[Devel] Re: [patch 1/2][NETNS][RFD] store the network namespace pointer in the dst_entry structure

[Daniel Lezcano]

Benjamin Thery wrote:
> Eric W. Biederman wrote:
>> Daniel Lezcano <dlezcano at fr.ibm.com> writes:
>>
>>>> Could you please place the struct net *net pointer up by the
>>>> network device pointer.
>>>>>  };
>>>> I know we need a net pointer in struct rt_table, because it
>>>> is a hash table that we can't dynamically allocate so we need
>>>> to place a network namespace pointer as part of the hash key.
>>>>
>>>> For the ipv6 fib tables I don't recall needing a net pointer as we didn't have
>>>> a hash table and could instead have separate
>>>> roots for different namespaces.
>>> Yes don't need for the hash table but we used it to pass the network namespace
>>> parameter to the underlying function which need the net parameter.
>>>
>>> We are facing two problems when removing the fl_net field from flowi:
>>>
>>>  * The first one is the fl_net is used as a key. This problem can be handled
>>> simply in moving the netns to the rtable.
>> Yes.
>>
>>>  * The second one is the usage made by the fl_net to pass through the different
>>> function calls the network namespace pointer without changing all functions
>>> signature. This problem can be solved if we put the netns pointer in the
>>> dst_entry structure, so when we are in ipv4, we use container_of on rtable and
>>> when we are in ipv6, we use the container_of on rt6_info. So everywhere with the
>>> flowi, we can retrieve the netns.
>> That doesn't work as rt6_info does not currently hold a struct flowi.
>>
>>>> I find this slightly odd as I didn't wind up needing to add
>>>> a struct net pointer in struct dst in my proof of concept tree
>>>> and struct dst doesn't have a struct flowi so that would not
>>>> have prevented it.
>>> The idea is to put the net in the dst_entry because it is accessible from rtable
>>> or rt6_info and these ones contain a flowi field.
>> And since that isn't true, the idea seems to fall flat on it's face.
> 
> My fault. 
> While talking with Daniel last week I suggested to put the net in 
> dst_entry instead of rtable, because dst_entry was common to rtable
> and rt6_info. I thought we could factorize some code this way. I
> wrongly assumed IPv6 was pretty similar to IPv4 in the way it handles 
> flowi. I should have checked that more carefully. Crap ;)

Me too :)
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