On 6/8/2020 6:18 PM, Bruno BEAUFILS wrote:
Hello everyone,

I have got a static leases issue with dnsmasq 2.80-1 installed as
Debian Buster package.

I search the man page and the mailing list archives without any
success. Thus I try here.

Here is short summary of what I have.

I am on a simple LAN with a screenless host running dnsmasq. It is the
only, and thus main, DHCP server on the network.

I use the dhcp-authoritative option in dnsmasq configuration.

It offers a dhcp-range looking like that...

     dhcp-range=192.168.0.200,192.168.0.250,12h

...and a bunch of static lease looking like something like that

     dhcp-host=xx:xx:xx:xx:xx:xx,id:*,192.168.0.2,somename

I want to use a new USB-ethernet adpator on a new laptop.

On the first connection the host get a IP from the open range
(192.168.0.203) as it is visible in the logs:

     Jun  7 17:38:29 b3 dnsmasq-dhcp[12907]: DHCPDISCOVER(eth1) 
12:34:56:78:9a:bc
     Jun  7 17:38:29 b3 dnsmasq-dhcp[12907]: DHCPOFFER(eth1) 192.168.0.203 
12:34:56:78:9a:bc
     Jun  7 17:38:29 b3 dnsmasq-dhcp[12907]: DHCPDISCOVER(eth1) 
12:34:56:78:9a:bc
     Jun  7 17:38:29 b3 dnsmasq-dhcp[12907]: DHCPOFFER(eth1) 192.168.0.203 
12:34:56:78:9a:bc
     Jun  7 17:38:29 b3 dnsmasq-dhcp[12907]: DHCPREQUEST(eth1) 192.168.0.203 
12:34:56:78:9a:bc
     Jun  7 17:38:29 b3 dnsmasq-dhcp[12907]: DHCPACK(eth1) 192.168.0.203 
12:34:56:78:9a:bc mechra

After the first connection I am able to log on the server and add a
dhcp-host specific to that host. For that I did the following things
in order :

1. stop the dnsmasq server

2. remove the leases file

3. modify the dnsmasq configuration in order to add the dhcp-host
    option

     dhcp-host=00:23:4d:df:a1:d1,id:*,192.168.0.15,somefancyname,24h

4. start the dnsmasq server

After that I unplug the adaptor from the laptop and replug it in order
for it to get the new IP from the static lease. Unfortunately I always
get the same "old" adress (192.168.0.203), as the log shows (because
the client asked it):

     juin  7 18:05:23 b3 dnsmasq-dhcp[29360]: DHCPREQUEST(eth1) 192.168.0.203 
12:34:56:78:9a:bc
     juin  7 18:05:23 b3 dnsmasq-dhcp[29360]: DHCPACK(eth1) 192.168.0.203 
12:34:56:78:9a:bc mechra

I thought the dnsmasq should have refused the client request of using
192.168.0.203 (through a DHCPNAK for instance) and sent it a new
OFFER with the correct static (192.168.0.15).

Did I miss something (aka this is normal behavior but I misconfigured
the whole stuff certainly because I did not understand the
documentation well enough) or am I struggling with some kind of bug?

Just in case it matters: all host used in the description are running Debian.


Try clearing the lease for the host in question:

$ systemctl stop dnsmasq
Remove the file altogether or remove the desired lease in the lease file:.
Lease file path: '/var/lib/misc/dnsmasq.leases'
$ systemctl start dnsmasq


IN plain English, you need to clear the lease or you need to wait for
the lease to expire.

HTH.

--
John Doe

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