[Dnsmasq-discuss] Option 12 hostname sent to RPi seems incorrect

Petr Menšík pemensik at redhat.com
Wed Oct 27 12:16:31 UTC 2021


Hi,

I would try tomorrow, but my rpi machines received hostname set from
dnsmasq. I used static allocations only for my testing. Can you share at
least relevant part of dnsmasq configuration?

Does it have dhcp-host record for that machine?

On 10/25/21 16:00, Shrenik Bhura wrote:
>
> On Mon, 25 Oct, 2021, 01:24 Matthias May via Dnsmasq-discuss,
> <dnsmasq-discuss at lists.thekelleys.org.uk> wrote:
>
>     On 21/10/2021 13:05, Shrenik Bhura wrote:
>     > May be the code that logs this line needs to be checked if it is
>     just printing part of the complete hostname i.e. IP
>     > address.
>     >
>
>     Hi Shrenik
>
>     The code is doing what it is supposed to do.
>
>     Please take a look at the definition of a hostname and what makes
>     up an FQDN.
>     * https://en.wikipedia.org/wiki/Hostname
>     * https://en.wikipedia.org/wiki/Fully_qualified_domain_name
>
>     Valid characters for hostnames are:
>     * ASCII(7) letters from a to z
>     * The digits from 0 to 9
>     * The hyphen (-)
>     * A hostname may not start with a hyphen
>     * When following the old RFC 952, a hostname may not start with a
>     digit.
>
>     The dot '.' is used to concatenate the different domain labels.
>
>     In your case you are using an IP address as hostname which is not
>     a valid hostname.
>     The first dot in the name you provide is interpreted as domain
>     label separator, thus the hostname is 192.
>
>
>     BR
>     Matthias
>
>
>
> Hi All,
>
> Clarifying on the last two posts -
>
> > In your case you are using an IP address as hostname which is not a
> valid hostname.
>
> > the problem here is the client looks to be misconfigured if it is
> telling the
> server its name is an IP address... they are very different...
>
> No, I am not using such an IP address anywhere as a hostname. 
> Nothing on the server is configured to set the same. 
> The Raspberry Pi client is netbooting, so nothing on the client side
> could be setting it. 
> Or may be it is something in the Raspberry Pi 4B and 400 netbooting
> firmware which could be responsible for this, if it is not something
> wrong with dnsmasq? 
>
> See -
> https://drive.google.com/file/d/1WmbdcjFf6OYU-lcwwHw2LM40eSEIvllL/view?usp=drivesdk
>
> May be something in the dns handling implementation within dnsmasq
> which doesn't differentiate the absence of a hostname uses the same IP
> address that has been served to the client to play along, eventually
> truncating what it calculates as the domain part (168.67.53) from the
> fqdn (i.e. after the first . "dot"), and serving just the hostname
> (192). This sequence is visible in the snap above.
>
> If this is still not clear then I suggest that the only way to
> understand this situation best is by netbooting a RPi 4B yourself from
> a dnsmasq powered authoritative dhcp server.
>
> Do note that this is not reproducible with a x86 client.
>
> @Petr Menšík <mailto:pemensik at redhat.com>  may be you will be able to
> replicate this easily as you have gone through this sequence while
> nailing the UEFI+non-proxy bug.
>
> Regards,
> Shrenik
>
> Regards,
> Shrenik

-- 
Petr Menšík
Software Engineer
Red Hat, http://www.redhat.com/
email: pemensik at redhat.com
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB
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