Thread (27 messages) 27 messages, 4 authors, 2026-01-14

Re: [PATCH net-next v14 01/12] vsock: add netns to vsock core

From: Stefano Garzarella <sgarzare@redhat.com>
Date: 2026-01-13 14:37:36
Also in: kvm, linux-hyperv, linux-kselftest, lkml, virtualization

On Mon, Jan 12, 2026 at 07:11:10PM -0800, Bobby Eshleman wrote:
quoted hunk ↗ jump to hunk
From: Bobby Eshleman <redacted>

Add netns logic to vsock core. Additionally, modify transport hook
prototypes to be used by later transport-specific patches (e.g.,
*_seqpacket_allow()).

Namespaces are supported primarily by changing socket lookup functions
(e.g., vsock_find_connected_socket()) to take into account the socket
namespace and the namespace mode before considering a candidate socket a
"match".

This patch also introduces the sysctl /proc/sys/net/vsock/ns_mode to
report the mode and /proc/sys/net/vsock/child_ns_mode to set the mode
for new namespaces.

Add netns functionality (initialization, passing to transports, procfs,
etc...) to the af_vsock socket layer. Later patches that add netns
support to transports depend on this patch.

dgram_allow(), stream_allow(), and seqpacket_allow() callbacks are
modified to take a vsk in order to perform logic on namespace modes. In
future patches, the net will also be used for socket
lookups in these functions.

Signed-off-by: Bobby Eshleman <redacted>
---
Changes in v14:
- include linux/sysctl.h in af_vsock.c
- squash patch 'vsock: add per-net vsock NS mode state' into this patch
 (prior version can be found here):
 https://lore.kernel.org/all/20251223-vsock-vmtest-v13-1-9d6db8e7c80b@meta.com/ (local))

Changes in v13:
- remove net_mode and replace with direct accesses to net->vsock.mode,
 since this is now immutable.
- update comments about mode behavior and mutability, and sysctl API
- only pass NULL for net when wanting global, instead of net_mode ==
 VSOCK_NET_MODE_GLOBAL. This reflects the new logic
 of vsock_net_check_mode() that only requires net pointers (not
 net_mode).
- refactor sysctl string code into a re-usable function, because
 child_ns_mode and ns_mode both handle the same strings.
- remove redundant vsock_net_init(&init_net) call in module init because
 pernet registration calls the callback on the init_net too

Changes in v12:
- return true in dgram_allow(), stream_allow(), and seqpacket_allow()
 only if net_mode == VSOCK_NET_MODE_GLOBAL (Stefano)
- document bind(VMADDR_CID_ANY) case in af_vsock.c (Stefano)
- change order of stream_allow() call in vmci so we can pass vsk
 to it

Changes in v10:
- add file-level comment about what happens to sockets/devices
 when the namespace mode changes (Stefano)
- change the 'if (write)' boolean in vsock_net_mode_string() to
 if (!write), this simplifies a later patch which adds "goto"
 for mutex unlocking on function exit.

Changes in v9:
- remove virtio_vsock_alloc_rx_skb() (Stefano)
- remove vsock_global_dummy_net, not needed as net=NULL +
 net_mode=VSOCK_NET_MODE_GLOBAL achieves identical result

Changes in v7:
- hv_sock: fix hyperv build error
- explain why vhost does not use the dummy
- explain usage of __vsock_global_dummy_net
- explain why VSOCK_NET_MODE_STR_MAX is 8 characters
- use switch-case in vsock_net_mode_string()
- avoid changing transports as much as possible
- add vsock_find_{bound,connected}_socket_net()
- rename `vsock_hdr` to `sysctl_hdr`
- add virtio_vsock_alloc_linear_skb() wrapper for setting dummy net and
 global mode for virtio-vsock, move skb->cb zero-ing into wrapper
- explain seqpacket_allow() change
- move net setting to __vsock_create() instead of vsock_create() so
 that child sockets also have their net assigned upon accept()

