Re: [lwip-users] DHCP usage with latest git code version

[Sylvain Rochet]

Hi Bram,

On Fri, Sep 11, 2015 at 09:10:28AM +0000, Bram Peeters wrote:
> Thanks for the clarification!
> 
> I had to add 
> #define LWIP_DHCP_CHECK_LINK_UP       1
> as well to make 
> 
> > netif_set_up(&gnetif);
> > dhcp_start(&gnetif);
> > Then DHCP will start if netif is already "link up" or at the next "link  
> > up" event.
> 
> work with the netif initially in link down Otherwise the DCHP state 
> was in DHCP_STATE_OFF mode, and stayed in that mode when 
> dhcp_network_changed(struct netif *netif) was called when link up 
> occurred.

I don't agree. Only dhcp_release()/dhcp_stop() (and obviously initial 
state) switches DHCP to DHCP_STATE_OFF. (Or did you find a bug ?, if so, 
please investigate a bit more about this issue ;-) )

The only difference LWIP_DHCP_CHECK_LINK_UP makes is that DHCP is not 
trying to send discover frames if link is down and then wait for a link 
up event, otherwise we are sending discover frames whatever the current 
link state is. The dhcp_network_changed() call just speed it up by 
cancelling retry timeout.


Indeed, DHCP without LWIP_DHCP_CHECK_LINK_UP does not care about current 
link state, I should have mentioned that. So it should work whatever the 
current shape of your link up/down events handler is.


Sylvain

signature.asc
Description: Digital signature