzanig, huh?
>>> --------------------------------------------------
>>>
>>> On 25 Mar 2021, at 13.01, Wayne Gemmell | Connect <
>>> wayne at connect-mobile.co.za> wrote:
>>>
>>> I tried it. No change. The issue still persists.
>>>
>>>
>>> <https://connect-mobile.co.za/mobile_marketing_solutions/>
>>>
>>>
>>> On Tue, 23 Mar 2021 at 16:19, Wayne Gemmell | Connect <
>>> wayne at connect-mobile.co.za> wrote:
>>>
>>>> I'll give it a try, thanks.
>>>>
>>>>
>>>> <https://connect-mobile.co.za/mobile_marketing_solutions/>
>>>>
>>>>
>>>> On Tue, 23 Mar 2021 at 01:32, Bill Shirley <
>>>> bill at c3po.polymerindustries.biz> wrote:
>>>>
>>>>> Try:
>>>>> update-optimization             off;
>>>>>
>>>>> Bill
>>>>> On 3/19/2021 2:22 AM, Wayne Gemmell | Connect wrote:
>>>>>
>>>>> Hi
>>>>>
>>>>> When my dhcp server gets a DHCPRELEASE followed by a DHCPDISCOVER then
>>>>> it randomly allocates the IP address or the backup IP address that are
>>>>> assigned to the host in the lease file to the host. The assignments always
>>>>> got to the correct host and the mac address doesn't change.
>>>>>
>>>>> When this backup IP address is allocated then dynamic DNS isn't
>>>>> updated and my container is unreachable.
>>>>>
>>>>> I've put all the relevant details in the link below but am more than
>>>>> happy enough to furnish anything that is missing. Can anyone help please?
>>>>>
>>>>> https://gitlab.isc.org/isc-projects/dhcp/-/issues/172
>>>>>
>>>>> <https://connect-mobile.co.za/mobile_marketing_solutions/>
>>>>>
>>>>> _______________________________________________
>>>>> ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information.
>>>>>
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>>>>>
>>>>> _______________________________________________
>>>>> ISC funds the development of this software with paid support
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>>>>> information.
>>>>>
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>>>>> dhcp-users at lists.isc.org
>>>>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>>>>
>>>> _______________________________________________
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>> _______________________________________________
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>>
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> _______________________________________________
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> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> dhcp-users at lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users
>
>
> _______________________________________________
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> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
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>
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