Changes in v6:
- unregister sysctl ops in vsock_exit()
- af_vsock: clarify description of CID behavior
- af_vsock: fix buf vs buffer naming, and length checking
- af_vsock: fix length checking w/ correct ctl_table->maxlen

Changes in v5:
- vsock_global_net() -> vsock_global_dummy_net()
- update comments for new uAPI
- use /proc/sys/net/vsock/ns_mode instead of /proc/net/vsock_ns_mode
- add prototype changes so patch remains compilable
---
MAINTAINERS                             |   1 +
drivers/vhost/vsock.c                   |   6 +-
include/linux/virtio_vsock.h            |   4 +-
include/net/af_vsock.h                  |  53 +++++-
include/net/net_namespace.h             |   4 +
include/net/netns/vsock.h               |  17 ++
net/vmw_vsock/af_vsock.c                | 297 +++++++++++++++++++++++++++++---
net/vmw_vsock/hyperv_transport.c        |   7 +-
net/vmw_vsock/virtio_transport.c        |   9 +-
net/vmw_vsock/virtio_transport_common.c |   6 +-
net/vmw_vsock/vmci_transport.c          |  26 ++-
net/vmw_vsock/vsock_loopback.c          |   8 +-
12 files changed, 394 insertions(+), 44 deletions(-)
diff --git a/MAINTAINERS b/MAINTAINERS
index 6737aad729d6..f4aa476427c8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -27522,6 +27522,7 @@ L:	netdev@vger.kernel.org
S:	Maintained
F:	drivers/vhost/vsock.c
F:	include/linux/virtio_vsock.h
+F:	include/net/netns/vsock.h
F:	include/uapi/linux/virtio_vsock.h
F:	net/vmw_vsock/virtio_transport.c
F:	net/vmw_vsock/virtio_transport_common.c
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 552cfb53498a..647ded6f6ea5 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -407,7 +407,8 @@ static bool vhost_transport_msgzerocopy_allow(void)
	return true;
}

-static bool vhost_transport_seqpacket_allow(u32 remote_cid);
+static bool vhost_transport_seqpacket_allow(struct vsock_sock *vsk,
+					    u32 remote_cid);

static struct virtio_transport vhost_transport = {
	.transport = {
@@ -463,7 +464,8 @@ static struct virtio_transport vhost_transport = {
	.send_pkt = vhost_transport_send_pkt,
};

-static bool vhost_transport_seqpacket_allow(u32 remote_cid)
+static bool vhost_transport_seqpacket_allow(struct vsock_sock *vsk,
+					    u32 remote_cid)
{
	struct vhost_vsock *vsock;
	bool seqpacket_allow = false;
diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 0c67543a45c8..1845e8d4f78d 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -256,10 +256,10 @@ void virtio_transport_notify_buffer_size(struct vsock_sock *vsk, u64 *val);
u64 virtio_transport_stream_rcvhiwat(struct vsock_sock *vsk);
bool virtio_transport_stream_is_active(struct vsock_sock *vsk);
-bool virtio_transport_stream_allow(u32 cid, u32 port);
+bool virtio_transport_stream_allow(struct vsock_sock *vsk, u32 cid, u32 port);
int virtio_transport_dgram_bind(struct vsock_sock *vsk,
				struct sockaddr_vm *addr);
-bool virtio_transport_dgram_allow(u32 cid, u32 port);
+bool virtio_transport_dgram_allow(struct vsock_sock *vsk, u32 cid, u32 port);

int virtio_transport_connect(struct vsock_sock *vsk);
diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index d40e978126e3..10c2846fcc58 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -10,6 +10,7 @@
#include <linux/kernel.h>
#include <linux/workqueue.h>
+#include <net/netns/vsock.h>
#include <net/sock.h>
#include <uapi/linux/vm_sockets.h>
@@ -124,7 +125,7 @@ struct vsock_transport {
			     size_t len, int flags);
	int (*dgram_enqueue)(struct vsock_sock *, struct sockaddr_vm *,
			     struct msghdr *, size_t len);
-	bool (*dgram_allow)(u32 cid, u32 port);
+	bool (*dgram_allow)(struct vsock_sock *vsk, u32 cid, u32 port);

