[v1] vsock: Fix SO_ZEROCOPY on accept()ed vsocks

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

Posted by Michal Luczaj 1 month, 2 weeks ago

SO_ZEROCOPY handling in vsock_connectible_setsockopt() does not get called
on accept()ed sockets due to a missing flag. Flip it.

Fixes: e0718bd82e27 ("vsock: enable setting SO_ZEROCOPY")
Signed-off-by: Michal Luczaj <mhal@rbox.co>
---
 net/vmw_vsock/af_vsock.c | 1 +
 1 file changed, 1 insertion(+)

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);
 			if (vsock_msgzerocopy_allow(vconnected->transport))
 				set_bit(SOCK_SUPPORT_ZC,
 					&connected->sk_socket->flags);

-- 
2.52.0

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

Posted by Stefano Garzarella 1 month, 2 weeks ago

On Tue, Dec 23, 2025 at 10:15:28AM +0100, Michal Luczaj wrote:
>SO_ZEROCOPY handling in vsock_connectible_setsockopt() does not get called
>on accept()ed sockets due to a missing flag. Flip it.
>
>Fixes: e0718bd82e27 ("vsock: enable setting SO_ZEROCOPY")
>Signed-off-by: Michal Luczaj <mhal@rbox.co>
>---
> net/vmw_vsock/af_vsock.c | 1 +
> 1 file changed, 1 insertion(+)

Thanks for the fix!

>
>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.

WDYT?

BTW the fix LGTM.
Thanks,
Stefano

> 			if (vsock_msgzerocopy_allow(vconnected->transport))
> 				set_bit(SOCK_SUPPORT_ZC,
> 					&connected->sk_socket->flags);
>
>-- 
>2.52.0
>

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

Posted by Michal Luczaj 1 month, 2 weeks ago

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? `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);

?

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

Posted by Stefano Garzarella 1 month, 2 weeks ago

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.

Thanks,
Stefano

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

Posted by Michal Luczaj 1 month, 1 week ago

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