Re: status in PACKET_RX_RING is actually a bit mask

["Michael Kerrisk (man-pages)" <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 04/24/2014 11:17 AM, Carsten Andrich wrote:
> I'd ack the patch, too.
> However if we start clarifying the bitmask situation, we should do it
> properly. packet.7 mentions TP_STATUS_xyz several times and never
> actually differentiates between setting bits and setting the whole
> tp_status variable. Actually both occurs inside the kernel:
> http://lingrok.org/xref/linux-net-next/net/packet/af_packet.c#798
> http://lingrok.org/xref/linux-net-next/net/packet/af_packet.c#2300
> 
> I could prepare another patch for review, that clarifies the tp_status
> usage for all references to TP_STATUS_xyz values.
> Unless Stefan would like to do this himself, since it's actually his
> "discovery" ;)

I'd be happy to receive a patch from either of you.

Cheers,

Michael


> Daniel Borkmann schrieb:
>> On 04/24/2014 10:04 AM, Michael Kerrisk (man-pages) wrote:
>>>> Now to your question. It can easily be seen from the if_packet.h header
>>>> file http://lingrok.org/xref/linux-net-next/include/uapi/linux/if_packet.h#93
>>>> that TP_STATUS_* are individual bits that are set in tp_status field.
>>>
>>> So, I take it that that's an Ack-for the patch by Stefan?
>>
>> Feel free to add my Ack. One nit below:
>>
>> diff --git a/man7/packet.7 b/man7/packet.7
>> index 1d3f222..6bac465 100644
>> --- a/man7/packet.7
>> +++ b/man7/packet.7
>> @@ -353,9 +353,9 @@ The packet socket owns all slots with status
>>  .BR TP_STATUS_KERNEL .
>>  After filling a slot, it changes the status of the slot to transfer
>>  ownership to the application.
>> -During normal operation, the new status is
>> -.BR TP_STATUS_USER ,
>> -to signal that a correctly received packet has been stored.
>> +During normal operation, the new status has the
>> +.BR TP_STATUS_USER
>> +bit set to signal that a correctly received packet has been stored.
>>
>> ^--- I would drop the 'correctly' here as it rather raises questions
>>      what 'incorrectly' would mean in this context.
>>
>>  When the application has finished processing a packet, it transfers
>>  ownership of the slot back to the socket by setting the status to
>>
>>
>>>
>>> Cheers,
>>>
>>> Michael
>>>
> 
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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