Re: [PATCH v2] dhcp: handle multiple offers from the same server

Hi James,

On 1/31/22 16:03, James Prestwood wrote:
> It was found that some DHCP servers send multiple offers on occation. Whether
> this is a bug or not its been seen in products and ELL should handle this
> gracefully.
> 
> The issue comes down to these DHCP servers expecting a request associated with
> the last offer they send. The existing behavior in ELL is to ignore all offers
> after the initial, and continue resending requests for the original offer. When
> this happens the DHCP server never responds with an ACK.
> 
> The spec briefly outlines multiple DHCP offers but in the context of multiple
> DHCP servers rather than multiple offers from the same DHCP server. In any
> case its left up to the DHCP client to choose whatever offer it wants, so this
> is what ELL will do.
> 
> Now only the last offer will be used while in the REQUESTING state. If another
> offer comes in before the ACK, that offer will be used and a new request will
> be sent out. Note this is only the case when the offers contain the same
> server ID as the first offer sent (this eliminates the multi DHCP server case
> and will maintain existing behavior, where the first offer is selected always).
> ---
>   ell/dhcp.c | 62 ++++++++++++++++++++++++++++++++++++++++++------------
>   1 file changed, 49 insertions(+), 13 deletions(-)
> 
> v2:
>   - Added a debug print in the multiple offer case
> 

I modified the commit description a bit and applied, thanks.

Regards,
-Denis