RE: Regarding the __netpoll_rx function in 2.6.21 kernel

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Hi Pradeep,
Which socket queues do you mean? When we already have a protocol handler for
the 


Regards,
Rajendra Stalekar(extn 2016)
Location:- Akruti
Mobile no:- +91 9860501143
 

-----Original Message-----
From: kernelnewbies-bounce@xxxxxxxxxxxx
[mailto:kernelnewbies-bounce@xxxxxxxxxxxx] On Behalf Of pradeep singh
Sent: Wednesday, July 04, 2007 2:56 PM
To: rajendra.stalekar@xxxxxxxxx
Cc: kernelnewbies@xxxxxxxxxxxx
Subject: Re: Regarding the __netpoll_rx function in 2.6.21 kernel

On 7/4/07, Rajendra Stalekar <rajendra.stalekar@xxxxxxxxx> wrote:
> Hi,
>
> I find that in the __netpoll_rx function in the netpoll.c , the
> iph->protocol is only checking for the UDP protocol in the transport layer
> for getting the true length of the frame.
>
> Why is this check not done for IPPROTO_TCP?
More important is why do you need even the UDP length at ethernet
layer at all during receiving????

AFAICS, this is something for better performance.
If you have a bad packet there is no point is pushing it to upper
layers, because eventually they 'll also reject it. Doing it
prematurely means less headache because of a supposedly bad packet.
Thats why there is even a fast checksum calculation for the packet few
lines below.

OTOH, tcp layer is a connection oriented protocol. If you discard the
packet this way here only, how are the pending socket queues coming to
know that packet was a bad seed???
They need to be carried up to the TCP layer for checking because of
the nature of the TCP protocol.

UDP is a conncetion less and UDP layer don't care if there is no
notification of packet dropping.

I may be wrong , so feel free to correct me.

Thanks
~psr

-- 
play the game

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