From: Bobby Eshleman <bobbyeshleman@meta.com>

Enable network namespace support in the virtio-vsock common transport
layer by declaring namespace pointers in the transmit and receive
paths.

The changes include:
1. Add a 'net' field to virtio_vsock_pkt_info to carry the namespace
   pointer for outgoing packets.
2. Store the namespace and namespace mode in the skb control buffer when
   allocating packets (except for VIRTIO_VSOCK_OP_RST packets which do
   not have an associated socket).
3. Retrieve namespace information from skbs on the receive path for
   lookups using vsock_find_connected_socket_net() and
   vsock_find_bound_socket_net().

This allows users of virtio transport common code
(vhost-vsock/virtio-vsock) to later enable namespace support.

Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
---
Changes in v7:
- add comment explaining the !vsk case in virtio_transport_alloc_skb()
---
 include/linux/virtio_vsock.h            |  1 +
 net/vmw_vsock/virtio_transport_common.c | 21 +++++++++++++++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 29290395054c..f90646f82993 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -217,6 +217,7 @@ struct virtio_vsock_pkt_info {
 	u32 remote_cid, remote_port;
 	struct vsock_sock *vsk;
 	struct msghdr *msg;
+	struct net *net;
 	u32 pkt_len;
 	u16 type;
 	u16 op;
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.
+	 */
+	if (vsk) {
+		virtio_vsock_skb_set_net(skb, info->net);
+		virtio_vsock_skb_set_net_mode(skb, vsk->net_mode);
+	}
+
 	return skb;
 out:
 	kfree_skb(skb);
@@ -527,6 +536,7 @@ static int virtio_transport_send_credit_update(struct vsock_sock *vsk)
 	struct virtio_vsock_pkt_info info = {
 		.op = VIRTIO_VSOCK_OP_CREDIT_UPDATE,
 		.vsk = vsk,
+		.net = sock_net(sk_vsock(vsk)),
 	};
 
 	return virtio_transport_send_pkt_info(vsk, &info);
@@ -1067,6 +1077,7 @@ int virtio_transport_connect(struct vsock_sock *vsk)
 	struct virtio_vsock_pkt_info info = {
 		.op = VIRTIO_VSOCK_OP_REQUEST,
 		.vsk = vsk,
+		.net = sock_net(sk_vsock(vsk)),
 	};
 
 	return virtio_transport_send_pkt_info(vsk, &info);
@@ -1082,6 +1093,7 @@ int virtio_transport_shutdown(struct vsock_sock *vsk, int mode)
 			 (mode & SEND_SHUTDOWN ?
 			  VIRTIO_VSOCK_SHUTDOWN_SEND : 0),
 		.vsk = vsk,
+		.net = sock_net(sk_vsock(vsk)),
 	};
 
 	return virtio_transport_send_pkt_info(vsk, &info);
@@ -1108,6 +1120,7 @@ virtio_transport_stream_enqueue(struct vsock_sock *vsk,
 		.msg = msg,
 		.pkt_len = len,
 		.vsk = vsk,
+		.net = sock_net(sk_vsock(vsk)),
 	};
 
 	return virtio_transport_send_pkt_info(vsk, &info);
@@ -1145,6 +1158,7 @@ static int virtio_transport_reset(struct vsock_sock *vsk,
 		.op = VIRTIO_VSOCK_OP_RST,
 		.reply = !!skb,
 		.vsk = vsk,
+		.net = sock_net(sk_vsock(vsk)),
 	};
 
 	/* Send RST only if the original pkt is not a RST pkt */
@@ -1465,6 +1479,7 @@ virtio_transport_send_response(struct vsock_sock *vsk,
 		.remote_port = le32_to_cpu(hdr->src_port),
 		.reply = true,
 		.vsk = vsk,
+		.net = sock_net(sk_vsock(vsk)),
 	};
 
