RE: [lwip-devel] UDP traffic without checksum

[Kjell Andersson XW (LM/EAB)]

Found it. I think UDP-sending without checksum is implemented too by setting 
the UDP_FLAGS_NOCHKSUM in pcb->flags.
I wonder why I didn't find this in the first place :)

 / Kjell

From: Kieran Mansley

On Fri, 3 Oct 2003, Kjell Andersson XW (LM/EAB) wrote:

> I was reading RFC 768 - User Datagram Protocol. 
> (http://www.faqs.org/rfcs/rfc768.html)
>
> The RFC states: "An all zero transmitted checksum value means that the
> transmitter generated no checksum (for debugging or for higher level
> protocols that don't care)."
>
> Does lwIP currently support reception of UDP traffic with a zero checksum?
> Can it be configured to send with a zero checksum?
>
> I don't seem to find the code that handles it.

src/core/udp.c

It supports receiving a packet with a zero checksum (it doesn't perform
any other checks if it's zero) but there's no way currently to configure
lwip to not checksum outgoing UDP data.  It would be a very easy change to
make if you need to though - take a look at udp_send() in src/core/udp.c

Kieran



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