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<p>I'm still trying to get an explanation of why having a valid DHCP
address is not in itself good enough. The only reason I've been
able to see is that after the lease is issued, and before the time
comes to refresh the lease, there could be a communication failure
somewhere between the switch the DHCP client is on and the home
office where the DHCP server is. One would assume that application
failures would be a reasonable clue.... Regardless, it seems to me
that it's not unreasonable for an application outside of
systemd-networkd to be able to obtain the DHCP lease information.
Am I off base here?<br>
</p>
<pre class="moz-signature" cols="72">Bruce A. Johnson | Firmware Engineer
Blue Ridge Networks, Inc.
14120 Parke Long Court Suite 103 | Chantilly, VA 20151
Main: 1.800.722.1168 | Direct: 703-633-7332
<a class="moz-txt-link-freetext" href="http://www.blueridgenetworks.com">http://www.blueridgenetworks.com</a>
OpenPGP key ID: 296D1CD6F2B84CAB <a class="moz-txt-link-freetext" href="https://keys.openpgp.org/">https://keys.openpgp.org/</a></pre>
<div class="moz-cite-prefix">On 22/04/2021 12:00, Mantas Mikulėnas
wrote:<br>
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<div dir="ltr">On Thu, Apr 22, 2021 at 6:17 PM Bruce A. Johnson
<<a href="mailto:bjohnson@blueridgenetworks.com"
moz-do-not-send="true">bjohnson@blueridgenetworks.com</a>>
wrote:<br>
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<p>Silvio, thanks for the suggestion. I'm not concerned
with keeping the lease forever; the system actually
experiences a topology change as it's switched from one
network to another, and I can catch that from the DBus
events that occur. The problem we're trying to solve is
to contact some address that we're sure exists on the
network, without knowing anything about that network.
The default gateway was an obvious choice, but someone
wants to cover the case of there being a private LAN
with no gateway. The only other choice I could see is
the DHCP server that issues the lease.</p>
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<div>Hmm, don't you also have the case of there being a
private LAN with no gateway and no DHCP? Or possibly the
case of a DHCP relay. And since you don't know anything
about the network, you also don't know whether the address
will respond to your communication attempts (other than ARP)
-- it might be pingable but it might be not.</div>
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<div>I'm curious about what brought this problem into
existence in the first place. Why *is* it necessary to
contact a random address within the network? (If it's to
check that the physical interface is working, then just the
fact that you somehow acquired a lease would be enough. no?)</div>
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-- <br>
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<div dir="ltr">Mantas Mikulėnas</div>
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