netdev - Re: [PATCH] snmp: add missing counters for RFC 4293

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Date:	Wed, 22 Apr 2009 07:17:53 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Neil Horman <nhorman@...driver.com>
CC:	netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH] snmp: add missing counters for RFC 4293

Neil Horman a écrit :
> On Tue, Apr 21, 2009 at 10:45:49PM +0200, Eric Dumazet wrote:
>> Neil Horman a écrit :
>>> On Tue, Apr 21, 2009 at 09:58:51PM +0200, Eric Dumazet wrote:
>>>> Neil Horman a écrit :
>>>>> The IP MIB (RFC 4293) defines stats for InOctets, OutOctets, InMcastOctets and
>>>>> OutMcastOctets:
>>>>> http://tools.ietf.org/html/rfc4293
>>>>> But it seems we don't track those in any way that easy to separate from other
>>>>> protocols.  This patch adds those missing counters to the stats file.  Tested
>>>>> successfully by me
>>>>>
>>>>> Signed-off-by: Neil Horman <nhorman@...driver.com>
>>>>>
>>>>>
>>>>>  include/linux/snmp.h  |    4 ++++
>>>>>  net/ipv4/ip_input.c   |    4 ++++
>>>>>  net/ipv4/ip_output.c  |    3 +++
>>>>>  net/ipv4/proc.c       |    4 ++++
>>>>>  net/ipv6/ip6_input.c  |    4 ++++
>>>>>  net/ipv6/ip6_output.c |    8 ++++++++
>>>>>  net/ipv6/mcast.c      |    9 +++++++++
>>>>>  net/ipv6/ndisc.c      |    3 +++
>>>>>  net/ipv6/proc.c       |    4 ++++
>>>>>  net/ipv6/raw.c        |    6 ++++++
>>>>>  10 files changed, 49 insertions(+)
>>>>>
>>>>> diff --git a/include/linux/snmp.h b/include/linux/snmp.h
>>>>> index aee3f1e..95c17f6 100644
>>>>> --- a/include/linux/snmp.h
>>>>> +++ b/include/linux/snmp.h
>>>>> @@ -19,6 +19,8 @@ enum
>>>>>  {
>>>>>  	IPSTATS_MIB_NUM = 0,
>>>>>  	IPSTATS_MIB_INRECEIVES,			/* InReceives */
>>>>> +	IPSTATS_MIB_INOCTETS,			/* InOctets */
>>>>> +	IPSTATS_MIB_INMCASTOCTETS,		/* InMcastOctets */
>>>>>  	IPSTATS_MIB_INHDRERRORS,		/* InHdrErrors */
>>>>>  	IPSTATS_MIB_INTOOBIGERRORS,		/* InTooBigErrors */
>>>>>  	IPSTATS_MIB_INNOROUTES,			/* InNoRoutes */
>>>>> @@ -29,6 +31,8 @@ enum
>>>>>  	IPSTATS_MIB_INDELIVERS,			/* InDelivers */
>>>>>  	IPSTATS_MIB_OUTFORWDATAGRAMS,		/* OutForwDatagrams */
>>>>>  	IPSTATS_MIB_OUTREQUESTS,		/* OutRequests */
>>>>> +	IPSTATS_MIB_OUTOCTETS,			/* OutOctets */
>>>>> +	IPSTATS_MIB_OUTMCASTOCTETS,		/* OutMcastOctets */
>>>>>  	IPSTATS_MIB_OUTDISCARDS,		/* OutDiscards */
>>>>>  	IPSTATS_MIB_OUTNOROUTES,		/* OutNoRoutes */
>>>>>  	IPSTATS_MIB_REASMTIMEOUT,		/* ReasmTimeout */
>>>>> diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
>>>>> index 1a58a6f..bc9169b 100644
>>>>> --- a/net/ipv4/ip_input.c
>>>>> +++ b/net/ipv4/ip_input.c
>>>>> @@ -385,6 +385,7 @@ int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
>>>>>  		goto drop;
>>>>>  
>>>>>  	IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INRECEIVES);
>>>>> +	IP_ADD_STATS_BH(dev_net(dev), IPSTATS_MIB_INOCTETS, skb->len);
>>>>>  
>>>>>  	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) {
>>>>>  		IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
>>>>> @@ -396,6 +397,9 @@ int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
>>>>>  
>>>>>  	iph = ip_hdr(skb);
>>>>>  
>>>>> +	if (ipv4_is_multicast(iph->daddr))
>>>>> +		IP_ADD_STATS_BH(dev_net(dev), IPSTATS_MIB_INMCASTOCTETS, skb->len);
>>>>> +
>>>>>  	/*
>>>>>  	 *	RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum.
>>>>>  	 *
>>>>> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
>>>>> index 3e7e910..8a68dc2 100644
>>>>> --- a/net/ipv4/ip_output.c
>>>>> +++ b/net/ipv4/ip_output.c
>>>>> @@ -245,6 +245,8 @@ int ip_mc_output(struct sk_buff *skb)
>>>>>  	 *	If the indicated interface is up and running, send the packet.
>>>>>  	 */
>>>>>  	IP_INC_STATS(dev_net(dev), IPSTATS_MIB_OUTREQUESTS);
>>>>> +	IP_ADD_STATS_BH(dev_net(dev), IPSTATS_MIB_OUTOCTETS, skb->len);
>>>>> +	IP_ADD_STATS_BH(dev_net(dev), IPSTATS_MIB_OUTMCASTOCTETS, skb->len);
>>>> So you use the _BH variant right after IP_INC_STATS() ?
>>>> Which one is right (or which one is false ?)
>>>>
>>> Both are correct (right now), at least as far as I can tell.  I'm not 100% sure why ADD
>>> was named ADD_BH, except for the fact that it doesn't toggle the use of the mib
>>> array passed in.  I think the right solution would be to simply rename
>>> IP_ADD_STATS_BH to IP_ADD_STATS, and modify its implementation to access
>>> mib[!in_softirq()] rather than just mib[0].  I had planned to do this in a
>>> followup cleanup patch.  Alternatively, I could add a new IP_ADD_STATS to be
>>> complete, but I don't really see the advantage (asside from not checking
>>> in_softirq quite as often).
>>>
>> Both usages in the same function cannot be correct.
>>
>> Either you use _BH variant because you know you are in softirq
>> (and non preemptable) context.
>>
>> Either you use non_BH variant because you are in possibly preemptable context.
>>
>> Mixing both just proves there is a problem.
>>
>> And we use _BH variant because it is currently faster (this might change in 2.6.31
>> thanks to per_cpu infra changes)
>>
>>
>>
> Yeah, Self-NAK.  I'm sorry, you're right. I had myself convinced it didn't
> really matter in the use-cases, but looking back over it, I'm not sure what I
> was thinking.  I need to implement IP_ADD_STATS (currently it doesn't exist),
> and replace all the use cases in this patch.  Simple enough.  I'll repost in the
> AM. 
> 
> Thanks for the whack with the clue stick :)

You are welcome.

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