linux-kernel - Re: [PATCH net-next v15 01/12] vsock: add netns to vsock core

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Message-ID: <4997118e-471c-45fe-bc1f-8f6140199db5@redhat.com>
Date: Wed, 21 Jan 2026 17:32:34 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Stefano Garzarella <sgarzare@...hat.com>,
 Bobby Eshleman <bobbyeshleman@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Simon Horman <horms@...nel.org>, Stefan Hajnoczi <stefanha@...hat.com>,
 "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
 Eugenio Pérez <eperezma@...hat.com>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, "K. Y. Srinivasan"
 <kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>,
 Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
 Bryan Tan <bryan-bt.tan@...adcom.com>, Vishnu Dasa
 <vishnu.dasa@...adcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, Shuah Khan <shuah@...nel.org>,
 Long Li <longli@...rosoft.com>, Jonathan Corbet <corbet@....net>,
 linux-kernel@...r.kernel.org, virtualization@...ts.linux.dev,
 netdev@...r.kernel.org, kvm@...r.kernel.org, linux-hyperv@...r.kernel.org,
 linux-kselftest@...r.kernel.org, berrange@...hat.com,
 Sargun Dhillon <sargun@...gun.me>, linux-doc@...r.kernel.org,
 Bobby Eshleman <bobbyeshleman@...a.com>
Subject: Re: [PATCH net-next v15 01/12] vsock: add netns to vsock core

On 1/21/26 3:48 PM, Stefano Garzarella wrote:
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index a8d0afde7f85..b6e3bfe365a1 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -8253,6 +8253,20 @@ Kernel parameters
>> 			            them quite hard to use for exploits but
>> 			            might break your system.
>>
>> +	vsock_init_ns_mode=
>> +			[KNL,NET] Set the vsock namespace mode for the init
>> +			(root) network namespace.
>> +
>> +			global      [default] The init namespace operates in
>> +			            global mode where CIDs are system-wide and
>> +			            sockets can communicate across global
>> +			            namespaces.
>> +
>> +			local       The init namespace operates in local mode
>> +			            where CIDs are private to the namespace and
>> +			            sockets can only communicate within the same
>> +			            namespace.
>> +
> 
> My comment on v14 was more to start a discussion :-) sorry to not be 
> clear.
> 
> I briefly discussed it with Paolo in chat to better understand our 
> policy between cmdline parameters and module parameters, and it seems 
> that both are discouraged.

Double checking the git log it looks like __setup() usage is less
constrained/restricted than what I thought.

> So he asked me if we have a use case for this, and thinking about it, I 
> don't have one at the moment. Also, if a user decides to set all netns 
> to local, whether init_net is local or global doesn't really matter, 
> right?
> 
> So perhaps before adding this, we should have a real use case.
> Perhaps more than this feature, I would add a way to change the default 
> of all netns (including init_net) from global to local. But we can do 
> that later, since all netns have a way to understand what mode they are 
> in, so we don't break anything and the user has to explicitly change it, 
> knowing that they are breaking compatibility with pre-netns support.\

Lacking a clear use-case for vsock_init_ns_mode I tend to think it would
be better to postpone its introduction. It should be easier to add it
later than vice-versa.

If there is a clear/well defined/known use-case, I guess the series can
go as-is.

/P