>>> "Bruce A. Johnson" <bjohn...@blueridgenetworks.com> schrieb am 22.04.2021 um 22:14 in Nachricht <5aaf83b2-9857-425d-2d7f-b9660abf9...@blueridgenetworks.com>: > 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?
Hi! I did not follow the discussion closely, but using USB tehering with my smartphone typically results in DHCP leases of one hour. I had made the experience that network stopped many times after about one hour (when the DHCP lease should have been refreshed, but wasn't). I ran "watch ip r sh" in a terminal to monitor: Once the "usb0" interface was gone, I knew there is a problem. Restarting the tethering fixed the problem in practically all cases. So long story short: I think there is a valid reason to be able to debug DHCP and fellows... Regars, Ulrich > > 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 22/04/2021 12:00, Mantas Mikulėnas wrote: >> On Thu, Apr 22, 2021 at 6:17 PM Bruce A. Johnson >> <bjohn...@blueridgenetworks.com >> <mailto:bjohn...@blueridgenetworks.com>> 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 _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
