Re: TCP checksum and device driver eri0

On Fri, Jun 27, 2003 at 04:30:41PM +0200, Giovanni Porcelli wrote:
> During a snoop session on a 280R with solaris 9 and network interface

The ERI interface calculates the checksum in hardware, so at the point in the stack where snoop is reading the data the checksum is indeed incorrect, but it will be calculated and updated before it leaves the physical interface. This is done for the fairly obvious performance improvement it provides.

> If I want to snoop locally *but* with the correct checksum value, how

The only way to see the correct checksum on the outgoing packets is to disable hardware checksum calculations by adding the following to /etc/system and rebooting :
set ip:dohwcksum=0

Obviously doing this will have a performance hit on the system.

  Scott Received on Wed Jul 2 11:21:00 2003