netdev - Re: [PATCH net-next 4/4] net: Don't clear skbuff hash for IP fragments

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Date:	Fri, 21 Mar 2014 15:41:07 -0700
From:	Tom Herbert <therbert@...gle.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 4/4] net: Don't clear skbuff hash for IP fragments

On Thu, Mar 20, 2014 at 6:47 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2014-03-20 at 17:09 -0700, Tom Herbert wrote:
>> There is nothing to gain by clearing hash, it shouldn't be an L4
>> hash anyway.
>>
>> Signed-off-by: Tom Herbert <therbert@...gle.com>
>> ---
>>  net/ipv4/ip_fragment.c | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
>> index c10a3ce..10a64de 100644
>> --- a/net/ipv4/ip_fragment.c
>> +++ b/net/ipv4/ip_fragment.c
>> @@ -704,7 +704,6 @@ struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user)
>>                       memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
>>                       if (ip_defrag(skb, user))
>>                               return NULL;
>> -                     skb_clear_hash(skb);
>>               }
>>       }
>>       return skb;
>
> It might be worth checking ip_defrag() will set skb->hash to the hash
> provided in the first fragment, the one that might give l4 info...
>
I believe we're already getting this, the head fragment which might
contain the l4_hash is being cloned into the skb for processing packet
in the stack.

>
>
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