dhcpcd-discuss

Hi

On 13/02/2017 16:31, Shahid Mahmood wrote:
> On Sun, Feb 12, 2017 at 5:12 PM, Roy Marples <roy@xxxxxxxxxxxx
> <mailto:roy@xxxxxxxxxxxx>> wrote:
> 
>     Hi Shahid
> 
>     On 10/02/17 15:37, Shahid Mahmood wrote:
>     > Hello Roy,
>     > Just a quick question on section 17.1.3 of RFC 3315. It states 3
>     options
>     > available to the client in order to select and Advertise message:
>     >
>     > --- quote
>     >
>     >    Upon receipt of one or more valid Advertise messages, the client
>     >    selects one or more Advertise messages based upon the following
>     >    criteria.
>     >
>     >    -  Those Advertise messages with the highest server preference
>     value
>     >       are preferred over all other Advertise messages.
>     >
>     >    -  Within a group of Advertise messages with the same server
>     >       preference value, a client MAY select those servers whose
>     >       Advertise messages advertise information of interest to the
>     >       client.  For example, the client may choose a server that
>     returned
>     >       an advertisement with configuration options of interest to the
>     >       client.
>     >
>     >    -  The client MAY choose a less-preferred server if that server
>     has a
>     >       better set of advertised parameters, such as the available
>     >       addresses advertised in IAs.
>     >
>     > --- end quote
>     >
>     > Specifically, when does client pick the last option:
>     >
>     >    -  The client MAY choose a less-preferred server if that server
>     has a
>     >       better set of advertised parameters, such as the available
>     >       addresses advertised in IAs.
>     >
>     > Also, can application influence this choice (with parameter or
>     something)?
> 
>     Currently there is no preference selection available.
>     dhcpcd binds the first one received and keeps it. It does not change to
>     another lease as such.
> 
>  
> It is observed that dhcpc picks the first server if two happen to send
> Advertize almost simultaneously.
> The first advertize has Pref-Value 250, 2nd one 253. It does not seem to
> follow 1st bullet in sec 17.1.3 in RFC 3315.
>  
> 
> 
>     Because dhcpcd can trivially remove the lease it applied, changing to a
>     new lease from a new server wouldn't be too onerous. How would you say
>     to prefer one over another?
> 
>  
> At this point, I just wanted to confirm if the behavior is in accordance
> with the RFC.

Section 17.1.3 says the client MAY select a better server, not MUST.
So yes, in the strict sense dhcpcd is in compliance even though it
ignores the option.

Making dhcpcd react to a more preferred server right away would be quite
easy.
Storing the adverts for a period of time and then choosing the more
preferred one to bind to would be trickier.
Right now, I'm not sure which is the better solution.

Roy