Jesper Skriver writes:
> On Tue, May 29, 2001 at 02:41:14PM -0500, Bob Willcox wrote:
> > Hi,
> >
> > I am working on a device driver for a GSN adapter that has hardware CRC
> > checking and need to know if there is a way to disable the software CRC
> > checking for TCP? This is on a FreeBSD 4.2-stable system.
>
Eegads. I think the original poster wanted to be able to use the
hardware CRC features of his nic, not ignore checksums altogther.
Bob -- Take a look at the /sys/pci/if_ti.c driver for an example of
how to use hardware checksum assist.
On the recieve side, you want to set the m_pkthdr.csum_flags
appropriately (depending on what your device can do) on each recieve,
as well as fill in the actual checksum in m_pkthdr.csum_data.
On the send side, you need to specify what your device is capable of
assisting with in the if_hwassist field of your driver's ifp struct.
Packets will come down w/o those fields filled in. The stack will
expect your device to calculate those fields in hardware.
I beleive these features appeared around 4.1, so if this is a 3rd
party driver, you may want to check __FreeBSD_version >= 410000.
Hope this helps,
Drew
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