	/* STREAM. */
	/* TODO: stream_bind() */
@@ -136,14 +137,14 @@ struct vsock_transport {
	s64 (*stream_has_space)(struct vsock_sock *);
	u64 (*stream_rcvhiwat)(struct vsock_sock *);
	bool (*stream_is_active)(struct vsock_sock *);
-	bool (*stream_allow)(u32 cid, u32 port);
+	bool (*stream_allow)(struct vsock_sock *vsk, u32 cid, u32 port);

	/* SEQ_PACKET. */
	ssize_t (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
				     int flags);
	int (*seqpacket_enqueue)(struct vsock_sock *vsk, struct msghdr *msg,
				 size_t len);
-	bool (*seqpacket_allow)(u32 remote_cid);
+	bool (*seqpacket_allow)(struct vsock_sock *vsk, u32 remote_cid);
	u32 (*seqpacket_has_data)(struct vsock_sock *vsk);

	/* Notification. */
@@ -216,6 +217,11 @@ void vsock_remove_connected(struct vsock_sock *vsk);
struct sock *vsock_find_bound_socket(struct sockaddr_vm *addr);
struct sock *vsock_find_connected_socket(struct sockaddr_vm *src,
					 struct sockaddr_vm *dst);
+struct sock *vsock_find_bound_socket_net(struct sockaddr_vm *addr,
+					 struct net *net);
+struct sock *vsock_find_connected_socket_net(struct sockaddr_vm *src,
+					     struct sockaddr_vm *dst,
+					     struct net *net);
void vsock_remove_sock(struct vsock_sock *vsk);
void vsock_for_each_connected_socket(struct vsock_transport *transport,
				     void (*fn)(struct sock *sk));
@@ -256,4 +262,45 @@ static inline bool vsock_msgzerocopy_allow(const struct vsock_transport *t)
{
	return t->msgzerocopy_allow && t->msgzerocopy_allow();
}
+
+static inline enum vsock_net_mode vsock_net_mode(struct net *net)
+{
What about moving here the check about NULL namespace?
(adding the comment we have later)

I mean just adding a
	if (!net)
		return VSOCK_NET_MODE_GLOBAL;

Or using the ternary operator, as you prefer.

+	return READ_ONCE(net->vsock.mode);
+}
+
+static inline void vsock_net_set_child_mode(struct net *net,
+					    enum vsock_net_mode mode)
+{
+	WRITE_ONCE(net->vsock.child_ns_mode, mode);
+}
+
+static inline enum vsock_net_mode vsock_net_child_mode(struct net *net)
+{
+	return READ_ONCE(net->vsock.child_ns_mode);
+}
+
+/* Return true if two namespaces pass the mode rules. Otherwise, return false.
+ *
+ * A NULL namespace is treated as VSOCK_NET_MODE_GLOBAL.
+ *
+ * Read more about modes in the comment header of net/vmw_vsock/af_vsock.c.
+ */
+static inline bool vsock_net_check_mode(struct net *ns0, struct net *ns1)
+{
+	enum vsock_net_mode mode0, mode1;
+
+	/* Any vsocks within the same network namespace are always reachable,
+	 * regardless of the mode.
+	 */
+	if (net_eq(ns0, ns1))
+		return true;
+
+	mode0 = ns0 ? vsock_net_mode(ns0) : VSOCK_NET_MODE_GLOBAL;
+	mode1 = ns1 ? vsock_net_mode(ns1) : VSOCK_NET_MODE_GLOBAL;
So we can avoid duplicating code here and maybe in other places where 
vsock_net_mode() is used.