 	return virtio_transport_send_pkt_info(vsk, &info);
@@ -1578,7 +1593,9 @@ static bool virtio_transport_valid_type(u16 type)
 void virtio_transport_recv_pkt(struct virtio_transport *t,
 			       struct sk_buff *skb)
 {
+	enum vsock_net_mode net_mode = virtio_vsock_skb_net_mode(skb);
 	struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
+	struct net *net = virtio_vsock_skb_net(skb);
 	struct sockaddr_vm src, dst;
 	struct vsock_sock *vsk;
 	struct sock *sk;
@@ -1606,9 +1623,9 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
 	/* The socket must be in connected or bound table
 	 * otherwise send reset back
 	 */
-	sk = vsock_find_connected_socket(&src, &dst);
+	sk = vsock_find_connected_socket_net(&src, &dst, net, net_mode);
 	if (!sk) {
-		sk = vsock_find_bound_socket(&dst);
+		sk = vsock_find_bound_socket_net(&dst, net, net_mode);
 		if (!sk) {
 			(void)virtio_transport_reset_no_sock(t, skb);
 			goto free_pkt;

-- 
2.47.3

On Thu, Oct 23, 2025 at 11:27:45AM -0700, Bobby Eshleman wrote:
>From: Bobby Eshleman <bobbyeshleman@meta.com>
>
>Enable network namespace support in the virtio-vsock common transport
>layer by declaring namespace pointers in the transmit and receive
>paths.
>
>The changes include:
>1. Add a 'net' field to virtio_vsock_pkt_info to carry the namespace
>   pointer for outgoing packets.
>2. Store the namespace and namespace mode in the skb control buffer when
>   allocating packets (except for VIRTIO_VSOCK_OP_RST packets which do
>   not have an associated socket).
>3. Retrieve namespace information from skbs on the receive path for
>   lookups using vsock_find_connected_socket_net() and
>   vsock_find_bound_socket_net().
>
>This allows users of virtio transport common code
>(vhost-vsock/virtio-vsock) to later enable namespace support.
>
>Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
>---
>Changes in v7:
>- add comment explaining the !vsk case in virtio_transport_alloc_skb()
>---
> include/linux/virtio_vsock.h            |  1 +
> net/vmw_vsock/virtio_transport_common.c | 21 +++++++++++++++++++--
> 2 files changed, 20 insertions(+), 2 deletions(-)
>
>diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>index 29290395054c..f90646f82993 100644
>--- a/include/linux/virtio_vsock.h
>+++ b/include/linux/virtio_vsock.h
>@@ -217,6 +217,7 @@ struct virtio_vsock_pkt_info {
> 	u32 remote_cid, remote_port;
> 	struct vsock_sock *vsk;
> 	struct msghdr *msg;
>+	struct net *net;
> 	u32 pkt_len;
> 	u16 type;
> 	u16 op;
>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?

>+	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?

>+		virtio_vsock_skb_set_net_mode(skb, vsk->net_mode);
>+	}
>+
> 	return skb;
> out:
> 	kfree_skb(skb);
>@@ -527,6 +536,7 @@ static int virtio_transport_send_credit_update(struct vsock_sock *vsk)
> 	struct virtio_vsock_pkt_info info = {
> 		.op = VIRTIO_VSOCK_OP_CREDIT_UPDATE,
> 		.vsk = vsk,
>+		.net = sock_net(sk_vsock(vsk)),
> 	};
>
> 	return virtio_transport_send_pkt_info(vsk, &info);
>@@ -1067,6 +1077,7 @@ int virtio_transport_connect(struct vsock_sock *vsk)
> 	struct virtio_vsock_pkt_info info = {
> 		.op = VIRTIO_VSOCK_OP_REQUEST,
> 		.vsk = vsk,
>+		.net = sock_net(sk_vsock(vsk)),
> 	};
>
> 	return virtio_transport_send_pkt_info(vsk, &info);
>@@ -1082,6 +1093,7 @@ int virtio_transport_shutdown(struct vsock_sock *vsk, int mode)
> 			 (mode & SEND_SHUTDOWN ?
> 			  VIRTIO_VSOCK_SHUTDOWN_SEND : 0),
> 		.vsk = vsk,
>+		.net = sock_net(sk_vsock(vsk)),
> 	};
>
> 	return virtio_transport_send_pkt_info(vsk, &info);
>@@ -1108,6 +1120,7 @@ virtio_transport_stream_enqueue(struct vsock_sock *vsk,
> 		.msg = msg,
> 		.pkt_len = len,
> 		.vsk = vsk,
>+		.net = sock_net(sk_vsock(vsk)),
> 	};
>
> 	return virtio_transport_send_pkt_info(vsk, &info);
>@@ -1145,6 +1158,7 @@ static int virtio_transport_reset(struct vsock_sock *vsk,
> 		.op = VIRTIO_VSOCK_OP_RST,
> 		.reply = !!skb,
> 		.vsk = vsk,
>+		.net = sock_net(sk_vsock(vsk)),
> 	};
>
> 	/* Send RST only if the original pkt is not a RST pkt */
>@@ -1465,6 +1479,7 @@ virtio_transport_send_response(struct vsock_sock *vsk,
> 		.remote_port = le32_to_cpu(hdr->src_port),
> 		.reply = true,
> 		.vsk = vsk,
>+		.net = sock_net(sk_vsock(vsk)),
> 	};
>
> 	return virtio_transport_send_pkt_info(vsk, &info);
>@@ -1578,7 +1593,9 @@ static bool virtio_transport_valid_type(u16 type)
> void virtio_transport_recv_pkt(struct virtio_transport *t,
> 			       struct sk_buff *skb)
> {
>+	enum vsock_net_mode net_mode = virtio_vsock_skb_net_mode(skb);
> 	struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
>+	struct net *net = virtio_vsock_skb_net(skb);

