From: Stefan Lendl <s.lendl@proxmox.com>
To: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>
Cc: "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>
Subject: Re: [pve-devel] [PATCH pve-network] dnsmasq: configure static range for each subnet
Date: Thu, 16 Nov 2023 13:53:45 +0100 [thread overview]
Message-ID: <87bkbt3lly.fsf@gmail.com> (raw)
In-Reply-To: <224f6b39b0d45e386dd32b1881169c17a89b2917.camel@groupe-cyllene.com>
"DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com> writes:
>
> I can reproduce easily 100%:
>
>
> - create a nic with mac:xx:xx:xx:xY ip: 192.168.0.10
> - 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
> 192.168.0.10 (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
>
I experimented with several approaches with dnsmasq leases.
I cannot reproduce your example because it works in my examples.
My procedure:
dnsmasq config:
dhcp-range=set:DHCPNAT-10.1.0.0-16,10.1.0.0,static,255.255.0.0,infinite
VM 108 net1: MAC: bc:24:11:ad:0e:2e
qm set 108 --delete net1
dnsmasq lease file still contains the lease for MAC bc:24:11:ad:0e:2e
qm set 108 --net1 model=virtio,bridge=dhcpnat
- ethers file gets updated to new mac: BC:24:11:51:10:AD
- soon after dnsmasq lease gets updated to the new lease as well!
- correct IP assigned in the VM
I also tried:
- ip link set down > ip link set upi
- reboot
- force Stop the VM
So far, *this all works!*
I also tried with a short dhcp lease in dnsmasq. With this
configuration, the new IP will even propagate to the VM and set
correctly after IPAM update.
In my tests I used 30s but something like 5 or 10min should be fine as well.
dhcp-range=set:DHCPNAT-10.1.0.0-16,10.1.0.0,static,255.255.0.0,30
The VM is polling every ~60s as seen on the wire with tcpdump:
tcpdump -i dhcpnat -n port 67 or port 68
After I manually update the ethers file and `systemctl *reload*
dnsmasq`, it will respond with the new IP.
dnsmasq is running *locally only* so any DHCP queries are limited to the
local bridge.
The biggest problem and for me the reason I think it's not a feasible
solution, is that dnsmasq becomes a single point of failure.
If dnsmasq is offline, all of the VMs will have *NO IP*.
next prev parent reply other threads:[~2023-11-16 12:53 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-15 15:13 Alexandre Derumier
2023-11-15 16:07 ` DERUMIER, Alexandre
[not found] ` <87il632clh.fsf@gmail.com>
2023-11-15 20:50 ` DERUMIER, Alexandre
2023-11-16 12:53 ` Stefan Lendl [this message]
2023-11-16 13:43 ` DERUMIER, Alexandre
2023-11-16 14:09 ` Stefan Lendl
2023-11-17 7:24 ` DERUMIER, Alexandre
2023-11-16 13:52 ` DERUMIER, Alexandre
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