About them, in all transports we use that in this way:

net/vmw_vsock/hyperv_transport.c:       if (vsock_net_mode(sock_net(sk_vsock(vsk))) != VSOCK_NET_MODE_GLOBAL)
net/vmw_vsock/virtio_transport.c:       return vsock_net_mode(sock_net(sk_vsock(vsk))) == VSOCK_NET_MODE_GLOBAL;
net/vmw_vsock/virtio_transport.c:       if (vsock_net_mode(sock_net(sk_vsock(vsk))) != VSOCK_NET_MODE_GLOBAL)
net/vmw_vsock/vmci_transport.c: if (vsock_net_mode(sock_net(sk_vsock(vsk))) != VSOCK_NET_MODE_GLOBAL)
net/vmw_vsock/vmci_transport.c: if (vsock_net_mode(sock_net(sk_vsock(vsk))) != VSOCK_NET_MODE_GLOBAL)
net/vmw_vsock/vsock_loopback.c: return vsock_net_mode(sock_net(sk_vsock(vsk))) == VSOCK_NET_MODE_GLOBAL;

So, I'm thinking if we should provide some `vsock_net_mode_global(vsk)` 
that can be used there, but not a strong opinion at all.
quoted hunk ↗ jump to hunk
+
+	/* Different namespaces are only reachable if they are both
+	 * global mode.
+	 */
+	return mode0 == VSOCK_NET_MODE_GLOBAL && mode0 == mode1;
+}
#endif /* __AF_VSOCK_H__ */
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index cb664f6e3558..66d3de1d935f 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -37,6 +37,7 @@
#include <net/netns/smc.h>
#include <net/netns/bpf.h>
#include <net/netns/mctp.h>
+#include <net/netns/vsock.h>
#include <net/net_trackers.h>
#include <linux/ns_common.h>
#include <linux/idr.h>
@@ -196,6 +197,9 @@ struct net {
	/* Move to a better place when the config guard is removed. */
	struct mutex		rtnl_mutex;
#endif
+#if IS_ENABLED(CONFIG_VSOCKETS)
+	struct netns_vsock	vsock;
+#endif
} __randomize_layout;

#include <linux/seq_file_net.h>
diff --git a/include/net/netns/vsock.h b/include/net/netns/vsock.h
new file mode 100644
index 000000000000..e2325e2d6ec5
--- /dev/null
+++ b/include/net/netns/vsock.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NET_NET_NAMESPACE_VSOCK_H
+#define __NET_NET_NAMESPACE_VSOCK_H
+
+#include <linux/types.h>
+
+enum vsock_net_mode {
+	VSOCK_NET_MODE_GLOBAL,
+	VSOCK_NET_MODE_LOCAL,
+};
+
+struct netns_vsock {
+	struct ctl_table_header *sysctl_hdr;
+	enum vsock_net_mode mode;
+	enum vsock_net_mode child_ns_mode;
+};
+#endif /* __NET_NET_NAMESPACE_VSOCK_H */
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index a3505a4dcee0..9d614e4a4fa5 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -83,6 +83,42 @@
 *   TCP_ESTABLISHED - connected
 *   TCP_CLOSING - disconnecting
 *   TCP_LISTEN - listening
+ *
+ * - Namespaces in vsock support two different modes configured
+ *   through /proc/sys/net/vsock/ns_mode. The modes are "local" and "global".
IIUC `/proc/sys/net/vsock/ns_mode` is read-only so "two different modes 
configured through /proc/sys/net/vsock/ns_mode" is not really clear IMO.
+ *   Each mode defines how the namespace interacts with CIDs.
+ *   /proc/sys/net/vsock/ns_mode is read-only and inherited from the
+ *   parent namespace's /proc/sys/net/vsock/child_ns_mode at creation
+ *   time and is immutable thereafter. The default is "global".
Here too, it is not clear to me that child_ns_mode is used to manage new 
children. What do you think about clarifying the situation a little in 
this way:

