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

From: Yang Hongyang <[email-masked]>
Date: Wed, 10 Dec 2008 08:42:20 +0800

Rémi Denis-Courmont wrote:
> On Tuesday 09 December 2008 09:12:59 ext Yang Hongyang, you wrote:
>> 1.When no interface is specified in an IPV6_PKTINFO ancillary data
>>   item, the interface specified in an IPV6_PKTINFO sticky optionis
>>   is used.
> 
>> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
>> index 8b48512..addd856 100644
>> --- a/net/ipv6/udp.c
>> +++ b/net/ipv6/udp.c
>> @@ -761,6 +761,9 @@ do_udp_sendmsg:
>>  	}
>>
>>  	if (!fl.oif)
>> +		fl.oif = np->sticky_pktinfo.ipi6_ifindex;
>> +
>> +	if (!fl.oif)
>>  		fl.oif = sk->sk_bound_dev_if;
>>
>>  	if (msg->msg_controllen) {
> 
> I believe overriding the outgoing interface is only allowed for link-local 
> destinations, _or_ with privileges (as with SO_BINDTODEVICE).
> 
> This patch seems to change this, and I am not convinced it's a good idea.
> 

It does not overriding the outgoing interface.
when no interface is specified in an IPV6_PKTINFO ancillary data item(as with
 SO_BINDTODEVICE), the interface specified in an IPV6_PKTINFO sticky 
optionins  is used.

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;