[Dnsmasq-discuss] android client does not check ip address with DHCPREQUEST

Inigo de la Fuente inigo.de.la.fuente at ict.nl
Wed Jan 9 15:48:54 GMT 2019


Hi All,

I have performed several test and already have opened one thread about this issue. I have seen unexpected behavior on android when DHCPv4 client tries to reuse a previously allocated network address and this address is unavailable on the server.

The test steps are the following:

  1.  Set the range of DHCP leases to only 1. Until now, DHCP can only lease one address.
  2.  Connect a device and get the only IPv4 address lease available then disconnect.
  3.  On the server dnsmasq leases file, replace the IPv4 lease and give the address to other machine.
  4.  Reconnect the device on point 1.


Basically on windows and IOS I can see that the first message on the DHCP client-server communication is a DHCPREQUEST sent by the client with the IPV4 address that wants to reuse. Then, the server respond with a DHCPNAK indicating the lease is not available anymore on the server. After that the client tries to get a new IPV4 but is not possible because no IPV4 range is available. (the only available address is assigned).
This is the correct behavior indicated on RFC1531

However, on Android the DHCPv4 client does not use DHCPREQUEST and then it reuses the address even when that address has been reassigned to other machine.

Did someone experience that?

Regards and thanks in advance




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