On 14/02/2023 22:48, David Wright wrote:
On Mon 13 Feb 2023 at 11:39:31 (+0100), Christoph Brinkhaus wrote:Today I have deleted almost everything of avahi and xfce4. After a reboot the 169.254.xxx.yyy is no more configured.Yes, and that's a problem for anyone trying to replicate the configuration of these addresses: we usually never see files and logs from offending systems, but just reports of package deletion or, even less helpful, so-called nuking of random files.
Are there design overview what avahi-autoipd is supposed to do and which way dhcp clients interact with it?
A dozen of years ago I purged avahi packages because they were adding more complexity to debugging of network issues. Avahi and 169.254.x.y addresses are noticed by users when network does not work. It may be caused by various reasons: provider's DHCP server is temporary unavailable, problems during negotiation for connection type and bandwidth, maybe ethernet card driver. Since other part is involved, it may be a problem to reproduce the issue when it is enough time to debug it. That times I did not find info when avahi may be useful for me. Quick search for zeroconf purpose did not result in useful links.
Recently I saw a 169.254.x.y address when I decided to take advantage of 1Gb ethernet ports in laptops to copy some large files. RTL8723BE WiFi sometimes may work unreliably. NetworkManager allows to start a DHCP server from UI by creation of shared connection. Unfortunately due to dust on rarely used ethernet connector connection was downgrading from 1Gb to 100Mb and NetworkManager considered it as failure. As a result on the other side avahi-autoipd assigned its address.
So to get 169.254.x.y address, ensure physical connection with no DHCP server. In real life it happens when you should complete some other tasks and you are upset due to broken network.
From my point of view, to improve reputation of Avahi, it is necessary to clearly explain the role of avahi-autoipd. Maybe better docs have appeared last years, I have not checked.