[Dnsmasq-discuss] dnsmasq caching lease file?

[Tautvydas Bruzas]

Hi,

I am running into the issue where dnsmasq seems to be caching dhcp leases
for a defined period of time and doesn't reload them on SIGHUP. I have and
openstack install and it uses dnsmasq to serve VMs and IP address, it
starts dnsmasq with these options:

--strict-order --bind-interfaces --conf-file= --domain=novalocal
--pid-file=/var/lib/nova/
networks/nova-br100.pid --listen-address=10.15.0.6 --except-interface=lo
--dhcp-range=10.15.0.2,static,7200s --dhcp-lease-max=65536
--dhcp-hostsfile=/var/lib/nova/networks/nova-br100.conf
--dhcp-script=/usr/bin/nova-dhcpbridge --leasefile-ro

Usually when you launch a new VM it gets added to the
/var/lib/nova/networks/nova-br100.conf file and dnsmasq get SIGHUP to
reload that file. Which works fine. However I've noticed that if you
already had an IP assigned and it's reused (you're launching new VM with
different mac, but it should get the old IP), dnsmasq doesn't update it's
cache? I've tried setting cache_size to 0 and that doesn't affect anything.
In the strace for the dnsmasq I still see the old name for the VM so I
assume it's cached somewhere. In the source file I've traced the SIGHUP and
it seems like it should clear cache and reload (there is a function for
that: void clear_cache_and_reload(time_t now)), but it doesn't do it. Not
sure if it's a bug or if it's intended by design.

I'd really appreciate if someone would help me on this. As I said I've
tried looking at the source code, and it didn't seem like it's
dhcp_read_ethers(); that reads from /etc/ethers file, doesn't look like
dhcp_update_configs(daemon->dhcp_conf) that one seems to be for /etc/hosts
file?

Thanks.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/attachments/20121013/5f469fa1/attachment.html>