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?
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 http://www.blueridgenetworks.com OpenPGP key ID: 296D1CD6F2B84CAB https://keys.openpgp.org/
On Thu, Apr 22, 2021 at 6:17 PM Bruce A. Johnson <bjohnson@xxxxxxxxxxxxxxxxxxxxx> wrote:
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.
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.
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?)--
Mantas Mikulėnas
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