netdev - Re: [PATCH net] ipv6: omit traffic class when calculating flow hash

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Date:   Fri, 1 Jun 2018 11:55:17 -0600
From:   David Ahern <dsahern@...il.com>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>,
        Tom Herbert <tom@...bertland.com>
Subject: Re: [PATCH net] ipv6: omit traffic class when calculating flow hash

On 6/1/18 11:51 AM, Michal Kubecek wrote:
> On Fri, Jun 01, 2018 at 10:42:10AM -0600, David Ahern wrote:
>>
>> Can you make an inline for the flowlabel conversion. Something like this:
>>
>> diff --git a/include/net/ipv6.h b/include/net/ipv6.h
>> index 798558fd1681..e36eca2f8531 100644
>> --- a/include/net/ipv6.h
>> +++ b/include/net/ipv6.h
>> @@ -284,6 +284,11 @@ struct ip6_flowlabel {
>>  #define IPV6_FLOWLABEL_MASK            cpu_to_be32(0x000FFFFF)
>>  #define IPV6_FLOWLABEL_STATELESS_FLAG  cpu_to_be32(0x00080000)
>>
>> +static inline u32 flowi6_get_flowlabel(const struct flowi6 *fl6)
>> +{
>> +       return (__force u32)(fl6->flowlabel & IPV6_FLOWLABEL_MASK);
>> +}
>> +
>>  #define IPV6_TCLASS_MASK (IPV6_FLOWINFO_MASK & ~IPV6_FLOWLABEL_MASK)
>>  #define IPV6_TCLASS_SHIFT      20
>>
>> From there we can fix the flow struct to have flowinfo instead of
>> flowlabel and use the macro to hide the conversion.
> 
> I'll send v2 with inline helper. I'm just not sure about including the
> cast as this way the helper would be useful for hash key which is not
> clear from the name. So it seems more appropriate to either introduce a
> helper which just does the masking or helper which does also the copying
> into struct flow_keys.
> 

I think the cast should stay in the helper. See the RFC patch flipping
the name from flowlabel to flowinfo. Makes the code the more readable IMHO.