    * - Namespaces in vsock support two different modes: "local" and "global".
    *   Each mode defines how the namespace interacts with CIDs.
    *   Each namespace exposes two sysctl files:
    *   - /proc/sys/net/vsock/ns_mode (read-only) reports the current namespace's
    *     mode, which is set at namespace creation and immutable thereafter.
    *   - /proc/sys/net/vsock/child_ns_mode (writable) controls what mode future
    *     child namespaces will inherit when created. The default is "global".
    *   Changing child_ns_mode only affects newly created namespaces, not the
    *   current namespace or existing children. At namespace creation, ns_mode
    *   is inherited from the parent's child_ns_mode.
+ *
+ *   The modes affect the allocation and accessibility of CIDs as follows:
+ *
+ *   - global - access and allocation are all system-wide
+ *      - all CID allocation from global namespaces draw from the same
+ *        system-wide pool.
+ *      - if one global namespace has already allocated some CID, another
+ *        global namespace will not be able to allocate the same CID.
+ *      - global mode AF_VSOCK sockets can reach any VM or socket in any global
+ *        namespace, they are not contained to only their own namespace.
+ *      - AF_VSOCK sockets in a global mode namespace cannot reach VMs or
+ *        sockets in any local mode namespace.
+ *   - local - access and allocation are contained within the namespace
+ *     - CID allocation draws only from a private pool local only to the
+ *       namespace, and does not affect the CIDs available for allocation in any
+ *       other namespace (global or local).
+ *     - VMs in a local namespace do not collide with CIDs in any other local
+ *       namespace or any global namespace. For example, if a VM in a local mode
+ *       namespace is given CID 10, then CID 10 is still available for
+ *       allocation in any other namespace, but not in the same namespace.
+ *     - AF_VSOCK sockets in a local mode namespace can connect only to VMs or
+ *       other sockets within their own namespace.
+ *     - sockets bound to VMADDR_CID_ANY in local namespaces will never resolve
+ *       to any transport that is not compatible with local mode. There is no
+ *       error that propagates to the user (as there is for connection attempts)
+ *       because it is possible for some packet to reach this socket from
+ *       a different transport that *does* support local mode. For
+ *       example, virtio-vsock may not support local mode, but the socket
+ *       may still accept a connection from vhost-vsock which does.
 */
So, compared to the previous implementation, now there is no way to 
specify the mode of `init_net` right?

At this point, it will always be global IIUC.

Should we provide something for init_net? Module parameter, kernel 
cmdline. I mean something that can be decided before af_vsock is loaded, 
so we don't have the previous problem of having sockets with different 
modes within the same namespace.

@Paolo any suggestion?
quoted hunk ↗ jump to hunk
#include <linux/compat.h>
@@ -100,20 +136,31 @@
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/net.h>
+#include <linux/proc_fs.h>
#include <linux/poll.h>
#include <linux/random.h>
#include <linux/skbuff.h>
#include <linux/smp.h>
#include <linux/socket.h>
#include <linux/stddef.h>
+#include <linux/sysctl.h>
#include <linux/unistd.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <net/sock.h>
#include <net/af_vsock.h>
+#include <net/netns/vsock.h>
#include <uapi/linux/vm_sockets.h>
#include <uapi/asm-generic/ioctls.h>

+#define VSOCK_NET_MODE_STR_GLOBAL "global"
+#define VSOCK_NET_MODE_STR_LOCAL "local"
+
+/* 6 chars for "global", 1 for null-terminator, and 1 more for '\n'.
+ * The newline is added by proc_dostring() for read operations.
+ */
+#define VSOCK_NET_MODE_STR_MAX 8
+
static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr);
static void vsock_sk_destruct(struct sock *sk);
static int vsock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
@@ -235,33 +282,42 @@ static void __vsock_remove_connected(struct vsock_sock *vsk)
	sock_put(&vsk->sk);
}

