[Kea-users] kea 2.2.0 - responding twice to broadcast requests

[Simon]

vom513 <vom513 at gmail.com> wrote:

> On my firewall I have a bit of a complex setup in terms of interfaces.  I do VLAN trunking / subifs, SQM for bufferbloat, and some “aliases” (ex: eth0:0 - secondary IP on same subnet).
> 
> Under ISC dhcpd I don’t see this behavior.  I discovered this (no pun intended) with a Nagios check_dhcp script.
> 
> If I send a unicast request direct to the server, I get one response.  If I send a broadcast - it seems the server is “hearing it twice” ?  I see multiple replies in the logs for actual clients as well.
> 
> In the middle of writing this message, I decided to try messing with the alias.  Seems to be the culprit.  If I ifdown the alias interface - I get one response.  Seems like Kea binds (??) to the alias as well - even though it’s not defined in the interfaces in config.  I could bring it back up after Kea was running and everything was fine.  It’s only when Kea starts and this alias exists that I get this behavior (i.e. on a fresh boot).
> 
> Also to be very clear, not only is this an alias, but it’s an alias on a VLAN subif.  Don’t know how much that matters:
> 
> enp1s0f4d1.10:0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>        inet 192.168.64.10  netmask 255.255.255.0  broadcast 192.168.64.255
>        ether 00:07:43:16:0d:e8  txqueuelen 1000  (Ethernet)
> 
> Is there some knob that can be turned to pare this down to just the actual interface in the config ?  Or did I stumble on a bug ?

Rather than adding an alias (extra interface), have you considered the more modern way of simply adding addresses ?
Using /etc/network/interfaces I just add a couple of lines (you’ll need to double check syntax as I’m typing from memory) :

iface eth0
  ...
  post-up ip addr add a.b.c.d dev eth0
  pre-down ip addr del a.b.c.d dev eth0

With other methods of network configuration, you’ll need to figure out how they handle the same thing.


Simon