netdev - Re: [PATCH net] net: ipv6: Fix ping to link-local addresses.

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Date:	Tue, 9 Aug 2016 01:22:12 +0900
From:	吉藤英明 <hideaki.yoshifuji@...aclelinux.com>
To:	Lorenzo Colitti <lorenzo@...gle.com>
Cc:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Erik Kline <ek@...gle.com>, David Miller <davem@...emloft.net>
Subject: Re: [PATCH net] net: ipv6: Fix ping to link-local addresses.

Hi,

2016-08-08 23:45 GMT+09:00 Lorenzo Colitti <lorenzo@...gle.com>:
> On Mon, Aug 8, 2016 at 11:26 PM, Hannes Frederic Sowa
> <hannes@...essinduktion.org> wrote:
>>> -             if (sk->sk_bound_dev_if &&
>>> -                 sk->sk_bound_dev_if != u->sin6_scope_id) {
>>> -                     return -EINVAL;
>>> -             }
>>
>> Hmm, sk->sk_bound_dev_if always has highest prio for the selection of
>> the output interface. Thus this code made sense to me.
>
> Removing it is consistent with the other sendmsg functions such as
> udpv6_sendmsg or rawv6_sendmsg.
>
> There is similar code in __ip6_datagram_connect, but that seems a bit
> different because that code also *sets* sk_bound_dev_if.
>
> Personally I think it's better for pingv6_sendmsg be consistent with
> the other *_sendmsg functions than with ip6_datagram_connect, and thus
> the code should be removed. But I don't feel particularly strongly
> about it.

Following must be met, at least, IMHO.
- SO_BINDTODEVICE requires "root", which sets sk_bound_dev_if.
- sin6_scope_id and sk_bound_dev_if should match (if the address it
link-local address), or each or both should equal to 0.

I think it would make more sense if former setting wins...

--yoshfuji