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Re: NKEs on Intel-based Macs
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Re: NKEs on Intel-based Macs


  • Subject: Re: NKEs on Intel-based Macs
  • From: "Peter Sichel" <email@hidden>
  • Date: Mon, 21 Aug 2006 17:39:51 -0400

Josh,

Thanks for taking the time to investigate.

On 8/21/06, Josh Graessley wrote:

>Unless there are bugs, the calls to mbuf_inbound_modified and
>mbuf_clear_csum_requested should not be required. In addition, if you
>don't want the stack to calculate the checksums, it should be possible
>to to just call mbuf_clear_csum_request.

In my testing, there were bugs that forced me to add the call to
mbuf_inbound_modified() in order to get it to work reliably.  The bugs
were subtle relating to what happens if you bridge or forward a packet
arriving on one data-link back out the same data-link or another one
(who is supposed to reset these flags when an mbuf gets re-used and
possibly turned around because IP forwarding is enabled?).  Testing the
simple case of sending and receiving TCP/IP over a single data-link
might not reveal the problem.

>mbuf_get_csum_requested: Intended for use by drivers. The stack will set
>flags indicating what checksums were postponed to be done in hardware.
>This is the function for the driver to pull this meta data out of the
>mbuf and convey that to the hardware as appropriate.

When I tested this (around 10.4.2), the flags returned correspond to the
Panther defined BSD constants, not what is documented in the KPI
reference or header files.

I realize this stuff is pretty obscure, but not fixing it creates bugs
that other developers end up stumbling over the hard way.

Kind Regards,

- Peter


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  • Follow-Ups:
    • Re: NKEs on Intel-based Macs
      • From: David A Rowland <email@hidden>
References: 
 >NKEs on Intel-based Macs (From: "Peter Lovell" <email@hidden>)
 >Re: NKEs on Intel-based Macs (From: Josh Graessley <email@hidden>)
 >Re: NKEs on Intel-based Macs (From: David A Rowland <email@hidden>)
 >Re: NKEs on Intel-based Macs (From: David A Rowland <email@hidden>)
 >Re: NKEs on Intel-based Macs (From: Josh Graessley <email@hidden>)
 >Re: NKEs on Intel-based Macs (From: "Peter Sichel" <email@hidden>)
 >Re: NKEs on Intel-based Macs (From: David A Rowland <email@hidden>)
 >Re: NKEs on Intel-based Macs (From: "Peter Sichel" <email@hidden>)
 >Re: NKEs on Intel-based Macs (From: David A Rowland <email@hidden>)
 >Re: NKEs on Intel-based Macs (From: David A Rowland <email@hidden>)
 >Re: NKEs on Intel-based Macs (From: Josh Graessley <email@hidden>)

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