Okay, so this is where the skb net is read, so why we touch the 
virtio-vsock driver (virtio_transport.c) in the other patch where we 
changed just af_vsock.c?

IMO we should move that change here, or in a separate commit.
Or maybe I missed some dependency :-)

Thanks,
Stefano

> 	struct sockaddr_vm src, dst;
> 	struct vsock_sock *vsk;
> 	struct sock *sk;
>@@ -1606,9 +1623,9 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
> 	/* The socket must be in connected or bound table
> 	 * otherwise send reset back
> 	 */
>-	sk = vsock_find_connected_socket(&src, &dst);
>+	sk = vsock_find_connected_socket_net(&src, &dst, net, net_mode);
> 	if (!sk) {
>-		sk = vsock_find_bound_socket(&dst);
>+		sk = vsock_find_bound_socket_net(&dst, net, net_mode);
> 		if (!sk) {
> 			(void)virtio_transport_reset_no_sock(t, skb);
> 			goto free_pkt;
>
>-- 
>2.47.3
>

On Thu, Nov 06, 2025 at 05:20:05PM +0100, Stefano Garzarella wrote:
> On Thu, Oct 23, 2025 at 11:27:45AM -0700, Bobby Eshleman wrote:
> > From: Bobby Eshleman <bobbyeshleman@meta.com>
> > 
> > Enable network namespace support in the virtio-vsock common transport
> > layer by declaring namespace pointers in the transmit and receive
> > paths.
> > 
> > The changes include:
> > 1. Add a 'net' field to virtio_vsock_pkt_info to carry the namespace
> >   pointer for outgoing packets.
> > 2. Store the namespace and namespace mode in the skb control buffer when
> >   allocating packets (except for VIRTIO_VSOCK_OP_RST packets which do
> >   not have an associated socket).
> > 3. Retrieve namespace information from skbs on the receive path for
> >   lookups using vsock_find_connected_socket_net() and
> >   vsock_find_bound_socket_net().
> > 
> > This allows users of virtio transport common code
> > (vhost-vsock/virtio-vsock) to later enable namespace support.
> > 
> > Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
> > ---
> > Changes in v7:
> > - add comment explaining the !vsk case in virtio_transport_alloc_skb()
> > ---
> > include/linux/virtio_vsock.h            |  1 +
> > net/vmw_vsock/virtio_transport_common.c | 21 +++++++++++++++++++--
> > 2 files changed, 20 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> > index 29290395054c..f90646f82993 100644
> > --- a/include/linux/virtio_vsock.h
> > +++ b/include/linux/virtio_vsock.h
> > @@ -217,6 +217,7 @@ struct virtio_vsock_pkt_info {
> > 	u32 remote_cid, remote_port;
> > 	struct vsock_sock *vsk;
> > 	struct msghdr *msg;
> > +	struct net *net;
> > 	u32 pkt_len;
> > 	u16 type;
> > 	u16 op;
> > 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?

[...]

