linux-kernel - Re: [PATCH net 1/2] vsock: Make accept()ed sockets use custom setsockopt()

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Message-ID: <1dad1adc-f287-4871-a86d-e77fe7f84b89@rbox.co>
Date: Mon, 29 Dec 2025 20:45:09 +0100
From: Michal Luczaj <mhal@...x.co>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
 Arseniy Krasnov <avkrasnov@...utedevices.com>,
 virtualization@...ts.linux.dev, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 1/2] vsock: Make accept()ed sockets use custom
 setsockopt()

On 12/23/25 14:15, Stefano Garzarella wrote:
> On Tue, Dec 23, 2025 at 12:09:51PM +0100, Michal Luczaj wrote:
>> On 12/23/25 11:26, Stefano Garzarella wrote:
>>> On Tue, Dec 23, 2025 at 10:15:28AM +0100, Michal Luczaj wrote:
>> ...
>>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>>>> index adcba1b7bf74..c093db8fec2d 100644
>>>> --- a/net/vmw_vsock/af_vsock.c
>>>> +++ b/net/vmw_vsock/af_vsock.c
>>>> @@ -1787,6 +1787,7 @@ static int vsock_accept(struct socket *sock, struct socket *newsock,
>>>> 		} else {
>>>> 			newsock->state = SS_CONNECTED;
>>>> 			sock_graft(connected, newsock);
>>>> +			set_bit(SOCK_CUSTOM_SOCKOPT, &newsock->flags);
>>>
>>> I was a bit confused about next lines calling set_bit on
>>> `connected->sk_socket->flags`, but after `sock_graft(connected,
>>> newsock)` they are equivalent.
>>>
>>> So, maybe I would move the new line before the sock_graft() call or use
>>> `connected->sk_socket->flags` if you want to keep it after it.
>> ...
>>>> 			if (vsock_msgzerocopy_allow(vconnected->transport))
>>>> 				set_bit(SOCK_SUPPORT_ZC,
>>>> 					&connected->sk_socket->flags);
>>
>> Hmm, isn't using both `connected->sk_socket->flags` and `newsock->flags` a
>> bit confusing?
> 
> Yep, for that reason I suggested to use `connected->sk_socket->flags`.
> 
>> `connected->sk_socket->flags` feels unnecessary long to me.
>> So how about a not-so-minimal-patch to have
>>
>> 	newsock->state = SS_CONNECTED;
>> 	set_bit(SOCK_CUSTOM_SOCKOPT, &newsock->flags);
>> 	if (vsock_msgzerocopy_allow(vconnected->transport))
>> 		set_bit(SOCK_SUPPORT_ZC, &newsock->flags);
>> 	sock_graft(connected, newsock);
> 
> No, please, this is a fix, so let's touch less as possible.
> 
> As I mentioned before, we have 2 options IMO:
> 1. use `set_bit(SOCK_CUSTOM_SOCKOPT, &newsock->flags);` but move it
>     before `sock_graft()`
> 2. use `connected->sk_socket->flags` and set it after `sock_graft()` if
>     we want to be a bit more consistent
> 
> I'd go with option 2, because I like to be consistent and it's less
> confusing IMHO, but I'm fine also with option 1.

Yeah, all right, here it is:
https://lore.kernel.org/netdev/20251229-vsock-child-sock-custom-sockopt-v2-0-64778d6c4f88@rbox.co/

Thanks,
Michal