Re: [lwip-users] DHCP, switch to static IP if no answer

[Claudius Zingerli]

Bill,

On 2011-06-22 16:01 PM, Bill Auerbach wrote:
> Walter,
>
> I used dhcp_start and then checked in a loop netif_is_up for a
> connection for 5 seconds. If the 5 seconds ran out, I used dhcp_stop,
> netif_set_down, netif_set_addr, netif_set_up, and dhcp_inform to set a
> static IP address.

Just for the protocol: Doing this, you might run into problems if you 
only wait 5s. RFC2131 (DHCP spec) says:

"4.4.1 [...] The time over which the client collects messages and the 
mechanism used to select one DHCPOFFER are implementation dependent."

Well, they don't give any numbers, but Windows/Linux/BSD all wait far 
more than 5s before giving up. Reasons might be ARP checking timeouts at 
the DHCP server wait longer before sending a DHCPOFFER.

Regards

Claudius