[libvirt-users] libvirt/dnsmasq is not adhering to static DHCP assignments

[Christian Kujau]

This is basically a continuation of an older posting[0] I found, but 
apparently no solution has been posted. So, I'm trying to setup static 
DHCP leases with dnsmasq that is being started by libvirtd:


-----------------------------------------------------------
$ sudo virsh net-dumpxml --network default
<network>
  [...]
  <dns enable='no'/>
  <ip address='192.168.122.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.122.130' end='192.168.122.250'/>
      <host mac='08:00:27:e2:81:39' name='f30' ip='192.168.56.139'/>
-----------------------------------------------------------


And the domain is indeed being started with that hardware address:


-----------------------------------------------------------
$ virsh dumpxml --domain f30 | grep -B1 -A3 mac\ a
    <interface type='bridge'>
      <mac address='08:00:27:e2:81:39'/>
      <source bridge='virbr0'/>
      <target dev='tap0'/>
      <model type='virtio'/>
-----------------------------------------------------------
  


But for some reason the domain gets a different address assigned, albeit 
from the correct DHCP pool:


-----------------------------------------------------------
$ ssh 192.168.122.233 "ip addr show"
[...]
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state 
UP group default qlen 1000
    link/ether 08:00:27:e2:81:39 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.233/24 brd 192.168.122.255 scope global dynamic enp1s0
-----------------------------------------------------------


See below for even more details. I've removed the virbr0.status file, 
restarted the network, still it gets this .233 address instead of the 
configured .139. Also, I'm not able to add a debug log to the 
libvirtd/dnsmasq instance, although it should be possible[1], the 
xmlns:dnsmasq stanza is overwritten as soon as the configuration is saved. 
Short of a debug (queries) log, strace on the libvirtd/dnsmasq process 
reveals that the client seems to request this strange IP address:

23002 19:01:59.053558 write(11, "<30>Jul 31 19:01:59 dnsmasq-dhcp[23002]: DHCPREQUEST(virbr0) 192.168.122.233 08:00:27:e2:81:39 ", 95) = 95
23002 19:01:59.054024 write(11, "<30>Jul 31 19:01:59 dnsmasq-dhcp[23002]: DHCPACK(virbr0) 192.168.122.233 08:00:27:e2:81:39 f30", 94) = 94

So I restarted the dhclient process in the domain (a freshly installed 
Fedora 30), removed all state files with "192.168.122.233" in them, but 
still the domains gets assigned the .233 instead of the .139 address.

The next step would be to disable libvirtd/dnsmasq altogether and run my 
own dnsmasq instance, but I wanted to avoid that. Any idead on where to 
look next?

Thanks,
Christian.

[0] https://www.redhat.com/archives/libvirt-users/2017-October/msg00070.html
[1] https://libvirt.org/formatnetwork.html#elementsNamespaces


# cd /var/lib/libvirt/dnsmasq/
# grep -r . . | fgrep -v \#
./default.conf:strict-order
./default.conf:port=0
./default.conf:pid-file=/var/run/libvirt/network/default.pid
./default.conf:except-interface=lo
./default.conf:bind-dynamic
./default.conf:interface=virbr0
./default.conf:dhcp-range=192.168.122.130,192.168.122.250,255.255.255.0
./default.conf:dhcp-no-override
./default.conf:dhcp-authoritative
./default.conf:dhcp-lease-max=121
./default.conf:dhcp-hostsfile=/var/lib/libvirt/dnsmasq/default.hostsfile
./default.hostsfile:08:00:27:e2:81:39,192.168.56.139,f30
./virbr0.status:[
./virbr0.status:  {
./virbr0.status:    "ip-address": "192.168.122.233",
./virbr0.status:    "mac-address": "08:00:27:e2:81:39",
./virbr0.status:    "hostname": "f30",
./virbr0.status:    "client-id": "ff:27:e2:81:39:00:04:8c:ad:c4:7d:04:e8:4b:de:93:4b:76:d8:75:82:86:c8",
./virbr0.status:    "expiry-time": 1564628519
./virbr0.status:  }
./virbr0.status:]





-- 
BOFH excuse #40:

not enough memory, go get system upgrade