Re: [lwip-users] DHCP recovery after network change

[Frédéric BERNON]

I wrote something like this in contrib/win32 port (see this port for the full code):

 

#if LWIP_NETIF_LINK_CALLBACK

void link_callback(struct netif *netif)

{ if (netif_is_link_up(netif)) {

    printf("link_callback==UP\n");

#if LWIP_DHCP

    if (netif->dhcp != NULL) {

        dhcp_renew(netif);

    }

#endif /* LWIP_DHCP */

  } else {

     printf("link_callback==DOWN\n");

  }

}

#endif /* LWIP_NETIF_LINK_CALLBACK */

 

But, with experience, it's faster and more efficient to replace "dhcp_renew(netif);" by a "dhcp_stop(netif);dhcp_start(netif);"

 

----- Original Message -----

From: "Jonathan Larmour" <address@hidden>

To: "Mailing list for lwIP users" <address@hidden>

Sent: Wednesday, February 20, 2008 5:13 PM

Subject: Re: [lwip-users] DHCP recovery after network change

Art R. wrote:
> If lwIP has acquired an IP addr by DHCP, and then 
the connection is switched
> from one network to another (think unplug 
from one subnet, walk across the
> hall, plug into different subnet), will 
it be able to release its current IP
> and acquire a new one? I.e., does 
it have that capability? Some preliminary
> tests we have done have not 
gone well...

It is meant to, although would not notice until the original 
DHCP lease
comes up for renewal. Higher level code could detect, for example, 
link
up/down events and check whether the network has 
changed.

Jifl
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