lwIP configuration option patch

[Andrew Lunn]

On Thu, Mar 02, 2006 at 09:23:50AM +0100, Uwe Kindler wrote:
> Hello Andrew,
> 
> I never used DHCP with lwIP here so I never discovered this problem. I 
> used a fixed IP address to run the tests. Today I compiled the tests 
> with DHCP support and tried to debug them but insight did not list the 
> dhcp.c file in its sources. I inserted an #error message into the dhcp.c 
> file to check if it is built - it is. So it must be linker garbage 
> collection because the dhcp functions are simply not referenced anywhere 
> in the code. I checked the lwip code and there is not initialisation for 
> dhcp and also the timer functions dhcp_fine_tmr() and dhcp_coarse_tmr() 
> are never called.
> 
> So obviously Jani Monoses, who contributed the original lwIP patch, also 
> never used DHCP ;o) I will try to add DHCP support as soon as I have the 
> time (maybe in some weeks). At least my patch did not broke DHCP support 
> - so please try a fixed IP address when testing.

Well the problem was not really DHCP, but it does not work as you say.

The problem i was having is that the synth build did not add the
ethernet interface. This turned out to be a CDL problem. Normally
net/common/current/cdl/net.cdl declares the interface
CYGPKG_NET_STACK. However lwip does not use this package. So the
interface was missing and nothing implemented the interface.  The
synth eth driver is only compiled when the interface is implemented.
So i added the interface to the lwip CDL file. 

Using static IP addresses the httpd test worked.

        Andrew