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<p>Hi Eric,</p>
<p>For example older windows were trying to send DNS updates on
their configured DNS servers. I am not sure if they are still
trying that, I assume they don't. That would work on ipv6-only
network. Only that machine knows its name.</p>
<p>As you have described, the name of the host is revealed anyway in
DHCPv4 request. I think the OS could try to send updates to the
local network DNS server, if it resides on local network. That
would be equivalent to using mdns, which I think is used by Apple
devices often. But unicast is more reliable. The question is after
which time such name should be removed. Because not paired with
DHCP lease time, it should not remain there forever.<br>
</p>
<div class="moz-cite-prefix">On 6/9/23 17:38, Eric Fahlgren wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAP2Qz+U6OkAvRWy3mRabno6dPOiJ=978-PP7ashRRrQBcUJzog@mail.gmail.com">
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<div style="font-family:arial,sans-serif;color:rgb(0,0,0)"
class="gmail_default">Hi Petr,</div>
<br>
</div>
<div style="font-family:arial,sans-serif;color:rgb(0,0,0)"
class="gmail_default">I have been looking into this off and
on for the last year or two and haven't found a good
solution (where "good" is defined as "apt install
give-me-ipv6-dns-auto-names").<br>
</div>
<div style="font-family:arial,sans-serif;color:rgb(0,0,0)"
class="gmail_default"><br>
</div>
<div style="font-family:arial,sans-serif;color:rgb(0,0,0)"
class="gmail_default">My two use cases are both on-LAN, so
privacy is a non-issue: <br>
</div>
<div style="font-family:arial,sans-serif;color:rgb(0,0,0)"
class="gmail_default"> 1) making tcpdump show host names
when I do traces; <br>
</div>
<div style="font-family:arial,sans-serif;color:rgb(0,0,0)"
class="gmail_default"> 2) allow wife and other home users
to just say "<a href="https://videos.lan/"
moz-do-not-send="true" class="moz-txt-link-freetext">https://videos.lan/</a>"
instead of me explaining and dealing with IP addresses.</div>
</div>
</div>
</blockquote>
For devices offering any services to network, I think DHCPv6 client
would make sense. That would register the name automagically. Static
records would be good for devices always there, like raspberry pi
service.<br>
<blockquote type="cite"
cite="mid:CAP2Qz+U6OkAvRWy3mRabno6dPOiJ=978-PP7ashRRrQBcUJzog@mail.gmail.com">
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<div style="font-family:arial,sans-serif;color:rgb(0,0,0)"
class="gmail_default">My solution is a cron script on my
(Linux/OpenWrt) gateway device that looks at the DHCPv4
table to collect MAC:host-name pairs, then looks at 'ip -6
neigh show' to get MAC:IPv6 pairs, matches up the names and
SLAAC IPv6s to the names and writes them to a dnsmasq config
file. (The config file still needs manual cleaning, as I
don't have anything logging expiration times.)<br>
</div>
</div>
</div>
</blockquote>
Sounds like working, but not too elegant hack. I think dhcp-range
with ra-names should help you in this case, if the dnsmasq is doing
this job. Should do something like your script in a bit more elegant
way. But needs IPv4 DHCP to obtain the name. If we ever stop using
it, that will stop providing names.<br>
<blockquote type="cite"
cite="mid:CAP2Qz+U6OkAvRWy3mRabno6dPOiJ=978-PP7ashRRrQBcUJzog@mail.gmail.com">
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class="gmail_default"><br>
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<div style="font-family:arial,sans-serif;color:rgb(0,0,0)"
class="gmail_default">It would be lovely if there were a
nice demon that just sat and watched for NDP NA/NS messages
and used that information (including TTLs) to do a DNS
UPDATE instead of my hack. I'm not sure where to get host
names on an IPv6-only network, as I haven't looked into that
part deeply...<br>
</div>
<div style="font-family:arial,sans-serif;color:rgb(0,0,0)"
class="gmail_default"><br>
</div>
<div style="font-family:arial,sans-serif;color:rgb(0,0,0)"
class="gmail_default">Eric<br>
</div>
</div>
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</blockquote>
<p>At least using MDNS responder on network gateway might push names
obtained via mdns into unicast dns too. I would expect some RA
option to say: try to register on the DNS server (if you wish).
But IANA has nothing such registered [1]. Because I would like to
have some names for all connected devices in my network, without a
need to register them manually.<br>
</p>
<p>1.
<a class="moz-txt-link-freetext" href="https://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml#icmpv6-parameters-5">https://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml#icmpv6-parameters-5</a><br>
</p>
<pre class="moz-signature" cols="72">--
Petr Menšík
Software Engineer, RHEL
Red Hat, <a class="moz-txt-link-freetext" href="https://www.redhat.com/">https://www.redhat.com/</a>
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB</pre>
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