[Dnsmasq-discuss] double DHCP leases

Simon Kelley simon at thekelleys.org.uk
Fri Aug 29 07:29:33 BST 2008


Nikos Mavrogiannopoulos wrote:
> I've come across to a situation where dnsmasq was giving two IP
> addresses to certain (windows) hosts. The problem was that the windows
> host was requesting two times for an IP but having a different client
> identifier (check the wireshark output). 
Looks like windows is using RFC2132-like behaviour (client-id derived 
from MAC address) then moving to RFC4361-like behaviour (DUID 
client-id). Is this a big problem? the first lease will expire and 
release the IP address in time.

I've fixed this using the
> attached patch. In that patch I make lease_find_by_client() to return
> the lease of any of the MAC and the ClientID match. The previous
> behaviour was that if client IDs are there, it didn't check the MAC
> address. What was the reason for that?
> 

Yes, it's what the RFCs mandate. If a client-id is provided, it shall be 
used as the host unique-identifier, and the MAC address ignored. See 
RFC4361 section 6.3 for the definative statement on this.

Cheers,

Simon.

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