-static struct sock *__vsock_find_bound_socket(struct sockaddr_vm *addr)
+static struct sock *__vsock_find_bound_socket_net(struct sockaddr_vm *addr,
+						  struct net *net)
{
	struct vsock_sock *vsk;

	list_for_each_entry(vsk, vsock_bound_sockets(addr), bound_table) {
-		if (vsock_addr_equals_addr(addr, &vsk->local_addr))
-			return sk_vsock(vsk);
+		struct sock *sk = sk_vsock(vsk);
+
+		if (vsock_addr_equals_addr(addr, &vsk->local_addr) &&
+		    vsock_net_check_mode(sock_net(sk), net))
+			return sk;

		if (addr->svm_port == vsk->local_addr.svm_port &&
		    (vsk->local_addr.svm_cid == VMADDR_CID_ANY ||
-		     addr->svm_cid == VMADDR_CID_ANY))
-			return sk_vsock(vsk);
+		     addr->svm_cid == VMADDR_CID_ANY) &&
+		     vsock_net_check_mode(sock_net(sk), net))
+			return sk;
	}

	return NULL;
}

-static struct sock *__vsock_find_connected_socket(struct sockaddr_vm *src,
-						  struct sockaddr_vm *dst)
+static struct sock *
+__vsock_find_connected_socket_net(struct sockaddr_vm *src,
+				  struct sockaddr_vm *dst, struct net *net)
{
	struct vsock_sock *vsk;

	list_for_each_entry(vsk, vsock_connected_sockets(src, dst),
			    connected_table) {
+		struct sock *sk = sk_vsock(vsk);
+
		if (vsock_addr_equals_addr(src, &vsk->remote_addr) &&
-		    dst->svm_port == vsk->local_addr.svm_port) {
-			return sk_vsock(vsk);
+		    dst->svm_port == vsk->local_addr.svm_port &&
+		    vsock_net_check_mode(sock_net(sk), net)) {
+			return sk;
		}
	}
@@ -304,12 +360,13 @@ void vsock_remove_connected(struct vsock_sock *vsk)
}
EXPORT_SYMBOL_GPL(vsock_remove_connected);

-struct sock *vsock_find_bound_socket(struct sockaddr_vm *addr)
+struct sock *vsock_find_bound_socket_net(struct sockaddr_vm *addr,
+					 struct net *net)
{
	struct sock *sk;

	spin_lock_bh(&vsock_table_lock);
-	sk = __vsock_find_bound_socket(addr);
+	sk = __vsock_find_bound_socket_net(addr, net);
	if (sk)
		sock_hold(sk);
@@ -317,15 +374,22 @@ struct sock *vsock_find_bound_socket(struct sockaddr_vm *addr)
	return sk;
}
+EXPORT_SYMBOL_GPL(vsock_find_bound_socket_net);
+
Can we document this and the _net version to make it clear to transports 
when using `vsock_find_bound_socket_net()` or 
`vsock_find_bound_socket()`?
quoted hunk ↗ jump to hunk
+struct sock *vsock_find_bound_socket(struct sockaddr_vm *addr)
+{
+	return vsock_find_bound_socket_net(addr, NULL);
+}
EXPORT_SYMBOL_GPL(vsock_find_bound_socket);

-struct sock *vsock_find_connected_socket(struct sockaddr_vm *src,
-					 struct sockaddr_vm *dst)
+struct sock *vsock_find_connected_socket_net(struct sockaddr_vm *src,
+					     struct sockaddr_vm *dst,
+					     struct net *net)
{
	struct sock *sk;

	spin_lock_bh(&vsock_table_lock);
-	sk = __vsock_find_connected_socket(src, dst);
+	sk = __vsock_find_connected_socket_net(src, dst, net);
	if (sk)
		sock_hold(sk);
@@ -333,6 +397,13 @@ struct sock *vsock_find_connected_socket(struct sockaddr_vm *src,
	return sk;
}
+EXPORT_SYMBOL_GPL(vsock_find_connected_socket_net);
+
Ditto about docuementation.
quoted hunk ↗ jump to hunk
+struct sock *vsock_find_connected_socket(struct sockaddr_vm *src,
+					 struct sockaddr_vm *dst)
+{
+	return vsock_find_connected_socket_net(src, dst, NULL);
+}
EXPORT_SYMBOL_GPL(vsock_find_connected_socket);

