Re: How to verify RX checksum offload??
Re: How to verify RX checksum offload??
- Subject: Re: How to verify RX checksum offload??
- From: mm w <email@hidden>
- Date: Tue, 7 Jul 2009 06:34:00 +0200
Hello,
http://www.opensource.apple.com/source/IONetworkingFamily/IONetworkingFamily-12/IONetworkController.cpp
everything you asked is there
"cpstat.tcps_rcvbadsum's value has not increased" 8-)
Best,
On Tue, Jul 7, 2009 at 5:15 AM, Chfon<email@hidden> wrote:
> When checksum offload is enabled, the driver calls setChecksumResult method
> to encode the checksum result on the each received packet before passing it
> up towards the protocol stacks.
>
> I want to verify checksum value computed by the hardware on received packets
> is correct or not. It is really not easy for me. It is because if the
> hardware provides error checksum value, protocol stacks seems re-calculate
> no matter in full or partial checksum mode.
>
> For instance, in partial checksum mode, driver provides a partial 16-bit
> checksum value to allow the protocol stacks to calculate and verify the
> final checksum. But if the driver provides error partial checksum value, the
> protocol stacks seems re-calculate checksum value and without any signal or
> log to tell users, even tcpstat.tcps_rcvbadsum's value has not increased. So
> I could not know the checksum value that hardware provided is correct or
> not.
>
> Question:
>
> 1. Does the OSX shows any message or log to User while stacks indicates
> a bad checksum calculated by h/w?
>
> 2. In a received packet, from which byte to which byte is the partial
> checksum calculated?
>
> 3. Does the calculation of partial checksum include the trailer?
>
> 4. If CRC code is appended into each packet, does partial checksum have
> to be calculated the CRC code?
>
> 5. Does the driver need to provide partial checksum to all the
> protocols?
>
> Any reply would appreciated...
>
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