netdev - Re: [PATCH] IPV4: add raw drops counter

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Message-ID: <473A4EF2.5090507@cn.fujitsu.com>
Date:	Wed, 14 Nov 2007 09:27:14 +0800
From:	Wang Chen <wangchen@...fujitsu.com>
To:	Eric Dumazet <dada1@...mosbay.com>
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH] IPV4: add raw drops counter

Eric Dumazet said the following on 2007-11-13 19:11:
> Wang Chen a écrit :
>> Add raw drops counter for IPv4 in /proc/net/raw .
>>
>> +    atomic_t        sk_drops;
>>   
> This doesnt need an atomic_t , just an 'unsigned int' is OK, since
> sock_queue_rcv_skb() is called on a locked socket.
> 

Yes, sock_queue_rcv_skb() is called on a locked socket. But sk_drops
will not only used with sock_queue_rcv_skb(), but also with 
xfrm4_policy_check(), skb_checksum_complete(), skb_kill_datagram(),etc.
So, atomic_t ensure sk_drops will be atomic increment.

> Also, I suggest doing the sk_drops increment in sock_queue_rcv_skb() so
> that it can be used for other sockets as well ?
> 

As I described before, sk_drops will be used on different conditions,
on which the raw drop happens.
So doing sk_drops increment in upper caller is better than in 
sock_queue_rcv_skb().

Thank you for your suggestion, I will make a new patch to add sk_drops
increment in other places.

> I like having this counter per socket, but only if an application can
> retrieve its value with a getsockopt() call, dont you think ?
> 
> getsockopt(sock, SOL_SOCKET, SO_DROPSCNT, &val, &vallen);
> 
> 

Yes. I agree.
How do other people think about it?

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