[Dnsmasq-discuss] [DHCPV4] android devices issue makes able to use a reserved ipv4 address in dnsmasq

[Geert Stappers]

On Mon, Dec 10, 2018 at 12:21:00PM +0000, Inigo de la Fuente wrote:
> Hi all,
> 
> I have a question regarding to DHCPv4 leases.
> Doing some tests I have faced a possible android issue
> that I want to share with you.
> 
> 1.- I set the DHCP range of ipv4 address from 192.168.72.51 to 192.168.72.150
>     in dnsmasq.conf.
> 2.- One windows pc is connected and get an ipv4 lease (192.168.72.65)
> 3.- One android device is connected and get an ipv4 lease (192.168.72.133)
> 4.- stop dnsmasq and remove all entries in dhcp.leases
> 5.- add dummy entries to dhcp.leases file till there is not any address
>     available in the dhcp range and start dnsmasq again.
> 6.- windows pc is not able to obtain an ipv4 lease because all are occupied.
>     Ping is not possible
> 7.- android device 'seems' to be able to use the saved leased ipv4 (192.168.72.133).
>     Ping is possible
> 
> Here the output of dnsmasq at step 7:
> dnsmasq-dhcp: 93920162 available DHCP range: 10.173.190.51 -- 10.173.190.150
> dnsmasq-dhcp: 93920162 vendor class: HUAWEI:android:ANE
> dnsmasq-dhcp: 93920162 client provides name: HUAWEI_P20_lite-9a7e63d7d
> dnsmasq-dhcp: 93920162 DHCPDISCOVER(eth1) 00:be:3b:02:c1:02 no address available
> dnsmasq-dhcp: 93920162 available DHCP range: 10.173.190.51 -- 10.173.190.150
> dnsmasq-dhcp: 93920162 vendor class: HUAWEI:android:ANE
> dnsmasq-dhcp: 93920162 client provides name: HUAWEI_P20_lite-9a7e63d7d
> dnsmasq-dhcp: 93920162 DHCPDISCOVER(eth1) 00:be:3b:02:c1:02 no address available
> dnsmasq-dhcp: 93920162 available DHCP range: 10.173.190.51 -- 10.173.190.150
> 
> Why my device is able to ping with the last saved leased ipv4 address
> even if this address is reserved in dhcp.leases file?
 
Imaginary problem


Groeten
Geert Stappers
-- 
Leven en laten leven