[pve-devel] [PATCH pve-network] dnsmasq: configure static range for each subnet

DERUMIER, Alexandre alexandre.derumier at groupe-cyllene.com
Wed Nov 15 21:50:52 CET 2023

>>I have a similar solution for the dhcp-range.
>>I played around with adding and removing IPs from IPAM and It looks
>>dnsmasq is offering the correct IP, as stored in IPAM and ethers
>>I tried with a regular reboot to get a new IP.
>>What I saw when testing with the previous dhcp-range config.
>>VM with an IP in IPAM, manually remove IP from ethers file,
>>the VM will still get an IP in the range, but not the one originally
>>If dnsmasq never saw the MAC, it will not offer an IP.
>>If you find a specific scenario that does not work, please post a
>>by step description so I can try to reproduce and to get a better
>>understanding of the dnsmasq config.

I can reproduce easily 100%:

- create a nic with mac:xx:xx:xx:xY  ip:
- start vm. (the ether file is filed + reload)
- the guest do a dhcp request, the dnsmasq respond  a store the lease
in /var/lib/misc/zone.lease

- delete the nic

- add a new nic in same vm or another vm,  free found ip is  (because it was removed)

- start the vm (the ether file is upgrade with the new ip mac + reload)

- the guest do a dhcp request: the dnsmasq can't respond (with my last
patch) or give a dynamic ip in the range (with current implementation)
because it's still see his lease file the old mac:ip assocation

so, the solution is to remove lease file and restart dnsmasq

others dhcp daemons:

With kea, it possible to update/del/add lease directly through unix
socket. (but not static reservation, it's a commercial plugin).
That mean that if an unknown client is doing a request, it can return a
lease in the pool range (and we don't known it, and could allocate it)

echo '{ "command": "lease4-get-all" }'  | socat /run/kea/kea4-ctrl-
socket -,ignoreeof

echo '{ "command": "lease4-del", "arguments": {"ip-address":
""} }'  | socat /run/kea/kea4-ctrl-socket -,ignoreeof

echo '{ "command": "lease4-add", "arguments": {"ip-address":
"", "hw-address": "1a:1b:1c:1d:1e:1f"} }'  | socat
/run/kea/kea4-ctrl-socket -,ignoreeof

echo '{ "command": "lease4-update", "arguments": {"ip-address":
"", "hw-address": "1a:1b:1c:1d:1e:1f"} }'  | socat
/run/kea/kea4-ctrl-socket -,ignoreeof


freeradius seem interesting, as it's possible to do custom
plugins,including perl


So, maybe it could be possible to read directly the macs.db database in
/etc/pve dynamically.

I need to read the doc to see how it's works

What we need is just a stupid daemon replying to dhcp request with dhcp
offers using static mac:ip  (with correct dhcp protocol implementation

Maybe some pure perl daemon exist ?
or python like https://github.com/flan/staticdhcpd ?

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