netdev - Re: [Patch net] macvlan: add NETIF_F_NETNS

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Date:	Wed, 12 Feb 2014 11:03:37 +0100
From:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	Cong Wang <cwang@...pensource.com>
CC:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Cong Wang <xiyou.wangcong@...il.com>,
	netdev <netdev@...r.kernel.org>,
	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [Patch net] macvlan: add NETIF_F_NETNS_LOCAL flag

Le 11/02/2014 06:38, Eric Dumazet a écrit :
> On Mon, 2014-02-10 at 21:37 -0800, Eric Dumazet wrote:
>
>>
>> Simple patch would be :
>>
>> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
>> index 048dc8d183aa..31bbba34fd1e 100644
>> --- a/net/core/rtnetlink.c
>> +++ b/net/core/rtnetlink.c
>> @@ -963,6 +963,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
>>   	    nla_put_u32(skb, IFLA_NUM_RX_QUEUES, dev->num_rx_queues) ||
>>   #endif
>>   	    (dev->ifindex != dev->iflink &&
>> +	     __dev_get_by_index(dev_net(dev), dev->iflink) &&
>>   	     nla_put_u32(skb, IFLA_LINK, dev->iflink)) ||
>>   	    (upper_dev &&
>>   	     nla_put_u32(skb, IFLA_MASTER, upper_dev->ifindex)) ||
>>
>
> Hmm, not enough.
>
> We probably need to keep a pointer to iflink net structure.
This is also used in ip tunnels, but when i/o device is not in the same netns
that the tunnel device, the userland can not interpret that IFLA_LINK attribute
(userland don't have necessary information to access another netns, maybe they
will be able to do it in the future ;-)).

The goal of your patch was to avoid filling this attribute when iflink is
into a netns != from dev_net(dev)?

If yes, I agree that we need to keep a pointer to the net structure of iflink.
This information is already available in ip tunnels (struct ip_tunnel->net,
struct ip6_tnl->net) but is not generic. Maybe we can move it to struct
net_device?
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