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From:   "Benjamin Coddington" <bcodding@redhat.com>
To:     "Trond Myklebust" <trondmy@hammerspace.com>
Cc:     linux-nfs@vger.kernel.org
Subject: Re: v4 clientid uniquifiers in containers/namespaces
Date:   Mon, 07 Feb 2022 09:05:10 -0500
Message-ID: <596C2475-76AA-4616-919C-9C22B6658CA7@redhat.com>
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On 5 Feb 2022, at 14:50, Benjamin Coddington wrote:

> On 5 Feb 2022, at 13:24, Trond Myklebust wrote:
>
>> On Sat, 2022-02-05 at 10:03 -0500, Benjamin Coddington wrote:
>>> Hi all,
>>>
>>> Is anyone using a udev(-like) implementation with
>>> NETLINK_LISTEN_ALL_NSID?
>>> It looks like that is at least necessary to allow the init namespaced
>>> udev
>>> to receive notifications on /sys/fs/nfs/net/nfs_client/identifier,
>>> which
>>> would be a pre-req to automatically uniquify in containers.
>>>
>>> I'md interested since it will inform whether I need to send patches
>>> to
>>> systemd's udev, and potentially open the can of worms over there. 
>>> Yet its
>>> not yet clear to me how an init namespaced udev process can write to
>>> a netns
>>> sysfs path.
>>>
>>> Another option might be to create yet another daemon/tool that would
>>> listen
>>> specifically for these notifications.  Ugh.
>>>
>>> Ben
>>>
>>
>> I don't understand. Why do you need a new daemon/tool?

Because what we've got only works for the init namespace.

Udev won't get kobject notifications because its not using
NETLINK_LISTEN_ALL_NSIDs.

We need to figure out if we want:

 1) the init namespace udevd to handle all client_id uniquifiers
 2) we expect network namespaces to run their own udevd
 3) or both.

I think 2 violates "least surprise", and 3 might not be something anyone
ever wants.  If they do, we can fix it at that point.

So to make 1 work, we can try to change udevd, or maybe just hacking about
with nfs_netns_object_child_ns_type will be sufficient.

Ben