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

Shrenik Bhura shrenik.bhura at gmail.com
Wed Oct 20 09:18:27 UTC 2021


On Wed, 20 Oct, 2021, 11:21 Geert Stappers via Dnsmasq-discuss, <
dnsmasq-discuss at lists.thekelleys.org.uk> wrote:

> On Wed, Oct 20, 2021 at 07:50:58AM +0530, Shrenik Bhura wrote:
> > On Tue, 19 Oct 2021 at 21:01, Dominik Derigs <dl6er at dl6er.de> wrote:
> >
> > > Hey Shrenik,
> > >
> > > On Tue, 2021-10-19 at 17:20 +0530, Shrenik Bhura wrote:
> > > > Option 12 hostname sent to RPi is the first octet of the IP
> > > > address. This seems incorrect.
> > >
> > > This can very well be desired behavior (if the hostname is set to
> > > "192"). Can you quote your configuration and related files (e.g.
> > > if you are using dhcp-hostsfile or dhcp-hostsdir)?
> > >
> > > Best,
> > > Dominik
> > >
> >
> > Hi Dominik,
>
> Hello Archive visitor,
> Hello Mailinglist subscriber,
>
>
> > There isn't anything specific in the configuration that serves the
> > hostname. I am aware of this feature and when defined it works as
> desired.
> > But when nothing is explicitly defined to serve hostnames, it is
> defaulting
> > to 192 as visible in the logs, and only in the case of an RPi.
> > When checked on the client with the hostname command, it shows the full
> > hostname - 192.168.67.53
>
> Such hostname do I call  IPaddress.
>
>
> > The same configuration works fine with a x86 system as no hostname is
> being
> > served when none is defined.
> >
> > Also it would be ideal to improve the logs as well to reflect the full
> > hostname, if at all.
> >
> > Have attached the config files involved.
>
> Make a packet capture and put the .pcap on a server.
> Then tell here how to fetch the file.
> Next can those who care examine the .pcap with their tool.
> (wireshark / tcpdump)
>
> > Once again, do note that this is the case only for an RPi. So there is
> some
> > specific logic in dnsmasq coming into play for an RPi that seems to be
> > serving the IP address as the default hostname when none is present.
>
> So beside the
>    /sbin/tcpdump  -w rpi.pcap ether host dc:a6:32:78:98:ae
> also
>    /sbin/tcpdump  -w worksfine.pcap ether host MAC_address_of_known_good
>
>
> > Best,
> > Shrenik
>
> Please make it possible to read in the discussion.  Show the world
> that you understand the concepts like "timezone" and "one to many
> communication".  In other words:  the response goes below previous text.
>
>
> Groeten
> Geert Stappers
> --
> Silence is hard to parse
>
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Hello All,

Apologies and thanks Geert for the wake up note on the mailing list posting
etiquette.

> > hostname - 192.168.67.53
> Such hostname do I call  IPaddress.
Sure, you may when coincidentally the string returned as a hostname is
equivalent to the IP address notation. ;)

Herein is the link to the related packet captures of an RPi and x86 system
-
https://drive.google.com/file/d/11RwpCdbE8W0ohS2QDj4BarZ_VHnEhwfs/view?usp=sharing

Regards / Groeten,
Shrenik
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