[En-Nut-Discussion] DHCP problems

[Joe Doubek]

Harald, 

I have the same problem on a device that has no easy way to cycle the
power. If I intervene I can send a packet to renew the address by
allowing the watchdog to timeout. But if I don't the device is just
stuck without a proper address. This issue is very serious to us because
our device is meant to stay on for extended periods of time and we have
potentially hundreds of such devices at a given location that would need
to be rebooted. Our devices are UDP only however, so we aren't worried
about TCP connections. Any tips on how to modify the code to accept the
new address without rebooting?


-----Original Message-----
From: en-nut-discussion-bounces at egnite.de
[mailto:en-nut-discussion-bounces at egnite.de] On Behalf Of Harald Kipp
Sent: Thursday, September 16, 2004 4:05 AM
To: Ethernut User Chat (English)
Subject: Re: [En-Nut-Discussion] DHCP problems 

Viktor,

this is probably a "missing feature" of the DHCP client
implementation. However, changing the DHCP code alone
won't help. Nut/Net has no provision to shut down its
interface and get it up again without reboot. This would
require major changes. For example, all existing TCP
sessions would become invalid.

Why is rebooting unacceptable?

Harald

At 11:28 16.09.2004 +0200, you wrote:
>Hi,
>
>This problem may be already solved since I am using ethernut v3.4.2,
but I 
>can't just upgrade because the program is already in the customer
system 
>and I have to find the way to patch it without any major changes.
>
>Set up:
>Ethernut <-> DHCP server.
>
>Problem:
>After reboot the program gets its network configuration using
>NutDhcpIfConfig ("eth0", my_mac, 0);
>and everything works just fine until the DHCP server admin changes the
IP 
>address for this MAC to a new one.
>
>For example:
>After reboot
>00:0c:30:d4:86:4e gets 192.168.250.10
>After some time the DHCP server changes the IP address for
>00:0c:30:d4:86:4e to 192.168.250.88.
>After that the Ethernut sends DHCPREQUEST packets to the server but
does 
>not see or does not accept the offers. I have checked with Ethereal and

>OFFER packets _do_ reach the Ethernut. If Ethernut is rebooted it
accepts 
>the new IP address and everything is just fine until the next change in

>the DHCP server configuration. The problem is that it's impossible to 
>restart the system every time there are some changes on the network.
>
>What do you think can be the problem?
>
>I am very thankful for any help, advice or idea.
>
>Regards,
>Viktor

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