Re: [RFC][PATCH 3/3]ipv6:fix the outgoing interface selection order in udpv6_sendmsg()

[Yang Hongyang <yanghy@cn.fujitsu.com>]

David Miller wrote:
> From: Yang Hongyang <yanghy@cn.fujitsu.com>
> Date: Wed, 10 Dec 2008 08:42:20 +0800
> 
>> If outgoing interface is set with SO_BINDTODEVICE and also sticky pktinfo
>> the outgoing interface is exactly what SO_BINDTODEVICE set,because in my
>> first patch,when set sticy pktinfo,outgoing interface set by SO_BINDTODEVICE
>> is checked:
>>
>> +		if(sk->sk_bound_dev_if && pkt.ipi6_ifindex != sk->sk_bound_dev_if)
>> +			goto e_inval;
>>
> 
> You may be checking this, but these two values can become out of sync
> if the application next makes a SO_BINDTODEVICE setsockopt() call to
> change the index setting.
> 
> Nothing makes sure the sticky ipv6 socket information is updated
> if that happens.  And the most obvious ways to handle that are
> very ugly, doing some kind of call into ipv6 from the generic
> socket SO_BINDTODEVICE setsockopt() handler.
> 
> 

Hum..can we just ignore the sync of the sticky option and the SO_BINDTODEVICE,
when send a message,first check sk_bound_dev_if,If it is specified,use it,otherwise
use sticky option?This was what i ment. and in my patch ,the outgoing interface 
specified by sticky options will be overrided by the interface specified by 
SO_BINDTODEVICE.