void vsock_remove_sock(struct vsock_sock *vsk)
@@ -528,7 +599,7 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
	if (sk->sk_type == SOCK_SEQPACKET) {
		if (!new_transport->seqpacket_allow ||
-		    !new_transport->seqpacket_allow(remote_cid)) {
+		    !new_transport->seqpacket_allow(vsk, remote_cid)) {
			module_put(new_transport->module);
			return -ESOCKTNOSUPPORT;
		}
@@ -676,6 +747,7 @@ static void vsock_pending_work(struct work_struct *work)
static int __vsock_bind_connectible(struct vsock_sock *vsk,
				    struct sockaddr_vm *addr)
{
+	struct net *net = sock_net(sk_vsock(vsk));
	static u32 port;
	struct sockaddr_vm new_addr;
@@ -695,7 +767,7 @@ static int __vsock_bind_connectible(struct vsock_sock *vsk,
			new_addr.svm_port = port++;

-			if (!__vsock_find_bound_socket(&new_addr)) {
+			if (!__vsock_find_bound_socket_net(&new_addr, net)) {
				found = true;
				break;
			}
@@ -712,7 +784,7 @@ static int __vsock_bind_connectible(struct vsock_sock *vsk,
			return -EACCES;
		}

-		if (__vsock_find_bound_socket(&new_addr))
+		if (__vsock_find_bound_socket_net(&new_addr, net))
			return -EADDRINUSE;
	}
@@ -1314,7 +1386,7 @@ static int vsock_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
		goto out;
	}

-	if (!transport->dgram_allow(remote_addr->svm_cid,
+	if (!transport->dgram_allow(vsk, remote_addr->svm_cid,
				    remote_addr->svm_port)) {
		err = -EINVAL;
		goto out;
@@ -1355,7 +1427,7 @@ static int vsock_dgram_connect(struct socket *sock,
	if (err)
		goto out;

-	if (!vsk->transport->dgram_allow(remote_addr->svm_cid,
+	if (!vsk->transport->dgram_allow(vsk, remote_addr->svm_cid,
					 remote_addr->svm_port)) {
		err = -EINVAL;
		goto out;
@@ -1585,7 +1657,7 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr,
		 * endpoints.
		 */
		if (!transport ||
-		    !transport->stream_allow(remote_addr->svm_cid,
+		    !transport->stream_allow(vsk, remote_addr->svm_cid,
					     remote_addr->svm_port)) {
			err = -ENETUNREACH;
			goto out;
@@ -2662,6 +2734,183 @@ static struct miscdevice vsock_device = {
	.fops		= &vsock_device_ops,
};