> > 
> > 	return virtio_transport_send_pkt_info(vsk, &info);
> > @@ -1578,7 +1593,9 @@ static bool virtio_transport_valid_type(u16 type)
> > void virtio_transport_recv_pkt(struct virtio_transport *t,
> > 			       struct sk_buff *skb)
> > {
> > +	enum vsock_net_mode net_mode = virtio_vsock_skb_net_mode(skb);
> > 	struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
> > +	struct net *net = virtio_vsock_skb_net(skb);
> 
> Okay, so this is where the skb net is read, so why we touch the virtio-vsock
> driver (virtio_transport.c) in the other patch where we changed just
> af_vsock.c?
> 
> IMO we should move that change here, or in a separate commit.
> Or maybe I missed some dependency :-)
> 

100% agree.

> Thanks,
> Stefano
> 

Thanks!

-Bobby

> > > 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.

Best,
Bobby

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

On Fri, Nov 07, 2025 at 04:07:39PM +0100, Stefano Garzarella wrote:
> 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
> 

That's a good point, the rx path only needs to pass to recv_pkt(), it is
not needed after the socket lookup there.

With TX, it does look like we could get rid of it via the
virtio_vsock_sock.

Best,
Bobby

On Thu, Nov 06, 2025 at 06:52:15PM -0800, Bobby Eshleman wrote:
>On Thu, Nov 06, 2025 at 05:20:05PM +0100, Stefano Garzarella wrote:
>> On Thu, Oct 23, 2025 at 11:27:45AM -0700, Bobby Eshleman wrote:
>> > From: Bobby Eshleman <bobbyeshleman@meta.com>
>> >
>> > Enable network namespace support in the virtio-vsock common transport
>> > layer by declaring namespace pointers in the transmit and receive
>> > paths.
>> >
>> > The changes include:
>> > 1. Add a 'net' field to virtio_vsock_pkt_info to carry the namespace
>> >   pointer for outgoing packets.
>> > 2. Store the namespace and namespace mode in the skb control buffer when
>> >   allocating packets (except for VIRTIO_VSOCK_OP_RST packets which do
>> >   not have an associated socket).
>> > 3. Retrieve namespace information from skbs on the receive path for
>> >   lookups using vsock_find_connected_socket_net() and
>> >   vsock_find_bound_socket_net().
>> >
>> > This allows users of virtio transport common code
>> > (vhost-vsock/virtio-vsock) to later enable namespace support.
>> >
>> > Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
>> > ---
>> > Changes in v7:
>> > - add comment explaining the !vsk case in 
>> > virtio_transport_alloc_skb()
>> > ---
>> > include/linux/virtio_vsock.h            |  1 +
>> > net/vmw_vsock/virtio_transport_common.c | 21 +++++++++++++++++++--
>> > 2 files changed, 20 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>> > index 29290395054c..f90646f82993 100644
>> > --- a/include/linux/virtio_vsock.h
>> > +++ b/include/linux/virtio_vsock.h
>> > @@ -217,6 +217,7 @@ struct virtio_vsock_pkt_info {
>> > 	u32 remote_cid, remote_port;
>> > 	struct vsock_sock *vsk;
>> > 	struct msghdr *msg;
>> > +	struct net *net;
>> > 	u32 pkt_len;
>> > 	u16 type;
>> > 	u16 op;
>> > 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?

If vsk == NULL, I'm expecting that also skb->sk is not valid, right?

Indeed we call skb_set_owner_w() only if vsk != NULL in 
virtio_transport_alloc_skb().

Maybe we need to change virtio_transport_recv_pkt() where the `net` 
should be passed in some way by the caller, so maybe this is the reason 
why you needed it in the cb. But also in that case, I think we can get 
the `net` in some way and pass it to virtio_transport_recv_pkt() and 
avoid the change in the cb:
- vsock_lookpback.c in vsock_loopback_work() we can use vsock->net
- vhost/vsock.c in vhost_vsock_handle_tx_kick(), ditto we can use 
   vsock->net
- virtio_transport.c we can just pass always the dummy_net

Same fot the net_mode.

Maybe the real problem is in the send_pkt callbacks, where the skb is 
used to get the socket, but as you mention, I think in this path 
skb_set_owner_w() is already called, so we can get that info from there 
in some way.

Not sure, but yeah, if we can remove that, it will be much clear IMO.

Thanks,
Stefano