Re: Need some help with IP/TCP Checksum Offload

[Benjamin LaHaise]

On Fri, Feb 22, 2002 at 02:57:22PM -0800, [e-mail] wrote:
> 
>  Then, in my start_xmit( ) routine, i am parsing for the right
> headers & when i get the IP/TCP header, i print out the checksum 
> & it is already the right checksum. When does the OS/Protocol 
> offload this task? Am i missing something here?

The network stack generates checksums for packets while copying, 
so the checksum offload feature is only used for packets that are 
not copied.  The easiest way to generate packets of this nature 
is to use the sendfile() syscall to transmit data from the page 
cache directly onto the wire.  If you need a couple of test 
programs I can forward a few to you offline.  Cheers,

		-ben