+static int __vsock_net_mode_string(const struct ctl_table *table, int write,
+				   void *buffer, size_t *lenp, loff_t *ppos,
+				   enum vsock_net_mode mode,
+				   enum vsock_net_mode *new_mode)
+{
+	char data[VSOCK_NET_MODE_STR_MAX] = {0};
+	struct ctl_table tmp;
+	int ret;
+
+	if (!table->data || !table->maxlen || !*lenp) {
+		*lenp = 0;
+		return 0;
+	}
+
+	tmp = *table;
+	tmp.data = data;
+
+	if (!write) {
+		const char *p;
+
+		switch (mode) {
+		case VSOCK_NET_MODE_GLOBAL:
+			p = VSOCK_NET_MODE_STR_GLOBAL;
+			break;
+		case VSOCK_NET_MODE_LOCAL:
+			p = VSOCK_NET_MODE_STR_LOCAL;
+			break;
+		default:
+			WARN_ONCE(true, "netns has invalid vsock mode");
+			*lenp = 0;
+			return 0;
+		}
+
+		strscpy(data, p, sizeof(data));
+		tmp.maxlen = strlen(p);
+	}
+
+	ret = proc_dostring(&tmp, write, buffer, lenp, ppos);
nit:
	if (ret || !write)
		return ret;
+	if (ret)
+		return ret;
+
+	if (!write)
+		return 0;
+
+	if (*lenp >= sizeof(data))
+		return -EINVAL;
+
+	if (!strncmp(data, VSOCK_NET_MODE_STR_GLOBAL, sizeof(data)))
+		*new_mode = VSOCK_NET_MODE_GLOBAL;
+	else if (!strncmp(data, VSOCK_NET_MODE_STR_LOCAL, sizeof(data)))
+		*new_mode = VSOCK_NET_MODE_LOCAL;
+	else
+		return -EINVAL;
+
+	return 0;
+}
+
+static int vsock_net_mode_string(const struct ctl_table *table, int write,
+				 void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct net *net;
+
+	if (write)
+		return -EPERM;
+
+	net = current->nsproxy->net_ns;
+
+	return __vsock_net_mode_string(table, write, buffer, lenp, ppos,
+				       vsock_net_mode(net), NULL);
+}
+
+static int vsock_net_child_mode_string(const struct ctl_table *table, int write,
+				       void *buffer, size_t *lenp, loff_t *ppos)
+{
+	enum vsock_net_mode new_mode;
+	struct net *net;
+	int ret;
+
+	net = current->nsproxy->net_ns;
+
+	ret = __vsock_net_mode_string(table, write, buffer, lenp, ppos,
+				      vsock_net_child_mode(net), &new_mode);
+	if (ret)
+		return ret;
+
+	if (write)
+		vsock_net_set_child_mode(net, new_mode);
+
+	return 0;
+}
+
+static struct ctl_table vsock_table[] = {
+	{
+		.procname	= "ns_mode",
+		.data		= &init_net.vsock.mode,
+		.maxlen		= VSOCK_NET_MODE_STR_MAX,
+		.mode		= 0444,
+		.proc_handler	= vsock_net_mode_string
+	},
+	{
+		.procname	= "child_ns_mode",
+		.data		= &init_net.vsock.child_ns_mode,
+		.maxlen		= VSOCK_NET_MODE_STR_MAX,
+		.mode		= 0644,
+		.proc_handler	= vsock_net_child_mode_string
+	},
+};
+
+static int __net_init vsock_sysctl_register(struct net *net)
+{
+	struct ctl_table *table;
+
+	if (net_eq(net, &init_net)) {
+		table = vsock_table;
+	} else {
+		table = kmemdup(vsock_table, sizeof(vsock_table), GFP_KERNEL);
+		if (!table)
+			goto err_alloc;
+
+		table[0].data = &net->vsock.mode;
+		table[1].data = &net->vsock.child_ns_mode;
+	}
+
+	net->vsock.sysctl_hdr = register_net_sysctl_sz(net, "net/vsock", table,
+						       ARRAY_SIZE(vsock_table));
+	if (!net->vsock.sysctl_hdr)
+		goto err_reg;
+
+	return 0;
+
+err_reg:
+	if (!net_eq(net, &init_net))
+		kfree(table);
+err_alloc:
+	return -ENOMEM;
+}
+
+static void vsock_sysctl_unregister(struct net *net)
+{
+	const struct ctl_table *table;
+
+	table = net->vsock.sysctl_hdr->ctl_table_arg;
+	unregister_net_sysctl_table(net->vsock.sysctl_hdr);
+	if (!net_eq(net, &init_net))
+		kfree(table);
+}
+
+static void vsock_net_init(struct net *net)
+{
+	if (net_eq(net, &init_net))
+		net->vsock.mode = VSOCK_NET_MODE_GLOBAL;
Right here, I mean, do we always have to use VSOCK_NET_MODE_GLOBAL or 
make it configurable somehow?

The rest LGTM.

Stefano
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