[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[lwip-devel] Re: DHCP option "Requested IP"
From: |
Jakob Stoklund Olesen |
Subject: |
[lwip-devel] Re: DHCP option "Requested IP" |
Date: |
Mon, 21 Sep 2009 20:27:00 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.0.91 (gnu/linux) |
Fabian Koch <address@hidden> writes:
> No I explicitly want to use the DHCP Option Code 50, which suggests an IP to
> the DHCP server while doing
> DISCOVER and REQUEST.
I see. Since REQUEST packets already contain option 50, I assume you
only want to change DISCOVER packets.
Note that REQUEST packets contain dhcp->offered_ip_addr while you propose
to send netif->ip_addr in DISCOVER packets.
> This is explained in RFC 2132. I'm just looking for a smooth way to integrate
> this into LwIP without changing
> too much code and especially any APIs.
> So I figured it would be nice to get your netif set up and give it the
> desired IP and send it to dhcp_start(),
> which calls dhcp_discover() and then the set IP is used for the DISCOVER and
> REQUEST packets inside the options
> field.
RFC 2131 explicitly allows option 50 in DISCOVER packets, so I don't see
anything wrong with your idea. As Kieran suggested, you may want to
consider a way of enabling this per netif.
> So if the Server agrees with your desired IP and it's free, he will OFFER it
> and ACK it.
You also talked about sending DHCP_INFORM, so I should warn you that it
is not the same thing.
INFORM tells the server that you are using a manually configured
address.
DISCOVER with option 50 is a polite hint to the server to please offer
the suggested address. The server is free to offer any address it pleases.
>
> Doesn't have to do anything with a reboot or lease.
>
> My question was: is the LwIP crew okay with that approach?
I think it sounds OK. You should definitely submit a patch.
You may not want to clear the netif->ip_addr in dhcp_discover(). It is
called multiple times on retransmissions.
/jakob