netdev - Re: [PATCH net-next 4/6] bonding: don't validate arp if we don't have to

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Date:	Thu, 20 Jun 2013 15:43:51 +0200
From:	Nikolay Aleksandrov <nikolay@...hat.com>
To:	Veaceslav Falico <vfalico@...hat.com>
CC:	netdev@...r.kernel.org, fubar@...ibm.com, andy@...yhouse.net,
	davem@...emloft.net, linux@...2.net, nicolas.2p.debian@...e.fr,
	rick.jones2@...com
Subject: Re: [PATCH net-next 4/6] bonding: don't validate arp if we don't
 have to

On 06/20/2013 10:43 AM, Veaceslav Falico wrote:
> On Thu, Jun 20, 2013 at 12:19:04AM +0200, Nikolay Aleksandrov wrote:
>> On 19/06/13 19:34, Veaceslav Falico wrote:
>>> Currently, we validate all the incoming arps if arp_validate not 0.
>>> However, we don't have to validate backup slaves if arp_validate == active
>>> and vice versa, so return early in bond_arp_rcv() in these cases.
>>>
>>> It works correctly now because we verify arp_validate in slave_last_rx(),
>>> however we're just doing useless work in bond_arp_rcv().
>>>
>>> Signed-off-by: Veaceslav Falico <vfalico@...hat.com>
>>> ---
>>>  drivers/net/bonding/bond_main.c |    4 ++++
>>>  1 files changed, 4 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>>> index b69c7f0..2cfbb2e 100644
>>> --- a/drivers/net/bonding/bond_main.c
>>> +++ b/drivers/net/bonding/bond_main.c
>>> @@ -2624,6 +2624,10 @@ static int bond_arp_rcv(const struct sk_buff *skb,
>>> struct bonding *bond,
>>>          return RX_HANDLER_ANOTHER;
>>>
>>>      read_lock(&bond->lock);
>>> +
>>> +    if (!slave_do_arp_validate(bond, slave))
>>> +        goto out_unlock;
>>> +
>>>      alen = arp_hdr_len(bond->dev);
>>>
>>>      pr_debug("bond_arp_rcv: bond %s skb->dev %s\n",
>> Hm, I think this issue runs deeper because recv_probe can be wrong and
>> also if arp_validate is enabled while the bond is running then
>> recv_probe is not set (or unset for that matter if disabled). I have a
>> patch which needs little more work for some time now in my queue that
>> fixes this, but if you'd like to fix it I'd suggest addressing that
>> issue (recv_probe), because then you can just drop these checks and
>> improve performance when disabled (after it's been enabled).
> 
> Yup, recv_probe value is really poorly synced with the arp_validate, I'll
> try to take a look at it when I have time and in case you won't fix it by
> that time :).
> 
> However, I don't think we should drop this check even in this case. This
> check just verifies if we should validate this exact slave - being it
> active or backup, and considering the value of arp_validate (which can be
> active/backup/both).
> 
> Maybe I've understood you wrong, though :).
> 
>> This got a bit confusing when I read it :-)
>>
>> Cheers,
>> Nik
I agree with this patch, I didn't mean to drop it :-) My intention was more to
augment it to include the fix for recv_probe as well. But that is not critical
so it can be done at a later time.

Cheers,
 Nik
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