Date:	Wed, 6 Jan 2016 16:18:03 +0800
From:	zhuyj <zyjzyj2000@...il.com>
To:	Wengang Wang <wen.gang.wang@...cle.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] net: take care of bonding in build_skb_flow_key

On 01/06/2016 04:14 PM, Wengang Wang wrote:
>
>
> 在 2016年01月06日 16:00, zhuyj 写道:
>> On 01/06/2016 03:45 PM, Wengang Wang wrote:
>>>
>>>
>>> 在 2016年01月06日 15:35, zhuyj 写道:
>>>> IMHO, "The path MTU is set to the active slave device, not the 
>>>> bonding master."
>>>> Can we set PMTU to bonding master when path MTU is set to the 
>>>> active slave device?
>>>>
>>> Actually the route is set on bonding master, not on any slave, the 
>>> trying to set PMTU to the active slave failed(it didn't found a 
>>> route on slave).
>> In your commit log:
>>
>> "
>> A problem is found that we are looking for route basing a bonding 
>> device and
>> deal with path MTU there: The path MTU is set to the active slave 
>> device, not
>> the bonding master.
>> "
>>
>> and
>>
>> "the trying to set PMTU to the active slave failed"
>>
>> I am confused.
>>
>
> Maybe changing "The path MTU is set to the active slave device, not 
> the bonding master" to
> "The path MTU is tried to set to the active slave device, not to the 
> bonding master" is better.
Maybe you should explain your problem clearly.

Zhu Yanjun
>
> It tried to change the PMTU to the slave. Whether the setting can 
> succeed depends:
> if the route is there(on slave), it goes successfully; if not no route 
> found, it goes unsuccessfully.
> For the no-route case, your suggestion breaks.
>
> thanks,
> wengang
>
>> Zhu Yanjun
>>
>>> So "set PMTU to bonding master when path MTU is set to the active 
>>> slave device" is lacking a base.
>>>
>>> thanks,
>>> wengang
>>>
>>>> If not appropriate, you can ignore it.
>>>>
>>>> Best Regards!
>>>> Zhu Yanjun
>>>>
>>>> On 01/06/2016 03:06 PM, Wengang Wang wrote:
>>>>> Hi Yanjun,
>>>>>
>>>>> Thanks for your review.
>>>>> Master MTU is same as that for slaves.
>>>>> Maybe fixing in bonding driver is a good idea, but I don't find a 
>>>>> good place to do that.
>>>>> Let's go through the simplified follow:
>>>>>
>>>>> ...
>>>>> 1) Fragmentation.
>>>>>    --This is is done is against the bonding master device(device 
>>>>> MTU and path MTU)
>>>>> 2) bond_start_xmit
>>>>> 3) ipoib_start_xmit(slaves are IPoIB interfaces)
>>>>>
>>>>> For the first send
>>>>> 1) fragment size is 7000(in my case)
>>>>> 2) bond_start_xmit its self is fine
>>>>> 3) ipoib_start_xmit sees the packet size 7000 is larger than the 
>>>>> internal limit 2044, drops the packet and try to update PMTU.
>>>>>     without the patch, it tried update PMTU on slave device(no 
>>>>> changes to master).
>>>>>
>>>>> the seconds send comes, since no changes happen on bonding 
>>>>> master(PMTU), the fragment size is still 7000 and the behavior is 
>>>>> just the same as the first send.
>>>>>
>>>>> With the patch, the bonding master PMTU is changed to 2044 after 
>>>>> the first send(hopefully), for the seconds send the fragment size 
>>>>> is set to 2044.
>>>>>
>>>>> To fix in bonding code, I don't find where we can.
>>>>>
>>>>> thanks,
>>>>> wengang
>>>>>
>>>>> 在 2016年01月06日 14:19, zhuyj 写道:
>>>>>>
>>>>>> IMHO, this should fix in bonding driver because the active slave 
>>>>>> mtu should be the same with the master.
>>>>>> bonding master's mtu is changed to path MTU, then slave dev's MTU 
>>>>>> should be changed, too.
>>>>>>
>>>>>> Zhu Yanjun
>>>>>> On 01/06/2016 01:49 PM, Wengang Wang wrote:
>>>>>>> A problem is found that we are looking for route basing a 
>>>>>>> bonding device and
>>>>>>> deal with path MTU there: The path MTU is set to the active 
>>>>>>> slave device, not
>>>>>>> the bonding master.
>>>>>>>
>>>>>>> The patch tries to fix the issue by letting build_skb_flow_key() 
>>>>>>> take care
>>>>>>> of the transition of device index from bonding slave to the master.
>>>>>>>
>>>>>>> Signed-off-by: Wengang Wang <wen.gang.wang@...cle.com>
>>>>>>> ---
>>>>>>>   net/ipv4/route.c | 11 ++++++++++-
>>>>>>>   1 file changed, 10 insertions(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
>>>>>>> index 85f184e..3053f10 100644
>>>>>>> --- a/net/ipv4/route.c
>>>>>>> +++ b/net/ipv4/route.c
>>>>>>> @@ -523,11 +523,20 @@ static void build_skb_flow_key(struct 
>>>>>>> flowi4 *fl4, const struct sk_buff *skb,
>>>>>>>                      const struct sock *sk)
>>>>>>>   {
>>>>>>>       const struct iphdr *iph = ip_hdr(skb);
>>>>>>> -    int oif = skb->dev->ifindex;
>>>>>>> +    int oif;
>>>>>>> +    struct net_device *master = NULL;
>>>>>>> +
>>>>>>>       u8 tos = RT_TOS(iph->tos);
>>>>>>>       u8 prot = iph->protocol;
>>>>>>>       u32 mark = skb->mark;
>>>>>>>   +    if (skb->dev->flags & IFF_SLAVE)
>>>>>>> +        master = netdev_master_upper_dev_get(skb->dev);
>>>>>>> +    if (master)
>>>>>>> +        oif = master->ifindex;
>>>>>>> +    else
>>>>>>> +        oif = skb->dev->ifindex;
>>>>>>> +
>>>>>>>       __build_flow_key(fl4, sk, iph, oif, tos, prot, mark, 0);
>>>>>>>   }
>>>>>>
>>>>>
>>>>
>>>
>>
>

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