dhcpcd-discuss

On 21/10/2014 19:59, David Hauck wrote:
>> I don't think there is any guidance as such.
>>
>> In the ideal world we should attempt both DHCP and IPv4LL at the same
>> time, but the dhcpcd event loop cannot do that easily yet. One
>> possibility is to create a pseudo interface for it as we do for the
>> IA_NA + IA_PD DHCPv6 case, but that was very hard to manage.
>>
>> But right now, dhcpcd rightly or wrongly attempts to configure IPv4LL
>> on carrier up if the last address was IPv4LL.
> 
> I am interested in your opinion/gut feeling about this. Mine tells me that this is the incorrect behaviour - i.e., there is now a DHCP server present on the network and the DHCP client now first try to establish contact with it. Another way to look at this is if I brought the interface down (ifdown eth1) and then back up (ifup eth1) the client would indeed establish contact with the DHCP server (and not attempt to renew the old IPV4LL lease).

dhcpcd cannot assume that if you plug in a cable there is a DHCP server.
Infact, if you have a DHCP lease, unplug the cable and replug it, it
will attempt to re-obtain that lease. The same is true for IPv4LL, so in
this view it is a perfect mirror of DHCP.

From the case where the user expects a working DHCP lease it's wrong
because his network probably won't function with IPv4LL.
From the use case where IPv4LL actually works as designed on the network
then DHCP isn't needed.

You know after working this for more years than I care to remember I
really don't know which of the two above is better. I'm probably leaning
slightly to your view.

Roy