dnsmasq: DNS not updating from DHCP leases when client IP address changes

[thomas.schmid]

In our development system we rebuild client VMs often. These client VMs receive an IPv4 address from DHCP which also uses the hostname of the client VM to build a DNS entry which is then reported by dnsmasq DNS to the developper.

It works fine for the first time the client VM starts: It gets IP address 1.2.3.4, its hostname "a" is used to form the FQDN "a.company.com" which together with the acual IP address is then reported by dnsmasq DNS.

Once the client VM is rebuilt, having a new MAC address assigned by the process and starts up, DHCP of course assigns a different IP address, but uses the old = new = same hostname "a" to form the FQDN "a.company.com". But dnsmasq ignores resp. doesn't receive this update (new IP address, old hostname), which can be seen by checking /var/etc/dnsmasq-leases: The entry for "a.company.com" still shows the now invalid old IP address.

This used to work just fine in OPNsense 22.7.

Any ideas ?

[thomas.schmid]

Added information: I have rolled back to 22.7.11_1 (thanks $deity for proxmox) and let the developper test this use case again: Conformed, it works with 22.7.11_1, but not with 23.1.7_3.
There are no useful infos in dnsmasq's log. DHCP's log shows the host with the same hostname but different IP address.
Somehow, the connection between DHCPd and dnsmasq is broken. The same problem was present with version 22.1 due to the instability of the "dhcpleases" binary which then provided the "glue" between DHCPd and dnsmasq. Since "dhcpleases" has been removed, I don't understand the technique used to couple DHCPd lease information towards dnsmasq.   

[franco]

The Dnsmasq watcher code is the same in 23.1.x and 22.7.x. I'm sure there is an issue somewhere but not enough information on it... and no other report regarding this.


Cheers,
Franco

[thomas.schmid]

Hi Franco,

Where would I look for information ? I could provide DHCPd and dnsmasq logs (I believe), as I still have the VM with 23.1.7:3 installed (cloned it away). Any other locations to look for clues ?

Kind regards,
Thomas