Re: [PATCH]IPv6:remove duplicate check of optlen when setsockopt with IPV6_PKTINFO option

[Shan Wei <shanwei@cn.fujitsu.com>]

Yang Hongyang said:
> Wei Yongjun wrote:
>> Yang Hongyang wrote:
>>> Herbert Xu wrote:
>>>  
>>>> Yang Hongyang <yanghy@cn.fujitsu.com> wrote:
>>>>    
>>>>> Actually the condition (optlen == 0) is included in (optlen <
>>>>> sizeof(struct in6_pktinfo)),
>>>>> so we do not need to check it separately.
>>>>>       
>>>> You don't need to check optval == NULL either since that's the
>>>> job of copy_from_user.
>>>>     
>>> If optval==NULL, what we should return?EINVAL or EFAULT?
>>> If it is EINVAL,then we should check it .otherwise it's the job of
>>> copy_from_user
>>>   
>> I think if optval==NULL, the in6_pktinfo which is set should be remove.
>> So, you should handle optval==NULL. Not just return error.
> 
> There's no RFC defines the behavior above,but:
>   RFC3542 said The application can remove any sticky Routing header or sticky 
> Destination options header or sticky Hop-by-Hop options header by calling 
> setsockopt() with a zero option length.
> 
> So,do we need to allow remove any sticky pktinfo option by calling 
> setsockopt() with a zero option length?
> 

Can remove the option using seting in6_pktinfo struct wiht 
ipi6_ifindex=0,ipi6_ifindex=IN6ADDR_ANY_INIT.

If no RFC definition, not to reset with optlen=0,
for example IPV6_TCLASS, PV6_2292DSTOPTS.

-- 
Best Regards
Shan Wei