netdev - Re: [patch net-next] vlan: Don't allow vlan devices to change network namespaces.

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Message-ID: <53590FC9.6090607@6wind.com>
Date:	Thu, 24 Apr 2014 15:21:13 +0200
From:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:	chenweilong <chenweilong@...wei.com>,
	Michal Kubecek <mkubecek@...e.cz>
CC:	Eric Dumazet <eric.dumazet@...il.com>, kaber@...sh.net,
	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [patch net-next] vlan: Don't allow vlan devices to change network
 namespaces.

Le 24/04/2014 14:41, chenweilong a écrit :
> On 2014/4/24 19:32, chenweilong wrote:
>> On 2014/4/24 13:47, Michal Kubecek wrote:
>>> On Thu, Apr 24, 2014 at 08:59:51AM +0800, chenweilong wrote:
>>>> On 2014/4/23 15:23, Nicolas Dichtel wrote:
>>>>> Le 23/04/2014 04:40, chenweilong a écrit :
>>>>>> And, 2) is not safe, if someone forgets to move eth1, eth1.5 will not work, making
>>>>>> things complex.
>>>>> We have to fix this case, because it is a valid use case to have eth1.5 in net0
>>>>> and eth1 in another ns.
>>>>>
>>>> eth1.5 can receive and send packets in net0, the problem is you can't add a new eth1.5
>>>> in old ns, report 'error: File exists'.
>>>
>>> And this is correct, as far as I can tell. If it was possible, which of
>>> the two interfaces would receive VLAN tagged packets with VID 5 coming
>>> to eth1?
>>>
>>>                                                           Michal Kubecek
>>>
>>>
>>>
>> If eth1 and eth1.5 can work in different ns,
>> my fist test(move eth1 first,and then eth1.5) should be success,
>> but it failed, if eth1 was moved to other ns, all related vlans were unregisted.
>> Strangely, if I move eth1.5 to net0, then move eth1 to net0, and then
>> move eth1 to net1, eth1.5 is still there!
>> It is a bug?
> Find at last it's a behavior of SUSE's udevd , not the kernel.
> When move eth1 to net0, udevd call /sbin/ifdown to down eth1
> and then ifdown eth1.5, and then ifdown-802.1q eth1.5 and then
> vconfig rem eth1.5!
>
> Thanks everybody!
>>
>> I agree with you there should be one interface tagged with VID 5 in the system.
>> But I think the network namespaces are independent, vlan port and its VID interfaces
>> spread in different ns break the rule.
VID are unique per interface, for example eth0 can only have one VID 5.
Even if eth1.5 stands in another netns, it is still "connected" to eth0.

I agree that network namespaces are independent, but there are mechanism to
connect them between each other or to connect these netns to a "physical"
network even if you don't have a NIC for each netns on your system. For
example, IP tunnels (ipip, sit, ip6_tunnels) allow to have encapsulation
addresses in one netns and the netdevice in another netns:

ip netns add ns1
ip netns exec ns1 ip link set lo up

ip link add ipip1 type ipip remote 10.16.0.121 local 10.16.0.249
ip link set ipip1 netns ns1
ip netns exec ns1 ip link set ipip1 up
ip netns exec ns1 ip addr add dev ipip1 192.168.2.123 remote 192.168.2.121

vlan may also provide this kind of mechanism.

Regards,
Nicolas
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