Le 07/06/2017 à 21:14, Flavio Leitner a écrit :
> On Mon, Jun 05, 2017 at 10:40:24AM +0200, Nicolas Dichtel wrote:
>>> Let me ask this instead: How do you think userspace should behave when
>>> netnsid allocation fails?
>>>
>> There is two ways to assign a nsid:
>> - manually with netlink ('ip netns set'). In this case, the error is
>> reported
>> to userspace via netlink.
>
> OK.
>
>> - automatically when a x-netns interface is created. The link-nsid is also
>> reported to userspace. If the allocation failed, NETNSA_NSID_NOT_ASSIGNED
>> is
>> reported. And if you were able to create this x-netns interface, it means
>> that you have access to this peer netns, thus you can try to assign the
>> nsid
>> manually.
>
> Does that prevent the interface to be created?
No.
>
>> So, in both cases, userland knows that something went wrong.
>> Do you have another scenario in mind?
>
> Let's say the app is restarted, or another monitoring app is executed
> with enough perms. How will it identify the error condition?
Your app wants to monitor a subset of netns. It means that you already have a
way to identify those netns, something like a file stored somewhere
(/var/run/netns/, /proc/<pid>/ns/net, ...). Thus, it's easy to check if those
netns have a nsid assigned in the netns where your app will open the socket.
This option was called NETLINK_F_LISTEN_ALL_NSID, because it only enables to
listen netns *with* a nsid assigned, nothing more. It's up to the user to ensure
that nsid are correctly assigned.
Regards,
Nicolas
