netdev - Re: [PATCH net-next v8 06/14] vsock/virtio: add netns to virtio transport common

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Message-ID: <g34g7deirdtzowtpz5pngfpuzvr62u43psmgct34iliu4bhju4@rkrxdy7n2at3>
Date: Fri, 7 Nov 2025 16:07:39 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Bobby Eshleman <bobbyeshleman@...il.com>
Cc: Shuah Khan <shuah@...nel.org>, "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>, 
	Stefan Hajnoczi <stefanha@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, 
	Jason Wang <jasowang@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, 
	Eugenio Pérez <eperezma@...hat.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>, virtualization@...ts.linux.dev, netdev@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	linux-hyperv@...r.kernel.org, berrange@...hat.com, Bobby Eshleman <bobbyeshleman@...a.com>
Subject: Re: [PATCH net-next v8 06/14] vsock/virtio: add netns to virtio
 transport common

On Fri, Nov 07, 2025 at 06:33:33AM -0800, Bobby Eshleman wrote:
>> > > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>> > > index dcc8a1d5851e..b8e52c71920a 100644
>> > > --- a/net/vmw_vsock/virtio_transport_common.c
>> > > +++ b/net/vmw_vsock/virtio_transport_common.c
>> > > @@ -316,6 +316,15 @@ static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *
>> > > 					 info->flags,
>> > > 					 zcopy);
>> > >
>> > > +	/*
>> > > +	 * If there is no corresponding socket, then we don't have a
>> > > +	 * corresponding namespace. This only happens For VIRTIO_VSOCK_OP_RST.
>> > > +	 */
>> >
>> > So, in virtio_transport_recv_pkt() should we check that `net` is not set?
>> >
>> > Should we set it to NULL here?
>> >
>>
>> Sounds good to me.
>>
>> > > +	if (vsk) {
>> > > +		virtio_vsock_skb_set_net(skb, info->net);
>> >
>> > Ditto here about the net refcnt, can the net disappear?
>> > Should we use get_net() in some way, or the socket will prevent that?
>> >
>>
>> As long as the socket has an outstanding skb it can't be destroyed and
>> so will have a reference to the net, that is after skb_set_owner_w() and
>> freeing... so I think this is okay.
>>
>> But, maybe we could simplify the implied relationship between skb, sk,
>> and net by removing the VIRTIO_VSOCK_SKB_CB(skb)->net entirely, and only
>> ever referring to sock_net(skb->sk)? I remember originally having a
>> reason for adding it to the cb, but my hunch is it that it was probably
>> some confusion over the !vsk case.
>>
>> WDYT?
>>
>
>... now I remember the reason, because I didn't want two different
>places for storing the net for RX and TX.

Yeah, but if we can reuse skb->sk for one path and pass it as parameter 
to the other path (see my prev email), why store it?

Or even in the TX maybe it can be passed to .send_pkt() in some way, 
e.g.  storing it in struct virtio_vsock_sock instead that for each skb.

Stefano