netdev - Re: [PATCH 1/2] [IPV4] UDP: Always checksum even if without socket filter

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Date:	Thu, 29 Nov 2007 15:55:38 +0800
From:	Wang Chen <wangchen@...fujitsu.com>
To:	David Miller <davem@...emloft.net>
CC:	andi@...stfloor.org, billfink@...dspring.com,
	herbert@...dor.apana.org.au, netdev@...r.kernel.org,
	gerrit@....abdn.ac.uk, bfields@...ldses.org, neilb@...e.de,
	okir@...ad.swb.de, Wang Chen <wangchen@...fujitsu.com>
Subject: Re: [PATCH 1/2] [IPV4] UDP: Always checksum even if without socket
 filter

David Miller said the following on 2007-11-21 9:39:
> From: Andi Kleen <andi@...stfloor.org>
> Date: Tue, 20 Nov 2007 15:05:18 +0100
> 
>> On Tue, Nov 20, 2007 at 12:29:45AM -0500, Bill Fink wrote:
>>> While I agree with your analysis that it could be worked around,
>>> who knows how all the various SNMP monitoring applications out there
>>> would interpret such an unusual event.  I liked Stephen's suggestion
>>> of a deferred decrement that would insure the counter didn't ever
>>> run backwards.  But the best approach seems to be just not to count
>>> it in the first place until tha application has actually received
>>> the packet, since as Herbert pointed out, that's what the RFC
>>> actually specifies for the meaning of the udpInDatagrams counter.
>> Together with another counter that counts "edge datagrams received"
>> that would be an excellent idea.
>>
>> Here's a patch.
> 
> NFS and friends that use the ->data_ready() callback needs to
> be updated as well.  Please fix this and resubmit, thanks.
> 

I tested nfsv3 & nfsv4. It seems that nfs calls recvmsg() like
following:nfsd()->svc_recv()->svc_udp_recvfrom()->udp_recvmsg().
So, I think putting the udpInDatagrams increment in udp_recvmsg()
is enough.

FYI:
http://www.mail-archive.com/netdev@vger.kernel.org/msg13817.html


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