From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [ PATCH 2.6.17-rc6 1/1] udp.c: counting InDatagrams which are
 never delivered
Date: Sun, 11 Jun 2006 21:29:13 -0700 (PDT)
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From: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Date: Tue, 6 Jun 2006 19:25:40 +0100

> Fix:   Move the `UDP_INC_STATS_BH(UDP_MIB_INDATAGRAMS)' statement from 
>        udp_queue_rcv_skb to udp_recvmsg. Now InDatagrams only counts those
>        datagrams which were really delivered (as per RFC 2013). 
> 
> Please CC: any correspondence to gerrit@erg.abdn.ac.uk  
> 
> Signed-off-by: <gerrit@erg.abdn.ac.uk>

Unfortunately this breaks NFS and other in-kernel UDP socket usages,
which never call recvmsg() and instead take the packet via the
->data_ready() callback done by sock_queue_receive_skb().

Your patch will make the counter never get incremented when such
a user is using the UDP socket.

Probably a better way to handle this is to correct the
INDATAGRAMS value by decrementing it when we notice that
the checksum is incorrect in a deferred manner.